const int TRIG_PIN_F = 6; 
const int ECHO_PIN_F = 5; 
const int THRESHOLD_F= 50; 

const int TRIG_PIN_R = 51; 
const int ECHO_PIN_R = 50; 
const int THRESHOLD_R= 20;

const int TRIG_PIN_L = 48; 
const int ECHO_PIN_L = 49; 
const int THRESHOLD_L= 20;



float duration_us_F, distance_cm_F,duration_us_R ;
float distance_cm_R,duration_us_L, distance_cm_L;

void setup() {
  Serial.begin (9600);       
  pinMode(TRIG_PIN_F, OUTPUT); 
  pinMode(ECHO_PIN_F, INPUT);   
  pinMode(TRIG_PIN_R, OUTPUT); 
  pinMode(ECHO_PIN_R, INPUT);  
  pinMode(TRIG_PIN_L, OUTPUT); 
  pinMode(ECHO_PIN_L, INPUT);   
  pinMode(13, OUTPUT);  
  pinMode(11, OUTPUT);

}

void loop() {
   ultrasonic_F();
  if(distance_cm_F < THRESHOLD_F) {
    ultrasonic_R();
    ultrasonic_L();
    if(distance_cm_R < 40 && distance_cm_L > 40) 
    {
      digitalWrite(13, LOW); 
      digitalWrite(11, HIGH);
   }
   if(distance_cm_R >40 && distance_cm_L < 40)
   {
     digitalWrite(13, HIGH); 
      digitalWrite(11, LOW);
   }
   if (distance_cm_R <= 40 && distance_cm_L <= 40){
     digitalWrite(13, HIGH); 
     digitalWrite(11, LOW); 
   }
   if (distance_cm_R > 40 && distance_cm_L > 40){
    digitalWrite(13, HIGH); 
     digitalWrite(11, LOW); 

   }
}else{
  digitalWrite(13, HIGH);
  digitalWrite(11, HIGH);
}
 
}

void ultrasonic_F(){
  digitalWrite(TRIG_PIN_F, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN_F, LOW);
  duration_us_F = pulseIn(ECHO_PIN_F, HIGH);
  distance_cm_F = 0.017 * duration_us_F;
  Serial.print("object distance in front : ");
  Serial.print(distance_cm_F);
  Serial.println(" cm");
  delay(500);
}
void ultrasonic_R(){
  digitalWrite(TRIG_PIN_R, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN_R, LOW);
  duration_us_R = pulseIn(ECHO_PIN_R, HIGH);
  distance_cm_R = 0.017 * duration_us_R;
  Serial.print("object distance in right : ");
  Serial.print(distance_cm_R);
  Serial.println(" cm");
  delay(500);
}
void ultrasonic_L(){
  digitalWrite(TRIG_PIN_L, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN_L, LOW);
  duration_us_L= pulseIn(ECHO_PIN_L, HIGH);
  distance_cm_L = 0.017 * duration_us_L;
  Serial.print("object distance in left  : ");
  Serial.print(distance_cm_L);
  Serial.println(" cm");
  delay(500);
}