
// stepper motor with crossed wires 
// for https://forum.arduino.cc/t/accelstepper-run-question/1121994/16
// https://wokwi.com/projects/363629517927347201
// Copied fron https://wokwi.com/projects/360399388158511105

// The center two coil wires are swapped, so the stepper only steps in
// one direction

#include "AccelStepper.h"

// Define a stepper and the pins it will use
AccelStepper stepper(AccelStepper::FULL4WIRE,2,3,4,5); // Defaults to AccelStepper::FULL4WIRE (4 pins) on 2, 3, 4, 5

// This defines the analog input pin for reading the control voltage
// Tested with a 10k linear pot between 5v and GND
#define ANALOG_IN A0

void setup()
{  
  stepper.setMaxSpeed(1000);
}

void loop()
{
  // Read new position
  int analog_in = analogRead(ANALOG_IN);
  stepper.moveTo(analog_in);
  stepper.setSpeed(1000);
  stepper.runSpeedToPosition();
}

stepper-motor-example.ino

Note the crossed wires at the Arduino pins 3&4. This causes one-directional, (CCW) motion.

diagram.json

# Wokwi Library List
# See https://docs.wokwi.com/guides/libraries

Stepper

libraries.txt

// AccelStepper.cpp
//
// Copyright (C) 2009-2020 Mike McCauley
// $Id: AccelStepper.cpp,v 1.24 2020/04/20 00:15:03 mikem Exp mikem $

#include "AccelStepper.h"

#if 0
// Some debugging assistance
void dump(uint8_t* p, int l)
{
    int i;

    for (i = 0; i < l; i++)
    {
	Serial.print(p[i], HEX);
	Serial.print(" ");
    }
    Serial.println("");
}
#endif

void AccelStepper::moveTo(long absolute)
{
    if (_targetPos != absolute)
    {
	_targetPos = absolute;
	computeNewSpeed();
	// compute new n?
    }
}

void AccelStepper::move(long relative)
{
    moveTo(_currentPos + relative);
}

// Implements steps according to the current step interval
// You must call this at least once per step
// returns true if a step occurred
boolean AccelStepper::runSpeed()
{
    // Dont do anything unless we actually have a step interval
    if (!_stepInterval)
	return false;

    unsigned long time = micros();   
    if (time - _lastStepTime >= _stepInterval)
    {
	if (_direction == DIRECTION_CW)
	{
	    // Clockwise
	    _currentPos += 1;
	}
	else
	{
	    // Anticlockwise  
	    _currentPos -= 1;
	}
	step(_currentPos);

	_lastStepTime = time; // Caution: does not account for costs in step()

	return true;
    }
    else
    {
	return false;
    }
}

long AccelStepper::distanceToGo()
{
    return _targetPos - _currentPos;
}

long AccelStepper::targetPosition()
{
    return _targetPos;
}

long AccelStepper::currentPosition()
{
    return _currentPos;
}

// Useful during initialisations or after initial positioning
// Sets speed to 0
void AccelStepper::setCurrentPosition(long position)
{
    _targetPos = _currentPos = position;
    _n = 0;
    _stepInterval = 0;
    _speed = 0.0;
}

// Subclasses can override
unsigned long AccelStepper::computeNewSpeed()
{
    long distanceTo = distanceToGo(); // +ve is clockwise from curent location

    long stepsToStop = (long)((_speed * _speed) / (2.0 * _acceleration)); // Equation 16

    if (distanceTo == 0 && stepsToStop <= 1)
    {
	// We are at the target and its time to stop
	_stepInterval = 0;
	_speed = 0.0;
	_n = 0;
	return _stepInterval;
    }

