/*
The software is provided "as is", without any warranty of any kind.
Feel free to edit it if needed.
@author lobodol <[email protected]>
modified for wokwi by @author f41ardu
wokwi servo range between 450 and 2500
add debug print statements
*/
// ---------------------------------------------------------------------------
#include <Wire.h>
// ------------------- Define some constants for convenience -----------------
#define CHANNEL1 0
#define CHANNEL2 1
#define CHANNEL3 2
#define CHANNEL4 3
#define YAW 0
#define PITCH 1
#define ROLL 2
#define THROTTLE 3
#define X 0 // X axis
#define Y 1 // Y axis
#define Z 2 // Z axis
#define MPU_ADDRESS 0x68 // I2C address of the MPU-6050
#define FREQ 250 // Sampling frequency
#define SSF_GYRO 65.5 // Sensitivity Scale Factor of the gyro from datasheet
#define STOPPED 0
#define STARTING 1
#define STARTED 2
// adopt this according your needs
#define servoMin 450 // wokwi 450, check your esc and change if required
#define servoMax 2500 // wokwi 2500, check your esc and change if required
#define servoMid 1025 // wokwo 1025 (servoMax - ServoMin)/2
#define pidRange 400 // keep pid caculation in acceptable range
// ---------------- Receiver variables ---------------------------------------
// Previous state of each channel (HIGH or LOW)
volatile byte previous_state[4];
// Duration of the pulse on each channel of the receiver in µs (must be within 1000µs & 2000µs)
volatile unsigned int pulse_length[4] = {servoMid, servoMid, servoMid, servoMid};
// Used to calculate pulse duration on each channel
volatile unsigned long current_time;
volatile unsigned long timer[4]; // Timer of each channel
// Used to configure which control (yaw, pitch, roll, throttle) is on which channel
int mode_mapping[4];
// ----------------------- MPU variables -------------------------------------
// The RAW values got from gyro (in °/sec) in that order: X, Y, Z
int gyro_raw[3] = {0, 0, 0};
// Average gyro offsets of each axis in that order: X, Y, Z
long gyro_offset[3] = {0, 0, 0};
// Calculated angles from gyro's values in that order: X, Y, Z
float gyro_angle[3] = {0, 0, 0};
// The RAW values got from accelerometer (in m/sec²) in that order: X, Y, Z
int acc_raw[3] = {0, 0, 0};
// Calculated angles from accelerometer's values in that order: X, Y, Z
float acc_angle[3] = {0, 0, 0};
// Total 3D acceleration vector in m/s²
long acc_total_vector;
// Calculated angular motion on each axis: Yaw, Pitch, Roll
float angular_motions[3] = {0, 0, 0};
/**
Real measures on 3 axis calculated from gyro AND accelerometer in that order : Yaw, Pitch, Roll
- Left wing up implies a positive roll
- Nose up implies a positive pitch
- Nose right implies a positive yaw
*/
float measures[3] = {0, 0, 0};
// MPU's temperature
int temperature;
// Init flag set to TRUE after first loop
boolean initialized;
// debbuging
boolean DEBUG_pulse = true;
boolean DEBUG_measures = true;
boolean DEBUG_angular_motions = true;
boolean DEBUG_RC = false;
// ----------------------- Variables for servo signal generation -------------
unsigned int period; // Sampling period
unsigned long loop_timer;
unsigned long now, difference;
unsigned long pulse_length_esc1 = servoMin,
pulse_length_esc2 = servoMin,
pulse_length_esc3 = servoMin,
pulse_length_esc4 = servoMin;
// ------------- Global variables used for PID controller --------------------
float pid_set_points[3] = {0, 0, 0}; // Yaw, Pitch, Roll
// Errors
float errors[3]; // Measured errors (compared to instructions) : [Yaw, Pitch, Roll]
float delta_err[3] = {0, 0, 0}; // Error deltas in that order : Yaw, Pitch, Roll
float error_sum[3] = {0, 0, 0}; // Error sums (used for integral component) : [Yaw, Pitch, Roll]
float previous_error[3] = {0, 0, 0}; // Last errors (used for derivative component) : [Yaw, Pitch, Roll]
// PID coefficients
float Kp[3] = {4.0, 1.3, 1.3}; // P coefficients in that order : Yaw, Pitch, Roll
float Ki[3] = {0.02, 0.04, 0.04}; // I coefficients in that order : Yaw, Pitch, Roll
float Kd[3] = {0, 18, 18}; // D coefficients in that order : Yaw, Pitch, Roll
// ---------------------------------------------------------------------------
/**
Status of the quadcopter:
- 0 : stopped
- 1 : starting
- 2 : started
@var int
*/
int status = STOPPED;
// ---------------------------------------------------------------------------
int battery_voltage;
// ---------------------------------------------------------------------------
/**
Setup configuration
*/
void setup() {
// Start I2C communication
Wire.begin();
TWBR = 12; // Set the I2C clock speed to 400kHz.
