#define echoPin 21 // Echo Pin
#define trigPin 13 // Trigger Pin
long duration, distance; // Duration used to calculate distance
void setup()
{
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
Serial.begin(9600); // Starts the serial communication
}
void loop()
{
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);

digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
//distance= duration*0.034/2;
distance = (duration/2) / 29.1;
Serial.print("ACTUAL-DIS: ");
Serial.println(distance);
delay(1500);
}