    if (distanceTo > 0)
    {
	// We are anticlockwise from the target
	// Need to go clockwise from here, maybe decelerate now
	if (_n > 0)
	{
	    // Currently accelerating, need to decel now? Or maybe going the wrong way?
	    if ((stepsToStop >= distanceTo) || _direction == DIRECTION_CCW)
		_n = -stepsToStop; // Start deceleration
	}
	else if (_n < 0)
	{
	    // Currently decelerating, need to accel again?
	    if ((stepsToStop < distanceTo) && _direction == DIRECTION_CW)
		_n = -_n; // Start accceleration
	}
    }
    else if (distanceTo < 0)
    {
	// We are clockwise from the target
	// Need to go anticlockwise from here, maybe decelerate
	if (_n > 0)
	{
	    // Currently accelerating, need to decel now? Or maybe going the wrong way?
	    if ((stepsToStop >= -distanceTo) || _direction == DIRECTION_CW)
		_n = -stepsToStop; // Start deceleration
	}
	else if (_n < 0)
	{
	    // Currently decelerating, need to accel again?
	    if ((stepsToStop < -distanceTo) && _direction == DIRECTION_CCW)
		_n = -_n; // Start accceleration
	}
    }

    // Need to accelerate or decelerate
    if (_n == 0)
    {
	// First step from stopped
	_cn = _c0;
	_direction = (distanceTo > 0) ? DIRECTION_CW : DIRECTION_CCW;
    }
    else
    {
	// Subsequent step. Works for accel (n is +_ve) and decel (n is -ve).
	_cn = _cn - ((2.0 * _cn) / ((4.0 * _n) + 1)); // Equation 13
	_cn = max(_cn, _cmin); 
    }
    _n++;
    _stepInterval = _cn;
    _speed = 1000000.0 / _cn;
    if (_direction == DIRECTION_CCW)
	_speed = -_speed;

#if 0
    Serial.println(_speed);
    Serial.println(_acceleration);
    Serial.println(_cn);
    Serial.println(_c0);
    Serial.println(_n);
    Serial.println(_stepInterval);
    Serial.println(distanceTo);
    Serial.println(stepsToStop);
    Serial.println("-----");
#endif
    return _stepInterval;
}

// Run the motor to implement speed and acceleration in order to proceed to the target position
// You must call this at least once per step, preferably in your main loop
// If the motor is in the desired position, the cost is very small
// returns true if the motor is still running to the target position.
boolean AccelStepper::run()
{
    if (runSpeed())
	computeNewSpeed();
    return _speed != 0.0 || distanceToGo() != 0;
}

AccelStepper::AccelStepper(uint8_t interface, uint8_t pin1, uint8_t pin2, uint8_t pin3, uint8_t pin4, bool enable)
{
    _interface = interface;
    _currentPos = 0;
    _targetPos = 0;
    _speed = 0.0;
    _maxSpeed = 0.0;
    _acceleration = 0.0;
    _sqrt_twoa = 1.0;
    _stepInterval = 0;
    _minPulseWidth = 1;
    _enablePin = 0xff;
    _lastStepTime = 0;
    _pin[0] = pin1;
    _pin[1] = pin2;
    _pin[2] = pin3;
    _pin[3] = pin4;
    _enableInverted = false;
    
    // NEW
    _n = 0;
    _c0 = 0.0;
    _cn = 0.0;
    _cmin = 1.0;
    _direction = DIRECTION_CCW;

    int i;
    for (i = 0; i < 4; i++)
	_pinInverted[i] = 0;
    if (enable)
	enableOutputs();
    // Some reasonable default
    setAcceleration(1);
    setMaxSpeed(1);
}

AccelStepper::AccelStepper(void (*forward)(), void (*backward)())
{
    _interface = 0;
    _currentPos = 0;
    _targetPos = 0;
    _speed = 0.0;
    _maxSpeed = 0.0;
    _acceleration = 0.0;
    _sqrt_twoa = 1.0;
    _stepInterval = 0;
    _minPulseWidth = 1;
    _enablePin = 0xff;
    _lastStepTime = 0;
    _pin[0] = 0;
    _pin[1] = 0;
    _pin[2] = 0;
    _pin[3] = 0;
    _forward = forward;
    _backward = backward;