// DEBUG
if (DEBUG_pulse || DEBUG_measures || DEBUG_angular_motions || DEBUG_RC) {
Serial.begin(57600);
}
// Turn LED on during setup
pinMode(13, OUTPUT);
digitalWrite(13, HIGH);
// Set pins #4 #5 #6 #7 as outputs
DDRD |= B11110000;
setupMpu6050Registers();
calibrateMpu6050();
configureChannelMapping();
//Serial.begin(9600);
// Configure interrupts for receiver
PCICR |= (1 << PCIE0); // Set PCIE0 to enable PCMSK0 scan
PCMSK0 |= (1 << PCINT0); // Set PCINT0 (digital input 8) to trigger an interrupt on state change
PCMSK0 |= (1 << PCINT1); // Set PCINT1 (digital input 9) to trigger an interrupt on state change
PCMSK0 |= (1 << PCINT2); // Set PCINT2 (digital input 10)to trigger an interrupt on state change
PCMSK0 |= (1 << PCINT3); // Set PCINT3 (digital input 11)to trigger an interrupt on state change
period = (1000000 / FREQ) ; // Sampling period in µs
// Initialize loop_timer
loop_timer = micros();
// Turn LED off now setup is done
digitalWrite(13, LOW);
stopAll();
}
/**
Main program loop
*/
void loop() {
// 1. First, read raw values from MPU-6050
readSensor();
// 2. Calculate angles from gyro & accelerometer's values
calculateAngles();
readAnalogue();
// 3. Calculate set points of PID controller
calculateSetPoints();
// 4. Calculate errors comparing angular motions to set points
calculateErrors();
//if (isStarted()) {
// 5. Calculate motors speed with PID controller
pidController();
//compensateBatteryDrop();
// }
// 6. Apply motors speed
//Serial.println(pulse_length[CHANNEL3]);
if (pulse_length[CHANNEL3] < (servoMin+18)) {
stopAll();
} else {
pidController();
}
applyMotorSpeed();
if (DEBUG_pulse) {
Serial.print(pulse_length_esc1);
Serial.print(",");
Serial.print(pulse_length_esc2);
Serial.print(",");
Serial.print(pulse_length_esc3);
Serial.print(",");
Serial.print(pulse_length_esc4);
Serial.print(",");
}
if (DEBUG_RC) {
Serial.print(pulse_length[CHANNEL1]);
Serial.print(",");
Serial.print(pulse_length[CHANNEL2]);
Serial.print(",");
Serial.print(pulse_length[CHANNEL3]);
Serial.print(",");
Serial.print(pulse_length[CHANNEL4]);
Serial.print(",");
}
if (DEBUG_measures) {
Serial.print(measures[ROLL]);
Serial.print(",");
Serial.print(measures[PITCH]);
Serial.print(",");
Serial.print(measures[YAW]);
Serial.print(",");
}
if (DEBUG_angular_motions) {
Serial.print(angular_motions[ROLL]);
Serial.print(",");
Serial.print(angular_motions[PITCH]);
Serial.print(",");
Serial.print(angular_motions[YAW]);
Serial.print(",");
}
if (DEBUG_pulse || DEBUG_measures || DEBUG_angular_motions || DEBUG_RC) {
Serial.print("\n");
}
}
/**
Generate servo-signal on digital pins #4 #5 #6 #7 with a frequency of 250Hz (4ms period).
