#include "grbl.h"

// Note that the simulator and grbl do not work properly together
// https://forum.arduino.cc/t/why-does-the-wokwi-simulator-hang-grbl/985524
// 

grbl.ino

Note that grbl hangs in Wokwi
https://forum.arduino.cc/t/why-does-the-wokwi-simulator-hang-grbl/985524
Read Description

diagram.json

config.h

/*
  coolant_control.c - coolant control methods
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


void coolant_init()
{
  COOLANT_FLOOD_DDR |= (1 << COOLANT_FLOOD_BIT); // Configure as output pin
  #ifdef ENABLE_M7
    COOLANT_MIST_DDR |= (1 << COOLANT_MIST_BIT);
  #endif
  coolant_stop();
}


// Returns current coolant output state. Overrides may alter it from programmed state.
uint8_t coolant_get_state()
{
  uint8_t cl_state = COOLANT_STATE_DISABLE;
  #ifdef INVERT_COOLANT_FLOOD_PIN
    if (bit_isfalse(COOLANT_FLOOD_PORT,(1 << COOLANT_FLOOD_BIT))) {
  #else
    if (bit_istrue(COOLANT_FLOOD_PORT,(1 << COOLANT_FLOOD_BIT))) {
  #endif
    cl_state |= COOLANT_STATE_FLOOD;
  }
  #ifdef ENABLE_M7
    #ifdef INVERT_COOLANT_MIST_PIN
      if (bit_isfalse(COOLANT_MIST_PORT,(1 << COOLANT_MIST_BIT))) {
    #else
      if (bit_istrue(COOLANT_MIST_PORT,(1 << COOLANT_MIST_BIT))) {
    #endif
      cl_state |= COOLANT_STATE_MIST;
    }
  #endif
  return(cl_state);
}


// Directly called by coolant_init(), coolant_set_state(), and mc_reset(), which can be at
// an interrupt-level. No report flag set, but only called by routines that don't need it.
void coolant_stop()
{
  #ifdef INVERT_COOLANT_FLOOD_PIN
    COOLANT_FLOOD_PORT |= (1 << COOLANT_FLOOD_BIT);
  #else
    COOLANT_FLOOD_PORT &= ~(1 << COOLANT_FLOOD_BIT);
  #endif
  #ifdef ENABLE_M7
    #ifdef INVERT_COOLANT_MIST_PIN
      COOLANT_MIST_PORT |= (1 << COOLANT_MIST_BIT);
    #else
      COOLANT_MIST_PORT &= ~(1 << COOLANT_MIST_BIT);
    #endif
  #endif
}


// Main program only. Immediately sets flood coolant running state and also mist coolant, 
// if enabled. Also sets a flag to report an update to a coolant state.
// Called by coolant toggle override, parking restore, parking retract, sleep mode, g-code
// parser program end, and g-code parser coolant_sync().
void coolant_set_state(uint8_t mode)
{
  if (sys.abort) { return; } // Block during abort.  
  
	if (mode & COOLANT_FLOOD_ENABLE) {
		#ifdef INVERT_COOLANT_FLOOD_PIN
			COOLANT_FLOOD_PORT &= ~(1 << COOLANT_FLOOD_BIT);
		#else
			COOLANT_FLOOD_PORT |= (1 << COOLANT_FLOOD_BIT);
		#endif
	} else {
	  #ifdef INVERT_COOLANT_FLOOD_PIN
			COOLANT_FLOOD_PORT |= (1 << COOLANT_FLOOD_BIT);
		#else
			COOLANT_FLOOD_PORT &= ~(1 << COOLANT_FLOOD_BIT);
		#endif
	}
  
	#ifdef ENABLE_M7
		if (mode & COOLANT_MIST_ENABLE) {
			#ifdef INVERT_COOLANT_MIST_PIN
				COOLANT_MIST_PORT &= ~(1 << COOLANT_MIST_BIT);
			#else
				COOLANT_MIST_PORT |= (1 << COOLANT_MIST_BIT);
			#endif
		} else {
			#ifdef INVERT_COOLANT_MIST_PIN
				COOLANT_MIST_PORT |= (1 << COOLANT_MIST_BIT);
			#else
				COOLANT_MIST_PORT &= ~(1 << COOLANT_MIST_BIT);
			#endif
		}
	#endif
	
  sys.report_ovr_counter = 0; // Set to report change immediately
}


// G-code parser entry-point for setting coolant state. Forces a planner buffer sync and bails 
// if an abort or check-mode is active.
void coolant_sync(uint8_t mode)
{
  if (sys.state == STATE_CHECK_MODE) { return; }
  protocol_buffer_synchronize(); // Ensure coolant turns on when specified in program.
  coolant_set_state(mode);
}


coolant_control.c

/*
  coolant_control.h - spindle control methods
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef coolant_control_h
#define coolant_control_h

#define COOLANT_NO_SYNC     false
#define COOLANT_FORCE_SYNC  true

#define COOLANT_STATE_DISABLE   0  // Must be zero
#define COOLANT_STATE_FLOOD     PL_COND_FLAG_COOLANT_FLOOD
#define COOLANT_STATE_MIST      PL_COND_FLAG_COOLANT_MIST


// Initializes coolant control pins.
void coolant_init();

// Returns current coolant output state. Overrides may alter it from programmed state.
uint8_t coolant_get_state();

// Immediately disables coolant pins.
void coolant_stop();

// Sets the coolant pins according to state specified.
void coolant_set_state(uint8_t mode);

// G-code parser entry-point for setting coolant states. Checks for and executes additional conditions.
void coolant_sync(uint8_t mode);

#endif


coolant_control.h

/*
  cpu_map.h - CPU and pin mapping configuration file
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

/* The cpu_map.h files serve as a central pin mapping selection file for different
   processor types or alternative pin layouts. This version of Grbl officially supports
   only the Arduino Mega328p. */


#ifndef cpu_map_h
#define cpu_map_h


#ifdef CPU_MAP_ATMEGA328P // (Arduino Uno) Officially supported by Grbl.

  // Define serial port pins and interrupt vectors.
  #define SERIAL_RX     USART_RX_vect
  #define SERIAL_UDRE   USART_UDRE_vect

  // Define step pulse output pins. NOTE: All step bit pins must be on the same port.
  #define STEP_DDR        DDRD
  #define STEP_PORT       PORTD
  #define X_STEP_BIT      2  // Uno Digital Pin 2
  #define Y_STEP_BIT      3  // Uno Digital Pin 3
  #define Z_STEP_BIT      4  // Uno Digital Pin 4
  #define STEP_MASK       ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)) // All step bits

  // Define step direction output pins. NOTE: All direction pins must be on the same port.
  #define DIRECTION_DDR     DDRD
  #define DIRECTION_PORT    PORTD
  #define X_DIRECTION_BIT   5  // Uno Digital Pin 5
  #define Y_DIRECTION_BIT   6  // Uno Digital Pin 6
  #define Z_DIRECTION_BIT   7  // Uno Digital Pin 7
  #define DIRECTION_MASK    ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) // All direction bits

  // Define stepper driver enable/disable output pin.
  #define STEPPERS_DISABLE_DDR    DDRB
  #define STEPPERS_DISABLE_PORT   PORTB
  #define STEPPERS_DISABLE_BIT    0  // Uno Digital Pin 8
  #define STEPPERS_DISABLE_MASK   (1<<STEPPERS_DISABLE_BIT)

  // Define homing/hard limit switch input pins and limit interrupt vectors.
  // NOTE: All limit bit pins must be on the same port, but not on a port with other input pins (CONTROL).
  #define LIMIT_DDR        DDRB
  #define LIMIT_PIN        PINB
  #define LIMIT_PORT       PORTB
  #define X_LIMIT_BIT      1  // Uno Digital Pin 9
  #define Y_LIMIT_BIT      2  // Uno Digital Pin 10
  #ifdef VARIABLE_SPINDLE // Z Limit pin and spindle enabled swapped to access hardware PWM on Pin 11.
    #define Z_LIMIT_BIT	   4 // Uno Digital Pin 12
  #else
    #define Z_LIMIT_BIT    3  // Uno Digital Pin 11
  #endif
  #if !defined(ENABLE_DUAL_AXIS)
    #define LIMIT_MASK     ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)|(1<<Z_LIMIT_BIT)) // All limit bits
  #endif
  #define LIMIT_INT        PCIE0  // Pin change interrupt enable pin
  #define LIMIT_INT_vect   PCINT0_vect
  #define LIMIT_PCMSK      PCMSK0 // Pin change interrupt register

  // Define user-control controls (cycle start, reset, feed hold) input pins.
  // NOTE: All CONTROLs pins must be on the same port and not on a port with other input pins (limits).
  #define CONTROL_DDR       DDRC
  #define CONTROL_PIN       PINC
  #define CONTROL_PORT      PORTC
  #define CONTROL_RESET_BIT         0  // Uno Analog Pin 0
  #define CONTROL_FEED_HOLD_BIT     1  // Uno Analog Pin 1
  #define CONTROL_CYCLE_START_BIT   2  // Uno Analog Pin 2
  #define CONTROL_SAFETY_DOOR_BIT   1  // Uno Analog Pin 1 NOTE: Safety door is shared with feed hold. Enabled by config define.
  #define CONTROL_INT       PCIE1  // Pin change interrupt enable pin
  #define CONTROL_INT_vect  PCINT1_vect
  #define CONTROL_PCMSK     PCMSK1 // Pin change interrupt register
  #define CONTROL_MASK      ((1<<CONTROL_RESET_BIT)|(1<<CONTROL_FEED_HOLD_BIT)|(1<<CONTROL_CYCLE_START_BIT)|(1<<CONTROL_SAFETY_DOOR_BIT))
  #define CONTROL_INVERT_MASK   CONTROL_MASK // May be re-defined to only invert certain control pins.

  // Define probe switch input pin.
  #define PROBE_DDR       DDRC
  #define PROBE_PIN       PINC
  #define PROBE_PORT      PORTC
  #define PROBE_BIT       5  // Uno Analog Pin 5
  #define PROBE_MASK      (1<<PROBE_BIT)

  #if !defined(ENABLE_DUAL_AXIS)

    // Define flood and mist coolant enable output pins.
    #define COOLANT_FLOOD_DDR   DDRC
    #define COOLANT_FLOOD_PORT  PORTC
    #define COOLANT_FLOOD_BIT   3  // Uno Analog Pin 3
    #define COOLANT_MIST_DDR   DDRC
    #define COOLANT_MIST_PORT  PORTC
    #define COOLANT_MIST_BIT   4  // Uno Analog Pin 4

    // Define spindle enable and spindle direction output pins.
    #define SPINDLE_ENABLE_DDR    DDRB
    #define SPINDLE_ENABLE_PORT   PORTB
    // Z Limit pin and spindle PWM/enable pin swapped to access hardware PWM on Pin 11.
    #ifdef VARIABLE_SPINDLE
      #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
        // If enabled, spindle direction pin now used as spindle enable, while PWM remains on D11.
        #define SPINDLE_ENABLE_BIT    5  // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
      #else
        #define SPINDLE_ENABLE_BIT    3  // Uno Digital Pin 11
      #endif
    #else
      #define SPINDLE_ENABLE_BIT    4  // Uno Digital Pin 12
    #endif
    #ifndef USE_SPINDLE_DIR_AS_ENABLE_PIN
      #define SPINDLE_DIRECTION_DDR   DDRB
      #define SPINDLE_DIRECTION_PORT  PORTB
      #define SPINDLE_DIRECTION_BIT   5  // Uno Digital Pin 13 (NOTE: D13 can't be pulled-high input due to LED.)
    #endif

    // Variable spindle configuration below. Do not change unless you know what you are doing.
    // NOTE: Only used when variable spindle is enabled.
    #define SPINDLE_PWM_MAX_VALUE     255 // Don't change. 328p fast PWM mode fixes top value as 255.
    #ifndef SPINDLE_PWM_MIN_VALUE
      #define SPINDLE_PWM_MIN_VALUE   1   // Must be greater than zero.
    #endif
    #define SPINDLE_PWM_OFF_VALUE     0
    #define SPINDLE_PWM_RANGE         (SPINDLE_PWM_MAX_VALUE-SPINDLE_PWM_MIN_VALUE)
    #define SPINDLE_TCCRA_REGISTER    TCCR2A
    #define SPINDLE_TCCRB_REGISTER    TCCR2B
    #define SPINDLE_OCR_REGISTER      OCR2A
    #define SPINDLE_COMB_BIT          COM2A1

    // Prescaled, 8-bit Fast PWM mode.
    #define SPINDLE_TCCRA_INIT_MASK   ((1<<WGM20) | (1<<WGM21))  // Configures fast PWM mode.
    // #define SPINDLE_TCCRB_INIT_MASK   (1<<CS20)               // Disable prescaler -> 62.5kHz
    // #define SPINDLE_TCCRB_INIT_MASK   (1<<CS21)               // 1/8 prescaler -> 7.8kHz (Used in v0.9)
    // #define SPINDLE_TCCRB_INIT_MASK   ((1<<CS21) | (1<<CS20)) // 1/32 prescaler -> 1.96kHz
    #define SPINDLE_TCCRB_INIT_MASK      (1<<CS22)               // 1/64 prescaler -> 0.98kHz (J-tech laser)

    // NOTE: On the 328p, these must be the same as the SPINDLE_ENABLE settings.
    #define SPINDLE_PWM_DDR   DDRB
    #define SPINDLE_PWM_PORT  PORTB
    #define SPINDLE_PWM_BIT   3    // Uno Digital Pin 11
  
  #else

    // Dual axis feature requires an independent step pulse pin to operate. The independent direction pin is not 
    // absolutely necessary but facilitates easy direction inverting with a Grbl $$ setting. These pins replace 
    // the spindle direction and optional coolant mist pins.

    #ifdef DUAL_AXIS_CONFIG_PROTONEER_V3_51
      // NOTE: Step pulse and direction pins may be on any port and output pin.
      #define STEP_DDR_DUAL       DDRC
      #define STEP_PORT_DUAL      PORTC
      #define DUAL_STEP_BIT       4  // Uno Analog Pin 4
      #define STEP_MASK_DUAL      ((1<<DUAL_STEP_BIT))
      #define DIRECTION_DDR_DUAL  DDRC
      #define DIRECTION_PORT_DUAL PORTC
      #define DUAL_DIRECTION_BIT  3  // Uno Analog Pin 3
      #define DIRECTION_MASK_DUAL ((1<<DUAL_DIRECTION_BIT))

      // NOTE: Dual axis limit is shared with the z-axis limit pin by default. Pin used must be on the same port
      // as other limit pins.
      #define DUAL_LIMIT_BIT    Z_LIMIT_BIT
      #define LIMIT_MASK        ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)|(1<<Z_LIMIT_BIT)|(1<<DUAL_LIMIT_BIT))

      // Define coolant enable output pins.
      // NOTE: Coolant flood moved from A3 to A4. Coolant mist not supported with dual axis feature on Arduino Uno.
      #define COOLANT_FLOOD_DDR   DDRB
      #define COOLANT_FLOOD_PORT  PORTB
      #define COOLANT_FLOOD_BIT   5  // Uno Digital Pin 13

      // Define spindle enable output pin.
      // NOTE: Spindle enable moved from D12 to A3 (old coolant flood enable pin). Spindle direction pin is removed.
      #define SPINDLE_ENABLE_DDR    DDRB
      #define SPINDLE_ENABLE_PORT   PORTB
      #ifdef VARIABLE_SPINDLE
        // NOTE: USE_SPINDLE_DIR_AS_ENABLE_PIN not supported with dual axis feature.
        #define SPINDLE_ENABLE_BIT    3  // Uno Digital Pin 11
      #else
        #define SPINDLE_ENABLE_BIT    4  // Uno Digital Pin 12
      #endif

      // Variable spindle configuration below. Do not change unless you know what you are doing.
      // NOTE: Only used when variable spindle is enabled.
      #define SPINDLE_PWM_MAX_VALUE     255 // Don't change. 328p fast PWM mode fixes top value as 255.
      #ifndef SPINDLE_PWM_MIN_VALUE
        #define SPINDLE_PWM_MIN_VALUE   1   // Must be greater than zero.
      #endif
      #define SPINDLE_PWM_OFF_VALUE     0
      #define SPINDLE_PWM_RANGE         (SPINDLE_PWM_MAX_VALUE-SPINDLE_PWM_MIN_VALUE)
      #define SPINDLE_TCCRA_REGISTER    TCCR2A
      #define SPINDLE_TCCRB_REGISTER    TCCR2B
      #define SPINDLE_OCR_REGISTER      OCR2A
      #define SPINDLE_COMB_BIT          COM2A1

      // Prescaled, 8-bit Fast PWM mode.
      #define SPINDLE_TCCRA_INIT_MASK   ((1<<WGM20) | (1<<WGM21))  // Configures fast PWM mode.
      // #define SPINDLE_TCCRB_INIT_MASK   (1<<CS20)               // Disable prescaler -> 62.5kHz
      // #define SPINDLE_TCCRB_INIT_MASK   (1<<CS21)               // 1/8 prescaler -> 7.8kHz (Used in v0.9)
      // #define SPINDLE_TCCRB_INIT_MASK   ((1<<CS21) | (1<<CS20)) // 1/32 prescaler -> 1.96kHz
      #define SPINDLE_TCCRB_INIT_MASK      (1<<CS22)               // 1/64 prescaler -> 0.98kHz (J-tech laser)

      // NOTE: On the 328p, these must be the same as the SPINDLE_ENABLE settings.
      #define SPINDLE_PWM_DDR   DDRB
      #define SPINDLE_PWM_PORT  PORTB
      #define SPINDLE_PWM_BIT   3    // Uno Digital Pin 11
    #endif

    // NOTE: Variable spindle not supported with this shield.
    #ifdef DUAL_AXIS_CONFIG_CNC_SHIELD_CLONE
      // NOTE: Step pulse and direction pins may be on any port and output pin.
      #define STEP_DDR_DUAL       DDRB
      #define STEP_PORT_DUAL      PORTB
      #define DUAL_STEP_BIT       4  // Uno Digital Pin 12
      #define STEP_MASK_DUAL      ((1<<DUAL_STEP_BIT))
      #define DIRECTION_DDR_DUAL  DDRB
      #define DIRECTION_PORT_DUAL PORTB
      #define DUAL_DIRECTION_BIT  5  // Uno Digital Pin 13
      #define DIRECTION_MASK_DUAL ((1<<DUAL_DIRECTION_BIT))

      // NOTE: Dual axis limit is shared with the z-axis limit pin by default.
      #define DUAL_LIMIT_BIT    Z_LIMIT_BIT
      #define LIMIT_MASK        ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)|(1<<Z_LIMIT_BIT)|(1<<DUAL_LIMIT_BIT))

      // Define coolant enable output pins.
      // NOTE: Coolant flood moved from A3 to A4. Coolant mist not supported with dual axis feature on Arduino Uno.
      #define COOLANT_FLOOD_DDR   DDRC
      #define COOLANT_FLOOD_PORT  PORTC
      #define COOLANT_FLOOD_BIT   4  // Uno Analog Pin 4

      // Define spindle enable output pin.
      // NOTE: Spindle enable moved from D12 to A3 (old coolant flood enable pin). Spindle direction pin is removed.
      #define SPINDLE_ENABLE_DDR    DDRC
      #define SPINDLE_ENABLE_PORT   PORTC
      #define SPINDLE_ENABLE_BIT    3  // Uno Analog Pin 3
    #endif

  #endif

#endif

/*
#ifdef CPU_MAP_CUSTOM_PROC
  // For a custom pin map or different processor, copy and edit one of the available cpu
  // map files and modify it to your needs. Make sure the defined name is also changed in
  // the config.h file.
#endif
*/

#endif


cpu_map.h

defaults.h

// This file has been prepared for Doxygen automatic documentation generation.
/*! \file ********************************************************************
*
* Atmel Corporation
*
* \li File:               eeprom.c
* \li Compiler:           IAR EWAAVR 3.10c
* \li Support mail:       avr@atmel.com
*
* \li Supported devices:  All devices with split EEPROM erase/write
*                         capabilities can be used.
*                         The example is written for ATmega48.
*
* \li AppNote:            AVR103 - Using the EEPROM Programming Modes.
*
* \li Description:        Example on how to use the split EEPROM erase/write
*                         capabilities in e.g. ATmega48. All EEPROM
*                         programming modes are tested, i.e. Erase+Write,
*                         Erase-only and Write-only.
*
*                         $Revision: 1.6 $
*                         $Date: Friday, February 11, 2005 07:16:44 UTC $
****************************************************************************/
#include <avr/io.h>
#include <avr/interrupt.h>

/* These EEPROM bits have different names on different devices. */
#ifndef EEPE
		#define EEPE  EEWE  //!< EEPROM program/write enable.
		#define EEMPE EEMWE //!< EEPROM master program/write enable.
#endif

/* These two are unfortunately not defined in the device include files. */
#define EEPM1 5 //!< EEPROM Programming Mode Bit 1.
#define EEPM0 4 //!< EEPROM Programming Mode Bit 0.

/* Define to reduce code size. */
#define EEPROM_IGNORE_SELFPROG //!< Remove SPM flag polling.

/*! \brief  Read byte from EEPROM.
 *
 *  This function reads one byte from a given EEPROM address.
 *
 *  \note  The CPU is halted for 4 clock cycles during EEPROM read.
 *
 *  \param  addr  EEPROM address to read from.
 *  \return  The byte read from the EEPROM address.
 */
unsigned char eeprom_get_char( unsigned int addr )
{
	do {} while( EECR & (1<<EEPE) ); // Wait for completion of previous write.
	EEAR = addr; // Set EEPROM address register.
	EECR = (1<<EERE); // Start EEPROM read operation.
	return EEDR; // Return the byte read from EEPROM.
}

/*! \brief  Write byte to EEPROM.
 *
 *  This function writes one byte to a given EEPROM address.
 *  The differences between the existing byte and the new value is used
 *  to select the most efficient EEPROM programming mode.
 *
 *  \note  The CPU is halted for 2 clock cycles during EEPROM programming.
 *
 *  \note  When this function returns, the new EEPROM value is not available
 *         until the EEPROM programming time has passed. The EEPE bit in EECR
 *         should be polled to check whether the programming is finished.
 *
 *  \note  The EEPROM_GetChar() function checks the EEPE bit automatically.
 *
 *  \param  addr  EEPROM address to write to.
 *  \param  new_value  New EEPROM value.
 */
void eeprom_put_char( unsigned int addr, unsigned char new_value )
{
	char old_value; // Old EEPROM value.
	char diff_mask; // Difference mask, i.e. old value XOR new value.

	cli(); // Ensure atomic operation for the write operation.
	
	do {} while( EECR & (1<<EEPE) ); // Wait for completion of previous write.
	#ifndef EEPROM_IGNORE_SELFPROG
	do {} while( SPMCSR & (1<<SELFPRGEN) ); // Wait for completion of SPM.
	#endif
	
	EEAR = addr; // Set EEPROM address register.
	EECR = (1<<EERE); // Start EEPROM read operation.
	old_value = EEDR; // Get old EEPROM value.
	diff_mask = old_value ^ new_value; // Get bit differences.
	
	// Check if any bits are changed to '1' in the new value.
	if( diff_mask & new_value ) {
		// Now we know that _some_ bits need to be erased to '1'.
		
		// Check if any bits in the new value are '0'.
		if( new_value != 0xff ) {
			// Now we know that some bits need to be programmed to '0' also.
			
			EEDR = new_value; // Set EEPROM data register.
			EECR = (1<<EEMPE) | // Set Master Write Enable bit...
			       (0<<EEPM1) | (0<<EEPM0); // ...and Erase+Write mode.
			EECR |= (1<<EEPE);  // Start Erase+Write operation.
		} else {
			// Now we know that all bits should be erased.

