Sketch 1

//Script and Notes by Viraj Doshi
//This script to allow the ardunio to print the direction in which the AR-Drone can travel
//Print FORWARD unless obsracle detected within range
//Print LEFT or RIGHT, which ever has the greatest detected distance
//Print FORWARD will resume when FORWARD is obstacle free

#define FRONT_TRIG 13 //FRONT
#define FRONT_ECHO 12 //FRONT
#define RIGHT_TRIG 11 //RIGHT
#define RIGHT_ECHO 10 //RIGHT
#define LEFT_TRIG 9 //LEFT
#define LEFT_ECHO 8 //LEFT
#define TOP_TRIG 7 //TOP
#define TOP_ECHO 6 //TOP

void setup() {
  Serial.begin (9600);
  pinMode(FRONT_TRIG, OUTPUT);
  pinMode(FRONT_ECHO, INPUT);
  pinMode(RIGHT_TRIG, OUTPUT);
  pinMode(RIGHT_ECHO, INPUT);
  pinMode(LEFT_TRIG, OUTPUT);
  pinMode(LEFT_ECHO, INPUT);
  pinMode(TOP_TRIG, OUTPUT);
  pinMode(TOP_ECHO, INPUT);
}

void loop() {
    long duration, FRONT, RIGHT, LEFT, TOP; // Duration used to calculate distance of an object from each sensor
 
  digitalWrite(TOP_TRIG, LOW);            // LOW triggered to ensure no interference from incoming signals, before triggering HIGH
  delayMicroseconds(2);
  digitalWrite(TOP_TRIG, HIGH);           // Send outs ultrasonic wave
  delayMicroseconds(10);                  // Delay allows for ample time to receive the echo signal from object
  digitalWrite(TOP_TRIG, LOW);
  duration = pulseIn(TOP_ECHO, HIGH);     // Calculates time taken to receive signal from reflected signal, pulse is HIGH when signal is received
  TOP = (duration/2) / 29.1;              // Calculates distances using the time calculated above and the speed of sound (300m/s)
  digitalWrite(FRONT_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(FRONT_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(FRONT_TRIG, LOW);
  duration = pulseIn(FRONT_ECHO, HIGH);
  FRONT = (duration/2) / 29.1;  
  digitalWrite(RIGHT_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(RIGHT_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(RIGHT_TRIG, LOW);
  duration = pulseIn(RIGHT_ECHO, HIGH);  
  RIGHT = (duration/2) / 29.1;
  digitalWrite(LEFT_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(LEFT_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(LEFT_TRIG, LOW);
  duration = pulseIn(LEFT_ECHO, HIGH);
  LEFT = (duration/2) / 29.1;
    
    if (TOP < 60) {
      Serial.println("T\n");
    }
    else{
    if ((RIGHT < 90) && (FRONT > 80)) {
        Serial.println("L\n");
    }
    if ((LEFT < 90) && (FRONT > 80)) {
        Serial.println("R\n");
    }  
    if (FRONT > 90) {
        Serial.println("F\n");
    }
    if (FRONT >= 7 && FRONT <= 50) {
        Serial.println("S\n");
    }
    else{   
       if ((LEFT < RIGHT) && (FRONT >=7 && FRONT <=89)) {
         Serial.println("P\n");
        }
       if ((LEFT > RIGHT) && (FRONT >=7 && FRONT <=89)) {
         Serial.println("Q\n");   
          }
       }
    }
}