    // NEW
    _n = 0;
    _c0 = 0.0;
    _cn = 0.0;
    _cmin = 1.0;
    _direction = DIRECTION_CCW;

    int i;
    for (i = 0; i < 4; i++)
	_pinInverted[i] = 0;
    // Some reasonable default
    setAcceleration(1);
    setMaxSpeed(1);
}

void AccelStepper::setMaxSpeed(float speed)
{
    if (speed < 0.0)
       speed = -speed;
    if (_maxSpeed != speed)
    {
	_maxSpeed = speed;
	_cmin = 1000000.0 / speed;
	// Recompute _n from current speed and adjust speed if accelerating or cruising
	if (_n > 0)
	{
	    _n = (long)((_speed * _speed) / (2.0 * _acceleration)); // Equation 16
	    computeNewSpeed();
	}
    }
}

float   AccelStepper::maxSpeed()
{
    return _maxSpeed;
}

void AccelStepper::setAcceleration(float acceleration)
{
    if (acceleration == 0.0)
	return;
    if (acceleration < 0.0)
      acceleration = -acceleration;
    if (_acceleration != acceleration)
    {
	// Recompute _n per Equation 17
	_n = _n * (_acceleration / acceleration);
	// New c0 per Equation 7, with correction per Equation 15
	_c0 = 0.676 * sqrt(2.0 / acceleration) * 1000000.0; // Equation 15
	_acceleration = acceleration;
	computeNewSpeed();
    }
}

float   AccelStepper::acceleration()
{
    return _acceleration;
}

void AccelStepper::setSpeed(float speed)
{
    if (speed == _speed)
        return;
    speed = constrain(speed, -_maxSpeed, _maxSpeed);
    if (speed == 0.0)
	_stepInterval = 0;
    else
    {
	_stepInterval = fabs(1000000.0 / speed);
	_direction = (speed > 0.0) ? DIRECTION_CW : DIRECTION_CCW;
    }
    _speed = speed;
}

float AccelStepper::speed()
{
    return _speed;
}

// Subclasses can override
void AccelStepper::step(long step)
{
    switch (_interface)
    {
        case FUNCTION:
            step0(step);
            break;

	case DRIVER:
	    step1(step);
	    break;
    
	case FULL2WIRE:
	    step2(step);
	    break;
    
	case FULL3WIRE:
	    step3(step);
	    break;  

	case FULL4WIRE:
	    step4(step);
	    break;  

	case HALF3WIRE:
	    step6(step);
	    break;  
		
	case HALF4WIRE:
	    step8(step);
	    break;  
    }
}

long AccelStepper::stepForward()
{
    // Clockwise
    _currentPos += 1;
	step(_currentPos);
	_lastStepTime = micros();
    return _currentPos;
}

long AccelStepper::stepBackward()
{
    // Counter-clockwise
    _currentPos -= 1;
	step(_currentPos);
	_lastStepTime = micros();
    return _currentPos;
}

// You might want to override this to implement eg serial output
// bit 0 of the mask corresponds to _pin[0]
// bit 1 of the mask corresponds to _pin[1]
// ....
void AccelStepper::setOutputPins(uint8_t mask)
{
    uint8_t numpins = 2;
    if (_interface == FULL4WIRE || _interface == HALF4WIRE)
	numpins = 4;
    else if (_interface == FULL3WIRE || _interface == HALF3WIRE)
	numpins = 3;
    uint8_t i;
    for (i = 0; i < numpins; i++)
	digitalWrite(_pin[i], (mask & (1 << i)) ? (HIGH ^ _pinInverted[i]) : (LOW ^ _pinInverted[i]));
}

// 0 pin step function (ie for functional usage)
void AccelStepper::step0(long step)
{
    (void)(step); // Unused
    if (_speed > 0)
	_forward();
    else
	_backward();
}

// 1 pin step function (ie for stepper drivers)
// This is passed the current step number (0 to 7)
// Subclasses can override
void AccelStepper::step1(long step)
{
    (void)(step); // Unused