			EECR = (1<<EEMPE) | // Set Master Write Enable bit...
			       (1<<EEPM0);  // ...and Erase-only mode.
			EECR |= (1<<EEPE);  // Start Erase-only operation.
		}
	} else {
		// Now we know that _no_ bits need to be erased to '1'.
		
		// Check if any bits are changed from '1' in the old value.
		if( diff_mask ) {
			// Now we know that _some_ bits need to the programmed to '0'.
			
			EEDR = new_value;   // Set EEPROM data register.
			EECR = (1<<EEMPE) | // Set Master Write Enable bit...
			       (1<<EEPM1);  // ...and Write-only mode.
			EECR |= (1<<EEPE);  // Start Write-only operation.
		}
	}
	
	sei(); // Restore interrupt flag state.
}

// Extensions added as part of Grbl 


void memcpy_to_eeprom_with_checksum(unsigned int destination, char *source, unsigned int size) {
  unsigned char checksum = 0;
  for(; size > 0; size--) { 
    checksum = (checksum << 1) || (checksum >> 7);
    checksum += *source;
    eeprom_put_char(destination++, *(source++)); 
  }
  eeprom_put_char(destination, checksum);
}

int memcpy_from_eeprom_with_checksum(char *destination, unsigned int source, unsigned int size) {
  unsigned char data, checksum = 0;
  for(; size > 0; size--) { 
    data = eeprom_get_char(source++);
    checksum = (checksum << 1) || (checksum >> 7);
    checksum += data;    
    *(destination++) = data; 
  }
  return(checksum == eeprom_get_char(source));
}

// end of file


eeprom.c

/*
  eeprom.h - EEPROM methods
  Part of Grbl

  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef eeprom_h
#define eeprom_h

unsigned char eeprom_get_char(unsigned int addr);
void eeprom_put_char(unsigned int addr, unsigned char new_value);
void memcpy_to_eeprom_with_checksum(unsigned int destination, char *source, unsigned int size);
int memcpy_from_eeprom_with_checksum(char *destination, unsigned int source, unsigned int size);

#endif


eeprom.h

gcode.c

/*
  gcode.h - rs274/ngc parser.
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef gcode_h
#define gcode_h


// Define modal group internal numbers for checking multiple command violations and tracking the
// type of command that is called in the block. A modal group is a group of g-code commands that are
// mutually exclusive, or cannot exist on the same line, because they each toggle a state or execute
// a unique motion. These are defined in the NIST RS274-NGC v3 g-code standard, available online,
// and are similar/identical to other g-code interpreters by manufacturers (Haas,Fanuc,Mazak,etc).
// NOTE: Modal group define values must be sequential and starting from zero.
#define MODAL_GROUP_G0 0 // [G4,G10,G28,G28.1,G30,G30.1,G53,G92,G92.1] Non-modal
#define MODAL_GROUP_G1 1 // [G0,G1,G2,G3,G38.2,G38.3,G38.4,G38.5,G80] Motion
#define MODAL_GROUP_G2 2 // [G17,G18,G19] Plane selection
#define MODAL_GROUP_G3 3 // [G90,G91] Distance mode
#define MODAL_GROUP_G4 4 // [G91.1] Arc IJK distance mode
#define MODAL_GROUP_G5 5 // [G93,G94] Feed rate mode
#define MODAL_GROUP_G6 6 // [G20,G21] Units
#define MODAL_GROUP_G7 7 // [G40] Cutter radius compensation mode. G41/42 NOT SUPPORTED.
#define MODAL_GROUP_G8 8 // [G43.1,G49] Tool length offset
#define MODAL_GROUP_G12 9 // [G54,G55,G56,G57,G58,G59] Coordinate system selection
#define MODAL_GROUP_G13 10 // [G61] Control mode

#define MODAL_GROUP_M4 11  // [M0,M1,M2,M30] Stopping
#define MODAL_GROUP_M7 12 // [M3,M4,M5] Spindle turning
#define MODAL_GROUP_M8 13 // [M7,M8,M9] Coolant control
#define MODAL_GROUP_M9 14 // [M56] Override control

// Define command actions for within execution-type modal groups (motion, stopping, non-modal). Used
// internally by the parser to know which command to execute.
// NOTE: Some macro values are assigned specific values to make g-code state reporting and parsing 
// compile a litte smaller. Necessary due to being completely out of flash on the 328p. Although not
// ideal, just be careful with values that state 'do not alter' and check both report.c and gcode.c 
// to see how they are used, if you need to alter them.

// Modal Group G0: Non-modal actions
#define NON_MODAL_NO_ACTION 0 // (Default: Must be zero)
#define NON_MODAL_DWELL 4 // G4 (Do not alter value)
#define NON_MODAL_SET_COORDINATE_DATA 10 // G10 (Do not alter value)
#define NON_MODAL_GO_HOME_0 28 // G28 (Do not alter value)
#define NON_MODAL_SET_HOME_0 38 // G28.1 (Do not alter value)
#define NON_MODAL_GO_HOME_1 30 // G30 (Do not alter value)
#define NON_MODAL_SET_HOME_1 40 // G30.1 (Do not alter value)
#define NON_MODAL_ABSOLUTE_OVERRIDE 53 // G53 (Do not alter value)
#define NON_MODAL_SET_COORDINATE_OFFSET 92 // G92 (Do not alter value)
#define NON_MODAL_RESET_COORDINATE_OFFSET 102 //G92.1 (Do not alter value)

// Modal Group G1: Motion modes
#define MOTION_MODE_SEEK 0 // G0 (Default: Must be zero)
#define MOTION_MODE_LINEAR 1 // G1 (Do not alter value)
#define MOTION_MODE_CW_ARC 2  // G2 (Do not alter value)
#define MOTION_MODE_CCW_ARC 3  // G3 (Do not alter value)
#define MOTION_MODE_PROBE_TOWARD 140 // G38.2 (Do not alter value)
#define MOTION_MODE_PROBE_TOWARD_NO_ERROR 141 // G38.3 (Do not alter value)
#define MOTION_MODE_PROBE_AWAY 142 // G38.4 (Do not alter value)
#define MOTION_MODE_PROBE_AWAY_NO_ERROR 143 // G38.5 (Do not alter value)
#define MOTION_MODE_NONE 80 // G80 (Do not alter value)

// Modal Group G2: Plane select
#define PLANE_SELECT_XY 0 // G17 (Default: Must be zero)
#define PLANE_SELECT_ZX 1 // G18 (Do not alter value)
#define PLANE_SELECT_YZ 2 // G19 (Do not alter value)

// Modal Group G3: Distance mode
#define DISTANCE_MODE_ABSOLUTE 0 // G90 (Default: Must be zero)
#define DISTANCE_MODE_INCREMENTAL 1 // G91 (Do not alter value)

// Modal Group G4: Arc IJK distance mode
#define DISTANCE_ARC_MODE_INCREMENTAL 0 // G91.1 (Default: Must be zero)

// Modal Group M4: Program flow
#define PROGRAM_FLOW_RUNNING 0 // (Default: Must be zero)
#define PROGRAM_FLOW_PAUSED 3 // M0
#define PROGRAM_FLOW_OPTIONAL_STOP 1 // M1 NOTE: Not supported, but valid and ignored.
#define PROGRAM_FLOW_COMPLETED_M2  2 // M2 (Do not alter value)
#define PROGRAM_FLOW_COMPLETED_M30 30 // M30 (Do not alter value)

// Modal Group G5: Feed rate mode
#define FEED_RATE_MODE_UNITS_PER_MIN  0 // G94 (Default: Must be zero)
#define FEED_RATE_MODE_INVERSE_TIME   1 // G93 (Do not alter value)

// Modal Group G6: Units mode
#define UNITS_MODE_MM 0 // G21 (Default: Must be zero)
#define UNITS_MODE_INCHES 1 // G20 (Do not alter value)

// Modal Group G7: Cutter radius compensation mode
#define CUTTER_COMP_DISABLE 0 // G40 (Default: Must be zero)

// Modal Group G13: Control mode
#define CONTROL_MODE_EXACT_PATH 0 // G61 (Default: Must be zero)

// Modal Group M7: Spindle control
#define SPINDLE_DISABLE 0 // M5 (Default: Must be zero)
#define SPINDLE_ENABLE_CW   PL_COND_FLAG_SPINDLE_CW // M3 (NOTE: Uses planner condition bit flag)
#define SPINDLE_ENABLE_CCW  PL_COND_FLAG_SPINDLE_CCW // M4 (NOTE: Uses planner condition bit flag)

// Modal Group M8: Coolant control
#define COOLANT_DISABLE 0 // M9 (Default: Must be zero)
#define COOLANT_FLOOD_ENABLE  PL_COND_FLAG_COOLANT_FLOOD // M8 (NOTE: Uses planner condition bit flag)
#define COOLANT_MIST_ENABLE   PL_COND_FLAG_COOLANT_MIST  // M7 (NOTE: Uses planner condition bit flag)

// Modal Group G8: Tool length offset
#define TOOL_LENGTH_OFFSET_CANCEL 0 // G49 (Default: Must be zero)
#define TOOL_LENGTH_OFFSET_ENABLE_DYNAMIC 1 // G43.1

// Modal Group M9: Override control
#ifdef DEACTIVATE_PARKING_UPON_INIT
  #define OVERRIDE_DISABLED  0 // (Default: Must be zero)
  #define OVERRIDE_PARKING_MOTION 1 // M56
#else
  #define OVERRIDE_PARKING_MOTION 0 // M56 (Default: Must be zero)
  #define OVERRIDE_DISABLED  1 // Parking disabled.
#endif

// Modal Group G12: Active work coordinate system
// N/A: Stores coordinate system value (54-59) to change to.

// Define parameter word mapping.
#define WORD_F  0
#define WORD_I  1
#define WORD_J  2
#define WORD_K  3
#define WORD_L  4
#define WORD_N  5
#define WORD_P  6
#define WORD_R  7
#define WORD_S  8
#define WORD_T  9
#define WORD_X  10
#define WORD_Y  11
#define WORD_Z  12

// Define g-code parser position updating flags
#define GC_UPDATE_POS_TARGET   0 // Must be zero
#define GC_UPDATE_POS_SYSTEM   1
#define GC_UPDATE_POS_NONE     2

// Define probe cycle exit states and assign proper position updating.
#define GC_PROBE_FOUND      GC_UPDATE_POS_SYSTEM
#define GC_PROBE_ABORT      GC_UPDATE_POS_NONE
#define GC_PROBE_FAIL_INIT  GC_UPDATE_POS_NONE
#define GC_PROBE_FAIL_END   GC_UPDATE_POS_TARGET
#ifdef SET_CHECK_MODE_PROBE_TO_START
  #define GC_PROBE_CHECK_MODE   GC_UPDATE_POS_NONE  
#else
  #define GC_PROBE_CHECK_MODE   GC_UPDATE_POS_TARGET
#endif

// Define gcode parser flags for handling special cases.
#define GC_PARSER_NONE                  0 // Must be zero.
#define GC_PARSER_JOG_MOTION            bit(0)
#define GC_PARSER_CHECK_MANTISSA        bit(1)
#define GC_PARSER_ARC_IS_CLOCKWISE      bit(2)
#define GC_PARSER_PROBE_IS_AWAY         bit(3)
#define GC_PARSER_PROBE_IS_NO_ERROR     bit(4)
#define GC_PARSER_LASER_FORCE_SYNC      bit(5)
#define GC_PARSER_LASER_DISABLE         bit(6)
#define GC_PARSER_LASER_ISMOTION        bit(7)


// NOTE: When this struct is zeroed, the above defines set the defaults for the system.
typedef struct {
  uint8_t motion;          // {G0,G1,G2,G3,G38.2,G80}
  uint8_t feed_rate;       // {G93,G94}
  uint8_t units;           // {G20,G21}
  uint8_t distance;        // {G90,G91}
  // uint8_t distance_arc; // {G91.1} NOTE: Don't track. Only default supported.
  uint8_t plane_select;    // {G17,G18,G19}
  // uint8_t cutter_comp;  // {G40} NOTE: Don't track. Only default supported.
  uint8_t tool_length;     // {G43.1,G49}
  uint8_t coord_select;    // {G54,G55,G56,G57,G58,G59}
  // uint8_t control;      // {G61} NOTE: Don't track. Only default supported.
  uint8_t program_flow;    // {M0,M1,M2,M30}
  uint8_t coolant;         // {M7,M8,M9}
  uint8_t spindle;         // {M3,M4,M5}
  uint8_t override;        // {M56}
} gc_modal_t;

typedef struct {
  float f;         // Feed
  float ijk[3];    // I,J,K Axis arc offsets
  uint8_t l;       // G10 or canned cycles parameters
  int32_t n;       // Line number
  float p;         // G10 or dwell parameters
  // float q;      // G82 peck drilling
  float r;         // Arc radius
  float s;         // Spindle speed
  uint8_t t;       // Tool selection
  float xyz[3];    // X,Y,Z Translational axes
} gc_values_t;


typedef struct {
  gc_modal_t modal;

  float spindle_speed;          // RPM
  float feed_rate;              // Millimeters/min
  uint8_t tool;                 // Tracks tool number. NOT USED.
  int32_t line_number;          // Last line number sent

  float position[N_AXIS];       // Where the interpreter considers the tool to be at this point in the code

  float coord_system[N_AXIS];    // Current work coordinate system (G54+). Stores offset from absolute machine
                                 // position in mm. Loaded from EEPROM when called.
  float coord_offset[N_AXIS];    // Retains the G92 coordinate offset (work coordinates) relative to
                                 // machine zero in mm. Non-persistent. Cleared upon reset and boot.
  float tool_length_offset;      // Tracks tool length offset value when enabled.
} parser_state_t;
extern parser_state_t gc_state;


typedef struct {
  uint8_t non_modal_command;
  gc_modal_t modal;
  gc_values_t values;
} parser_block_t;


// Initialize the parser
void gc_init();

// Execute one block of rs275/ngc/g-code
uint8_t gc_execute_line(char *line);

// Set g-code parser position. Input in steps.
void gc_sync_position();

#endif


gcode.h

/*
  grbl.h - main Grbl include file
  Part of Grbl

  Copyright (c) 2015-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef grbl_h
#define grbl_h

// Grbl versioning system
#define GRBL_VERSION "1.1h"
#define GRBL_VERSION_BUILD "20190830"

// Define standard libraries used by Grbl.
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <util/delay.h>
#include <math.h>
#include <inttypes.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>

// Define the Grbl system include files. NOTE: Do not alter organization.
#include "config.h"
#include "nuts_bolts.h"
#include "settings.h"
#include "system.h"
#include "defaults.h"
#include "cpu_map.h"
#include "planner.h"
#include "coolant_control.h"
#include "eeprom.h"
#include "gcode.h"
#include "limits.h"
#include "motion_control.h"
#include "planner.h"
#include "print.h"
#include "probe.h"
#include "protocol.h"
#include "report.h"
#include "serial.h"
#include "spindle_control.h"
#include "stepper.h"
#include "jog.h"

// ---------------------------------------------------------------------------------------
// COMPILE-TIME ERROR CHECKING OF DEFINE VALUES:

#ifndef HOMING_CYCLE_0
  #error "Required HOMING_CYCLE_0 not defined."
#endif

#if defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && !defined(VARIABLE_SPINDLE)
  #error "USE_SPINDLE_DIR_AS_ENABLE_PIN may only be used with VARIABLE_SPINDLE enabled"
#endif

#if defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && !defined(CPU_MAP_ATMEGA328P)
  #error "USE_SPINDLE_DIR_AS_ENABLE_PIN may only be used with a 328p processor"
#endif

#if !defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && defined(SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED)
  #error "SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED may only be used with USE_SPINDLE_DIR_AS_ENABLE_PIN enabled"
#endif

#if defined(PARKING_ENABLE)
  #if defined(HOMING_FORCE_SET_ORIGIN)
    #error "HOMING_FORCE_SET_ORIGIN is not supported with PARKING_ENABLE at this time."
  #endif
#endif

#if defined(ENABLE_PARKING_OVERRIDE_CONTROL)
  #if !defined(PARKING_ENABLE)
    #error "ENABLE_PARKING_OVERRIDE_CONTROL must be enabled with PARKING_ENABLE."
  #endif
#endif

#if defined(SPINDLE_PWM_MIN_VALUE)
  #if !(SPINDLE_PWM_MIN_VALUE > 0)
    #error "SPINDLE_PWM_MIN_VALUE must be greater than zero."
  #endif
#endif

#if (REPORT_WCO_REFRESH_BUSY_COUNT < REPORT_WCO_REFRESH_IDLE_COUNT)
  #error "WCO busy refresh is less than idle refresh."
#endif
#if (REPORT_OVR_REFRESH_BUSY_COUNT < REPORT_OVR_REFRESH_IDLE_COUNT)
  #error "Override busy refresh is less than idle refresh."
#endif
#if (REPORT_WCO_REFRESH_IDLE_COUNT < 2)
  #error "WCO refresh must be greater than one."
#endif
#if (REPORT_OVR_REFRESH_IDLE_COUNT < 1)
  #error "Override refresh must be greater than zero."
#endif

#if defined(ENABLE_DUAL_AXIS)
  #if !((DUAL_AXIS_SELECT == X_AXIS) || (DUAL_AXIS_SELECT == Y_AXIS))
    #error "Dual axis currently supports X or Y axes only."
  #endif
  #if defined(DUAL_AXIS_CONFIG_CNC_SHIELD_CLONE) && defined(VARIABLE_SPINDLE)
    #error "VARIABLE_SPINDLE not supported with DUAL_AXIS_CNC_SHIELD_CLONE."
  #endif
  #if defined(DUAL_AXIS_CONFIG_CNC_SHIELD_CLONE) && defined(DUAL_AXIS_CONFIG_PROTONEER_V3_51)
    #error "More than one dual axis configuration found. Select one."
  #endif
  #if !defined(DUAL_AXIS_CONFIG_CNC_SHIELD_CLONE) && !defined(DUAL_AXIS_CONFIG_PROTONEER_V3_51)
    #error "No supported dual axis configuration found. Select one."
  #endif
  #if defined(COREXY)
    #error "CORE XY not supported with dual axis feature."
  #endif
  #if defined(USE_SPINDLE_DIR_AS_ENABLE_PIN)
    #error "USE_SPINDLE_DIR_AS_ENABLE_PIN not supported with dual axis feature."
  #endif
  #if defined(ENABLE_M7)
    #error "ENABLE_M7 not supported with dual axis feature."
  #endif
#endif

// ---------------------------------------------------------------------------------------

#endif


grbl.h

/*
  jog.h - Jogging methods
  Part of Grbl

  Copyright (c) 2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


// Sets up valid jog motion received from g-code parser, checks for soft-limits, and executes the jog.
uint8_t jog_execute(plan_line_data_t *pl_data, parser_block_t *gc_block)
{
  // Initialize planner data struct for jogging motions.
  // NOTE: Spindle and coolant are allowed to fully function with overrides during a jog.
  pl_data->feed_rate = gc_block->values.f;
  pl_data->condition |= PL_COND_FLAG_NO_FEED_OVERRIDE;
  #ifdef USE_LINE_NUMBERS
    pl_data->line_number = gc_block->values.n;
  #endif

  if (bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE)) {
    if (system_check_travel_limits(gc_block->values.xyz)) { return(STATUS_TRAVEL_EXCEEDED); }
  }

  // Valid jog command. Plan, set state, and execute.
  mc_line(gc_block->values.xyz,pl_data);
  if (sys.state == STATE_IDLE) {
    if (plan_get_current_block() != NULL) { // Check if there is a block to execute.
      sys.state = STATE_JOG;
      st_prep_buffer();
      st_wake_up();  // NOTE: Manual start. No state machine required.
    }
  }

  return(STATUS_OK);
}


jog.c

/*
  jog.h - Jogging methods
  Part of Grbl

  Copyright (c) 2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef jog_h
#define jog_h

#include "gcode.h"

// System motion line numbers must be zero.
#define JOG_LINE_NUMBER 0

// Sets up valid jog motion received from g-code parser, checks for soft-limits, and executes the jog.
uint8_t jog_execute(plan_line_data_t *pl_data, parser_block_t *gc_block);

#endif


jog.h

/*
  limits.c - code pertaining to limit-switches and performing the homing cycle
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


// Homing axis search distance multiplier. Computed by this value times the cycle travel.
#ifndef HOMING_AXIS_SEARCH_SCALAR
  #define HOMING_AXIS_SEARCH_SCALAR  1.5 // Must be > 1 to ensure limit switch will be engaged.
#endif
#ifndef HOMING_AXIS_LOCATE_SCALAR
  #define HOMING_AXIS_LOCATE_SCALAR  5.0 // Must be > 1 to ensure limit switch is cleared.
#endif

#ifdef ENABLE_DUAL_AXIS
  // Flags for dual axis async limit trigger check.
  #define DUAL_AXIS_CHECK_DISABLE     0  // Must be zero
  #define DUAL_AXIS_CHECK_ENABLE      bit(0)
  #define DUAL_AXIS_CHECK_TRIGGER_1   bit(1)
  #define DUAL_AXIS_CHECK_TRIGGER_2   bit(2)
#endif

void limits_init()
{
  LIMIT_DDR &= ~(LIMIT_MASK); // Set as input pins

  #ifdef DISABLE_LIMIT_PIN_PULL_UP
    LIMIT_PORT &= ~(LIMIT_MASK); // Normal low operation. Requires external pull-down.
  #else
    LIMIT_PORT |= (LIMIT_MASK);  // Enable internal pull-up resistors. Normal high operation.
  #endif

  if (bit_istrue(settings.flags,BITFLAG_HARD_LIMIT_ENABLE)) {
    LIMIT_PCMSK |= LIMIT_MASK; // Enable specific pins of the Pin Change Interrupt
    PCICR |= (1 << LIMIT_INT); // Enable Pin Change Interrupt
  } else {
    limits_disable();
  }

  #ifdef ENABLE_SOFTWARE_DEBOUNCE
    MCUSR &= ~(1<<WDRF);
    WDTCSR |= (1<<WDCE) | (1<<WDE);
    WDTCSR = (1<<WDP0); // Set time-out at ~32msec.
  #endif
}


// Disables hard limits.
void limits_disable()
{
  LIMIT_PCMSK &= ~LIMIT_MASK;  // Disable specific pins of the Pin Change Interrupt
  PCICR &= ~(1 << LIMIT_INT);  // Disable Pin Change Interrupt
}


// Returns limit state as a bit-wise uint8 variable. Each bit indicates an axis limit, where
// triggered is 1 and not triggered is 0. Invert mask is applied. Axes are defined by their
// number in bit position, i.e. Z_AXIS is (1<<2) or bit 2, and Y_AXIS is (1<<1) or bit 1.
uint8_t limits_get_state()
{
  uint8_t limit_state = 0;
  uint8_t pin = (LIMIT_PIN & LIMIT_MASK);
  #ifdef INVERT_LIMIT_PIN_MASK
    pin ^= INVERT_LIMIT_PIN_MASK;
  #endif
  if (bit_isfalse(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) { pin ^= LIMIT_MASK; }
  if (pin) {
    uint8_t idx;
    for (idx=0; idx<N_AXIS; idx++) {
      if (pin & get_limit_pin_mask(idx)) { limit_state |= (1 << idx); }
    }
    #ifdef ENABLE_DUAL_AXIS
      if (pin & (1<<DUAL_LIMIT_BIT)) { limit_state |= (1 << N_AXIS); }
    #endif
  }
  return(limit_state);
}


// This is the Limit Pin Change Interrupt, which handles the hard limit feature. A bouncing
// limit switch can cause a lot of problems, like false readings and multiple interrupt calls.
// If a switch is triggered at all, something bad has happened and treat it as such, regardless
// if a limit switch is being disengaged. It's impossible to reliably tell the state of a
// bouncing pin because the Arduino microcontroller does not retain any state information when
// detecting a pin change. If we poll the pins in the ISR, you can miss the correct reading if the 
// switch is bouncing.
// NOTE: Do not attach an e-stop to the limit pins, because this interrupt is disabled during
// homing cycles and will not respond correctly. Upon user request or need, there may be a
// special pinout for an e-stop, but it is generally recommended to just directly connect
// your e-stop switch to the Arduino reset pin, since it is the most correct way to do this.
#ifndef ENABLE_SOFTWARE_DEBOUNCE
  ISR(LIMIT_INT_vect) // DEFAULT: Limit pin change interrupt process.
  {
    // Ignore limit switches if already in an alarm state or in-process of executing an alarm.
    // When in the alarm state, Grbl should have been reset or will force a reset, so any pending
    // moves in the planner and serial buffers are all cleared and newly sent blocks will be
    // locked out until a homing cycle or a kill lock command. Allows the user to disable the hard
    // limit setting if their limits are constantly triggering after a reset and move their axes.
    if (sys.state != STATE_ALARM) {
      if (!(sys_rt_exec_alarm)) {
        #ifdef HARD_LIMIT_FORCE_STATE_CHECK
          // Check limit pin state.
          if (limits_get_state()) {
            mc_reset(); // Initiate system kill.
            system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT); // Indicate hard limit critical event
          }
        #else
          mc_reset(); // Initiate system kill.
          system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT); // Indicate hard limit critical event
        #endif
      }
    }
  }
#else // OPTIONAL: Software debounce limit pin routine.
  // Upon limit pin change, enable watchdog timer to create a short delay. 
  ISR(LIMIT_INT_vect) { if (!(WDTCSR & (1<<WDIE))) { WDTCSR |= (1<<WDIE); } }
  ISR(WDT_vect) // Watchdog timer ISR
  {
    WDTCSR &= ~(1<<WDIE); // Disable watchdog timer. 
    if (sys.state != STATE_ALARM) {  // Ignore if already in alarm state. 
      if (!(sys_rt_exec_alarm)) {
        // Check limit pin state. 
        if (limits_get_state()) {
          mc_reset(); // Initiate system kill.
          system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT); // Indicate hard limit critical event
        }
      }  
    }
  }
#endif

// Homes the specified cycle axes, sets the machine position, and performs a pull-off motion after
// completing. Homing is a special motion case, which involves rapid uncontrolled stops to locate
// the trigger point of the limit switches. The rapid stops are handled by a system level axis lock
// mask, which prevents the stepper algorithm from executing step pulses. Homing motions typically
// circumvent the processes for executing motions in normal operation.
// NOTE: Only the abort realtime command can interrupt this process.
// TODO: Move limit pin-specific calls to a general function for portability.
void limits_go_home(uint8_t cycle_mask)
{
  if (sys.abort) { return; } // Block if system reset has been issued.