Direct port manipulation is used for performances.
This function might not take more than 2ms to run, which lets 2ms remaining to do other stuff.
@see https:// www.arduino.cc/en/Reference/PortManipulation
*/
void applyMotorSpeed() {
// Refresh rate is 250Hz: send ESC pulses every 4000µs
while ((now = micros()) - loop_timer < period);
// Update loop timer
loop_timer = now;
// Set pins #4 #5 #6 #7 HIGH
PORTD |= B11110000;
// Wait until all pins #4 #5 #6 #7 are LOW
while (PORTD >= 16) {
now = micros();
difference = now - loop_timer;
if (difference >= pulse_length_esc1) PORTD &= B11101111; // Set pin #4 LOW
if (difference >= pulse_length_esc2) PORTD &= B11011111; // Set pin #5 LOW
if (difference >= pulse_length_esc3) PORTD &= B10111111; // Set pin #6 LOW
if (difference >= pulse_length_esc4) PORTD &= B01111111; // Set pin #7 LOW
}
}
/**
Request raw values from MPU6050.
*/
void readSensor() {
Wire.beginTransmission(MPU_ADDRESS); // Start communicating with the MPU-6050
Wire.write(0x3B); // Send the requested starting register
Wire.endTransmission(); // End the transmission
Wire.requestFrom(MPU_ADDRESS, 14); // Request 14 bytes from the MPU-6050
// Wait until all the bytes are received
while (Wire.available() < 14);
acc_raw[X] = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the acc_raw[X] variable
acc_raw[Y] = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the acc_raw[Y] variable
acc_raw[Z] = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the acc_raw[Z] variable
temperature = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the temperature variable
gyro_raw[X] = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the gyro_raw[X] variable
gyro_raw[Y] = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the gyro_raw[Y] variable
gyro_raw[Z] = Wire.read() << 8 | Wire.read(); // Add the low and high byte to the gyro_raw[Z] variable
}
/**
Calculate real angles from gyro and accelerometer's values
*/
void calculateAngles() {
calculateGyroAngles();
calculateAccelerometerAngles();
if (initialized) {
// Correct the drift of the gyro with the accelerometer
gyro_angle[X] = gyro_angle[X] * 0.9996 + acc_angle[X] * 0.0004;
gyro_angle[Y] = gyro_angle[Y] * 0.9996 + acc_angle[Y] * 0.0004;
} else {
// At very first start, init gyro angles with accelerometer angles
resetGyroAngles();
initialized = true;
}
// To dampen the pitch and roll angles a complementary filter is used
measures[ROLL] = measures[ROLL] * 0.9 + gyro_angle[X] * 0.1;
measures[PITCH] = measures[PITCH] * 0.9 + gyro_angle[Y] * 0.1;
measures[YAW] = -gyro_raw[Z] / SSF_GYRO; // Store the angular motion for this axis
// Apply low-pass filter (10Hz cutoff frequency)
angular_motions[ROLL] = 0.7 * angular_motions[ROLL] + 0.3 * gyro_raw[X] / SSF_GYRO;
angular_motions[PITCH] = 0.7 * angular_motions[PITCH] + 0.3 * gyro_raw[Y] / SSF_GYRO;
angular_motions[YAW] = 0.7 * angular_motions[YAW] + 0.3 * gyro_raw[Z] / SSF_GYRO;
}
/**
Calculate pitch & roll angles using only the gyro.
*/
void calculateGyroAngles() {
// Subtract offsets
gyro_raw[X] -= gyro_offset[X];
gyro_raw[Y] -= gyro_offset[Y];
gyro_raw[Z] -= gyro_offset[Z];
// Angle calculation using integration
gyro_angle[X] += (gyro_raw[X] / (FREQ * SSF_GYRO));
gyro_angle[Y] += (-gyro_raw[Y] / (FREQ * SSF_GYRO)); // Change sign to match the accelerometer's one
// Transfer roll to pitch if IMU has yawed
gyro_angle[Y] += gyro_angle[X] * sin(gyro_raw[Z] * (PI / (FREQ * SSF_GYRO * 180)));
gyro_angle[X] -= gyro_angle[Y] * sin(gyro_raw[Z] * (PI / (FREQ * SSF_GYRO * 180)));
}
/**
Calculate pitch & roll angles using only the accelerometer.
