Help with obstacle Avoidance Code

Projects Programming
1

I can't seem to figure out why this code won't work ( I'm a noob). When It runs all it does is activate the drive motor in a continuous loop. I want it to use the ultrasonic sensor then back up and repeat.

void setup() {

pinMode(12, OUTPUT); //drive motor -- HIGH = forwards and LOW = backwards
pinMode(13, OUTPUT); //turn motor -- HIGH = left and LOW = right

//establish motor brake pins
pinMode(9, OUTPUT); //brake (disable) the drive motor
pinMode(8, OUTPUT); //brake (disable) the turn motor

//Turns brake off for drive motor
digitalWrite(9, LOW);

//Turns brake on for turn motor
digitalWrite(8, HIGH);

//Sets initial speed of drive motor
analogWrite(3, 50);

//Sets initial direction of drive motor
digitalWrite(12, HIGH);

pinMode(13,OUTPUT);//sonar trig
pinMode(11,INPUT);//sonar echo

}

void loop()
{
digitalWrite(13, LOW);//clear trig
delayMicroseconds(2);
digitalWrite(13, HIGH);//trig
delayMicroseconds(10);
digitalWrite(13, LOW);//clear trig
long duration = pulseIn(11, HIGH);//read echo
long distance = (duration/2) / 29.1;

if (distance < 30){

//brake drive motor and pause 1/10 second
digitalWrite(9, HIGH);
delay(100);

//
//setting turn motor
//

//turn off brake for turn motor
digitalWrite(8, LOW);

//set turn motor direction
digitalWrite(13, HIGH);

//activate turn motor
analogWrite(11, 255);

//
//setting drive motor
//

//turn off brake of drive motor
digitalWrite(9, LOW);

//set drive motor backwards direction
digitalWrite(12, LOW);

//activate the drive motor
analogWrite(3, 200);

//backup for 2 seconds
delay(2000);

//
//stopping
//

//brake both motors
digitalWrite(8, HIGH);
digitalWrite(9, HIGH);

}

//
//when nothing is within 12"
//the robot simply drives forwards
//

else{

//Setting drive motor
//

//set drive motor forward direction
digitalWrite(12, HIGH);

//turn off brake of drive motor
digitalWrite(9, LOW);

//activate drive motor
analogWrite(3, 20);

}

delay(100);
}

2 
  long distance = (duration/2) / 29.1;

What value IS in distance? if you don't KNOW, why is the rest of that code in there? You can't use the value in a variable until you know that the value is reliable.

What, exactly, are you using pin 13 for? More precisely, how many things are you using pin 13 for? One is the correct answer, but not the one you should come up with.

3

Pin 13 is used for controlling the motor (foward/backwards). Also, I forgot to mention I'm using a motor shield.

4 
 pinMode(13,OUTPUT);//sonar trig

{cough}

5

Thank you >.<