#define EN1 9 // Pin9 (P2.1) : Motor1 speed (PWM)
#define M1 10 // Pin10 (P2.2) : Motor1 direction (Left Motor)

#define EN2 12  // Pin13 (P2.4) : Motor2 speed (PWM)  
#define M2 11 // Pin12 (P2.3) : Motor2 direction (Right Motor)

int LeftSensor = A4; // Left sensor on A4 - Pin6 (P1.4) 
int RightSensor = A7;  // Right sensor on A7 - Pin15 (P1.7)
int leftvalue;    // Left sensor value
int rightvalue;    // Right sensor value
int treshold = 720;  //sensor treshold value
int MotorSpeed = 30;   // motor speed

void setup() 
{ 
  pinMode(EN1, OUTPUT);  // Motor1 speed (PWM)
  pinMode(EN2, OUTPUT);  // Motor2 speed (PWM)
  pinMode(M1, OUTPUT);   // Motor1 direction (Left Motor)
  pinMode(M2, OUTPUT);   // Motor2 direction (Right Motor)
  MotorLeft(MotorSpeed);  // Robot: Forward
  MotorRight(MotorSpeed);
   Serial.begin(9600); // set up serial communication with PC
} 

void loop()  // infinite loop
{ 
  leftvalue = analogRead(LeftSensor);    // reading Left sensor value (0 - 1023) 
  rightvalue = analogRead(RightSensor);    // reading Right sensor value (0 - 1023) 
  
// if both sensors over carpet: move forward 
  if (leftvalue>treshold && rightvalue>treshold) 
  {
   MotorLeft(MotorSpeed);  //Left motor: forward 
   MotorRight(MotorSpeed);   //Right motor: forward 
  }
 // If Left sensor is over the line and Right sensor is over the carpet: turn left 
  else if (leftvalue<treshold && rightvalue>treshold)
  {
   MotorLeft(0);     //Left motor: stop 
   MotorRight(MotorSpeed);   //Right motor: forward 
  }
// If Left sensor is over the carpet and Right sensor is over the line: turn right
  else if (leftvalue>treshold && rightvalue<treshold)
  {
   MotorLeft(MotorSpeed);  //Left motor: forward 
   MotorRight(0);     //Right motor: stop 
  }
// If both sensor is over the line (line crossing): move forward 
    else if (leftvalue>treshold && rightvalue>treshold)
  {
   MotorLeft(MotorSpeed);  //Left motor: forward 
   MotorRight(MotorSpeed);   //Right motor: forward 
  }
  
// sending sensor data to PC via serial port
// (used for treshold setup and debugging)
  Serial.print("Left Sensor = " );                       
  Serial.print(leftvalue);        
  Serial.print(" Right Sensor = ");  
  Serial.println(rightvalue);  
  
  delay(50);  // wait for 50ms      
} 


void MotorLeft(int speed) 
{   
    if (speed>0)
	{
	digitalWrite(M1,HIGH);
    	analogWrite(EN1,speed*255/100);
	} 
	else
	{
	digitalWrite(M1,LOW);
    	analogWrite(EN1,abs(speed)*255/100);
	}
} 

void MotorRight(int speed) 
{   
    if (speed>0)
	{
	digitalWrite(M2,HIGH);
    	analogWrite(EN2,speed*255/100);
	} 
	else
	{
	digitalWrite(M2,LOW);
    	analogWrite(EN2,abs(speed)*255/100);
	}
}