LineFollower.ino

/*
** Line Follower Basic
** Version 0.6
** Last Update: 2013-05-24
** By Stan, http://42bots.com
*/

/* Define motor controll inputs */
const int motorRPin1 = 2; // signal pin 1 for the right motor, connect to IN1               
const int motorRPin2 = 3;  // signal pin 2 for the right motor, connect to IN2
const int motorREnable = 5; // enable pin for the right motor (PWM enabled)

const int motorLPin1 = 4; // signal pin 1 for the left motor, connect to IN3           
const int motorLPin2 = 7; // signal pin 2 for the left motor, connect to IN4
const int motorLEnable = 6; // enable pin for the left motor (PWM enabled)

/* Define the pins for the IR receivers */
const int irPins[6] = {A0, A1, A2, A3, A4, A5};

/* Define values for the IR Sensor readings */

// an array to hold values from analogRead on the ir sensor (0-1023)
int irSensorAnalog[6] = {0,0,0,0,0,0}; 

// an array to hold boolean values (1/0) for the ir sensors
int irSensorDigital[6] = {0,0,0,0,0,0};

int treashold = 700; // IR sensor treashold value for line detection

// binary representation of the sensor reading 
//from left to right when facing the same direction as the robot
int irSensors = B000000; 

int count = 0; // number of sensors detecting the line

// A score to determine deviation from the line [-180 ; +180]. 
// Negative means the robot is left of the line.
int error = 0;  

int errorLast = 0;  //  store the last value of error

// A correction value, based on the error from target. 
// It is used to change the relative motor speed with PWM.
int correction = 0; 

int lap = 0; // keep track of the laps

/* Set up maximum speed and speed for turning (to be used with PWM) */
int maxSpeed = 255; // used for PWM to control motor speed [0 - 255]

/* variables to keep track of current speed of motors */
int motorLSpeed = 0;
int motorRSpeed = 0;

void setup() {

  /* Set up motor controll pins as output */
  pinMode(motorLPin1,OUTPUT);        
  pinMode(motorLPin2,OUTPUT);
  pinMode(motorLEnable,OUTPUT);
  
  pinMode(motorRPin1,OUTPUT);        
  pinMode(motorRPin2,OUTPUT);
  pinMode(motorREnable,OUTPUT);
   
  /* Set-up IR sensor pins as input */
  for (int i = 0; i < 6; i++) {
    pinMode(irPins[i], INPUT);
  }
  
  /* 
  Optional change for better PWM control of the DC motors below.
  
  Change the PWM frequency of digital pins 5 and 6 (timer0) to Phase-correct 
  PWM of 31.250 kHz from the default of ~500Hz. Using code from "Adjusting PWM 
  Frequencies http://playground.arduino.cc/Main/TimerPWMCheatsheet".
  
  This requires a separate change in the wiring.c function in the Arduino 
  program file hardware\arduino\cores\arduino\wiring.c from:
  #define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(64 * 256))
  
  to:
  #define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(1 * 510))
  
  Without the change to wiring.c time functions (millis, delay, as well as 
  libraries using them will not work corectly.
  */
  TCCR0A = _BV(COM0A1) | _BV(COM0B1) | _BV(WGM01) | _BV(WGM00); 
  TCCR0B = _BV(CS00); 
    
  /* Set-up console output for debugging.  */
  //Serial.begin(115200);
}

void loop() {
 Scan();
 UpdateError();
 UpdateCorrection();
 Drive();
 //Serial.println();
}

void Scan() {
  // Initialize the sensor counter and binary value
  count = 0;
  irSensors = B000000;
    
  for (int i = 0; i < 6; i++) {
    irSensorAnalog[i] = analogRead(irPins[i]);

    if (irSensorAnalog[i] >= treashold) {
        irSensorDigital[i] = 1;
    }
    else {irSensorDigital[i] = 0;}
    //Serial.print(irSensorAnalog[i]);
    //Serial.print("|");
    count = count + irSensorDigital[i];
    int b = 5-i;
    irSensors = irSensors + (irSensorDigital[i]<<b);
    }    
}

void UpdateError() {
  
  errorLast = error;  
  
  switch (irSensors) {
     
    case B000000:
       if (errorLast < 0) { error = -180;}
       else if (errorLast > 0) {error = 180;}
       break;
     
     case B100000: // leftmost sensor on the line
       error = -150;
       break;
      
     case B010000:
       error = -90;
       break;

     case B001000: 
       error = -30;
       break;

     case B000100:  
       error = 30;
       break;
       
     case B000010: 
       error = 90;
       break;           

     case B000001: // rightmost sensor on the line
       error = 150;
       break;
       