  // Initialize plan data struct for homing motion. Spindle and coolant are disabled.
  plan_line_data_t plan_data;
  plan_line_data_t *pl_data = &plan_data;
  memset(pl_data,0,sizeof(plan_line_data_t));
  pl_data->condition = (PL_COND_FLAG_SYSTEM_MOTION|PL_COND_FLAG_NO_FEED_OVERRIDE);
  #ifdef USE_LINE_NUMBERS
    pl_data->line_number = HOMING_CYCLE_LINE_NUMBER;
  #endif

  // Initialize variables used for homing computations.
  uint8_t n_cycle = (2*N_HOMING_LOCATE_CYCLE+1);
  uint8_t step_pin[N_AXIS];
  #ifdef ENABLE_DUAL_AXIS
    uint8_t step_pin_dual;
    uint8_t dual_axis_async_check;
    int32_t dual_trigger_position;
    #if (DUAL_AXIS_SELECT == X_AXIS)
      float fail_distance = (-DUAL_AXIS_HOMING_FAIL_AXIS_LENGTH_PERCENT/100.0)*settings.max_travel[Y_AXIS];
    #else
      float fail_distance = (-DUAL_AXIS_HOMING_FAIL_AXIS_LENGTH_PERCENT/100.0)*settings.max_travel[X_AXIS];
    #endif
    fail_distance = min(fail_distance, DUAL_AXIS_HOMING_FAIL_DISTANCE_MAX);
    fail_distance = max(fail_distance, DUAL_AXIS_HOMING_FAIL_DISTANCE_MIN);
    int32_t dual_fail_distance = trunc(fail_distance*settings.steps_per_mm[DUAL_AXIS_SELECT]);
    // int32_t dual_fail_distance = trunc((DUAL_AXIS_HOMING_TRIGGER_FAIL_DISTANCE)*settings.steps_per_mm[DUAL_AXIS_SELECT]);
  #endif
  float target[N_AXIS];
  float max_travel = 0.0;
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    // Initialize step pin masks
    step_pin[idx] = get_step_pin_mask(idx);
    #ifdef COREXY
      if ((idx==A_MOTOR)||(idx==B_MOTOR)) { step_pin[idx] = (get_step_pin_mask(X_AXIS)|get_step_pin_mask(Y_AXIS)); }
    #endif

    if (bit_istrue(cycle_mask,bit(idx))) {
      // Set target based on max_travel setting. Ensure homing switches engaged with search scalar.
      // NOTE: settings.max_travel[] is stored as a negative value.
      max_travel = max(max_travel,(-HOMING_AXIS_SEARCH_SCALAR)*settings.max_travel[idx]);
    }
  }
  #ifdef ENABLE_DUAL_AXIS
    step_pin_dual = (1<<DUAL_STEP_BIT);
  #endif

  // Set search mode with approach at seek rate to quickly engage the specified cycle_mask limit switches.
  bool approach = true;
  float homing_rate = settings.homing_seek_rate;

  uint8_t limit_state, axislock, n_active_axis;
  do {

    system_convert_array_steps_to_mpos(target,sys_position);

    // Initialize and declare variables needed for homing routine.
    axislock = 0;
    #ifdef ENABLE_DUAL_AXIS
      sys.homing_axis_lock_dual = 0;
      dual_trigger_position = 0;
      dual_axis_async_check = DUAL_AXIS_CHECK_DISABLE;
    #endif
    n_active_axis = 0;
    for (idx=0; idx<N_AXIS; idx++) {
      // Set target location for active axes and setup computation for homing rate.
      if (bit_istrue(cycle_mask,bit(idx))) {
        n_active_axis++;
        #ifdef COREXY
          if (idx == X_AXIS) {
            int32_t axis_position = system_convert_corexy_to_y_axis_steps(sys_position);
            sys_position[A_MOTOR] = axis_position;
            sys_position[B_MOTOR] = -axis_position;
          } else if (idx == Y_AXIS) {
            int32_t axis_position = system_convert_corexy_to_x_axis_steps(sys_position);
            sys_position[A_MOTOR] = sys_position[B_MOTOR] = axis_position;
          } else {
            sys_position[Z_AXIS] = 0;
          }
        #else
          sys_position[idx] = 0;
        #endif
        // Set target direction based on cycle mask and homing cycle approach state.
        // NOTE: This happens to compile smaller than any other implementation tried.
        if (bit_istrue(settings.homing_dir_mask,bit(idx))) {
          if (approach) { target[idx] = -max_travel; }
          else { target[idx] = max_travel; }
        } else {
          if (approach) { target[idx] = max_travel; }
          else { target[idx] = -max_travel; }
        }
        // Apply axislock to the step port pins active in this cycle.
        axislock |= step_pin[idx];
        #ifdef ENABLE_DUAL_AXIS
          if (idx == DUAL_AXIS_SELECT) { sys.homing_axis_lock_dual = step_pin_dual; }
        #endif
      }

    }
    homing_rate *= sqrt(n_active_axis); // [sqrt(N_AXIS)] Adjust so individual axes all move at homing rate.
    sys.homing_axis_lock = axislock;

    // Perform homing cycle. Planner buffer should be empty, as required to initiate the homing cycle.
    pl_data->feed_rate = homing_rate; // Set current homing rate.
    plan_buffer_line(target, pl_data); // Bypass mc_line(). Directly plan homing motion.

    sys.step_control = STEP_CONTROL_EXECUTE_SYS_MOTION; // Set to execute homing motion and clear existing flags.
    st_prep_buffer(); // Prep and fill segment buffer from newly planned block.
    st_wake_up(); // Initiate motion
    do {
      if (approach) {
        // Check limit state. Lock out cycle axes when they change.
        limit_state = limits_get_state();
        for (idx=0; idx<N_AXIS; idx++) {
          if (axislock & step_pin[idx]) {
            if (limit_state & (1 << idx)) {
              #ifdef COREXY
                if (idx==Z_AXIS) { axislock &= ~(step_pin[Z_AXIS]); }
                else { axislock &= ~(step_pin[A_MOTOR]|step_pin[B_MOTOR]); }
              #else
                axislock &= ~(step_pin[idx]);
                #ifdef ENABLE_DUAL_AXIS
                  if (idx == DUAL_AXIS_SELECT) { dual_axis_async_check |= DUAL_AXIS_CHECK_TRIGGER_1; }
                #endif
              #endif
            }
          }
        }
        sys.homing_axis_lock = axislock;
        #ifdef ENABLE_DUAL_AXIS
          if (sys.homing_axis_lock_dual) { // NOTE: Only true when homing dual axis.
            if (limit_state & (1 << N_AXIS)) { 
              sys.homing_axis_lock_dual = 0;
              dual_axis_async_check |= DUAL_AXIS_CHECK_TRIGGER_2;
            }
          }
          
          // When first dual axis limit triggers, record position and begin checking distance until other limit triggers. Bail upon failure.
          if (dual_axis_async_check) {
            if (dual_axis_async_check & DUAL_AXIS_CHECK_ENABLE) {
              if (( dual_axis_async_check &  (DUAL_AXIS_CHECK_TRIGGER_1 | DUAL_AXIS_CHECK_TRIGGER_2)) == (DUAL_AXIS_CHECK_TRIGGER_1 | DUAL_AXIS_CHECK_TRIGGER_2)) {
                dual_axis_async_check = DUAL_AXIS_CHECK_DISABLE;
              } else {
                if (abs(dual_trigger_position - sys_position[DUAL_AXIS_SELECT]) > dual_fail_distance) {
                  system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_DUAL_APPROACH);
                  mc_reset();
                  protocol_execute_realtime();
                  return;
                }
              }
            } else {
              dual_axis_async_check |= DUAL_AXIS_CHECK_ENABLE;
              dual_trigger_position = sys_position[DUAL_AXIS_SELECT];
            }
          }
        #endif
      }

      st_prep_buffer(); // Check and prep segment buffer. NOTE: Should take no longer than 200us.

      // Exit routines: No time to run protocol_execute_realtime() in this loop.
      if (sys_rt_exec_state & (EXEC_SAFETY_DOOR | EXEC_RESET | EXEC_CYCLE_STOP)) {
        uint8_t rt_exec = sys_rt_exec_state;
        // Homing failure condition: Reset issued during cycle.
        if (rt_exec & EXEC_RESET) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_RESET); }
        // Homing failure condition: Safety door was opened.
        if (rt_exec & EXEC_SAFETY_DOOR) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_DOOR); }
        // Homing failure condition: Limit switch still engaged after pull-off motion
        if (!approach && (limits_get_state() & cycle_mask)) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_PULLOFF); }
        // Homing failure condition: Limit switch not found during approach.
        if (approach && (rt_exec & EXEC_CYCLE_STOP)) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_APPROACH); }
        if (sys_rt_exec_alarm) {
          mc_reset(); // Stop motors, if they are running.
          protocol_execute_realtime();
          return;
        } else {
          // Pull-off motion complete. Disable CYCLE_STOP from executing.
          system_clear_exec_state_flag(EXEC_CYCLE_STOP);
          break;
        }
      }

    #ifdef ENABLE_DUAL_AXIS
      } while ((STEP_MASK & axislock) || (sys.homing_axis_lock_dual));
    #else
      } while (STEP_MASK & axislock);
    #endif

    st_reset(); // Immediately force kill steppers and reset step segment buffer.
    delay_ms(settings.homing_debounce_delay); // Delay to allow transient dynamics to dissipate.

    // Reverse direction and reset homing rate for locate cycle(s).
    approach = !approach;

    // After first cycle, homing enters locating phase. Shorten search to pull-off distance.
    if (approach) {
      max_travel = settings.homing_pulloff*HOMING_AXIS_LOCATE_SCALAR;
      homing_rate = settings.homing_feed_rate;
    } else {
      max_travel = settings.homing_pulloff;
      homing_rate = settings.homing_seek_rate;
    }

  } while (n_cycle-- > 0);

  // The active cycle axes should now be homed and machine limits have been located. By
  // default, Grbl defines machine space as all negative, as do most CNCs. Since limit switches
  // can be on either side of an axes, check and set axes machine zero appropriately. Also,
  // set up pull-off maneuver from axes limit switches that have been homed. This provides
  // some initial clearance off the switches and should also help prevent them from falsely
  // triggering when hard limits are enabled or when more than one axes shares a limit pin.
  int32_t set_axis_position;
  // Set machine positions for homed limit switches. Don't update non-homed axes.
  for (idx=0; idx<N_AXIS; idx++) {
    // NOTE: settings.max_travel[] is stored as a negative value.
    if (cycle_mask & bit(idx)) {
      #ifdef HOMING_FORCE_SET_ORIGIN
        set_axis_position = 0;
      #else
        if ( bit_istrue(settings.homing_dir_mask,bit(idx)) ) {
          set_axis_position = lround((settings.max_travel[idx]+settings.homing_pulloff)*settings.steps_per_mm[idx]);
        } else {
          set_axis_position = lround(-settings.homing_pulloff*settings.steps_per_mm[idx]);
        }
      #endif

      #ifdef COREXY
        if (idx==X_AXIS) {
          int32_t off_axis_position = system_convert_corexy_to_y_axis_steps(sys_position);
          sys_position[A_MOTOR] = set_axis_position + off_axis_position;
          sys_position[B_MOTOR] = set_axis_position - off_axis_position;
        } else if (idx==Y_AXIS) {
          int32_t off_axis_position = system_convert_corexy_to_x_axis_steps(sys_position);
          sys_position[A_MOTOR] = off_axis_position + set_axis_position;
          sys_position[B_MOTOR] = off_axis_position - set_axis_position;
        } else {
          sys_position[idx] = set_axis_position;
        }
      #else
        sys_position[idx] = set_axis_position;
      #endif

    }
  }
  sys.step_control = STEP_CONTROL_NORMAL_OP; // Return step control to normal operation.
}


// Performs a soft limit check. Called from mc_line() only. Assumes the machine has been homed,
// the workspace volume is in all negative space, and the system is in normal operation.
// NOTE: Used by jogging to limit travel within soft-limit volume.
void limits_soft_check(float *target)
{
  if (system_check_travel_limits(target)) {
    sys.soft_limit = true;
    // Force feed hold if cycle is active. All buffered blocks are guaranteed to be within
    // workspace volume so just come to a controlled stop so position is not lost. When complete
    // enter alarm mode.
    if (sys.state == STATE_CYCLE) {
      system_set_exec_state_flag(EXEC_FEED_HOLD);
      do {
        protocol_execute_realtime();
        if (sys.abort) { return; }
      } while ( sys.state != STATE_IDLE );
    }
    mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
    system_set_exec_alarm(EXEC_ALARM_SOFT_LIMIT); // Indicate soft limit critical event
    protocol_execute_realtime(); // Execute to enter critical event loop and system abort
    return;
  }
}


limits.c

/*
  limits.h - code pertaining to limit-switches and performing the homing cycle
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef limits_h
#define limits_h


// Initialize the limits module
void limits_init();

// Disables hard limits.
void limits_disable();

// Returns limit state as a bit-wise uint8 variable.
uint8_t limits_get_state();

// Perform one portion of the homing cycle based on the input settings.
void limits_go_home(uint8_t cycle_mask);

// Check for soft limit violations
void limits_soft_check(float *target);

#endif


limits.h

/*
  main.c - An embedded CNC Controller with rs274/ngc (g-code) support
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


// Declare system global variable structure
system_t sys;
int32_t sys_position[N_AXIS];      // Real-time machine (aka home) position vector in steps.
int32_t sys_probe_position[N_AXIS]; // Last probe position in machine coordinates and steps.
volatile uint8_t sys_probe_state;   // Probing state value.  Used to coordinate the probing cycle with stepper ISR.
volatile uint8_t sys_rt_exec_state;   // Global realtime executor bitflag variable for state management. See EXEC bitmasks.
volatile uint8_t sys_rt_exec_alarm;   // Global realtime executor bitflag variable for setting various alarms.
volatile uint8_t sys_rt_exec_motion_override; // Global realtime executor bitflag variable for motion-based overrides.
volatile uint8_t sys_rt_exec_accessory_override; // Global realtime executor bitflag variable for spindle/coolant overrides.
#ifdef DEBUG
  volatile uint8_t sys_rt_exec_debug;
#endif


int main(void)
{
  // Initialize system upon power-up.
  serial_init();   // Setup serial baud rate and interrupts
  settings_init(); // Load Grbl settings from EEPROM
  stepper_init();  // Configure stepper pins and interrupt timers
  system_init();   // Configure pinout pins and pin-change interrupt

  memset(sys_position,0,sizeof(sys_position)); // Clear machine position.
  sei(); // Enable interrupts

  // Initialize system state.
  #ifdef FORCE_INITIALIZATION_ALARM
    // Force Grbl into an ALARM state upon a power-cycle or hard reset.
    sys.state = STATE_ALARM;
  #else
    sys.state = STATE_IDLE;
  #endif
  
  // Check for power-up and set system alarm if homing is enabled to force homing cycle
  // by setting Grbl's alarm state. Alarm locks out all g-code commands, including the
  // startup scripts, but allows access to settings and internal commands. Only a homing
  // cycle '$H' or kill alarm locks '$X' will disable the alarm.
  // NOTE: The startup script will run after successful completion of the homing cycle, but
  // not after disabling the alarm locks. Prevents motion startup blocks from crashing into
  // things uncontrollably. Very bad.
  #ifdef HOMING_INIT_LOCK
    if (bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE)) { sys.state = STATE_ALARM; }
  #endif

  // Grbl initialization loop upon power-up or a system abort. For the latter, all processes
  // will return to this loop to be cleanly re-initialized.
  for(;;) {

    // Reset system variables.
    uint8_t prior_state = sys.state;
    memset(&sys, 0, sizeof(system_t)); // Clear system struct variable.
    sys.state = prior_state;
    sys.f_override = DEFAULT_FEED_OVERRIDE;  // Set to 100%
    sys.r_override = DEFAULT_RAPID_OVERRIDE; // Set to 100%
    sys.spindle_speed_ovr = DEFAULT_SPINDLE_SPEED_OVERRIDE; // Set to 100%
		memset(sys_probe_position,0,sizeof(sys_probe_position)); // Clear probe position.
    sys_probe_state = 0;
    sys_rt_exec_state = 0;
    sys_rt_exec_alarm = 0;
    sys_rt_exec_motion_override = 0;
    sys_rt_exec_accessory_override = 0;

    // Reset Grbl primary systems.
    serial_reset_read_buffer(); // Clear serial read buffer
    gc_init(); // Set g-code parser to default state
    spindle_init();
    coolant_init();
    limits_init();
    probe_init();
    plan_reset(); // Clear block buffer and planner variables
    st_reset(); // Clear stepper subsystem variables.
    
    // Sync cleared gcode and planner positions to current system position.
    plan_sync_position();
    gc_sync_position();

    // Print welcome message. Indicates an initialization has occured at power-up or with a reset.
    report_init_message();

    // Start Grbl main loop. Processes program inputs and executes them.
    protocol_main_loop();

  }
  return 0;   /* Never reached */
}


main.c

/*
  motion_control.c - high level interface for issuing motion commands
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


// Execute linear motion in absolute millimeter coordinates. Feed rate given in millimeters/second
// unless invert_feed_rate is true. Then the feed_rate means that the motion should be completed in
// (1 minute)/feed_rate time.
// NOTE: This is the primary gateway to the grbl planner. All line motions, including arc line
// segments, must pass through this routine before being passed to the planner. The seperation of
// mc_line and plan_buffer_line is done primarily to place non-planner-type functions from being
// in the planner and to let backlash compensation or canned cycle integration simple and direct.
void mc_line(float *target, plan_line_data_t *pl_data)
{
  // If enabled, check for soft limit violations. Placed here all line motions are picked up
  // from everywhere in Grbl.
  if (bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE)) {
    // NOTE: Block jog state. Jogging is a special case and soft limits are handled independently.
    if (sys.state != STATE_JOG) { limits_soft_check(target); }
  }

  // If in check gcode mode, prevent motion by blocking planner. Soft limits still work.
  if (sys.state == STATE_CHECK_MODE) { return; }

  // NOTE: Backlash compensation may be installed here. It will need direction info to track when
  // to insert a backlash line motion(s) before the intended line motion and will require its own
  // plan_check_full_buffer() and check for system abort loop. Also for position reporting
  // backlash steps will need to be also tracked, which will need to be kept at a system level.
  // There are likely some other things that will need to be tracked as well. However, we feel
  // that backlash compensation should NOT be handled by Grbl itself, because there are a myriad
  // of ways to implement it and can be effective or ineffective for different CNC machines. This
  // would be better handled by the interface as a post-processor task, where the original g-code
  // is translated and inserts backlash motions that best suits the machine.
  // NOTE: Perhaps as a middle-ground, all that needs to be sent is a flag or special command that
  // indicates to Grbl what is a backlash compensation motion, so that Grbl executes the move but
  // doesn't update the machine position values. Since the position values used by the g-code
  // parser and planner are separate from the system machine positions, this is doable.

  // If the buffer is full: good! That means we are well ahead of the robot.
  // Remain in this loop until there is room in the buffer.
  do {
    protocol_execute_realtime(); // Check for any run-time commands
    if (sys.abort) { return; } // Bail, if system abort.
    if ( plan_check_full_buffer() ) { protocol_auto_cycle_start(); } // Auto-cycle start when buffer is full.
    else { break; }
  } while (1);

  // Plan and queue motion into planner buffer
  if (plan_buffer_line(target, pl_data) == PLAN_EMPTY_BLOCK) {
    if (bit_istrue(settings.flags,BITFLAG_LASER_MODE)) {
      // Correctly set spindle state, if there is a coincident position passed. Forces a buffer
      // sync while in M3 laser mode only.
      if (pl_data->condition & PL_COND_FLAG_SPINDLE_CW) {
        spindle_sync(PL_COND_FLAG_SPINDLE_CW, pl_data->spindle_speed);
      }
    }
  }
}


// Execute an arc in offset mode format. position == current xyz, target == target xyz,
// offset == offset from current xyz, axis_X defines circle plane in tool space, axis_linear is
// the direction of helical travel, radius == circle radius, isclockwise boolean. Used
// for vector transformation direction.
// The arc is approximated by generating a huge number of tiny, linear segments. The chordal tolerance
// of each segment is configured in settings.arc_tolerance, which is defined to be the maximum normal
// distance from segment to the circle when the end points both lie on the circle.
void mc_arc(float *target, plan_line_data_t *pl_data, float *position, float *offset, float radius,
  uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc)
{
  float center_axis0 = position[axis_0] + offset[axis_0];
  float center_axis1 = position[axis_1] + offset[axis_1];
  float r_axis0 = -offset[axis_0];  // Radius vector from center to current location
  float r_axis1 = -offset[axis_1];
  float rt_axis0 = target[axis_0] - center_axis0;
  float rt_axis1 = target[axis_1] - center_axis1;

  // CCW angle between position and target from circle center. Only one atan2() trig computation required.
  float angular_travel = atan2(r_axis0*rt_axis1-r_axis1*rt_axis0, r_axis0*rt_axis0+r_axis1*rt_axis1);
  if (is_clockwise_arc) { // Correct atan2 output per direction
    if (angular_travel >= -ARC_ANGULAR_TRAVEL_EPSILON) { angular_travel -= 2*M_PI; }
  } else {
    if (angular_travel <= ARC_ANGULAR_TRAVEL_EPSILON) { angular_travel += 2*M_PI; }
  }

  // NOTE: Segment end points are on the arc, which can lead to the arc diameter being smaller by up to
  // (2x) settings.arc_tolerance. For 99% of users, this is just fine. If a different arc segment fit
  // is desired, i.e. least-squares, midpoint on arc, just change the mm_per_arc_segment calculation.
  // For the intended uses of Grbl, this value shouldn't exceed 2000 for the strictest of cases.
  uint16_t segments = floor(fabs(0.5*angular_travel*radius)/
                          sqrt(settings.arc_tolerance*(2*radius - settings.arc_tolerance)) );

  if (segments) {
    // Multiply inverse feed_rate to compensate for the fact that this movement is approximated
    // by a number of discrete segments. The inverse feed_rate should be correct for the sum of
    // all segments.
    if (pl_data->condition & PL_COND_FLAG_INVERSE_TIME) { 
      pl_data->feed_rate *= segments; 
      bit_false(pl_data->condition,PL_COND_FLAG_INVERSE_TIME); // Force as feed absolute mode over arc segments.
    }
    
    float theta_per_segment = angular_travel/segments;
    float linear_per_segment = (target[axis_linear] - position[axis_linear])/segments;

    /* Vector rotation by transformation matrix: r is the original vector, r_T is the rotated vector,
       and phi is the angle of rotation. Solution approach by Jens Geisler.
           r_T = [cos(phi) -sin(phi);
                  sin(phi)  cos(phi] * r ;

       For arc generation, the center of the circle is the axis of rotation and the radius vector is
       defined from the circle center to the initial position. Each line segment is formed by successive
       vector rotations. Single precision values can accumulate error greater than tool precision in rare
       cases. So, exact arc path correction is implemented. This approach avoids the problem of too many very
       expensive trig operations [sin(),cos(),tan()] which can take 100-200 usec each to compute.