*/
void calculateAccelerometerAngles() {
// Calculate total 3D acceleration vector : √(X² + Y² + Z²)
acc_total_vector = sqrt(pow(acc_raw[X], 2) + pow(acc_raw[Y], 2) + pow(acc_raw[Z], 2));
// To prevent asin to produce a NaN, make sure the input value is within [-1;+1]
if (abs(acc_raw[X]) < acc_total_vector) {
acc_angle[X] = asin((float)acc_raw[Y] / acc_total_vector) * (180 / PI); // asin gives angle in radian. Convert to degree multiplying by 180/pi
}
if (abs(acc_raw[Y]) < acc_total_vector) {
acc_angle[Y] = asin((float)acc_raw[X] / acc_total_vector) * (180 / PI);
}
}
/**
Calculate motor speed for each motor of an X quadcopter depending on received instructions and measures from sensor
by applying PID control.
(A) (B) x
\ / z ↑
X \|
/ \ +----→ y
(C) (D)
Motors A & D run clockwise.
Motors B & C run counter-clockwise.
Each motor output is considered as a servomotor. As a result, value range is about 1000µs to 2000µs
*/
void pidController() {
float yaw_pid = 0;
float pitch_pid = 0;
float roll_pid = 0;
int throttle = pulse_length[mode_mapping[THROTTLE]];
// Initialize motor commands with throttle
pulse_length_esc1 = throttle;
pulse_length_esc2 = throttle;
pulse_length_esc3 = throttle;
pulse_length_esc4 = throttle;
// Do not calculate anything if throttle is 0
if (throttle >= 450) {
// PID = e.Kp + ∫e.Ki + Δe.Kd
yaw_pid = (errors[YAW] * Kp[YAW]) + (error_sum[YAW] * Ki[YAW]) + (delta_err[YAW] * Kd[YAW]);
pitch_pid = (errors[PITCH] * Kp[PITCH]) + (error_sum[PITCH] * Ki[PITCH]) + (delta_err[PITCH] * Kd[PITCH]);
roll_pid = (errors[ROLL] * Kp[ROLL]) + (error_sum[ROLL] * Ki[ROLL]) + (delta_err[ROLL] * Kd[ROLL]);
// Keep values within acceptable range. TODO export hard-coded values in variables/const
yaw_pid = minMax(yaw_pid, -pidRange, pidRange);
pitch_pid = minMax(pitch_pid, -pidRange, pidRange);
roll_pid = minMax(roll_pid, -pidRange, pidRange);
// Calculate pulse duration for each ESC
pulse_length_esc1 = throttle - roll_pid - pitch_pid + yaw_pid;
pulse_length_esc2 = throttle + roll_pid - pitch_pid - yaw_pid;
pulse_length_esc3 = throttle - roll_pid + pitch_pid - yaw_pid;
pulse_length_esc4 = throttle + roll_pid + pitch_pid + yaw_pid;
}
// Prevent out-of-range-values
pulse_length_esc1 = minMax(pulse_length_esc1, servoMin, servoMax);
pulse_length_esc2 = minMax(pulse_length_esc2, servoMin, servoMax);
pulse_length_esc3 = minMax(pulse_length_esc3, servoMin, servoMax);
pulse_length_esc4 = minMax(pulse_length_esc4, servoMin, servoMax);
}
/**
Calculate errors used by PID controller
*/
void calculateErrors() {
// Calculate current errors
errors[YAW] = angular_motions[YAW] - pid_set_points[YAW];
errors[PITCH] = angular_motions[PITCH] - pid_set_points[PITCH];
errors[ROLL] = angular_motions[ROLL] - pid_set_points[ROLL];
// Calculate sum of errors : Integral coefficients
error_sum[YAW] += errors[YAW];
error_sum[PITCH] += errors[PITCH];
error_sum[ROLL] += errors[ROLL];
// Keep values in acceptable range
error_sum[YAW] = minMax(error_sum[YAW], -pidRange / Ki[YAW], pidRange / Ki[YAW]);
error_sum[PITCH] = minMax(error_sum[PITCH], -pidRange / Ki[PITCH], pidRange / Ki[PITCH]);
error_sum[ROLL] = minMax(error_sum[ROLL], -pidRange / Ki[ROLL], pidRange / Ki[ROLL]);
// Calculate error delta : Derivative coefficients
delta_err[YAW] = errors[YAW] - previous_error[YAW];
delta_err[PITCH] = errors[PITCH] - previous_error[PITCH];
delta_err[ROLL] = errors[ROLL] - previous_error[ROLL];
// Save current error as previous_error for next time
previous_error[YAW] = errors[YAW];
previous_error[PITCH] = errors[PITCH];
previous_error[ROLL] = errors[ROLL];
}
/**
Customize mapping of controls: set here which command is on which channel and call
this function in setup() routine.