/* 2 Sensors on the line */         
     
     case B110000:
       error = -120;
       break;
      
     case B011000:
       error = -60;
       break;

     case B001100: 
       error = 0;
       break;

     case B000110: 
       error = 60;
       break;           

     case B000011:
       error = 120;
       break;

/* 3 Sensors on the line */    
       
     case B111000:
     case B011100:
       error = -150;
       break;
      
     case B000111:
     case B001110:
       error = 150;
       break;

 /* 4 Sensors on the line */       
     case B111100:
       error = -150;
       break;
       
     case B111010:
       error = -150;
       break;
      
     case B001111:
       error = 150;
       break;
       
     case B010111:
       error = 150;
       break;

/* 5 Sensors on the line */      
     case B111110:
       error = -150;
       break;
      
     case B011111:
       error = +150;
       break;
      
     case B111111:
       lap = lap + 1;
       error = 0;
       break;
   
     default:
     	error = errorLast;
//      Serial.print("Unhandled case: ");
//      Serial.println(count);
//      Serial.print("| ");
//      Serial.println(irSensors);    
  }
}

void UpdateCorrection() {

  if (error >= 0 && error < 30) {
    correction = 0;
  }
  
  else if (error >=30 && error < 60) {
    correction = 15;
  }
  
  else if (error >=60 && error < 90) {
    correction = 40;
  }
  
  else if (error >=90 && error < 120) {
    correction = 55;
  }  
  
  else if (error >=120 && error < 150) {
    correction = 75;
  } 
  
  else if (error >=150 && error < 180) {
    correction = 255;
  }   

  else if (error >=180) {
    correction = 305;
  }

  if (error <= 0 && error > -30) {
    correction = 0;
  }
  
  else if (error <= -30 && error > -60) {
    correction = -15;
  }
  
  else if (error <= -60 && error > -90) {
    correction = -40;
  }
  
  else if (error <= -90 && error > -120) {
    correction = -55;
  }  
  
  else if (error <= -120 && error > -150) {
    correction = -75;
  } 
  
  else if (error <= -150 && error > -180) {
    correction = -255;
  }   

  else if (error <= -180) {
    correction = -305;
  }
  
  /* Adjust the correction value if maxSpeed is less than 255 */
  correction = (int) (correction * maxSpeed / 255 + 0.5);
  
  if (correction >= 0) {
    motorRSpeed = maxSpeed - correction;
    motorLSpeed = maxSpeed;
  }
  
  else if (correction < 0) {
    motorRSpeed = maxSpeed;
    motorLSpeed = maxSpeed + correction;
  }
}

void Drive() {
  if (motorRSpeed > 255) {motorRSpeed = 255;}
  else if (motorRSpeed < -255) {motorRSpeed = -255;}
  
  if (motorLSpeed > 255) {motorLSpeed = 255;}
  else if (motorLSpeed < -255) {motorLSpeed = -255;}
  
  if (motorRSpeed > 0) { // right motor forward (using PWM)
     analogWrite(motorREnable, motorRSpeed);
     digitalWrite(motorRPin1, HIGH);
     digitalWrite(motorRPin2, LOW);
  } 
  
  else if (motorRSpeed < 0) {// right motor reverse (using PWM)
     analogWrite(motorREnable, abs(motorRSpeed));
     digitalWrite(motorRPin1, LOW);
     digitalWrite(motorRPin2, HIGH);
  } 
  
  else if (motorRSpeed == 0) { // right motor fast stop
     digitalWrite(motorREnable, HIGH);
     digitalWrite(motorRPin1, LOW);
     digitalWrite(motorRPin2, LOW);
  }
  
  if (motorLSpeed > 0) { // left motor forward (using PWM)
     analogWrite(motorLEnable, motorLSpeed);
     digitalWrite(motorLPin1, HIGH);
     digitalWrite(motorLPin2, LOW);
  } 
  
  else if (motorLSpeed < 0) { // right motor reverse (using PWM)
     analogWrite(motorLEnable, abs(motorLSpeed));
     digitalWrite(motorLPin1, LOW);
     digitalWrite(motorLPin2, HIGH);
  } 
  
    else if (motorLSpeed == 0) { // left motor fast stop
     digitalWrite(motorLEnable, HIGH);
     digitalWrite(motorLPin1, LOW);
     digitalWrite(motorLPin2, LOW);
  }
}