       Small angle approximation may be used to reduce computation overhead further. A third-order approximation
       (second order sin() has too much error) holds for most, if not, all CNC applications. Note that this
       approximation will begin to accumulate a numerical drift error when theta_per_segment is greater than
       ~0.25 rad(14 deg) AND the approximation is successively used without correction several dozen times. This
       scenario is extremely unlikely, since segment lengths and theta_per_segment are automatically generated
       and scaled by the arc tolerance setting. Only a very large arc tolerance setting, unrealistic for CNC
       applications, would cause this numerical drift error. However, it is best to set N_ARC_CORRECTION from a
       low of ~4 to a high of ~20 or so to avoid trig operations while keeping arc generation accurate.

       This approximation also allows mc_arc to immediately insert a line segment into the planner
       without the initial overhead of computing cos() or sin(). By the time the arc needs to be applied
       a correction, the planner should have caught up to the lag caused by the initial mc_arc overhead.
       This is important when there are successive arc motions.
    */
    // Computes: cos_T = 1 - theta_per_segment^2/2, sin_T = theta_per_segment - theta_per_segment^3/6) in ~52usec
    float cos_T = 2.0 - theta_per_segment*theta_per_segment;
    float sin_T = theta_per_segment*0.16666667*(cos_T + 4.0);
    cos_T *= 0.5;

    float sin_Ti;
    float cos_Ti;
    float r_axisi;
    uint16_t i;
    uint8_t count = 0;

    for (i = 1; i<segments; i++) { // Increment (segments-1).

      if (count < N_ARC_CORRECTION) {
        // Apply vector rotation matrix. ~40 usec
        r_axisi = r_axis0*sin_T + r_axis1*cos_T;
        r_axis0 = r_axis0*cos_T - r_axis1*sin_T;
        r_axis1 = r_axisi;
        count++;
      } else {
        // Arc correction to radius vector. Computed only every N_ARC_CORRECTION increments. ~375 usec
        // Compute exact location by applying transformation matrix from initial radius vector(=-offset).
        cos_Ti = cos(i*theta_per_segment);
        sin_Ti = sin(i*theta_per_segment);
        r_axis0 = -offset[axis_0]*cos_Ti + offset[axis_1]*sin_Ti;
        r_axis1 = -offset[axis_0]*sin_Ti - offset[axis_1]*cos_Ti;
        count = 0;
      }

      // Update arc_target location
      position[axis_0] = center_axis0 + r_axis0;
      position[axis_1] = center_axis1 + r_axis1;
      position[axis_linear] += linear_per_segment;

      mc_line(position, pl_data);

      // Bail mid-circle on system abort. Runtime command check already performed by mc_line.
      if (sys.abort) { return; }
    }
  }
  // Ensure last segment arrives at target location.
  mc_line(target, pl_data);
}


// Execute dwell in seconds.
void mc_dwell(float seconds)
{
  if (sys.state == STATE_CHECK_MODE) { return; }
  protocol_buffer_synchronize();
  delay_sec(seconds, DELAY_MODE_DWELL);
}


// Perform homing cycle to locate and set machine zero. Only '$H' executes this command.
// NOTE: There should be no motions in the buffer and Grbl must be in an idle state before
// executing the homing cycle. This prevents incorrect buffered plans after homing.
void mc_homing_cycle(uint8_t cycle_mask)
{
  // Check and abort homing cycle, if hard limits are already enabled. Helps prevent problems
  // with machines with limits wired on both ends of travel to one limit pin.
  // TODO: Move the pin-specific LIMIT_PIN call to limits.c as a function.
  #ifdef LIMITS_TWO_SWITCHES_ON_AXES
    if (limits_get_state()) {
      mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
      system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT);
      return;
    }
  #endif

  limits_disable(); // Disable hard limits pin change register for cycle duration

  // -------------------------------------------------------------------------------------
  // Perform homing routine. NOTE: Special motion case. Only system reset works.
  
  #ifdef HOMING_SINGLE_AXIS_COMMANDS
    if (cycle_mask) { limits_go_home(cycle_mask); } // Perform homing cycle based on mask.
    else
  #endif
  {
    // Search to engage all axes limit switches at faster homing seek rate.
    limits_go_home(HOMING_CYCLE_0);  // Homing cycle 0
    #ifdef HOMING_CYCLE_1
      limits_go_home(HOMING_CYCLE_1);  // Homing cycle 1
    #endif
    #ifdef HOMING_CYCLE_2
      limits_go_home(HOMING_CYCLE_2);  // Homing cycle 2
    #endif
  }

  protocol_execute_realtime(); // Check for reset and set system abort.
  if (sys.abort) { return; } // Did not complete. Alarm state set by mc_alarm.

  // Homing cycle complete! Setup system for normal operation.
  // -------------------------------------------------------------------------------------

  // Sync gcode parser and planner positions to homed position.
  gc_sync_position();
  plan_sync_position();

  // If hard limits feature enabled, re-enable hard limits pin change register after homing cycle.
  limits_init();
}


// Perform tool length probe cycle. Requires probe switch.
// NOTE: Upon probe failure, the program will be stopped and placed into ALARM state.
uint8_t mc_probe_cycle(float *target, plan_line_data_t *pl_data, uint8_t parser_flags)
{
  // TODO: Need to update this cycle so it obeys a non-auto cycle start.
  if (sys.state == STATE_CHECK_MODE) { return(GC_PROBE_CHECK_MODE); }

  // Finish all queued commands and empty planner buffer before starting probe cycle.
  protocol_buffer_synchronize();
  if (sys.abort) { return(GC_PROBE_ABORT); } // Return if system reset has been issued.

  // Initialize probing control variables
  uint8_t is_probe_away = bit_istrue(parser_flags,GC_PARSER_PROBE_IS_AWAY);
  uint8_t is_no_error = bit_istrue(parser_flags,GC_PARSER_PROBE_IS_NO_ERROR);
  sys.probe_succeeded = false; // Re-initialize probe history before beginning cycle.
  probe_configure_invert_mask(is_probe_away);

  // After syncing, check if probe is already triggered. If so, halt and issue alarm.
  // NOTE: This probe initialization error applies to all probing cycles.
  if ( probe_get_state() ) { // Check probe pin state.
    system_set_exec_alarm(EXEC_ALARM_PROBE_FAIL_INITIAL);
    protocol_execute_realtime();
    probe_configure_invert_mask(false); // Re-initialize invert mask before returning.
    return(GC_PROBE_FAIL_INIT); // Nothing else to do but bail.
  }

  // Setup and queue probing motion. Auto cycle-start should not start the cycle.
  mc_line(target, pl_data);

  // Activate the probing state monitor in the stepper module.
  sys_probe_state = PROBE_ACTIVE;

  // Perform probing cycle. Wait here until probe is triggered or motion completes.
  system_set_exec_state_flag(EXEC_CYCLE_START);
  do {
    protocol_execute_realtime();
    if (sys.abort) { return(GC_PROBE_ABORT); } // Check for system abort
  } while (sys.state != STATE_IDLE);

  // Probing cycle complete!

  // Set state variables and error out, if the probe failed and cycle with error is enabled.
  if (sys_probe_state == PROBE_ACTIVE) {
    if (is_no_error) { memcpy(sys_probe_position, sys_position, sizeof(sys_position)); }
    else { system_set_exec_alarm(EXEC_ALARM_PROBE_FAIL_CONTACT); }
  } else {
    sys.probe_succeeded = true; // Indicate to system the probing cycle completed successfully.
  }
  sys_probe_state = PROBE_OFF; // Ensure probe state monitor is disabled.
  probe_configure_invert_mask(false); // Re-initialize invert mask.
  protocol_execute_realtime();   // Check and execute run-time commands

  // Reset the stepper and planner buffers to remove the remainder of the probe motion.
  st_reset(); // Reset step segment buffer.
  plan_reset(); // Reset planner buffer. Zero planner positions. Ensure probing motion is cleared.
  plan_sync_position(); // Sync planner position to current machine position.

  #ifdef MESSAGE_PROBE_COORDINATES
    // All done! Output the probe position as message.
    report_probe_parameters();
  #endif

  if (sys.probe_succeeded) { return(GC_PROBE_FOUND); } // Successful probe cycle.
  else { return(GC_PROBE_FAIL_END); } // Failed to trigger probe within travel. With or without error.
}


// Plans and executes the single special motion case for parking. Independent of main planner buffer.
// NOTE: Uses the always free planner ring buffer head to store motion parameters for execution.
#ifdef PARKING_ENABLE
  void mc_parking_motion(float *parking_target, plan_line_data_t *pl_data)
  {
    if (sys.abort) { return; } // Block during abort.

    uint8_t plan_status = plan_buffer_line(parking_target, pl_data);

    if (plan_status) {
      bit_true(sys.step_control, STEP_CONTROL_EXECUTE_SYS_MOTION);
      bit_false(sys.step_control, STEP_CONTROL_END_MOTION); // Allow parking motion to execute, if feed hold is active.
      st_parking_setup_buffer(); // Setup step segment buffer for special parking motion case
      st_prep_buffer();
      st_wake_up();
      do {
        protocol_exec_rt_system();
        if (sys.abort) { return; }
      } while (sys.step_control & STEP_CONTROL_EXECUTE_SYS_MOTION);
      st_parking_restore_buffer(); // Restore step segment buffer to normal run state.
    } else {
      bit_false(sys.step_control, STEP_CONTROL_EXECUTE_SYS_MOTION);
      protocol_exec_rt_system();
    }

  }
#endif


#ifdef ENABLE_PARKING_OVERRIDE_CONTROL
  void mc_override_ctrl_update(uint8_t override_state)
  {
    // Finish all queued commands before altering override control state
    protocol_buffer_synchronize();
    if (sys.abort) { return; }
    sys.override_ctrl = override_state;
  }
#endif


// Method to ready the system to reset by setting the realtime reset command and killing any
// active processes in the system. This also checks if a system reset is issued while Grbl
// is in a motion state. If so, kills the steppers and sets the system alarm to flag position
// lost, since there was an abrupt uncontrolled deceleration. Called at an interrupt level by
// realtime abort command and hard limits. So, keep to a minimum.
void mc_reset()
{
  // Only this function can set the system reset. Helps prevent multiple kill calls.
  if (bit_isfalse(sys_rt_exec_state, EXEC_RESET)) {
    system_set_exec_state_flag(EXEC_RESET);

    // Kill spindle and coolant.
    spindle_stop();
    coolant_stop();

    // Kill steppers only if in any motion state, i.e. cycle, actively holding, or homing.
    // NOTE: If steppers are kept enabled via the step idle delay setting, this also keeps
    // the steppers enabled by avoiding the go_idle call altogether, unless the motion state is
    // violated, by which, all bets are off.
    if ((sys.state & (STATE_CYCLE | STATE_HOMING | STATE_JOG)) ||
    		(sys.step_control & (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_SYS_MOTION))) {
      if (sys.state == STATE_HOMING) { 
        if (!sys_rt_exec_alarm) {system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_RESET); }
      } else { system_set_exec_alarm(EXEC_ALARM_ABORT_CYCLE); }
      st_go_idle(); // Force kill steppers. Position has likely been lost.
    }
  }
}


motion_control.c

/*
  motion_control.h - high level interface for issuing motion commands
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef motion_control_h
#define motion_control_h


// System motion commands must have a line number of zero.
#define HOMING_CYCLE_LINE_NUMBER 0
#define PARKING_MOTION_LINE_NUMBER 0

#define HOMING_CYCLE_ALL  0  // Must be zero.
#define HOMING_CYCLE_X    bit(X_AXIS)
#define HOMING_CYCLE_Y    bit(Y_AXIS)
#define HOMING_CYCLE_Z    bit(Z_AXIS)


// Execute linear motion in absolute millimeter coordinates. Feed rate given in millimeters/second
// unless invert_feed_rate is true. Then the feed_rate means that the motion should be completed in
// (1 minute)/feed_rate time.
void mc_line(float *target, plan_line_data_t *pl_data);

// Execute an arc in offset mode format. position == current xyz, target == target xyz,
// offset == offset from current xyz, axis_XXX defines circle plane in tool space, axis_linear is
// the direction of helical travel, radius == circle radius, is_clockwise_arc boolean. Used
// for vector transformation direction.
void mc_arc(float *target, plan_line_data_t *pl_data, float *position, float *offset, float radius,
  uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc);

// Dwell for a specific number of seconds
void mc_dwell(float seconds);

// Perform homing cycle to locate machine zero. Requires limit switches.
void mc_homing_cycle(uint8_t cycle_mask);

// Perform tool length probe cycle. Requires probe switch.
uint8_t mc_probe_cycle(float *target, plan_line_data_t *pl_data, uint8_t parser_flags);

// Handles updating the override control state.
void mc_override_ctrl_update(uint8_t override_state);

// Plans and executes the single special motion case for parking. Independent of main planner buffer.
void mc_parking_motion(float *parking_target, plan_line_data_t *pl_data);

// Performs system reset. If in motion state, kills all motion and sets system alarm.
void mc_reset();

#endif


motion_control.h

/*
  nuts_bolts.c - Shared functions
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


#define MAX_INT_DIGITS 8 // Maximum number of digits in int32 (and float)


// Extracts a floating point value from a string. The following code is based loosely on
// the avr-libc strtod() function by Michael Stumpf and Dmitry Xmelkov and many freely
// available conversion method examples, but has been highly optimized for Grbl. For known
// CNC applications, the typical decimal value is expected to be in the range of E0 to E-4.
// Scientific notation is officially not supported by g-code, and the 'E' character may
// be a g-code word on some CNC systems. So, 'E' notation will not be recognized.
// NOTE: Thanks to Radu-Eosif Mihailescu for identifying the issues with using strtod().
uint8_t read_float(char *line, uint8_t *char_counter, float *float_ptr)
{
  char *ptr = line + *char_counter;
  unsigned char c;

  // Grab first character and increment pointer. No spaces assumed in line.
  c = *ptr++;

  // Capture initial positive/minus character
  bool isnegative = false;
  if (c == '-') {
    isnegative = true;
    c = *ptr++;
  } else if (c == '+') {
    c = *ptr++;
  }

  // Extract number into fast integer. Track decimal in terms of exponent value.
  uint32_t intval = 0;
  int8_t exp = 0;
  uint8_t ndigit = 0;
  bool isdecimal = false;
  while(1) {
    c -= '0';
    if (c <= 9) {
      ndigit++;
      if (ndigit <= MAX_INT_DIGITS) {
        if (isdecimal) { exp--; }
        intval = (((intval << 2) + intval) << 1) + c; // intval*10 + c
      } else {
        if (!(isdecimal)) { exp++; }  // Drop overflow digits
      }
    } else if (c == (('.'-'0') & 0xff)  &&  !(isdecimal)) {
      isdecimal = true;
    } else {
      break;
    }
    c = *ptr++;
  }

  // Return if no digits have been read.
  if (!ndigit) { return(false); };

  // Convert integer into floating point.
  float fval;
  fval = (float)intval;

  // Apply decimal. Should perform no more than two floating point multiplications for the
  // expected range of E0 to E-4.
  if (fval != 0) {
    while (exp <= -2) {
      fval *= 0.01;
      exp += 2;
    }
    if (exp < 0) {
      fval *= 0.1;
    } else if (exp > 0) {
      do {
        fval *= 10.0;
      } while (--exp > 0);
    }
  }

  // Assign floating point value with correct sign.
  if (isnegative) {
    *float_ptr = -fval;
  } else {
    *float_ptr = fval;
  }

  *char_counter = ptr - line - 1; // Set char_counter to next statement

  return(true);
}


// Non-blocking delay function used for general operation and suspend features.
void delay_sec(float seconds, uint8_t mode)
{
 	uint16_t i = ceil(1000/DWELL_TIME_STEP*seconds);
	while (i-- > 0) {
		if (sys.abort) { return; }
		if (mode == DELAY_MODE_DWELL) {
			protocol_execute_realtime();
		} else { // DELAY_MODE_SYS_SUSPEND
		  // Execute rt_system() only to avoid nesting suspend loops.
		  protocol_exec_rt_system();
		  if (sys.suspend & SUSPEND_RESTART_RETRACT) { return; } // Bail, if safety door reopens.
		}
		_delay_ms(DWELL_TIME_STEP); // Delay DWELL_TIME_STEP increment
	}
}


// Delays variable defined milliseconds. Compiler compatibility fix for _delay_ms(),
// which only accepts constants in future compiler releases.
void delay_ms(uint16_t ms)
{
  while ( ms-- ) { _delay_ms(1); }
}


// Delays variable defined microseconds. Compiler compatibility fix for _delay_us(),
// which only accepts constants in future compiler releases. Written to perform more
// efficiently with larger delays, as the counter adds parasitic time in each iteration.
void delay_us(uint32_t us)
{
  while (us) {
    if (us < 10) {
      _delay_us(1);
      us--;
    } else if (us < 100) {
      _delay_us(10);
      us -= 10;
    } else if (us < 1000) {
      _delay_us(100);
      us -= 100;
    } else {
      _delay_ms(1);
      us -= 1000;
    }
  }
}


// Simple hypotenuse computation function.
float hypot_f(float x, float y) { return(sqrt(x*x + y*y)); }


float convert_delta_vector_to_unit_vector(float *vector)
{
  uint8_t idx;
  float magnitude = 0.0;
  for (idx=0; idx<N_AXIS; idx++) {
    if (vector[idx] != 0.0) {
      magnitude += vector[idx]*vector[idx];
    }
  }
  magnitude = sqrt(magnitude);
  float inv_magnitude = 1.0/magnitude;
  for (idx=0; idx<N_AXIS; idx++) { vector[idx] *= inv_magnitude; }
  return(magnitude);
}


float limit_value_by_axis_maximum(float *max_value, float *unit_vec)
{
  uint8_t idx;
  float limit_value = SOME_LARGE_VALUE;
  for (idx=0; idx<N_AXIS; idx++) {
    if (unit_vec[idx] != 0) {  // Avoid divide by zero.
      limit_value = min(limit_value,fabs(max_value[idx]/unit_vec[idx]));
    }
  }
  return(limit_value);
}


nuts_bolts.c

/*
  nuts_bolts.h - Header file for shared definitions, variables, and functions
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef nuts_bolts_h
#define nuts_bolts_h

#define false 0
#define true 1

#define SOME_LARGE_VALUE 1.0E+38

// Axis array index values. Must start with 0 and be continuous.
#define N_AXIS 3 // Number of axes
#define X_AXIS 0 // Axis indexing value.
#define Y_AXIS 1
#define Z_AXIS 2
// #define A_AXIS 3

// CoreXY motor assignments. DO NOT ALTER.
// NOTE: If the A and B motor axis bindings are changed, this effects the CoreXY equations.
#ifdef COREXY
 #define A_MOTOR X_AXIS // Must be X_AXIS
 #define B_MOTOR Y_AXIS // Must be Y_AXIS
#endif

// Conversions
#define MM_PER_INCH (25.40)
#define INCH_PER_MM (0.0393701)
#define TICKS_PER_MICROSECOND (F_CPU/1000000)

#define DELAY_MODE_DWELL       0
#define DELAY_MODE_SYS_SUSPEND 1

// Useful macros
#define clear_vector(a) memset(a, 0, sizeof(a))
#define clear_vector_float(a) memset(a, 0.0, sizeof(float)*N_AXIS)
// #define clear_vector_long(a) memset(a, 0.0, sizeof(long)*N_AXIS)
#define max(a,b) (((a) > (b)) ? (a) : (b))
#define min(a,b) (((a) < (b)) ? (a) : (b))
#define isequal_position_vector(a,b) !(memcmp(a, b, sizeof(float)*N_AXIS))

// Bit field and masking macros
#define bit(n) (1 << n)
#define bit_true(x,mask) (x) |= (mask)
#define bit_false(x,mask) (x) &= ~(mask)
#define bit_istrue(x,mask) ((x & mask) != 0)
#define bit_isfalse(x,mask) ((x & mask) == 0)

// Read a floating point value from a string. Line points to the input buffer, char_counter
// is the indexer pointing to the current character of the line, while float_ptr is
// a pointer to the result variable. Returns true when it succeeds
uint8_t read_float(char *line, uint8_t *char_counter, float *float_ptr);

// Non-blocking delay function used for general operation and suspend features.
void delay_sec(float seconds, uint8_t mode);

// Delays variable-defined milliseconds. Compiler compatibility fix for _delay_ms().
void delay_ms(uint16_t ms);

// Delays variable-defined microseconds. Compiler compatibility fix for _delay_us().
void delay_us(uint32_t us);

// Computes hypotenuse, avoiding avr-gcc's bloated version and the extra error checking.
float hypot_f(float x, float y);

float convert_delta_vector_to_unit_vector(float *vector);
float limit_value_by_axis_maximum(float *max_value, float *unit_vec);

#endif


nuts_bolts.h

planner.c

/*
  planner.h - buffers movement commands and manages the acceleration profile plan
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef planner_h
#define planner_h


// The number of linear motions that can be in the plan at any give time
#ifndef BLOCK_BUFFER_SIZE
  #ifdef USE_LINE_NUMBERS
    #define BLOCK_BUFFER_SIZE 15
  #else
    #define BLOCK_BUFFER_SIZE 16
  #endif
#endif

// Returned status message from planner.
#define PLAN_OK true
#define PLAN_EMPTY_BLOCK false

// Define planner data condition flags. Used to denote running conditions of a block.
#define PL_COND_FLAG_RAPID_MOTION      bit(0)
#define PL_COND_FLAG_SYSTEM_MOTION     bit(1) // Single motion. Circumvents planner state. Used by home/park.
#define PL_COND_FLAG_NO_FEED_OVERRIDE  bit(2) // Motion does not honor feed override.
#define PL_COND_FLAG_INVERSE_TIME      bit(3) // Interprets feed rate value as inverse time when set.
#define PL_COND_FLAG_SPINDLE_CW        bit(4)
#define PL_COND_FLAG_SPINDLE_CCW       bit(5)
#define PL_COND_FLAG_COOLANT_FLOOD     bit(6)
#define PL_COND_FLAG_COOLANT_MIST      bit(7)
#define PL_COND_MOTION_MASK    (PL_COND_FLAG_RAPID_MOTION|PL_COND_FLAG_SYSTEM_MOTION|PL_COND_FLAG_NO_FEED_OVERRIDE)
#define PL_COND_SPINDLE_MASK   (PL_COND_FLAG_SPINDLE_CW|PL_COND_FLAG_SPINDLE_CCW)
#define PL_COND_ACCESSORY_MASK (PL_COND_FLAG_SPINDLE_CW|PL_COND_FLAG_SPINDLE_CCW|PL_COND_FLAG_COOLANT_FLOOD|PL_COND_FLAG_COOLANT_MIST)


// This struct stores a linear movement of a g-code block motion with its critical "nominal" values
// are as specified in the source g-code.
typedef struct {
  // Fields used by the bresenham algorithm for tracing the line
  // NOTE: Used by stepper algorithm to execute the block correctly. Do not alter these values.
  uint32_t steps[N_AXIS];    // Step count along each axis
  uint32_t step_event_count; // The maximum step axis count and number of steps required to complete this block.
  uint8_t direction_bits;    // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)

  // Block condition data to ensure correct execution depending on states and overrides.
  uint8_t condition;      // Block bitflag variable defining block run conditions. Copied from pl_line_data.
  #ifdef USE_LINE_NUMBERS
    int32_t line_number;  // Block line number for real-time reporting. Copied from pl_line_data.
  #endif

  // Fields used by the motion planner to manage acceleration. Some of these values may be updated
  // by the stepper module during execution of special motion cases for replanning purposes.
  float entry_speed_sqr;     // The current planned entry speed at block junction in (mm/min)^2
  float max_entry_speed_sqr; // Maximum allowable entry speed based on the minimum of junction limit and
                             //   neighboring nominal speeds with overrides in (mm/min)^2
  float acceleration;        // Axis-limit adjusted line acceleration in (mm/min^2). Does not change.
  float millimeters;         // The remaining distance for this block to be executed in (mm).
                             // NOTE: This value may be altered by stepper algorithm during execution.