    // _pin[0] is step, _pin[1] is direction
    setOutputPins(_direction ? 0b10 : 0b00); // Set direction first else get rogue pulses
    setOutputPins(_direction ? 0b11 : 0b01); // step HIGH
    // Caution 200ns setup time 
    // Delay the minimum allowed pulse width
    delayMicroseconds(_minPulseWidth);
    setOutputPins(_direction ? 0b10 : 0b00); // step LOW
}


// 2 pin step function
// This is passed the current step number (0 to 7)
// Subclasses can override
void AccelStepper::step2(long step)
{
    switch (step & 0x3)
    {
	case 0: /* 01 */
	    setOutputPins(0b10);
	    break;

	case 1: /* 11 */
	    setOutputPins(0b11);
	    break;

	case 2: /* 10 */
	    setOutputPins(0b01);
	    break;

	case 3: /* 00 */
	    setOutputPins(0b00);
	    break;
    }
}
// 3 pin step function
// This is passed the current step number (0 to 7)
// Subclasses can override
void AccelStepper::step3(long step)
{
    switch (step % 3)
    {
	case 0:    // 100
	    setOutputPins(0b100);
	    break;

	case 1:    // 001
	    setOutputPins(0b001);
	    break;

	case 2:    //010
	    setOutputPins(0b010);
	    break;
	    
    }
}

// 4 pin step function for half stepper
// This is passed the current step number (0 to 7)
// Subclasses can override
void AccelStepper::step4(long step)
{
    switch (step & 0x3)
    {
	case 0:    // 1010
	    setOutputPins(0b0101);
	    break;

	case 1:    // 0110
	    setOutputPins(0b0110);
	    break;

	case 2:    //0101
	    setOutputPins(0b1010);
	    break;

	case 3:    //1001
	    setOutputPins(0b1001);
	    break;
    }
}

// 3 pin half step function
// This is passed the current step number (0 to 7)
// Subclasses can override
void AccelStepper::step6(long step)
{
    switch (step % 6)
    {
	case 0:    // 100
	    setOutputPins(0b100);
            break;
	    
        case 1:    // 101
	    setOutputPins(0b101);
            break;
	    
	case 2:    // 001
	    setOutputPins(0b001);
            break;
	    
        case 3:    // 011
	    setOutputPins(0b011);
            break;
	    
	case 4:    // 010
	    setOutputPins(0b010);
            break;
	    
	case 5:    // 011
	    setOutputPins(0b110);
            break;
	    
    }
}

// 4 pin half step function
// This is passed the current step number (0 to 7)
// Subclasses can override
void AccelStepper::step8(long step)
{
    switch (step & 0x7)
    {
	case 0:    // 1000
	    setOutputPins(0b0001);
            break;
	    
        case 1:    // 1010
	    setOutputPins(0b0101);
            break;
	    
	case 2:    // 0010
	    setOutputPins(0b0100);
            break;
	    
        case 3:    // 0110
	    setOutputPins(0b0110);
            break;
	    
	case 4:    // 0100
	    setOutputPins(0b0010);
            break;
	    
        case 5:    //0101
	    setOutputPins(0b1010);
            break;
	    
	case 6:    // 0001
	    setOutputPins(0b1000);
            break;
	    
        case 7:    //1001
	    setOutputPins(0b1001);
            break;
    }
}
    
// Prevents power consumption on the outputs
void    AccelStepper::disableOutputs()
{   
    if (! _interface) return;

    setOutputPins(0); // Handles inversion automatically
    if (_enablePin != 0xff)
    {
        pinMode(_enablePin, OUTPUT);
        digitalWrite(_enablePin, LOW ^ _enableInverted);
    }
}

void    AccelStepper::enableOutputs()
{
    if (! _interface) 
	return;

    pinMode(_pin[0], OUTPUT);
    pinMode(_pin[1], OUTPUT);
    if (_interface == FULL4WIRE || _interface == HALF4WIRE)
    {
        pinMode(_pin[2], OUTPUT);
        pinMode(_pin[3], OUTPUT);
    }
    else if (_interface == FULL3WIRE || _interface == HALF3WIRE)
    {
        pinMode(_pin[2], OUTPUT);
    }

    if (_enablePin != 0xff)
    {
        pinMode(_enablePin, OUTPUT);
        digitalWrite(_enablePin, HIGH ^ _enableInverted);
    }
}

void AccelStepper::setMinPulseWidth(unsigned int minWidth)
{
    _minPulseWidth = minWidth;
}

void AccelStepper::setEnablePin(uint8_t enablePin)
{
    _enablePin = enablePin;