*/
void configureChannelMapping() {
mode_mapping[YAW] = CHANNEL4;
mode_mapping[PITCH] = CHANNEL2;
mode_mapping[ROLL] = CHANNEL1;
mode_mapping[THROTTLE] = CHANNEL3;
}
/**
Configure gyro and accelerometer precision as following:
- accelerometer: ±8g
- gyro: ±500°/s
@see https://www.invensense.com/wp-content/uploads/2015/02/MPU-6000-Register-Map1.pdf
*/
void setupMpu6050Registers() {
// Configure power management
Wire.beginTransmission(MPU_ADDRESS); // Start communication with MPU
Wire.write(0x6B); // Request the PWR_MGMT_1 register
Wire.write(0x00); // Apply the desired configuration to the register
Wire.endTransmission(); // End the transmission
// Configure the gyro's sensitivity
Wire.beginTransmission(MPU_ADDRESS); // Start communication with MPU
Wire.write(0x1B); // Request the GYRO_CONFIG register
Wire.write(0x08); // Apply the desired configuration to the register : ±500°/s
Wire.endTransmission(); // End the transmission
// Configure the acceleromter's sensitivity
Wire.beginTransmission(MPU_ADDRESS); // Start communication with MPU
Wire.write(0x1C); // Request the ACCEL_CONFIG register
Wire.write(0x10); // Apply the desired configuration to the register : ±8g
Wire.endTransmission(); // End the transmission
// Configure low pass filter
Wire.beginTransmission(MPU_ADDRESS); // Start communication with MPU
Wire.write(0x1A); // Request the CONFIG register
Wire.write(0x03); // Set Digital Low Pass Filter about ~43Hz
Wire.endTransmission(); // End the transmission
}
/**
Calibrate MPU6050: take 2000 samples to calculate average offsets.
During this step, the quadcopter needs to be static and on a horizontal surface.
This function also sends low throttle signal to each ESC to init and prevent them beeping annoyingly.
This function might take ~2sec for 2000 samples.
*/
void calibrateMpu6050() {
int max_samples = 10;
for (int i = 0; i < max_samples; i++) {
readSensor();
gyro_offset[X] += gyro_raw[X];
gyro_offset[Y] += gyro_raw[Y];
gyro_offset[Z] += gyro_raw[Z];
// Generate low throttle pulse to init ESC and prevent them beeping
PORTD |= B11110000; // Set pins #4 #5 #6 #7 HIGH
delayMicroseconds(600); // Wait 1000µs
PORTD &= B00001111; // Then set LOW
// Just wait a bit before next loop
delay(3);
}
// Calculate average offsets
gyro_offset[X] /= max_samples;
gyro_offset[Y] /= max_samples;
gyro_offset[Z] /= max_samples;
}
/**
Make sure that given value is not over min_value/max_value range.
@param float value : The value to convert
@param float min_value : The min value
@param float max_value : The max value
@return float
*/
float minMax(float value, float min_value, float max_value) {
if (value > max_value) {
value = max_value;
} else if (value < min_value) {
value = min_value;
}
return value;
}
/**
Return whether the quadcopter is started.
To start the quadcopter, move the left stick in bottom left corner then, move it back in center position.