  // Stored rate limiting data used by planner when changes occur.
  float max_junction_speed_sqr; // Junction entry speed limit based on direction vectors in (mm/min)^2
  float rapid_rate;             // Axis-limit adjusted maximum rate for this block direction in (mm/min)
  float programmed_rate;        // Programmed rate of this block (mm/min).

  #ifdef VARIABLE_SPINDLE
    // Stored spindle speed data used by spindle overrides and resuming methods.
    float spindle_speed;    // Block spindle speed. Copied from pl_line_data.
  #endif
} plan_block_t;


// Planner data prototype. Must be used when passing new motions to the planner.
typedef struct {
  float feed_rate;          // Desired feed rate for line motion. Value is ignored, if rapid motion.
  float spindle_speed;      // Desired spindle speed through line motion.
  uint8_t condition;        // Bitflag variable to indicate planner conditions. See defines above.
  #ifdef USE_LINE_NUMBERS
    int32_t line_number;    // Desired line number to report when executing.
  #endif
} plan_line_data_t;


// Initialize and reset the motion plan subsystem
void plan_reset(); // Reset all
void plan_reset_buffer(); // Reset buffer only.

// Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position
// in millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
// rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
uint8_t plan_buffer_line(float *target, plan_line_data_t *pl_data);

// Called when the current block is no longer needed. Discards the block and makes the memory
// availible for new blocks.
void plan_discard_current_block();

// Gets the planner block for the special system motion cases. (Parking/Homing)
plan_block_t *plan_get_system_motion_block();

// Gets the current block. Returns NULL if buffer empty
plan_block_t *plan_get_current_block();

// Called periodically by step segment buffer. Mostly used internally by planner.
uint8_t plan_next_block_index(uint8_t block_index);

// Called by step segment buffer when computing executing block velocity profile.
float plan_get_exec_block_exit_speed_sqr();

// Called by main program during planner calculations and step segment buffer during initialization.
float plan_compute_profile_nominal_speed(plan_block_t *block);

// Re-calculates buffered motions profile parameters upon a motion-based override change.
void plan_update_velocity_profile_parameters();

// Reset the planner position vector (in steps)
void plan_sync_position();

// Reinitialize plan with a partially completed block
void plan_cycle_reinitialize();

// Returns the number of available blocks are in the planner buffer.
uint8_t plan_get_block_buffer_available();

// Returns the number of active blocks are in the planner buffer.
// NOTE: Deprecated. Not used unless classic status reports are enabled in config.h
uint8_t plan_get_block_buffer_count();

// Returns the status of the block ring buffer. True, if buffer is full.
uint8_t plan_check_full_buffer();

void plan_get_planner_mpos(float *target);


#endif


planner.h

/*
  print.c - Functions for formatting output strings
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


void printString(const char *s)
{
  while (*s)
    serial_write(*s++);
}


// Print a string stored in PGM-memory
void printPgmString(const char *s)
{
  char c;
  while ((c = pgm_read_byte_near(s++)))
    serial_write(c);
}


// void printIntegerInBase(unsigned long n, unsigned long base)
// {
// 	unsigned char buf[8 * sizeof(long)]; // Assumes 8-bit chars.
// 	unsigned long i = 0;
//
// 	if (n == 0) {
// 		serial_write('0');
// 		return;
// 	}
//
// 	while (n > 0) {
// 		buf[i++] = n % base;
// 		n /= base;
// 	}
//
// 	for (; i > 0; i--)
// 		serial_write(buf[i - 1] < 10 ?
// 			'0' + buf[i - 1] :
// 			'A' + buf[i - 1] - 10);
// }


// Prints an uint8 variable in base 10.
void print_uint8_base10(uint8_t n)
{
  uint8_t digit_a = 0;
  uint8_t digit_b = 0;
  if (n >= 100) { // 100-255
    digit_a = '0' + n % 10;
    n /= 10;
  }
  if (n >= 10) { // 10-99
    digit_b = '0' + n % 10;
    n /= 10;
  }
  serial_write('0' + n);
  if (digit_b) { serial_write(digit_b); }
  if (digit_a) { serial_write(digit_a); }
}


// Prints an uint8 variable in base 2 with desired number of desired digits.
void print_uint8_base2_ndigit(uint8_t n, uint8_t digits) {
  unsigned char buf[digits];
  uint8_t i = 0;

  for (; i < digits; i++) {
      buf[i] = n % 2 ;
      n /= 2;
  }

  for (; i > 0; i--)
      serial_write('0' + buf[i - 1]);
}


void print_uint32_base10(uint32_t n)
{
  if (n == 0) {
    serial_write('0');
    return;
  }

  unsigned char buf[10];
  uint8_t i = 0;

  while (n > 0) {
    buf[i++] = n % 10;
    n /= 10;
  }

  for (; i > 0; i--)
    serial_write('0' + buf[i-1]);
}


void printInteger(long n)
{
  if (n < 0) {
    serial_write('-');
    print_uint32_base10(-n);
  } else {
    print_uint32_base10(n);
  }
}


// Convert float to string by immediately converting to a long integer, which contains
// more digits than a float. Number of decimal places, which are tracked by a counter,
// may be set by the user. The integer is then efficiently converted to a string.
// NOTE: AVR '%' and '/' integer operations are very efficient. Bitshifting speed-up
// techniques are actually just slightly slower. Found this out the hard way.
void printFloat(float n, uint8_t decimal_places)
{
  if (n < 0) {
    serial_write('-');
    n = -n;
  }

  uint8_t decimals = decimal_places;
  while (decimals >= 2) { // Quickly convert values expected to be E0 to E-4.
    n *= 100;
    decimals -= 2;
  }
  if (decimals) { n *= 10; }
  n += 0.5; // Add rounding factor. Ensures carryover through entire value.

  // Generate digits backwards and store in string.
  unsigned char buf[13];
  uint8_t i = 0;
  uint32_t a = (long)n;
  while(a > 0) {
    buf[i++] = (a % 10) + '0'; // Get digit
    a /= 10;
  }
  while (i < decimal_places) {
     buf[i++] = '0'; // Fill in zeros to decimal point for (n < 1)
  }
  if (i == decimal_places) { // Fill in leading zero, if needed.
    buf[i++] = '0';
  }

  // Print the generated string.
  for (; i > 0; i--) {
    if (i == decimal_places) { serial_write('.'); } // Insert decimal point in right place.
    serial_write(buf[i-1]);
  }
}


// Floating value printing handlers for special variables types used in Grbl and are defined
// in the config.h.
//  - CoordValue: Handles all position or coordinate values in inches or mm reporting.
//  - RateValue: Handles feed rate and current velocity in inches or mm reporting.
void printFloat_CoordValue(float n) {
  if (bit_istrue(settings.flags,BITFLAG_REPORT_INCHES)) {
    printFloat(n*INCH_PER_MM,N_DECIMAL_COORDVALUE_INCH);
  } else {
    printFloat(n,N_DECIMAL_COORDVALUE_MM);
  }
}

void printFloat_RateValue(float n) {
  if (bit_istrue(settings.flags,BITFLAG_REPORT_INCHES)) {
    printFloat(n*INCH_PER_MM,N_DECIMAL_RATEVALUE_INCH);
  } else {
    printFloat(n,N_DECIMAL_RATEVALUE_MM);
  }
}

// Debug tool to print free memory in bytes at the called point.
// NOTE: Keep commented unless using. Part of this function always gets compiled in.
// void printFreeMemory()
// {
//   extern int __heap_start, *__brkval;
//   uint16_t free;  // Up to 64k values.
//   free = (int) &free - (__brkval == 0 ? (int) &__heap_start : (int) __brkval);
//   printInteger((int32_t)free);
//   printString(" ");
// }


print.c

/*
  print.h - Functions for formatting output strings
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef print_h
#define print_h


void printString(const char *s);

void printPgmString(const char *s);

void printInteger(long n);

void print_uint32_base10(uint32_t n);

// Prints an uint8 variable in base 10.
void print_uint8_base10(uint8_t n);

// Prints an uint8 variable in base 2 with desired number of desired digits.
void print_uint8_base2_ndigit(uint8_t n, uint8_t digits);

void printFloat(float n, uint8_t decimal_places);

// Floating value printing handlers for special variables types used in Grbl.
//  - CoordValue: Handles all position or coordinate values in inches or mm reporting.
//  - RateValue: Handles feed rate and current velocity in inches or mm reporting.
void printFloat_CoordValue(float n);
void printFloat_RateValue(float n);

// Debug tool to print free memory in bytes at the called point. Not used otherwise.
void printFreeMemory();

#endif


print.h

/*
  probe.c - code pertaining to probing methods
  Part of Grbl

  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


// Inverts the probe pin state depending on user settings and probing cycle mode.
uint8_t probe_invert_mask;


// Probe pin initialization routine.
void probe_init()
{
  PROBE_DDR &= ~(PROBE_MASK); // Configure as input pins
  #ifdef DISABLE_PROBE_PIN_PULL_UP
    PROBE_PORT &= ~(PROBE_MASK); // Normal low operation. Requires external pull-down.
  #else
    PROBE_PORT |= PROBE_MASK;    // Enable internal pull-up resistors. Normal high operation.
  #endif
  probe_configure_invert_mask(false); // Initialize invert mask.
}


// Called by probe_init() and the mc_probe() routines. Sets up the probe pin invert mask to
// appropriately set the pin logic according to setting for normal-high/normal-low operation
// and the probing cycle modes for toward-workpiece/away-from-workpiece.
void probe_configure_invert_mask(uint8_t is_probe_away)
{
  probe_invert_mask = 0; // Initialize as zero.
  if (bit_isfalse(settings.flags,BITFLAG_INVERT_PROBE_PIN)) { probe_invert_mask ^= PROBE_MASK; }
  if (is_probe_away) { probe_invert_mask ^= PROBE_MASK; }
}


// Returns the probe pin state. Triggered = true. Called by gcode parser and probe state monitor.
uint8_t probe_get_state() { return((PROBE_PIN & PROBE_MASK) ^ probe_invert_mask); }


// Monitors probe pin state and records the system position when detected. Called by the
// stepper ISR per ISR tick.
// NOTE: This function must be extremely efficient as to not bog down the stepper ISR.
void probe_state_monitor()
{
  if (probe_get_state()) {
    sys_probe_state = PROBE_OFF;
    memcpy(sys_probe_position, sys_position, sizeof(sys_position));
    bit_true(sys_rt_exec_state, EXEC_MOTION_CANCEL);
  }
}


probe.c

/*
  probe.h - code pertaining to probing methods
  Part of Grbl

  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef probe_h
#define probe_h

// Values that define the probing state machine.
#define PROBE_OFF     0 // Probing disabled or not in use. (Must be zero.)
#define PROBE_ACTIVE  1 // Actively watching the input pin.

// Probe pin initialization routine.
void probe_init();

// Called by probe_init() and the mc_probe() routines. Sets up the probe pin invert mask to
// appropriately set the pin logic according to setting for normal-high/normal-low operation
// and the probing cycle modes for toward-workpiece/away-from-workpiece.
void probe_configure_invert_mask(uint8_t is_probe_away);

// Returns probe pin state. Triggered = true. Called by gcode parser and probe state monitor.
uint8_t probe_get_state();

// Monitors probe pin state and records the system position when detected. Called by the
// stepper ISR per ISR tick.
void probe_state_monitor();

#endif


probe.h

protocol.c

/*
  protocol.h - controls Grbl execution protocol and procedures
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef protocol_h
#define protocol_h

// Line buffer size from the serial input stream to be executed.
// NOTE: Not a problem except for extreme cases, but the line buffer size can be too small
// and g-code blocks can get truncated. Officially, the g-code standards support up to 256
// characters. In future versions, this will be increased, when we know how much extra
// memory space we can invest into here or we re-write the g-code parser not to have this
// buffer.
#ifndef LINE_BUFFER_SIZE
  #define LINE_BUFFER_SIZE 80
#endif

// Starts Grbl main loop. It handles all incoming characters from the serial port and executes
// them as they complete. It is also responsible for finishing the initialization procedures.
void protocol_main_loop();

// Checks and executes a realtime command at various stop points in main program
void protocol_execute_realtime();
void protocol_exec_rt_system();

// Executes the auto cycle feature, if enabled.
void protocol_auto_cycle_start();

// Block until all buffered steps are executed
void protocol_buffer_synchronize();

#endif


protocol.h

report.c

/*
  report.h - reporting and messaging methods
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef report_h
#define report_h

// Define Grbl status codes. Valid values (0-255)
#define STATUS_OK 0
#define STATUS_EXPECTED_COMMAND_LETTER 1
#define STATUS_BAD_NUMBER_FORMAT 2
#define STATUS_INVALID_STATEMENT 3
#define STATUS_NEGATIVE_VALUE 4
#define STATUS_SETTING_DISABLED 5
#define STATUS_SETTING_STEP_PULSE_MIN 6
#define STATUS_SETTING_READ_FAIL 7
#define STATUS_IDLE_ERROR 8
#define STATUS_SYSTEM_GC_LOCK 9
#define STATUS_SOFT_LIMIT_ERROR 10
#define STATUS_OVERFLOW 11
#define STATUS_MAX_STEP_RATE_EXCEEDED 12
#define STATUS_CHECK_DOOR 13
#define STATUS_LINE_LENGTH_EXCEEDED 14
#define STATUS_TRAVEL_EXCEEDED 15
#define STATUS_INVALID_JOG_COMMAND 16
#define STATUS_SETTING_DISABLED_LASER 17

#define STATUS_GCODE_UNSUPPORTED_COMMAND 20
#define STATUS_GCODE_MODAL_GROUP_VIOLATION 21
#define STATUS_GCODE_UNDEFINED_FEED_RATE 22
#define STATUS_GCODE_COMMAND_VALUE_NOT_INTEGER 23
#define STATUS_GCODE_AXIS_COMMAND_CONFLICT 24
#define STATUS_GCODE_WORD_REPEATED 25
#define STATUS_GCODE_NO_AXIS_WORDS 26
#define STATUS_GCODE_INVALID_LINE_NUMBER 27
#define STATUS_GCODE_VALUE_WORD_MISSING 28
#define STATUS_GCODE_UNSUPPORTED_COORD_SYS 29
#define STATUS_GCODE_G53_INVALID_MOTION_MODE 30
#define STATUS_GCODE_AXIS_WORDS_EXIST 31
#define STATUS_GCODE_NO_AXIS_WORDS_IN_PLANE 32
#define STATUS_GCODE_INVALID_TARGET 33
#define STATUS_GCODE_ARC_RADIUS_ERROR 34
#define STATUS_GCODE_NO_OFFSETS_IN_PLANE 35
#define STATUS_GCODE_UNUSED_WORDS 36
#define STATUS_GCODE_G43_DYNAMIC_AXIS_ERROR 37
#define STATUS_GCODE_MAX_VALUE_EXCEEDED 38

// Define Grbl alarm codes. Valid values (1-255). 0 is reserved.
#define ALARM_HARD_LIMIT_ERROR      EXEC_ALARM_HARD_LIMIT
#define ALARM_SOFT_LIMIT_ERROR      EXEC_ALARM_SOFT_LIMIT
#define ALARM_ABORT_CYCLE           EXEC_ALARM_ABORT_CYCLE
#define ALARM_PROBE_FAIL_INITIAL    EXEC_ALARM_PROBE_FAIL_INITIAL
#define ALARM_PROBE_FAIL_CONTACT    EXEC_ALARM_PROBE_FAIL_CONTACT
#define ALARM_HOMING_FAIL_RESET     EXEC_ALARM_HOMING_FAIL_RESET
#define ALARM_HOMING_FAIL_DOOR      EXEC_ALARM_HOMING_FAIL_DOOR
#define ALARM_HOMING_FAIL_PULLOFF   EXEC_ALARM_HOMING_FAIL_PULLOFF
#define ALARM_HOMING_FAIL_APPROACH  EXEC_ALARM_HOMING_FAIL_APPROACH

// Define Grbl feedback message codes. Valid values (0-255).
#define MESSAGE_CRITICAL_EVENT 1
#define MESSAGE_ALARM_LOCK 2
#define MESSAGE_ALARM_UNLOCK 3
#define MESSAGE_ENABLED 4
#define MESSAGE_DISABLED 5
#define MESSAGE_SAFETY_DOOR_AJAR 6
#define MESSAGE_CHECK_LIMITS 7
#define MESSAGE_PROGRAM_END 8
#define MESSAGE_RESTORE_DEFAULTS 9
#define MESSAGE_SPINDLE_RESTORE 10
#define MESSAGE_SLEEP_MODE 11

// Prints system status messages.
void report_status_message(uint8_t status_code);

// Prints system alarm messages.
void report_alarm_message(uint8_t alarm_code);

// Prints miscellaneous feedback messages.
void report_feedback_message(uint8_t message_code);

// Prints welcome message
void report_init_message();

// Prints Grbl help and current global settings
void report_grbl_help();

// Prints Grbl global settings
void report_grbl_settings();

// Prints an echo of the pre-parsed line received right before execution.
void report_echo_line_received(char *line);

// Prints realtime status report
void report_realtime_status();

// Prints recorded probe position
void report_probe_parameters();

// Prints Grbl NGC parameters (coordinate offsets, probe)
void report_ngc_parameters();

// Prints current g-code parser mode state
void report_gcode_modes();

// Prints startup line when requested and executed.
void report_startup_line(uint8_t n, char *line);
void report_execute_startup_message(char *line, uint8_t status_code);

// Prints build info and user info
void report_build_info(char *line);

#ifdef DEBUG
  void report_realtime_debug();
#endif

#endif


report.h

/*
  serial.c - Low level functions for sending and recieving bytes via the serial port
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"

#define RX_RING_BUFFER (RX_BUFFER_SIZE+1)
#define TX_RING_BUFFER (TX_BUFFER_SIZE+1)

uint8_t serial_rx_buffer[RX_RING_BUFFER];
uint8_t serial_rx_buffer_head = 0;
volatile uint8_t serial_rx_buffer_tail = 0;

uint8_t serial_tx_buffer[TX_RING_BUFFER];
uint8_t serial_tx_buffer_head = 0;
volatile uint8_t serial_tx_buffer_tail = 0;


// Returns the number of bytes available in the RX serial buffer.
uint8_t serial_get_rx_buffer_available()
{
  uint8_t rtail = serial_rx_buffer_tail; // Copy to limit multiple calls to volatile
  if (serial_rx_buffer_head >= rtail) { return(RX_BUFFER_SIZE - (serial_rx_buffer_head-rtail)); }
  return((rtail-serial_rx_buffer_head-1));
}


// Returns the number of bytes used in the RX serial buffer.
// NOTE: Deprecated. Not used unless classic status reports are enabled in config.h.
uint8_t serial_get_rx_buffer_count()
{
  uint8_t rtail = serial_rx_buffer_tail; // Copy to limit multiple calls to volatile
  if (serial_rx_buffer_head >= rtail) { return(serial_rx_buffer_head-rtail); }
  return (RX_BUFFER_SIZE - (rtail-serial_rx_buffer_head));
}


// Returns the number of bytes used in the TX serial buffer.
// NOTE: Not used except for debugging and ensuring no TX bottlenecks.
uint8_t serial_get_tx_buffer_count()
{
  uint8_t ttail = serial_tx_buffer_tail; // Copy to limit multiple calls to volatile
  if (serial_tx_buffer_head >= ttail) { return(serial_tx_buffer_head-ttail); }
  return (TX_RING_BUFFER - (ttail-serial_tx_buffer_head));
}


void serial_init()
{
  // Set baud rate
  #if BAUD_RATE < 57600
    uint16_t UBRR0_value = ((F_CPU / (8L * BAUD_RATE)) - 1)/2 ;
    UCSR0A &= ~(1 << U2X0); // baud doubler off  - Only needed on Uno XXX
  #else
    uint16_t UBRR0_value = ((F_CPU / (4L * BAUD_RATE)) - 1)/2;
    UCSR0A |= (1 << U2X0);  // baud doubler on for high baud rates, i.e. 115200
  #endif
  UBRR0H = UBRR0_value >> 8;
  UBRR0L = UBRR0_value;

  // enable rx, tx, and interrupt on complete reception of a byte
  UCSR0B |= (1<<RXEN0 | 1<<TXEN0 | 1<<RXCIE0);

  // defaults to 8-bit, no parity, 1 stop bit
}


// Writes one byte to the TX serial buffer. Called by main program.
void serial_write(uint8_t data) {
  // Calculate next head
  uint8_t next_head = serial_tx_buffer_head + 1;
  if (next_head == TX_RING_BUFFER) { next_head = 0; }

  // Wait until there is space in the buffer
  while (next_head == serial_tx_buffer_tail) {
    // TODO: Restructure st_prep_buffer() calls to be executed here during a long print.
    if (sys_rt_exec_state & EXEC_RESET) { return; } // Only check for abort to avoid an endless loop.
  }

  // Store data and advance head
  serial_tx_buffer[serial_tx_buffer_head] = data;
  serial_tx_buffer_head = next_head;

  // Enable Data Register Empty Interrupt to make sure tx-streaming is running
  UCSR0B |=  (1 << UDRIE0);
}


// Data Register Empty Interrupt handler
ISR(SERIAL_UDRE)
{
  uint8_t tail = serial_tx_buffer_tail; // Temporary serial_tx_buffer_tail (to optimize for volatile)

  // Send a byte from the buffer
  UDR0 = serial_tx_buffer[tail];

  // Update tail position
  tail++;
  if (tail == TX_RING_BUFFER) { tail = 0; }

  serial_tx_buffer_tail = tail;