    // This happens after construction, so init pin now.
    if (_enablePin != 0xff)
    {
        pinMode(_enablePin, OUTPUT);
        digitalWrite(_enablePin, HIGH ^ _enableInverted);
    }
}

void AccelStepper::setPinsInverted(bool directionInvert, bool stepInvert, bool enableInvert)
{
    _pinInverted[0] = stepInvert;
    _pinInverted[1] = directionInvert;
    _enableInverted = enableInvert;
}

void AccelStepper::setPinsInverted(bool pin1Invert, bool pin2Invert, bool pin3Invert, bool pin4Invert, bool enableInvert)
{    
    _pinInverted[0] = pin1Invert;
    _pinInverted[1] = pin2Invert;
    _pinInverted[2] = pin3Invert;
    _pinInverted[3] = pin4Invert;
    _enableInverted = enableInvert;
}

// Blocks until the target position is reached and stopped
void AccelStepper::runToPosition()
{
    while (run())
	YIELD; // Let system housekeeping occur
}

boolean AccelStepper::runSpeedToPosition()
{
    if (_targetPos == _currentPos)
	return false;
    if (_targetPos >_currentPos)
	_direction = DIRECTION_CW;
    else
	_direction = DIRECTION_CCW;
    return runSpeed();
}

// Blocks until the new target position is reached
void AccelStepper::runToNewPosition(long position)
{
    moveTo(position);
    runToPosition();
}

void AccelStepper::stop()
{
    if (_speed != 0.0)
    {    
	long stepsToStop = (long)((_speed * _speed) / (2.0 * _acceleration)) + 1; // Equation 16 (+integer rounding)
	if (_speed > 0)
	    move(stepsToStop);
	else
	    move(-stepsToStop);
    }
}

bool AccelStepper::isRunning()
{
    return !(_speed == 0.0 && _targetPos == _currentPos);
}


AccelStepper.cpp

AccelStepper.h

// MultiStepper.cpp
//
// Copyright (C) 2015 Mike McCauley
// $Id: MultiStepper.cpp,v 1.3 2020/04/20 00:15:03 mikem Exp mikem $

#include "MultiStepper.h"
#include "AccelStepper.h"

MultiStepper::MultiStepper()
    : _num_steppers(0)
{
}

boolean MultiStepper::addStepper(AccelStepper& stepper)
{
    if (_num_steppers >= MULTISTEPPER_MAX_STEPPERS)
	return false; // No room for more
    _steppers[_num_steppers++] = &stepper;
    return true;
}

void MultiStepper::moveTo(long absolute[])
{
    // First find the stepper that will take the longest time to move
    float longestTime = 0.0;

    uint8_t i;
    for (i = 0; i < _num_steppers; i++)
    {
	long thisDistance = absolute[i] - _steppers[i]->currentPosition();
	float thisTime = abs(thisDistance) / _steppers[i]->maxSpeed();

	if (thisTime > longestTime)
	    longestTime = thisTime;
    }

    if (longestTime > 0.0)
    {
	// Now work out a new max speed for each stepper so they will all 
	// arrived at the same time of longestTime
	for (i = 0; i < _num_steppers; i++)
	{
	    long thisDistance = absolute[i] - _steppers[i]->currentPosition();
	    float thisSpeed = thisDistance / longestTime;
	    _steppers[i]->moveTo(absolute[i]); // New target position (resets speed)
	    _steppers[i]->setSpeed(thisSpeed); // New speed
	}
    }
}

