Project 2 - Measuring the distance of an object using ultrasonic sensor and also smoothen the sensor data using moving average filter

// this constant won't change. It's the pin number of the sensor's output:
const int pingPin = 7;
long sum = 0;
int i;
 void setup() {
  // initialize serial communication:
  Serial.begin(9600);
}
  void loop() {
  // establish variables for duration of the ping, and the distance result
  // in inches and centimeters:
    
  long duration, inches, cm, avg;
  // 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(7, OUTPUT);
  digitalWrite(7, LOW);
  delayMicroseconds(2);
  digitalWrite(7, HIGH);
  delayMicroseconds(5);
  digitalWrite(7, 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(7, INPUT);
  duration = pulseIn(7, HIGH);
  // convert the time into a distance  
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);
  for (i=0; i<3; i++)
		{
			sum=sum+inches;
			avg = sum/3;
		}

  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm, ");
  Serial.print(avg);
  Serial.print("avg");
  Serial.println();
  

  delay(100);
}

long microsecondsToInches(long microseconds) {
// According to Parallax's datasheet for the PING))), there are 73.746
// This gives the distance travelled by the ping, outbound and return,
// so we divide by 2 to get the distance of the obstacle.
  return microseconds / 74 / 2;
}
long microsecondsToCentimeters(long microseconds) {
// The speed of sound is 340 m/s or 29 microseconds per centimeter.
// The ping travels out and back, so to find the distance of the object we
// take half of the distance travelled.  
   return microseconds / 29 / 2;
}