  // Turn off Data Register Empty Interrupt to stop tx-streaming if this concludes the transfer
  if (tail == serial_tx_buffer_head) { UCSR0B &= ~(1 << UDRIE0); }
}


// Fetches the first byte in the serial read buffer. Called by main program.
uint8_t serial_read()
{
  uint8_t tail = serial_rx_buffer_tail; // Temporary serial_rx_buffer_tail (to optimize for volatile)
  if (serial_rx_buffer_head == tail) {
    return SERIAL_NO_DATA;
  } else {
    uint8_t data = serial_rx_buffer[tail];

    tail++;
    if (tail == RX_RING_BUFFER) { tail = 0; }
    serial_rx_buffer_tail = tail;

    return data;
  }
}


ISR(SERIAL_RX)
{
  uint8_t data = UDR0;
  uint8_t next_head;

  // Pick off realtime command characters directly from the serial stream. These characters are
  // not passed into the main buffer, but these set system state flag bits for realtime execution.
  switch (data) {
    case CMD_RESET:         mc_reset(); break; // Call motion control reset routine.
    case CMD_STATUS_REPORT: system_set_exec_state_flag(EXEC_STATUS_REPORT); break; // Set as true
    case CMD_CYCLE_START:   system_set_exec_state_flag(EXEC_CYCLE_START); break; // Set as true
    case CMD_FEED_HOLD:     system_set_exec_state_flag(EXEC_FEED_HOLD); break; // Set as true
    default :
      if (data > 0x7F) { // Real-time control characters are extended ACSII only.
        switch(data) {
          case CMD_SAFETY_DOOR:   system_set_exec_state_flag(EXEC_SAFETY_DOOR); break; // Set as true
          case CMD_JOG_CANCEL:   
            if (sys.state & STATE_JOG) { // Block all other states from invoking motion cancel.
              system_set_exec_state_flag(EXEC_MOTION_CANCEL); 
            }
            break; 
          #ifdef DEBUG
            case CMD_DEBUG_REPORT: {uint8_t sreg = SREG; cli(); bit_true(sys_rt_exec_debug,EXEC_DEBUG_REPORT); SREG = sreg;} break;
          #endif
          case CMD_FEED_OVR_RESET: system_set_exec_motion_override_flag(EXEC_FEED_OVR_RESET); break;
          case CMD_FEED_OVR_COARSE_PLUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_COARSE_PLUS); break;
          case CMD_FEED_OVR_COARSE_MINUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_COARSE_MINUS); break;
          case CMD_FEED_OVR_FINE_PLUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_FINE_PLUS); break;
          case CMD_FEED_OVR_FINE_MINUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_FINE_MINUS); break;
          case CMD_RAPID_OVR_RESET: system_set_exec_motion_override_flag(EXEC_RAPID_OVR_RESET); break;
          case CMD_RAPID_OVR_MEDIUM: system_set_exec_motion_override_flag(EXEC_RAPID_OVR_MEDIUM); break;
          case CMD_RAPID_OVR_LOW: system_set_exec_motion_override_flag(EXEC_RAPID_OVR_LOW); break;
          case CMD_SPINDLE_OVR_RESET: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_RESET); break;
          case CMD_SPINDLE_OVR_COARSE_PLUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_COARSE_PLUS); break;
          case CMD_SPINDLE_OVR_COARSE_MINUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_COARSE_MINUS); break;
          case CMD_SPINDLE_OVR_FINE_PLUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_FINE_PLUS); break;
          case CMD_SPINDLE_OVR_FINE_MINUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_FINE_MINUS); break;
          case CMD_SPINDLE_OVR_STOP: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_STOP); break;
          case CMD_COOLANT_FLOOD_OVR_TOGGLE: system_set_exec_accessory_override_flag(EXEC_COOLANT_FLOOD_OVR_TOGGLE); break;
          #ifdef ENABLE_M7
            case CMD_COOLANT_MIST_OVR_TOGGLE: system_set_exec_accessory_override_flag(EXEC_COOLANT_MIST_OVR_TOGGLE); break;
          #endif
        }
        // Throw away any unfound extended-ASCII character by not passing it to the serial buffer.
      } else { // Write character to buffer
        next_head = serial_rx_buffer_head + 1;
        if (next_head == RX_RING_BUFFER) { next_head = 0; }

        // Write data to buffer unless it is full.
        if (next_head != serial_rx_buffer_tail) {
          serial_rx_buffer[serial_rx_buffer_head] = data;
          serial_rx_buffer_head = next_head;
        }
      }
  }
}


void serial_reset_read_buffer()
{
  serial_rx_buffer_tail = serial_rx_buffer_head;
}


serial.c

/*
  serial.c - Low level functions for sending and recieving bytes via the serial port
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef serial_h
#define serial_h


#ifndef RX_BUFFER_SIZE
  #define RX_BUFFER_SIZE 128
#endif
#ifndef TX_BUFFER_SIZE
  #ifdef USE_LINE_NUMBERS
    #define TX_BUFFER_SIZE 112
  #else
    #define TX_BUFFER_SIZE 104
  #endif
#endif

#define SERIAL_NO_DATA 0xff


void serial_init();

// Writes one byte to the TX serial buffer. Called by main program.
void serial_write(uint8_t data);

// Fetches the first byte in the serial read buffer. Called by main program.
uint8_t serial_read();

// Reset and empty data in read buffer. Used by e-stop and reset.
void serial_reset_read_buffer();

// Returns the number of bytes available in the RX serial buffer.
uint8_t serial_get_rx_buffer_available();

// Returns the number of bytes used in the RX serial buffer.
// NOTE: Deprecated. Not used unless classic status reports are enabled in config.h.
uint8_t serial_get_rx_buffer_count();

// Returns the number of bytes used in the TX serial buffer.
// NOTE: Not used except for debugging and ensuring no TX bottlenecks.
uint8_t serial_get_tx_buffer_count();

#endif


serial.h

/*
  settings.c - eeprom configuration handling
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"

settings_t settings;

const __flash settings_t defaults = {\
    .pulse_microseconds = DEFAULT_STEP_PULSE_MICROSECONDS,
    .stepper_idle_lock_time = DEFAULT_STEPPER_IDLE_LOCK_TIME,
    .step_invert_mask = DEFAULT_STEPPING_INVERT_MASK,
    .dir_invert_mask = DEFAULT_DIRECTION_INVERT_MASK,
    .status_report_mask = DEFAULT_STATUS_REPORT_MASK,
    .junction_deviation = DEFAULT_JUNCTION_DEVIATION,
    .arc_tolerance = DEFAULT_ARC_TOLERANCE,
    .rpm_max = DEFAULT_SPINDLE_RPM_MAX,
    .rpm_min = DEFAULT_SPINDLE_RPM_MIN,
    .homing_dir_mask = DEFAULT_HOMING_DIR_MASK,
    .homing_feed_rate = DEFAULT_HOMING_FEED_RATE,
    .homing_seek_rate = DEFAULT_HOMING_SEEK_RATE,
    .homing_debounce_delay = DEFAULT_HOMING_DEBOUNCE_DELAY,
    .homing_pulloff = DEFAULT_HOMING_PULLOFF,
    .flags = (DEFAULT_REPORT_INCHES << BIT_REPORT_INCHES) | \
             (DEFAULT_LASER_MODE << BIT_LASER_MODE) | \
             (DEFAULT_INVERT_ST_ENABLE << BIT_INVERT_ST_ENABLE) | \
             (DEFAULT_HARD_LIMIT_ENABLE << BIT_HARD_LIMIT_ENABLE) | \
             (DEFAULT_HOMING_ENABLE << BIT_HOMING_ENABLE) | \
             (DEFAULT_SOFT_LIMIT_ENABLE << BIT_SOFT_LIMIT_ENABLE) | \
             (DEFAULT_INVERT_LIMIT_PINS << BIT_INVERT_LIMIT_PINS) | \
             (DEFAULT_INVERT_PROBE_PIN << BIT_INVERT_PROBE_PIN),
    .steps_per_mm[X_AXIS] = DEFAULT_X_STEPS_PER_MM,
    .steps_per_mm[Y_AXIS] = DEFAULT_Y_STEPS_PER_MM,
    .steps_per_mm[Z_AXIS] = DEFAULT_Z_STEPS_PER_MM,
    .max_rate[X_AXIS] = DEFAULT_X_MAX_RATE,
    .max_rate[Y_AXIS] = DEFAULT_Y_MAX_RATE,
    .max_rate[Z_AXIS] = DEFAULT_Z_MAX_RATE,
    .acceleration[X_AXIS] = DEFAULT_X_ACCELERATION,
    .acceleration[Y_AXIS] = DEFAULT_Y_ACCELERATION,
    .acceleration[Z_AXIS] = DEFAULT_Z_ACCELERATION,
    .max_travel[X_AXIS] = (-DEFAULT_X_MAX_TRAVEL),
    .max_travel[Y_AXIS] = (-DEFAULT_Y_MAX_TRAVEL),
    .max_travel[Z_AXIS] = (-DEFAULT_Z_MAX_TRAVEL)};


// Method to store startup lines into EEPROM
void settings_store_startup_line(uint8_t n, char *line)
{
  #ifdef FORCE_BUFFER_SYNC_DURING_EEPROM_WRITE
    protocol_buffer_synchronize(); // A startup line may contain a motion and be executing. 
  #endif
  uint32_t addr = n*(LINE_BUFFER_SIZE+1)+EEPROM_ADDR_STARTUP_BLOCK;
  memcpy_to_eeprom_with_checksum(addr,(char*)line, LINE_BUFFER_SIZE);
}


// Method to store build info into EEPROM
// NOTE: This function can only be called in IDLE state.
void settings_store_build_info(char *line)
{
  // Build info can only be stored when state is IDLE.
  memcpy_to_eeprom_with_checksum(EEPROM_ADDR_BUILD_INFO,(char*)line, LINE_BUFFER_SIZE);
}


// Method to store coord data parameters into EEPROM
void settings_write_coord_data(uint8_t coord_select, float *coord_data)
{
  #ifdef FORCE_BUFFER_SYNC_DURING_EEPROM_WRITE
    protocol_buffer_synchronize();
  #endif
  uint32_t addr = coord_select*(sizeof(float)*N_AXIS+1) + EEPROM_ADDR_PARAMETERS;
  memcpy_to_eeprom_with_checksum(addr,(char*)coord_data, sizeof(float)*N_AXIS);
}


// Method to store Grbl global settings struct and version number into EEPROM
// NOTE: This function can only be called in IDLE state.
void write_global_settings()
{
  eeprom_put_char(0, SETTINGS_VERSION);
  memcpy_to_eeprom_with_checksum(EEPROM_ADDR_GLOBAL, (char*)&settings, sizeof(settings_t));
}


// Method to restore EEPROM-saved Grbl global settings back to defaults.
void settings_restore(uint8_t restore_flag) {
  if (restore_flag & SETTINGS_RESTORE_DEFAULTS) {    
    settings = defaults;
    write_global_settings();
  }

  if (restore_flag & SETTINGS_RESTORE_PARAMETERS) {
    uint8_t idx;
    float coord_data[N_AXIS];
    memset(&coord_data, 0, sizeof(coord_data));
    for (idx=0; idx <= SETTING_INDEX_NCOORD; idx++) { settings_write_coord_data(idx, coord_data); }
  }

  if (restore_flag & SETTINGS_RESTORE_STARTUP_LINES) {
    #if N_STARTUP_LINE > 0
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK, 0);
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK+1, 0); // Checksum
    #endif
    #if N_STARTUP_LINE > 1
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK+(LINE_BUFFER_SIZE+1), 0);
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK+(LINE_BUFFER_SIZE+2), 0); // Checksum
    #endif
  }

  if (restore_flag & SETTINGS_RESTORE_BUILD_INFO) {
    eeprom_put_char(EEPROM_ADDR_BUILD_INFO , 0);
    eeprom_put_char(EEPROM_ADDR_BUILD_INFO+1 , 0); // Checksum
  }
}


// Reads startup line from EEPROM. Updated pointed line string data.
uint8_t settings_read_startup_line(uint8_t n, char *line)
{
  uint32_t addr = n*(LINE_BUFFER_SIZE+1)+EEPROM_ADDR_STARTUP_BLOCK;
  if (!(memcpy_from_eeprom_with_checksum((char*)line, addr, LINE_BUFFER_SIZE))) {
    // Reset line with default value
    line[0] = 0; // Empty line
    settings_store_startup_line(n, line);
    return(false);
  }
  return(true);
}


// Reads startup line from EEPROM. Updated pointed line string data.
uint8_t settings_read_build_info(char *line)
{
  if (!(memcpy_from_eeprom_with_checksum((char*)line, EEPROM_ADDR_BUILD_INFO, LINE_BUFFER_SIZE))) {
    // Reset line with default value
    line[0] = 0; // Empty line
    settings_store_build_info(line);
    return(false);
  }
  return(true);
}


// Read selected coordinate data from EEPROM. Updates pointed coord_data value.
uint8_t settings_read_coord_data(uint8_t coord_select, float *coord_data)
{
  uint32_t addr = coord_select*(sizeof(float)*N_AXIS+1) + EEPROM_ADDR_PARAMETERS;
  if (!(memcpy_from_eeprom_with_checksum((char*)coord_data, addr, sizeof(float)*N_AXIS))) {
    // Reset with default zero vector
    clear_vector_float(coord_data);
    settings_write_coord_data(coord_select,coord_data);
    return(false);
  }
  return(true);
}


// Reads Grbl global settings struct from EEPROM.
uint8_t read_global_settings() {
  // Check version-byte of eeprom
  uint8_t version = eeprom_get_char(0);
  if (version == SETTINGS_VERSION) {
    // Read settings-record and check checksum
    if (!(memcpy_from_eeprom_with_checksum((char*)&settings, EEPROM_ADDR_GLOBAL, sizeof(settings_t)))) {
      return(false);
    }
  } else {
    return(false);
  }
  return(true);
}


// A helper method to set settings from command line
uint8_t settings_store_global_setting(uint8_t parameter, float value) {
  if (value < 0.0) { return(STATUS_NEGATIVE_VALUE); }
  if (parameter >= AXIS_SETTINGS_START_VAL) {
    // Store axis configuration. Axis numbering sequence set by AXIS_SETTING defines.
    // NOTE: Ensure the setting index corresponds to the report.c settings printout.
    parameter -= AXIS_SETTINGS_START_VAL;
    uint8_t set_idx = 0;
    while (set_idx < AXIS_N_SETTINGS) {
      if (parameter < N_AXIS) {
        // Valid axis setting found.
        switch (set_idx) {
          case 0:
            #ifdef MAX_STEP_RATE_HZ
              if (value*settings.max_rate[parameter] > (MAX_STEP_RATE_HZ*60.0)) { return(STATUS_MAX_STEP_RATE_EXCEEDED); }
            #endif
            settings.steps_per_mm[parameter] = value;
            break;
          case 1:
            #ifdef MAX_STEP_RATE_HZ
              if (value*settings.steps_per_mm[parameter] > (MAX_STEP_RATE_HZ*60.0)) {  return(STATUS_MAX_STEP_RATE_EXCEEDED); }
            #endif
            settings.max_rate[parameter] = value;
            break;
          case 2: settings.acceleration[parameter] = value*60*60; break; // Convert to mm/min^2 for grbl internal use.
          case 3: settings.max_travel[parameter] = -value; break;  // Store as negative for grbl internal use.
        }
        break; // Exit while-loop after setting has been configured and proceed to the EEPROM write call.
      } else {
        set_idx++;
        // If axis index greater than N_AXIS or setting index greater than number of axis settings, error out.
        if ((parameter < AXIS_SETTINGS_INCREMENT) || (set_idx == AXIS_N_SETTINGS)) { return(STATUS_INVALID_STATEMENT); }
        parameter -= AXIS_SETTINGS_INCREMENT;
      }
    }
  } else {
    // Store non-axis Grbl settings
    uint8_t int_value = trunc(value);
    switch(parameter) {
      case 0:
        if (int_value < 3) { return(STATUS_SETTING_STEP_PULSE_MIN); }
        settings.pulse_microseconds = int_value; break;
      case 1: settings.stepper_idle_lock_time = int_value; break;
      case 2:
        settings.step_invert_mask = int_value;
        st_generate_step_dir_invert_masks(); // Regenerate step and direction port invert masks.
        break;
      case 3:
        settings.dir_invert_mask = int_value;
        st_generate_step_dir_invert_masks(); // Regenerate step and direction port invert masks.
        break;
      case 4: // Reset to ensure change. Immediate re-init may cause problems.
        if (int_value) { settings.flags |= BITFLAG_INVERT_ST_ENABLE; }
        else { settings.flags &= ~BITFLAG_INVERT_ST_ENABLE; }
        break;
      case 5: // Reset to ensure change. Immediate re-init may cause problems.
        if (int_value) { settings.flags |= BITFLAG_INVERT_LIMIT_PINS; }
        else { settings.flags &= ~BITFLAG_INVERT_LIMIT_PINS; }
        break;
      case 6: // Reset to ensure change. Immediate re-init may cause problems.
        if (int_value) { settings.flags |= BITFLAG_INVERT_PROBE_PIN; }
        else { settings.flags &= ~BITFLAG_INVERT_PROBE_PIN; }
        probe_configure_invert_mask(false);
        break;
      case 10: settings.status_report_mask = int_value; break;
      case 11: settings.junction_deviation = value; break;
      case 12: settings.arc_tolerance = value; break;
      case 13:
        if (int_value) { settings.flags |= BITFLAG_REPORT_INCHES; }
        else { settings.flags &= ~BITFLAG_REPORT_INCHES; }
        system_flag_wco_change(); // Make sure WCO is immediately updated.
        break;
      case 20:
        if (int_value) {
          if (bit_isfalse(settings.flags, BITFLAG_HOMING_ENABLE)) { return(STATUS_SOFT_LIMIT_ERROR); }
          settings.flags |= BITFLAG_SOFT_LIMIT_ENABLE;
        } else { settings.flags &= ~BITFLAG_SOFT_LIMIT_ENABLE; }
        break;
      case 21:
        if (int_value) { settings.flags |= BITFLAG_HARD_LIMIT_ENABLE; }
        else { settings.flags &= ~BITFLAG_HARD_LIMIT_ENABLE; }
        limits_init(); // Re-init to immediately change. NOTE: Nice to have but could be problematic later.
        break;
      case 22:
        if (int_value) { settings.flags |= BITFLAG_HOMING_ENABLE; }
        else {
          settings.flags &= ~BITFLAG_HOMING_ENABLE;
          settings.flags &= ~BITFLAG_SOFT_LIMIT_ENABLE; // Force disable soft-limits.
        }
        break;
      case 23: settings.homing_dir_mask = int_value; break;
      case 24: settings.homing_feed_rate = value; break;
      case 25: settings.homing_seek_rate = value; break;
      case 26: settings.homing_debounce_delay = int_value; break;
      case 27: settings.homing_pulloff = value; break;
      case 30: settings.rpm_max = value; spindle_init(); break; // Re-initialize spindle rpm calibration
      case 31: settings.rpm_min = value; spindle_init(); break; // Re-initialize spindle rpm calibration
      case 32:
        #ifdef VARIABLE_SPINDLE
          if (int_value) { settings.flags |= BITFLAG_LASER_MODE; }
          else { settings.flags &= ~BITFLAG_LASER_MODE; }
        #else
          return(STATUS_SETTING_DISABLED_LASER);
        #endif
        break;
      default:
        return(STATUS_INVALID_STATEMENT);
    }
  }
  write_global_settings();
  return(STATUS_OK);
}


// Initialize the config subsystem
void settings_init() {
  if(!read_global_settings()) {
    report_status_message(STATUS_SETTING_READ_FAIL);
    settings_restore(SETTINGS_RESTORE_ALL); // Force restore all EEPROM data.
    report_grbl_settings();
  }
}


// Returns step pin mask according to Grbl internal axis indexing.
uint8_t get_step_pin_mask(uint8_t axis_idx)
{
  if ( axis_idx == X_AXIS ) { return((1<<X_STEP_BIT)); }
  if ( axis_idx == Y_AXIS ) { return((1<<Y_STEP_BIT)); }
  return((1<<Z_STEP_BIT));
}


// Returns direction pin mask according to Grbl internal axis indexing.
uint8_t get_direction_pin_mask(uint8_t axis_idx)
{
  if ( axis_idx == X_AXIS ) { return((1<<X_DIRECTION_BIT)); }
  if ( axis_idx == Y_AXIS ) { return((1<<Y_DIRECTION_BIT)); }
  return((1<<Z_DIRECTION_BIT));
}


// Returns limit pin mask according to Grbl internal axis indexing.
uint8_t get_limit_pin_mask(uint8_t axis_idx)
{
  if ( axis_idx == X_AXIS ) { return((1<<X_LIMIT_BIT)); }
  if ( axis_idx == Y_AXIS ) { return((1<<Y_LIMIT_BIT)); }
  return((1<<Z_LIMIT_BIT));
}


settings.c

/*
  settings.h - eeprom configuration handling
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef settings_h
#define settings_h

#include "grbl.h"


// Version of the EEPROM data. Will be used to migrate existing data from older versions of Grbl
// when firmware is upgraded. Always stored in byte 0 of eeprom
#define SETTINGS_VERSION 10  // NOTE: Check settings_reset() when moving to next version.