// Returns true if any motor is still running to the target position.
boolean MultiStepper::run()
{
    uint8_t i;
    boolean ret = false;
    for (i = 0; i < _num_steppers; i++)
    {
	if ( _steppers[i]->distanceToGo() != 0)
	{
	    _steppers[i]->runSpeed();
	    ret = true;
	}
	// Caution: it has een reported that if any motor is used with acceleration outside of
	// MultiStepper, this code is necessary, you get 
	// strange results where it moves in the wrong direction for a while then 
	// slams back the correct way.
#if 0
	else
	{
	    // Need to call this to clear _stepInterval, _speed and _n 
	    otherwise future calls will fail.
		_steppers[i]->setCurrentPosition(_steppers[i]->currentPosition());
	}
#endif
	
    }
    return ret;
}

// Blocks until all steppers reach their target position and are stopped
void    MultiStepper::runSpeedToPosition()
{ 
    while (run())
	;
}



MultiStepper.cpp

// MultiStepper.h

#ifndef MultiStepper_h
#define MultiStepper_h

#include <stdlib.h>
#if ARDUINO >= 100
#include <Arduino.h>
#else
#include <WProgram.h>
#include <wiring.h>
#endif

#define MULTISTEPPER_MAX_STEPPERS 10

class AccelStepper;

/////////////////////////////////////////////////////////////////////
/// \class MultiStepper MultiStepper.h <MultiStepper.h>
/// \brief Operate multiple AccelSteppers in a co-ordinated fashion
///
/// This class can manage multiple AccelSteppers (up to MULTISTEPPER_MAX_STEPPERS = 10), 
/// and cause them all to move
/// to selected positions at such a (constant) speed that they all arrive at their
/// target position at the same time. This can be used to support devices with multiple steppers
/// on say multiple axes to cause linear diagonal motion. Suitable for use with X-Y plotters, flatbeds,
/// 3D printers etc
/// to get linear straight line movement between arbitrary 2d (or 3d or ...) positions.
///
/// Caution: only constant speed stepper motion is supported: acceleration and deceleration is not supported
/// All the steppers managed by MultiStepper will step at a constant speed to their
/// target (albeit perhaps different speeds for each stepper).
class MultiStepper
{
public:
    /// Constructor
    MultiStepper();

    /// Add a stepper to the set of managed steppers
    /// There is an upper limit of MULTISTEPPER_MAX_STEPPERS = 10 to the number of steppers that can be managed
    /// \param[in] stepper Reference to a stepper to add to the managed list
    /// \return true if successful. false if the number of managed steppers would exceed MULTISTEPPER_MAX_STEPPERS
    boolean addStepper(AccelStepper& stepper);

    /// Set the target positions of all managed steppers 
    /// according to a coordinate array.
    /// New speeds will be computed for each stepper so they will all arrive at their 
    /// respective targets at very close to the same time.
    /// \param[in] absolute An array of desired absolute stepper positions. absolute[0] will be used to set
    /// the absolute position of the first stepper added by addStepper() etc. The array must be at least as long as 
    /// the number of steppers that have been added by addStepper, else results are undefined.
    void moveTo(long absolute[]);
    
    /// Calls runSpeed() on all the managed steppers
    /// that have not acheived their target position.
    /// \return true if any stepper is still in the process of running to its target position.
    boolean run();

    /// Runs all managed steppers until they acheived their target position.
    /// Blocks until all that position is acheived. If you dont
    /// want blocking consider using run() instead.
    void    runSpeedToPosition();
    
private:
    /// Array of pointers to the steppers we are controlling.
    /// Fills from 0 onwards
    AccelStepper* _steppers[MULTISTEPPER_MAX_STEPPERS];

    /// Number of steppers we are controlling and the number
    /// of steppers in _steppers[]
    uint8_t       _num_steppers;
};

/// @example MultiStepper.pde
/// Use MultiStepper class to manage multiple steppers and make them all move to 
/// the same position at the same time for linear 2d (or 3d) motion.

#endif