To stop the quadcopter move the left stick in bottom right corner.
@return bool
*/
bool isStarted() {
// When left stick is moved in the bottom left corner
if (status == STOPPED && pulse_length[mode_mapping[YAW]] <= 462 && pulse_length[mode_mapping[THROTTLE]] <= 462) {
status = STARTING;
}
// When left stick is moved back in the center position
if (status == STARTING && pulse_length[mode_mapping[YAW]] == 1025 && pulse_length[mode_mapping[THROTTLE]] <= 462) {
status = STARTED;
// Reset PID controller's variables to prevent bump start
resetPidController();
resetGyroAngles();
}
// When left stick is moved in the bottom right corner
if (status == STARTED && pulse_length[mode_mapping[YAW]] >= 2480 && pulse_length[mode_mapping[THROTTLE]] <= 462) {
status = STOPPED;
// Make sure to always stop motors when status is STOPPED
stopAll();
}
resetPidController();
resetGyroAngles();
return status == STARTED;
}
/**
Reset gyro's angles with accelerometer's angles.
*/
void resetGyroAngles() {
gyro_angle[X] = acc_angle[X];
gyro_angle[Y] = acc_angle[Y];
}
/**
Reset motors' pulse length to 1000µs to totally stop them.
*/
void stopAll() {
pulse_length_esc1 = servoMin;
pulse_length_esc2 = servoMin;
pulse_length_esc3 = servoMin;
pulse_length_esc4 = servoMin;
}
/**
Reset all PID controller's variables.
*/
void resetPidController() {
errors[YAW] = 0;
errors[PITCH] = 0;
errors[ROLL] = 0;
error_sum[YAW] = 0;
error_sum[PITCH] = 0;
error_sum[ROLL] = 0;
previous_error[YAW] = 0;
previous_error[PITCH] = 0;
previous_error[ROLL] = 0;
}
/**
Calculate PID set points on axis YAW, PITCH, ROLL
*/
void calculateSetPoints() {
pid_set_points[YAW] = calculateYawSetPoint(pulse_length[mode_mapping[YAW]], pulse_length[mode_mapping[THROTTLE]]);
pid_set_points[PITCH] = calculateSetPoint(measures[PITCH], pulse_length[mode_mapping[PITCH]]);
pid_set_points[ROLL] = calculateSetPoint(measures[ROLL], pulse_length[mode_mapping[ROLL]]);
}
/**
Calculate the PID set point in °/s
@param float angle Measured angle (in °) on an axis
@param int channel_pulse Pulse length of the corresponding receiver channel
@return float
*/
float calculateSetPoint(float angle, int channel_pulse) {
float level_adjust = angle * 15; // Value 15 limits maximum angle value to ±32.8°
float set_point = 0;
// Need a dead band of 16µs for better result
if (channel_pulse > servoMid + 8 ) {
set_point = channel_pulse - servoMid + 8;
} else if (channel_pulse < servoMid - 8) {
set_point = channel_pulse - servoMid -8;
}
set_point -= level_adjust;
set_point /= 3;
return set_point;
}
/**
Calculate the PID set point of YAW axis in °/s
@param int yaw_pulse Receiver pulse length of yaw's channel
@param int throttle_pulse Receiver pulse length of throttle's channel
@return float
*/
float calculateYawSetPoint(int yaw_pulse, int throttle_pulse) {
float set_point = 0;
// Do not yaw when turning off the motors
if (throttle_pulse > servoMin) {
// There is no notion of angle on this axis as the quadcopter can turn on itself
set_point = calculateSetPoint(0, yaw_pulse);
}
return set_point;
}
/**
Compensate battery drop applying a coefficient on output values
*/
void compensateBatteryDrop() {
if (isBatteryConnected()) {
pulse_length_esc1 += pulse_length_esc1 * ((1240 - battery_voltage) / (float) 3500);
pulse_length_esc2 += pulse_length_esc2 * ((1240 - battery_voltage) / (float) 3500);
pulse_length_esc3 += pulse_length_esc3 * ((1240 - battery_voltage) / (float) 3500);
pulse_length_esc4 += pulse_length_esc4 * ((1240 - battery_voltage) / (float) 3500);
}
}
/**
Read battery voltage & return whether the battery seems connected
@return boolean
*/
bool isBatteryConnected() {
// Reduce noise with a low-pass filter (10Hz cutoff frequency)
battery_voltage = battery_voltage * 0.92 + (analogRead(0) + 65) * 0.09853;
return battery_voltage < 1240 && battery_voltage > 800;
}
/**
This Interrupt Sub Routine is called each time input 8, 9, 10 or 11 changed state.