// Define bit flag masks for the boolean settings in settings.flag.
#define BIT_REPORT_INCHES      0
#define BIT_LASER_MODE         1
#define BIT_INVERT_ST_ENABLE   2
#define BIT_HARD_LIMIT_ENABLE  3
#define BIT_HOMING_ENABLE      4
#define BIT_SOFT_LIMIT_ENABLE  5
#define BIT_INVERT_LIMIT_PINS  6
#define BIT_INVERT_PROBE_PIN   7

#define BITFLAG_REPORT_INCHES      bit(BIT_REPORT_INCHES)
#define BITFLAG_LASER_MODE         bit(BIT_LASER_MODE)
#define BITFLAG_INVERT_ST_ENABLE   bit(BIT_INVERT_ST_ENABLE)
#define BITFLAG_HARD_LIMIT_ENABLE  bit(BIT_HARD_LIMIT_ENABLE)
#define BITFLAG_HOMING_ENABLE      bit(BIT_HOMING_ENABLE)
#define BITFLAG_SOFT_LIMIT_ENABLE  bit(BIT_SOFT_LIMIT_ENABLE)
#define BITFLAG_INVERT_LIMIT_PINS  bit(BIT_INVERT_LIMIT_PINS)
#define BITFLAG_INVERT_PROBE_PIN   bit(BIT_INVERT_PROBE_PIN)

// Define status reporting boolean enable bit flags in settings.status_report_mask
#define BITFLAG_RT_STATUS_POSITION_TYPE     bit(0)
#define BITFLAG_RT_STATUS_BUFFER_STATE      bit(1)

// Define settings restore bitflags.
#define SETTINGS_RESTORE_DEFAULTS bit(0)
#define SETTINGS_RESTORE_PARAMETERS bit(1)
#define SETTINGS_RESTORE_STARTUP_LINES bit(2)
#define SETTINGS_RESTORE_BUILD_INFO bit(3)
#ifndef SETTINGS_RESTORE_ALL
  #define SETTINGS_RESTORE_ALL 0xFF // All bitflags
#endif

// Define EEPROM memory address location values for Grbl settings and parameters
// NOTE: The Atmega328p has 1KB EEPROM. The upper half is reserved for parameters and
// the startup script. The lower half contains the global settings and space for future
// developments.
#define EEPROM_ADDR_GLOBAL         1U
#define EEPROM_ADDR_PARAMETERS     512U
#define EEPROM_ADDR_STARTUP_BLOCK  768U
#define EEPROM_ADDR_BUILD_INFO     942U

// Define EEPROM address indexing for coordinate parameters
#define N_COORDINATE_SYSTEM 6  // Number of supported work coordinate systems (from index 1)
#define SETTING_INDEX_NCOORD N_COORDINATE_SYSTEM+1 // Total number of system stored (from index 0)
// NOTE: Work coordinate indices are (0=G54, 1=G55, ... , 6=G59)
#define SETTING_INDEX_G28    N_COORDINATE_SYSTEM    // Home position 1
#define SETTING_INDEX_G30    N_COORDINATE_SYSTEM+1  // Home position 2
// #define SETTING_INDEX_G92    N_COORDINATE_SYSTEM+2  // Coordinate offset (G92.2,G92.3 not supported)

// Define Grbl axis settings numbering scheme. Starts at START_VAL, every INCREMENT, over N_SETTINGS.
#define AXIS_N_SETTINGS          4
#define AXIS_SETTINGS_START_VAL  100 // NOTE: Reserving settings values >= 100 for axis settings. Up to 255.
#define AXIS_SETTINGS_INCREMENT  10  // Must be greater than the number of axis settings

// Global persistent settings (Stored from byte EEPROM_ADDR_GLOBAL onwards)
typedef struct {
  // Axis settings
  float steps_per_mm[N_AXIS];
  float max_rate[N_AXIS];
  float acceleration[N_AXIS];
  float max_travel[N_AXIS];

  // Remaining Grbl settings
  uint8_t pulse_microseconds;
  uint8_t step_invert_mask;
  uint8_t dir_invert_mask;
  uint8_t stepper_idle_lock_time; // If max value 255, steppers do not disable.
  uint8_t status_report_mask; // Mask to indicate desired report data.
  float junction_deviation;
  float arc_tolerance;

  float rpm_max;
  float rpm_min;

  uint8_t flags;  // Contains default boolean settings

  uint8_t homing_dir_mask;
  float homing_feed_rate;
  float homing_seek_rate;
  uint16_t homing_debounce_delay;
  float homing_pulloff;
} settings_t;
extern settings_t settings;

// Initialize the configuration subsystem (load settings from EEPROM)
void settings_init();

// Helper function to clear and restore EEPROM defaults
void settings_restore(uint8_t restore_flag);

// A helper method to set new settings from command line
uint8_t settings_store_global_setting(uint8_t parameter, float value);

// Stores the protocol line variable as a startup line in EEPROM
void settings_store_startup_line(uint8_t n, char *line);

// Reads an EEPROM startup line to the protocol line variable
uint8_t settings_read_startup_line(uint8_t n, char *line);

// Stores build info user-defined string
void settings_store_build_info(char *line);

// Reads build info user-defined string
uint8_t settings_read_build_info(char *line);

// Writes selected coordinate data to EEPROM
void settings_write_coord_data(uint8_t coord_select, float *coord_data);

// Reads selected coordinate data from EEPROM
uint8_t settings_read_coord_data(uint8_t coord_select, float *coord_data);

// Returns the step pin mask according to Grbl's internal axis numbering
uint8_t get_step_pin_mask(uint8_t i);

// Returns the direction pin mask according to Grbl's internal axis numbering
uint8_t get_direction_pin_mask(uint8_t i);

// Returns the limit pin mask according to Grbl's internal axis numbering
uint8_t get_limit_pin_mask(uint8_t i);


#endif


settings.h

/*
  spindle_control.c - spindle control methods
  Part of Grbl

  Copyright (c) 2012-2017 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


#ifdef VARIABLE_SPINDLE
  static float pwm_gradient; // Precalulated value to speed up rpm to PWM conversions.
#endif


void spindle_init()
{
  #ifdef VARIABLE_SPINDLE
    // Configure variable spindle PWM and enable pin, if requried. On the Uno, PWM and enable are
    // combined unless configured otherwise.
    SPINDLE_PWM_DDR |= (1<<SPINDLE_PWM_BIT); // Configure as PWM output pin.
    SPINDLE_TCCRA_REGISTER = SPINDLE_TCCRA_INIT_MASK; // Configure PWM output compare timer
    SPINDLE_TCCRB_REGISTER = SPINDLE_TCCRB_INIT_MASK;
    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
      SPINDLE_ENABLE_DDR |= (1<<SPINDLE_ENABLE_BIT); // Configure as output pin.
    #else
      #ifndef ENABLE_DUAL_AXIS
        SPINDLE_DIRECTION_DDR |= (1<<SPINDLE_DIRECTION_BIT); // Configure as output pin.
      #endif
    #endif
    pwm_gradient = SPINDLE_PWM_RANGE/(settings.rpm_max-settings.rpm_min);
  #else
    SPINDLE_ENABLE_DDR |= (1<<SPINDLE_ENABLE_BIT); // Configure as output pin.
    #ifndef ENABLE_DUAL_AXIS
      SPINDLE_DIRECTION_DDR |= (1<<SPINDLE_DIRECTION_BIT); // Configure as output pin.
    #endif
  #endif

  spindle_stop();
}


uint8_t spindle_get_state()
{
  #ifdef VARIABLE_SPINDLE
    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
      // No spindle direction output pin. 
      #ifdef INVERT_SPINDLE_ENABLE_PIN
        if (bit_isfalse(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) { return(SPINDLE_STATE_CW); }
      #else
        if (bit_istrue(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) { return(SPINDLE_STATE_CW); }
      #endif
    #else
      if (SPINDLE_TCCRA_REGISTER & (1<<SPINDLE_COMB_BIT)) { // Check if PWM is enabled.
        #ifdef ENABLE_DUAL_AXIS
          return(SPINDLE_STATE_CW);
        #else
          if (SPINDLE_DIRECTION_PORT & (1<<SPINDLE_DIRECTION_BIT)) { return(SPINDLE_STATE_CCW); }
          else { return(SPINDLE_STATE_CW); }
        #endif
      }
    #endif
  #else
    #ifdef INVERT_SPINDLE_ENABLE_PIN
      if (bit_isfalse(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) { 
    #else
      if (bit_istrue(SPINDLE_ENABLE_PORT,(1<<SPINDLE_ENABLE_BIT))) {
    #endif
      #ifdef ENABLE_DUAL_AXIS    
        return(SPINDLE_STATE_CW);
      #else
        if (SPINDLE_DIRECTION_PORT & (1<<SPINDLE_DIRECTION_BIT)) { return(SPINDLE_STATE_CCW); }
        else { return(SPINDLE_STATE_CW); }
      #endif
    }
  #endif
  return(SPINDLE_STATE_DISABLE);
}


// Disables the spindle and sets PWM output to zero when PWM variable spindle speed is enabled.
// Called by various main program and ISR routines. Keep routine small, fast, and efficient.
// Called by spindle_init(), spindle_set_speed(), spindle_set_state(), and mc_reset().
void spindle_stop()
{
  #ifdef VARIABLE_SPINDLE
    SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
      #ifdef INVERT_SPINDLE_ENABLE_PIN
        SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);  // Set pin to high
      #else
        SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT); // Set pin to low
      #endif
    #endif
  #else
    #ifdef INVERT_SPINDLE_ENABLE_PIN
      SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);  // Set pin to high
    #else
      SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT); // Set pin to low
    #endif
  #endif
}


#ifdef VARIABLE_SPINDLE
  // Sets spindle speed PWM output and enable pin, if configured. Called by spindle_set_state()
  // and stepper ISR. Keep routine small and efficient.
  void spindle_set_speed(uint8_t pwm_value)
  {
    SPINDLE_OCR_REGISTER = pwm_value; // Set PWM output level.
    #ifdef SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED
      if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
        spindle_stop();
      } else {
        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
        #ifdef INVERT_SPINDLE_ENABLE_PIN
          SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
        #else
          SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);
        #endif
      }
    #else
      if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
        SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
      } else {
        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
      }
    #endif
  }


  #ifdef ENABLE_PIECEWISE_LINEAR_SPINDLE
  
    // Called by spindle_set_state() and step segment generator. Keep routine small and efficient.
    uint8_t spindle_compute_pwm_value(float rpm) // 328p PWM register is 8-bit.
    {
      uint8_t pwm_value;
      rpm *= (0.010*sys.spindle_speed_ovr); // Scale by spindle speed override value.
      // Calculate PWM register value based on rpm max/min settings and programmed rpm.
      if ((settings.rpm_min >= settings.rpm_max) || (rpm >= RPM_MAX)) {
        rpm = RPM_MAX;
        pwm_value = SPINDLE_PWM_MAX_VALUE;
      } else if (rpm <= RPM_MIN) {
        if (rpm == 0.0) { // S0 disables spindle
          pwm_value = SPINDLE_PWM_OFF_VALUE;
        } else {
          rpm = RPM_MIN;
          pwm_value = SPINDLE_PWM_MIN_VALUE;
        }
      } else {
        // Compute intermediate PWM value with linear spindle speed model via piecewise linear fit model.
        #if (N_PIECES > 3)
          if (rpm > RPM_POINT34) {
            pwm_value = floor(RPM_LINE_A4*rpm - RPM_LINE_B4);
          } else 
        #endif
        #if (N_PIECES > 2)
          if (rpm > RPM_POINT23) {
            pwm_value = floor(RPM_LINE_A3*rpm - RPM_LINE_B3);
          } else 
        #endif
        #if (N_PIECES > 1)
          if (rpm > RPM_POINT12) {
            pwm_value = floor(RPM_LINE_A2*rpm - RPM_LINE_B2);
          } else 
        #endif
        {
          pwm_value = floor(RPM_LINE_A1*rpm - RPM_LINE_B1);
        }
      }
      sys.spindle_speed = rpm;
      return(pwm_value);
    }
    
  #else 
  
    // Called by spindle_set_state() and step segment generator. Keep routine small and efficient.
    uint8_t spindle_compute_pwm_value(float rpm) // 328p PWM register is 8-bit.
    {
      uint8_t pwm_value;
      rpm *= (0.010*sys.spindle_speed_ovr); // Scale by spindle speed override value.
      // Calculate PWM register value based on rpm max/min settings and programmed rpm.
      if ((settings.rpm_min >= settings.rpm_max) || (rpm >= settings.rpm_max)) {
        // No PWM range possible. Set simple on/off spindle control pin state.
        sys.spindle_speed = settings.rpm_max;
        pwm_value = SPINDLE_PWM_MAX_VALUE;
      } else if (rpm <= settings.rpm_min) {
        if (rpm == 0.0) { // S0 disables spindle
          sys.spindle_speed = 0.0;
          pwm_value = SPINDLE_PWM_OFF_VALUE;
        } else { // Set minimum PWM output
          sys.spindle_speed = settings.rpm_min;
          pwm_value = SPINDLE_PWM_MIN_VALUE;
        }
      } else { 
        // Compute intermediate PWM value with linear spindle speed model.
        // NOTE: A nonlinear model could be installed here, if required, but keep it VERY light-weight.
        sys.spindle_speed = rpm;
        pwm_value = floor((rpm-settings.rpm_min)*pwm_gradient) + SPINDLE_PWM_MIN_VALUE;
      }
      return(pwm_value);
    }
    
  #endif
#endif


// Immediately sets spindle running state with direction and spindle rpm via PWM, if enabled.
// Called by g-code parser spindle_sync(), parking retract and restore, g-code program end,
// sleep, and spindle stop override.
#ifdef VARIABLE_SPINDLE
  void spindle_set_state(uint8_t state, float rpm)
#else
  void _spindle_set_state(uint8_t state)
#endif
{
  if (sys.abort) { return; } // Block during abort.

  if (state == SPINDLE_DISABLE) { // Halt or set spindle direction and rpm.
  
    #ifdef VARIABLE_SPINDLE
      sys.spindle_speed = 0.0;
    #endif
    spindle_stop();
  
  } else {
    
    #if !defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && !defined(ENABLE_DUAL_AXIS)
      if (state == SPINDLE_ENABLE_CW) {
        SPINDLE_DIRECTION_PORT &= ~(1<<SPINDLE_DIRECTION_BIT);
      } else {
        SPINDLE_DIRECTION_PORT |= (1<<SPINDLE_DIRECTION_BIT);
      }
    #endif
  
    #ifdef VARIABLE_SPINDLE
      // NOTE: Assumes all calls to this function is when Grbl is not moving or must remain off.
      if (settings.flags & BITFLAG_LASER_MODE) { 
        if (state == SPINDLE_ENABLE_CCW) { rpm = 0.0; } // TODO: May need to be rpm_min*(100/MAX_SPINDLE_SPEED_OVERRIDE);
      }
      spindle_set_speed(spindle_compute_pwm_value(rpm));
    #endif
    #if (defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) && \
        !defined(SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED)) || !defined(VARIABLE_SPINDLE)
      // NOTE: Without variable spindle, the enable bit should just turn on or off, regardless
      // if the spindle speed value is zero, as its ignored anyhow.
      #ifdef INVERT_SPINDLE_ENABLE_PIN
        SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
      #else
        SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);
      #endif    
    #endif
  
  }
  
  sys.report_ovr_counter = 0; // Set to report change immediately
}


// G-code parser entry-point for setting spindle state. Forces a planner buffer sync and bails 
// if an abort or check-mode is active.
#ifdef VARIABLE_SPINDLE
  void spindle_sync(uint8_t state, float rpm)
  {
    if (sys.state == STATE_CHECK_MODE) { return; }
    protocol_buffer_synchronize(); // Empty planner buffer to ensure spindle is set when programmed.
    spindle_set_state(state,rpm);
  }
#else
  void _spindle_sync(uint8_t state)
  {
    if (sys.state == STATE_CHECK_MODE) { return; }
    protocol_buffer_synchronize(); // Empty planner buffer to ensure spindle is set when programmed.
    _spindle_set_state(state);
  }
#endif


spindle_control.c

/*
  spindle_control.h - spindle control methods
  Part of Grbl

  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef spindle_control_h
#define spindle_control_h

#define SPINDLE_NO_SYNC false
#define SPINDLE_FORCE_SYNC true

#define SPINDLE_STATE_DISABLE  0  // Must be zero.
#define SPINDLE_STATE_CW       bit(0)
#define SPINDLE_STATE_CCW      bit(1)


// Initializes spindle pins and hardware PWM, if enabled.
void spindle_init();

// Returns current spindle output state. Overrides may alter it from programmed states.
uint8_t spindle_get_state();

// Called by g-code parser when setting spindle state and requires a buffer sync.
// Immediately sets spindle running state with direction and spindle rpm via PWM, if enabled.
// Called by spindle_sync() after sync and parking motion/spindle stop override during restore.
#ifdef VARIABLE_SPINDLE

  // Called by g-code parser when setting spindle state and requires a buffer sync.
  void spindle_sync(uint8_t state, float rpm);

  // Sets spindle running state with direction, enable, and spindle PWM.
  void spindle_set_state(uint8_t state, float rpm); 
  
  // Sets spindle PWM quickly for stepper ISR. Also called by spindle_set_state().
  // NOTE: 328p PWM register is 8-bit.
  void spindle_set_speed(uint8_t pwm_value);
  
  // Computes 328p-specific PWM register value for the given RPM for quick updating.
  uint8_t spindle_compute_pwm_value(float rpm);
  
#else
  
  // Called by g-code parser when setting spindle state and requires a buffer sync.
  #define spindle_sync(state, rpm) _spindle_sync(state)
  void _spindle_sync(uint8_t state);

  // Sets spindle running state with direction and enable.
  #define spindle_set_state(state, rpm) _spindle_set_state(state)
  void _spindle_set_state(uint8_t state);

#endif

// Stop and start spindle routines. Called by all spindle routines and stepper ISR.
void spindle_stop();


#endif


spindle_control.h

stepper.c

/*
  stepper.h - stepper motor driver: executes motion plans of planner.c using the stepper motors
  Part of Grbl

  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef stepper_h
#define stepper_h

#ifndef SEGMENT_BUFFER_SIZE
  #define SEGMENT_BUFFER_SIZE 6
#endif

// Initialize and setup the stepper motor subsystem
void stepper_init();

// Enable steppers, but cycle does not start unless called by motion control or realtime command.
void st_wake_up();

// Immediately disables steppers
void st_go_idle();

// Generate the step and direction port invert masks.
void st_generate_step_dir_invert_masks();

// Reset the stepper subsystem variables
void st_reset();

// Changes the run state of the step segment buffer to execute the special parking motion.
void st_parking_setup_buffer();

// Restores the step segment buffer to the normal run state after a parking motion.
void st_parking_restore_buffer();

// Reloads step segment buffer. Called continuously by realtime execution system.
void st_prep_buffer();

// Called by planner_recalculate() when the executing block is updated by the new plan.
void st_update_plan_block_parameters();

// Called by realtime status reporting if realtime rate reporting is enabled in config.h.
float st_get_realtime_rate();

#endif


stepper.h

/*
  system.c - Handles system level commands and real-time processes
  Part of Grbl

  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "grbl.h"


void system_init()
{
  CONTROL_DDR &= ~(CONTROL_MASK); // Configure as input pins
  #ifdef DISABLE_CONTROL_PIN_PULL_UP
    CONTROL_PORT &= ~(CONTROL_MASK); // Normal low operation. Requires external pull-down.
  #else
    CONTROL_PORT |= CONTROL_MASK;   // Enable internal pull-up resistors. Normal high operation.
  #endif
  CONTROL_PCMSK |= CONTROL_MASK;  // Enable specific pins of the Pin Change Interrupt
  PCICR |= (1 << CONTROL_INT);   // Enable Pin Change Interrupt
}


// Returns control pin state as a uint8 bitfield. Each bit indicates the input pin state, where
// triggered is 1 and not triggered is 0. Invert mask is applied. Bitfield organization is
// defined by the CONTROL_PIN_INDEX in the header file.
uint8_t system_control_get_state()
{
  uint8_t control_state = 0;
  uint8_t pin = (CONTROL_PIN & CONTROL_MASK) ^ CONTROL_MASK;
  #ifdef INVERT_CONTROL_PIN_MASK
    pin ^= INVERT_CONTROL_PIN_MASK;
  #endif
  if (pin) {
    #ifdef ENABLE_SAFETY_DOOR_INPUT_PIN
      if (bit_istrue(pin,(1<<CONTROL_SAFETY_DOOR_BIT))) { control_state |= CONTROL_PIN_INDEX_SAFETY_DOOR; }
    #else
      if (bit_istrue(pin,(1<<CONTROL_FEED_HOLD_BIT))) { control_state |= CONTROL_PIN_INDEX_FEED_HOLD; }
    #endif
    if (bit_istrue(pin,(1<<CONTROL_RESET_BIT))) { control_state |= CONTROL_PIN_INDEX_RESET; }
    if (bit_istrue(pin,(1<<CONTROL_CYCLE_START_BIT))) { control_state |= CONTROL_PIN_INDEX_CYCLE_START; }
  }
  return(control_state);
}


// Pin change interrupt for pin-out commands, i.e. cycle start, feed hold, and reset. Sets
// only the realtime command execute variable to have the main program execute these when
// its ready. This works exactly like the character-based realtime commands when picked off
// directly from the incoming serial data stream.
ISR(CONTROL_INT_vect)
{
  uint8_t pin = system_control_get_state();
  if (pin) {
    if (bit_istrue(pin,CONTROL_PIN_INDEX_RESET)) {
      mc_reset();
    }
    if (bit_istrue(pin,CONTROL_PIN_INDEX_CYCLE_START)) {
      bit_true(sys_rt_exec_state, EXEC_CYCLE_START);
    }
    #ifndef ENABLE_SAFETY_DOOR_INPUT_PIN
      if (bit_istrue(pin,CONTROL_PIN_INDEX_FEED_HOLD)) {
        bit_true(sys_rt_exec_state, EXEC_FEED_HOLD);
    #else
      if (bit_istrue(pin,CONTROL_PIN_INDEX_SAFETY_DOOR)) {
        bit_true(sys_rt_exec_state, EXEC_SAFETY_DOOR);
    #endif
    }
  }
}


// Returns if safety door is ajar(T) or closed(F), based on pin state.
uint8_t system_check_safety_door_ajar()
{
  #ifdef ENABLE_SAFETY_DOOR_INPUT_PIN
    return(system_control_get_state() & CONTROL_PIN_INDEX_SAFETY_DOOR);
  #else
    return(false); // Input pin not enabled, so just return that it's closed.
  #endif
}


// Executes user startup script, if stored.
void system_execute_startup(char *line)
{
  uint8_t n;
  for (n=0; n < N_STARTUP_LINE; n++) {
    if (!(settings_read_startup_line(n, line))) {
      line[0] = 0;
      report_execute_startup_message(line,STATUS_SETTING_READ_FAIL);
    } else {
      if (line[0] != 0) {
        uint8_t status_code = gc_execute_line(line);
        report_execute_startup_message(line,status_code);
      }
    }
  }
}


