const int trigPin = 7; 
  const int echoPin=4; 
  void setup() { 
  Serial.begin(9600); 
  //establish motor direction toggle pins 
  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, 200); 
   
  //Sets initial direction of drive motor 
  digitalWrite(12, HIGH); 
  } 
   
  void loop() 
  { 
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters: 
  long duration, inches, cm; 
   
  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds. 
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse: 
  pinMode(trigPin, OUTPUT); 
  digitalWrite(trigPin, LOW); 
  delayMicroseconds(2); 
  digitalWrite(trigPin, HIGH); 
  delayMicroseconds(5); 
  digitalWrite(trigPin, LOW); 
   
  // The same pin is used to read the signal from the PING))): a HIGH 
  // pulse whose duration is the time (in microseconds) from the sending 
  // of the ping to the reception of its echo off of an object. 
  pinMode(echoPin, INPUT); 
  duration = pulseIn(echoPin, HIGH); 
   
  // convert the time into a distance 
  inches = microsecondsToInches(duration); 
   
  // 
  //if objects are less than 12 inches away 
  //the robot reverses and turns to the right 
  //for 2 seconds 
  // 
   
  if (inches < 12){ 
   
  //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, 200); 
   
  } 
   
  delay(100); 
  } 
   
  long microsecondsToInches(long microseconds) 
  { 
  return microseconds / 74 / 2; 
  }