Read the receiver signals in order to get flight instructions.
This routine must be as fast as possible to prevent main program to be messed up.
The trick here is to use port registers to read pin state.
Doing (PINB & B00000001) is the same as digitalRead(8) with the advantage of using less CPU loops.
It is less convenient but more efficient, which is the most important here.
@see https://www.arduino.cc/en/Reference/PortManipulation
@see https://www.firediy.fr/article/utiliser-sa-radiocommande-avec-un-arduino-drone-ch-6
*/
ISR(PCINT0_vect) {
current_time = micros();
// Channel 1 -------------------------------------------------
if (PINB & B00000001) { // Is input 8 high ?
if (previous_state[CHANNEL1] == LOW) { // Input 8 changed from 0 to 1 (rising edge)
previous_state[CHANNEL1] = HIGH; // Save current state
timer[CHANNEL1] = current_time; // Save current time
}
} else if (previous_state[CHANNEL1] == HIGH) { // Input 8 changed from 1 to 0 (falling edge)
previous_state[CHANNEL1] = LOW; // Save current state
pulse_length[CHANNEL1] = current_time - timer[CHANNEL1]; // Calculate pulse duration & save it
}
// Channel 2 -------------------------------------------------
if (PINB & B00000010) { // Is input 9 high ?
if (previous_state[CHANNEL2] == LOW) { // Input 9 changed from 0 to 1 (rising edge)
previous_state[CHANNEL2] = HIGH; // Save current state
timer[CHANNEL2] = current_time; // Save current time
}
} else if (previous_state[CHANNEL2] == HIGH) { // Input 9 changed from 1 to 0 (falling edge)
previous_state[CHANNEL2] = LOW; // Save current state
pulse_length[CHANNEL2] = current_time - timer[CHANNEL2]; // Calculate pulse duration & save it
}
// Channel 3 -------------------------------------------------
if (PINB & B00000100) { // Is input 10 high ?
if (previous_state[CHANNEL3] == LOW) { // Input 10 changed from 0 to 1 (rising edge)
previous_state[CHANNEL3] = HIGH; // Save current state
timer[CHANNEL3] = current_time; // Save current time
}
} else if (previous_state[CHANNEL3] == HIGH) { // Input 10 changed from 1 to 0 (falling edge)
previous_state[CHANNEL3] = LOW; // Save current state
pulse_length[CHANNEL3] = current_time - timer[CHANNEL3]; // Calculate pulse duration & save it
}
// Channel 4 -------------------------------------------------
if (PINB & B00001000) { // Is input 11 high ?
if (previous_state[CHANNEL4] == LOW) { // Input 11 changed from 0 to 1 (rising edge)
previous_state[CHANNEL4] = HIGH; // Save current state
timer[CHANNEL4] = current_time; // Save current time
}
} else if (previous_state[CHANNEL4] == HIGH) { // Input 11 changed from 1 to 0 (falling edge)
previous_state[CHANNEL4] = LOW; // Save current state
pulse_length[CHANNEL4] = current_time - timer[CHANNEL4]; // Calculate pulse duration & save it
}
}
void readAnalogue() {
pulse_length[CHANNEL1] = servoMid; //map(analogRead(A0),0,1023,450,2500); // ROLL
pulse_length[CHANNEL2] = servoMid; //map(analogRead(A1),0,1023,450,2500); // PITCH
pulse_length[CHANNEL3] = map(analogRead(A3), 0, 1023, 450, 2500); // THROTTLE
pulse_length[CHANNEL4] = servoMid; //map(analogRead(A2),0,1023,450,2500); // YAW
}