// Directs and executes one line of formatted input from protocol_process. While mostly
// incoming streaming g-code blocks, this also executes Grbl internal commands, such as
// settings, initiating the homing cycle, and toggling switch states. This differs from
// the realtime command module by being susceptible to when Grbl is ready to execute the
// next line during a cycle, so for switches like block delete, the switch only effects
// the lines that are processed afterward, not necessarily real-time during a cycle,
// since there are motions already stored in the buffer. However, this 'lag' should not
// be an issue, since these commands are not typically used during a cycle.
uint8_t system_execute_line(char *line)
{
  uint8_t char_counter = 1;
  uint8_t helper_var = 0; // Helper variable
  float parameter, value;
  switch( line[char_counter] ) {
    case 0 : report_grbl_help(); break;
    case 'J' : // Jogging
      // Execute only if in IDLE or JOG states.
      if (sys.state != STATE_IDLE && sys.state != STATE_JOG) { return(STATUS_IDLE_ERROR); }
      if(line[2] != '=') { return(STATUS_INVALID_STATEMENT); }
      return(gc_execute_line(line)); // NOTE: $J= is ignored inside g-code parser and used to detect jog motions.
      break;
    case '$': case 'G': case 'C': case 'X':
      if ( line[2] != 0 ) { return(STATUS_INVALID_STATEMENT); }
      switch( line[1] ) {
        case '$' : // Prints Grbl settings
          if ( sys.state & (STATE_CYCLE | STATE_HOLD) ) { return(STATUS_IDLE_ERROR); } // Block during cycle. Takes too long to print.
          else { report_grbl_settings(); }
          break;
        case 'G' : // Prints gcode parser state
          // TODO: Move this to realtime commands for GUIs to request this data during suspend-state.
          report_gcode_modes();
          break;
        case 'C' : // Set check g-code mode [IDLE/CHECK]
          // Perform reset when toggling off. Check g-code mode should only work if Grbl
          // is idle and ready, regardless of alarm locks. This is mainly to keep things
          // simple and consistent.
          if ( sys.state == STATE_CHECK_MODE ) {
            mc_reset();
            report_feedback_message(MESSAGE_DISABLED);
          } else {
            if (sys.state) { return(STATUS_IDLE_ERROR); } // Requires no alarm mode.
            sys.state = STATE_CHECK_MODE;
            report_feedback_message(MESSAGE_ENABLED);
          }
          break;
        case 'X' : // Disable alarm lock [ALARM]
          if (sys.state == STATE_ALARM) {
            // Block if safety door is ajar.
            if (system_check_safety_door_ajar()) { return(STATUS_CHECK_DOOR); }
            report_feedback_message(MESSAGE_ALARM_UNLOCK);
            sys.state = STATE_IDLE;
            // Don't run startup script. Prevents stored moves in startup from causing accidents.
          } // Otherwise, no effect.
          break;
      }
      break;
    default :
      // Block any system command that requires the state as IDLE/ALARM. (i.e. EEPROM, homing)
      if ( !(sys.state == STATE_IDLE || sys.state == STATE_ALARM) ) { return(STATUS_IDLE_ERROR); }
      switch( line[1] ) {
        case '#' : // Print Grbl NGC parameters
          if ( line[2] != 0 ) { return(STATUS_INVALID_STATEMENT); }
          else { report_ngc_parameters(); }
          break;
        case 'H' : // Perform homing cycle [IDLE/ALARM]
          if (bit_isfalse(settings.flags,BITFLAG_HOMING_ENABLE)) {return(STATUS_SETTING_DISABLED); }
          if (system_check_safety_door_ajar()) { return(STATUS_CHECK_DOOR); } // Block if safety door is ajar.
          sys.state = STATE_HOMING; // Set system state variable
          if (line[2] == 0) {
            mc_homing_cycle(HOMING_CYCLE_ALL);
          #ifdef HOMING_SINGLE_AXIS_COMMANDS
            } else if (line[3] == 0) {
              switch (line[2]) {
                case 'X': mc_homing_cycle(HOMING_CYCLE_X); break;
                case 'Y': mc_homing_cycle(HOMING_CYCLE_Y); break;
                case 'Z': mc_homing_cycle(HOMING_CYCLE_Z); break;
                default: return(STATUS_INVALID_STATEMENT);
              }
          #endif
          } else { return(STATUS_INVALID_STATEMENT); }
          if (!sys.abort) {  // Execute startup scripts after successful homing.
            sys.state = STATE_IDLE; // Set to IDLE when complete.
            st_go_idle(); // Set steppers to the settings idle state before returning.
            if (line[2] == 0) { system_execute_startup(line); }
          }
          break;
        case 'S' : // Puts Grbl to sleep [IDLE/ALARM]
          if ((line[2] != 'L') || (line[3] != 'P') || (line[4] != 0)) { return(STATUS_INVALID_STATEMENT); }
          system_set_exec_state_flag(EXEC_SLEEP); // Set to execute sleep mode immediately
          break;
        case 'I' : // Print or store build info. [IDLE/ALARM]
          if ( line[++char_counter] == 0 ) {
            settings_read_build_info(line);
            report_build_info(line);
          #ifdef ENABLE_BUILD_INFO_WRITE_COMMAND
            } else { // Store startup line [IDLE/ALARM]
              if(line[char_counter++] != '=') { return(STATUS_INVALID_STATEMENT); }
              helper_var = char_counter; // Set helper variable as counter to start of user info line.
              do {
                line[char_counter-helper_var] = line[char_counter];
              } while (line[char_counter++] != 0);
              settings_store_build_info(line);
          #endif
          }
          break;
        case 'R' : // Restore defaults [IDLE/ALARM]
          if ((line[2] != 'S') || (line[3] != 'T') || (line[4] != '=') || (line[6] != 0)) { return(STATUS_INVALID_STATEMENT); }
          switch (line[5]) {
            #ifdef ENABLE_RESTORE_EEPROM_DEFAULT_SETTINGS
              case '$': settings_restore(SETTINGS_RESTORE_DEFAULTS); break;
            #endif
            #ifdef ENABLE_RESTORE_EEPROM_CLEAR_PARAMETERS
              case '#': settings_restore(SETTINGS_RESTORE_PARAMETERS); break;
            #endif
            #ifdef ENABLE_RESTORE_EEPROM_WIPE_ALL
              case '*': settings_restore(SETTINGS_RESTORE_ALL); break;
            #endif
            default: return(STATUS_INVALID_STATEMENT);
          }
          report_feedback_message(MESSAGE_RESTORE_DEFAULTS);
          mc_reset(); // Force reset to ensure settings are initialized correctly.
          break;
        case 'N' : // Startup lines. [IDLE/ALARM]
          if ( line[++char_counter] == 0 ) { // Print startup lines
            for (helper_var=0; helper_var < N_STARTUP_LINE; helper_var++) {
              if (!(settings_read_startup_line(helper_var, line))) {
                report_status_message(STATUS_SETTING_READ_FAIL);
              } else {
                report_startup_line(helper_var,line);
              }
            }
            break;
          } else { // Store startup line [IDLE Only] Prevents motion during ALARM.
            if (sys.state != STATE_IDLE) { return(STATUS_IDLE_ERROR); } // Store only when idle.
            helper_var = true;  // Set helper_var to flag storing method.
            // No break. Continues into default: to read remaining command characters.
          }
        default :  // Storing setting methods [IDLE/ALARM]
          if(!read_float(line, &char_counter, &parameter)) { return(STATUS_BAD_NUMBER_FORMAT); }
          if(line[char_counter++] != '=') { return(STATUS_INVALID_STATEMENT); }
          if (helper_var) { // Store startup line
            // Prepare sending gcode block to gcode parser by shifting all characters
            helper_var = char_counter; // Set helper variable as counter to start of gcode block
            do {
              line[char_counter-helper_var] = line[char_counter];
            } while (line[char_counter++] != 0);
            // Execute gcode block to ensure block is valid.
            helper_var = gc_execute_line(line); // Set helper_var to returned status code.
            if (helper_var) { return(helper_var); }
            else {
              helper_var = trunc(parameter); // Set helper_var to int value of parameter
              settings_store_startup_line(helper_var,line);
            }
          } else { // Store global setting.
            if(!read_float(line, &char_counter, &value)) { return(STATUS_BAD_NUMBER_FORMAT); }
            if((line[char_counter] != 0) || (parameter > 255)) { return(STATUS_INVALID_STATEMENT); }
            return(settings_store_global_setting((uint8_t)parameter, value));
          }
      }
  }
  return(STATUS_OK); // If '$' command makes it to here, then everything's ok.
}



void system_flag_wco_change()
{
  #ifdef FORCE_BUFFER_SYNC_DURING_WCO_CHANGE
    protocol_buffer_synchronize();
  #endif
  sys.report_wco_counter = 0;
}


// Returns machine position of axis 'idx'. Must be sent a 'step' array.
// NOTE: If motor steps and machine position are not in the same coordinate frame, this function
//   serves as a central place to compute the transformation.
float system_convert_axis_steps_to_mpos(int32_t *steps, uint8_t idx)
{
  float pos;
  #ifdef COREXY
    if (idx==X_AXIS) {
      pos = (float)system_convert_corexy_to_x_axis_steps(steps) / settings.steps_per_mm[idx];
    } else if (idx==Y_AXIS) {
      pos = (float)system_convert_corexy_to_y_axis_steps(steps) / settings.steps_per_mm[idx];
    } else {
      pos = steps[idx]/settings.steps_per_mm[idx];
    }
  #else
    pos = steps[idx]/settings.steps_per_mm[idx];
  #endif
  return(pos);
}


void system_convert_array_steps_to_mpos(float *position, int32_t *steps)
{
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    position[idx] = system_convert_axis_steps_to_mpos(steps, idx);
  }
  return;
}


// CoreXY calculation only. Returns x or y-axis "steps" based on CoreXY motor steps.
#ifdef COREXY
  int32_t system_convert_corexy_to_x_axis_steps(int32_t *steps)
  {
    return( (steps[A_MOTOR] + steps[B_MOTOR])/2 );
  }
  int32_t system_convert_corexy_to_y_axis_steps(int32_t *steps)
  {
    return( (steps[A_MOTOR] - steps[B_MOTOR])/2 );
  }
#endif


// Checks and reports if target array exceeds machine travel limits.
uint8_t system_check_travel_limits(float *target)
{
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    #ifdef HOMING_FORCE_SET_ORIGIN
      // When homing forced set origin is enabled, soft limits checks need to account for directionality.
      // NOTE: max_travel is stored as negative
      if (bit_istrue(settings.homing_dir_mask,bit(idx))) {
        if (target[idx] < 0 || target[idx] > -settings.max_travel[idx]) { return(true); }
      } else {
        if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { return(true); }
      }
    #else
      // NOTE: max_travel is stored as negative
      if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { return(true); }
    #endif
  }
  return(false);
}


// Special handlers for setting and clearing Grbl's real-time execution flags.
void system_set_exec_state_flag(uint8_t mask) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_state |= (mask);
  SREG = sreg;
}

void system_clear_exec_state_flag(uint8_t mask) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_state &= ~(mask);
  SREG = sreg;
}

void system_set_exec_alarm(uint8_t code) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_alarm = code;
  SREG = sreg;
}

void system_clear_exec_alarm() {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_alarm = 0;
  SREG = sreg;
}

void system_set_exec_motion_override_flag(uint8_t mask) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_motion_override |= (mask);
  SREG = sreg;
}

void system_set_exec_accessory_override_flag(uint8_t mask) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_accessory_override |= (mask);
  SREG = sreg;
}

void system_clear_exec_motion_overrides() {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_motion_override = 0;
  SREG = sreg;
}

void system_clear_exec_accessory_overrides() {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_accessory_override = 0;
  SREG = sreg;
}


system.c

/*
  system.h - Header for system level commands and real-time processes
  Part of Grbl

  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC

  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef system_h
#define system_h

#include "grbl.h"

// Define system executor bit map. Used internally by realtime protocol as realtime command flags,
// which notifies the main program to execute the specified realtime command asynchronously.
// NOTE: The system executor uses an unsigned 8-bit volatile variable (8 flag limit.) The default
// flags are always false, so the realtime protocol only needs to check for a non-zero value to
// know when there is a realtime command to execute.
#define EXEC_STATUS_REPORT  bit(0) // bitmask 00000001
#define EXEC_CYCLE_START    bit(1) // bitmask 00000010
#define EXEC_CYCLE_STOP     bit(2) // bitmask 00000100
#define EXEC_FEED_HOLD      bit(3) // bitmask 00001000
#define EXEC_RESET          bit(4) // bitmask 00010000
#define EXEC_SAFETY_DOOR    bit(5) // bitmask 00100000
#define EXEC_MOTION_CANCEL  bit(6) // bitmask 01000000
#define EXEC_SLEEP          bit(7) // bitmask 10000000

// Alarm executor codes. Valid values (1-255). Zero is reserved.
#define EXEC_ALARM_HARD_LIMIT                 1
#define EXEC_ALARM_SOFT_LIMIT                 2
#define EXEC_ALARM_ABORT_CYCLE                3
#define EXEC_ALARM_PROBE_FAIL_INITIAL         4
#define EXEC_ALARM_PROBE_FAIL_CONTACT         5
#define EXEC_ALARM_HOMING_FAIL_RESET          6
#define EXEC_ALARM_HOMING_FAIL_DOOR           7
#define EXEC_ALARM_HOMING_FAIL_PULLOFF        8
#define EXEC_ALARM_HOMING_FAIL_APPROACH       9
#define EXEC_ALARM_HOMING_FAIL_DUAL_APPROACH  10

// Override bit maps. Realtime bitflags to control feed, rapid, spindle, and coolant overrides.
// Spindle/coolant and feed/rapids are separated into two controlling flag variables.
#define EXEC_FEED_OVR_RESET         bit(0)
#define EXEC_FEED_OVR_COARSE_PLUS   bit(1)
#define EXEC_FEED_OVR_COARSE_MINUS  bit(2)
#define EXEC_FEED_OVR_FINE_PLUS     bit(3)
#define EXEC_FEED_OVR_FINE_MINUS    bit(4)
#define EXEC_RAPID_OVR_RESET        bit(5)
#define EXEC_RAPID_OVR_MEDIUM       bit(6)
#define EXEC_RAPID_OVR_LOW          bit(7)
// #define EXEC_RAPID_OVR_EXTRA_LOW   bit(*) // *NOT SUPPORTED*

#define EXEC_SPINDLE_OVR_RESET         bit(0)
#define EXEC_SPINDLE_OVR_COARSE_PLUS   bit(1)
#define EXEC_SPINDLE_OVR_COARSE_MINUS  bit(2)
#define EXEC_SPINDLE_OVR_FINE_PLUS     bit(3)
#define EXEC_SPINDLE_OVR_FINE_MINUS    bit(4)
#define EXEC_SPINDLE_OVR_STOP          bit(5)
#define EXEC_COOLANT_FLOOD_OVR_TOGGLE  bit(6)
#define EXEC_COOLANT_MIST_OVR_TOGGLE   bit(7)

// Define system state bit map. The state variable primarily tracks the individual functions
// of Grbl to manage each without overlapping. It is also used as a messaging flag for
// critical events.
#define STATE_IDLE          0      // Must be zero. No flags.
#define STATE_ALARM         bit(0) // In alarm state. Locks out all g-code processes. Allows settings access.
#define STATE_CHECK_MODE    bit(1) // G-code check mode. Locks out planner and motion only.
#define STATE_HOMING        bit(2) // Performing homing cycle
#define STATE_CYCLE         bit(3) // Cycle is running or motions are being executed.
#define STATE_HOLD          bit(4) // Active feed hold
#define STATE_JOG           bit(5) // Jogging mode.
#define STATE_SAFETY_DOOR   bit(6) // Safety door is ajar. Feed holds and de-energizes system.
#define STATE_SLEEP         bit(7) // Sleep state.

// Define system suspend flags. Used in various ways to manage suspend states and procedures.
#define SUSPEND_DISABLE           0      // Must be zero.
#define SUSPEND_HOLD_COMPLETE     bit(0) // Indicates initial feed hold is complete.
#define SUSPEND_RESTART_RETRACT   bit(1) // Flag to indicate a retract from a restore parking motion.
#define SUSPEND_RETRACT_COMPLETE  bit(2) // (Safety door only) Indicates retraction and de-energizing is complete.
#define SUSPEND_INITIATE_RESTORE  bit(3) // (Safety door only) Flag to initiate resume procedures from a cycle start.
#define SUSPEND_RESTORE_COMPLETE  bit(4) // (Safety door only) Indicates ready to resume normal operation.
#define SUSPEND_SAFETY_DOOR_AJAR  bit(5) // Tracks safety door state for resuming.
#define SUSPEND_MOTION_CANCEL     bit(6) // Indicates a canceled resume motion. Currently used by probing routine.
#define SUSPEND_JOG_CANCEL        bit(7) // Indicates a jog cancel in process and to reset buffers when complete.

// Define step segment generator state flags.
#define STEP_CONTROL_NORMAL_OP            0  // Must be zero.
#define STEP_CONTROL_END_MOTION           bit(0)
#define STEP_CONTROL_EXECUTE_HOLD         bit(1)
#define STEP_CONTROL_EXECUTE_SYS_MOTION   bit(2)
#define STEP_CONTROL_UPDATE_SPINDLE_PWM   bit(3)

// Define control pin index for Grbl internal use. Pin maps may change, but these values don't.
#ifdef ENABLE_SAFETY_DOOR_INPUT_PIN
  #define N_CONTROL_PIN 4
  #define CONTROL_PIN_INDEX_SAFETY_DOOR   bit(0)
  #define CONTROL_PIN_INDEX_RESET         bit(1)
  #define CONTROL_PIN_INDEX_FEED_HOLD     bit(2)
  #define CONTROL_PIN_INDEX_CYCLE_START   bit(3)
#else
  #define N_CONTROL_PIN 3
  #define CONTROL_PIN_INDEX_RESET         bit(0)
  #define CONTROL_PIN_INDEX_FEED_HOLD     bit(1)
  #define CONTROL_PIN_INDEX_CYCLE_START   bit(2)
#endif

// Define spindle stop override control states.
#define SPINDLE_STOP_OVR_DISABLED       0  // Must be zero.
#define SPINDLE_STOP_OVR_ENABLED        bit(0)
#define SPINDLE_STOP_OVR_INITIATE       bit(1)
#define SPINDLE_STOP_OVR_RESTORE        bit(2)
#define SPINDLE_STOP_OVR_RESTORE_CYCLE  bit(3)


// Define global system variables
typedef struct {
  uint8_t state;               // Tracks the current system state of Grbl.
  uint8_t abort;               // System abort flag. Forces exit back to main loop for reset.             
  uint8_t suspend;             // System suspend bitflag variable that manages holds, cancels, and safety door.
  uint8_t soft_limit;          // Tracks soft limit errors for the state machine. (boolean)
  uint8_t step_control;        // Governs the step segment generator depending on system state.
  uint8_t probe_succeeded;     // Tracks if last probing cycle was successful.
  uint8_t homing_axis_lock;    // Locks axes when limits engage. Used as an axis motion mask in the stepper ISR.
  #ifdef ENABLE_DUAL_AXIS
    uint8_t homing_axis_lock_dual;
  #endif
  uint8_t f_override;          // Feed rate override value in percent
  uint8_t r_override;          // Rapids override value in percent
  uint8_t spindle_speed_ovr;   // Spindle speed value in percent
  uint8_t spindle_stop_ovr;    // Tracks spindle stop override states
  uint8_t report_ovr_counter;  // Tracks when to add override data to status reports.
  uint8_t report_wco_counter;  // Tracks when to add work coordinate offset data to status reports.
  #ifdef ENABLE_PARKING_OVERRIDE_CONTROL
    uint8_t override_ctrl;     // Tracks override control states.
  #endif
  #ifdef VARIABLE_SPINDLE
    float spindle_speed;
  #endif
} system_t;
extern system_t sys;

// NOTE: These position variables may need to be declared as volatiles, if problems arise.
extern int32_t sys_position[N_AXIS];      // Real-time machine (aka home) position vector in steps.
extern int32_t sys_probe_position[N_AXIS]; // Last probe position in machine coordinates and steps.

extern volatile uint8_t sys_probe_state;   // Probing state value.  Used to coordinate the probing cycle with stepper ISR.
extern volatile uint8_t sys_rt_exec_state;   // Global realtime executor bitflag variable for state management. See EXEC bitmasks.
extern volatile uint8_t sys_rt_exec_alarm;   // Global realtime executor bitflag variable for setting various alarms.
extern volatile uint8_t sys_rt_exec_motion_override; // Global realtime executor bitflag variable for motion-based overrides.
extern volatile uint8_t sys_rt_exec_accessory_override; // Global realtime executor bitflag variable for spindle/coolant overrides.

#ifdef DEBUG
  #define EXEC_DEBUG_REPORT  bit(0)
  extern volatile uint8_t sys_rt_exec_debug;
#endif

// Initialize the serial protocol
void system_init();

// Returns bitfield of control pin states, organized by CONTROL_PIN_INDEX. (1=triggered, 0=not triggered).
uint8_t system_control_get_state();

// Returns if safety door is open or closed, based on pin state.
uint8_t system_check_safety_door_ajar();

// Executes an internal system command, defined as a string starting with a '$'
uint8_t system_execute_line(char *line);

// Execute the startup script lines stored in EEPROM upon initialization
void system_execute_startup(char *line);


void system_flag_wco_change();

// Returns machine position of axis 'idx'. Must be sent a 'step' array.
float system_convert_axis_steps_to_mpos(int32_t *steps, uint8_t idx);

// Updates a machine 'position' array based on the 'step' array sent.
void system_convert_array_steps_to_mpos(float *position, int32_t *steps);

// CoreXY calculation only. Returns x or y-axis "steps" based on CoreXY motor steps.
#ifdef COREXY
  int32_t system_convert_corexy_to_x_axis_steps(int32_t *steps);
  int32_t system_convert_corexy_to_y_axis_steps(int32_t *steps);
#endif

// Checks and reports if target array exceeds machine travel limits.
uint8_t system_check_travel_limits(float *target);

// Special handlers for setting and clearing Grbl's real-time execution flags.
void system_set_exec_state_flag(uint8_t mask);
void system_clear_exec_state_flag(uint8_t mask);
void system_set_exec_alarm(uint8_t code);
void system_clear_exec_alarm();
void system_set_exec_motion_override_flag(uint8_t mask);
void system_set_exec_accessory_override_flag(uint8_t mask);
void system_clear_exec_motion_overrides();
void system_clear_exec_accessory_overrides();


#endif


system.h




Note that grbl becomes unresponsive in Wokwi after movement commands

See discussion at 
* https://forum.arduino.cc/t/why-does-the-wokwi-simulator-hang-grbl/985524
* https://github.com/wokwi/avr8js/issues/55

---
I think I found the problem in  https://github.com/wokwi/avr8js/issues/122 -- 
CTC mode 4 with OCR1A=0 doesn't work as expected. See https://wokwi.com/projects/360749451904483329 for a test case.

A workaround is to set OCR1A above 0 (0x7FFF seems to work) in `stepper.c:st_wake_up(){...}`

---
# Pinouts

The grbl default pinouts match the protoneer documentation at https://blog.protoneer.co.nz/grbl-arduino-g-code-processor-pin-layout/
![pinout](https://i0.wp.com/blog.protoneer.co.nz/wp-content/uploads/2013/01/Grbl_Pin_Layout.png) plus:

    A3 = Flood coolant Output
    A4 = Mist coolant Output  (PINC = bit(4) for toggling debug)
    A5 = probe input


# Operation and Fault diagnosis

Note that Homing is disabled ($22=0) and that the HOMING_INIT_LOCK is disabled (see config.h:89)

* '`$$`' prints the settings (Only works in Idle mode, else give error:8)
* '`?`' prints the status report (modulated by $10) Periodic Work Coordinate Offset (WCO) or 
Override (Ov) status reports happen every 10 status reports.

```
<Idle|MPos:0.000,0.000,0.000|FS:0,0|WCO:0.000,0.000,0.000>
ok
<Idle|MPos:0.000,0.000,0.000|FS:0,0|Ov:100,100,100>
ok
<Idle|MPos:0.000,0.000,0.000|FS:0,0>
ok

```

From starting the simulation, you can see the transcript below:

*  `error:7` which is an [EEPROM read fail](https://docs.sainsmart.com/article/dm4jbd5jce-grbl-error-codes), which would be expected on Wokwi.  After which the system is set for default
*  A default $$ report on the settings

```
rror:7
$0=10
$1=25
$2=0
$3=0
$4=0
$5=0
$6=0
$10=1
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=0
$23=0
$24=25.000
$25=500.000
$26=250
$27=1.000
$30=1000
$31=0
$32=0
$100=250.000
$101=250.000
$102=250.000
$110=500.000
$111=500.000
$112=500.000
$120=10.000
$121=10.000
$122=10.000
$130=200.000
$131=200.000
$132=200.000

Grbl 1.1h ['$' for help]
>:error:7
>:error:7

```



Some test code from
https://diymachining.com/g-code-example/
```
G17 ;  Use X-Y plane
G20 ;  Inches vs G21 mm
G90 ;  Absolute coordinates
G94 ;  Feed rates in dist/minute vs G93 inverse time
G54 ;  Activate saved origin
; Everything works as expected up to here.

; This line puts grbl into Run state
; a ? status report will show run mode, and $$ will error 8: not Idle
G0 Z0.25 ; rapid up 0.25in

X-0.5 Y0. ; left
Z0.1      ; down
G01 Z0. F5. ; move down at 5in/min 
G02 X0. Y0.5 I0.5 J0. F2.5  ; CW Arc to 
X0.5 Y0. I0. J-0.5
X0. Y-0.5 I-0.5 J0.
X-0.5 Y0. I0. J0.5
G01 Z0.1 F5.
G00 X0. Y0. Z0.25
```

For investigating, I try toggling A4 with this: 

   PINC = bit(4); // drf5n

in various routines to detect cycles

* protocol.c toggles with each line
* stepper.c
 * ISR(TIMER1_COMPA_vect) no toggling
 * ISR(TIMER0_OVF_vect) no toggling
 * ISR(TIMER0_COMPA_vect) no toggling

From this, it seems like no interrupts are being triggered, pointing to a problem with
timer interrupt configuration.

I added a "^" command in protocol.c to print the time configuration variables:

```

```
 and got this result

 ```
 
^ TCCR0A:0b00000000
^ TCCR0B:0b00000000
^ TIMSK0:0b00000001
^ TCCR1A:0b00000000
^ TCCR1B:0b00001001
^ TIMSK1:0b00000000
ok
G0X1
^ TCCR0A:0b00000000
^ TCCR0B:0b00000000
^ TIMSK0:0b00000001
^ TCCR1A:0b00000000
^ TCCR1B:0b00001001
^ TIMSK1:0b00000010
```

* This link is a good explanation of Grbl's internals: https://awesome.tech/grbl-demystified/
* https://www.sainsmart.com/blogs/news/grbl-v1-1-quick-reference
