#define trigPin 9 // define the trig pin
#define echoPin 10 // define the echo pin

void setup() {
  Serial.begin(9600); // initialize serial communication
  pinMode(trigPin, OUTPUT); // set trig pin as output
  pinMode(echoPin, INPUT); // set echo pin as input
}

void loop() {
  long duration, distance; // declare variables for duration and distance

  // send a 10us pulse to the ultrasonic sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // measure the duration of the pulse from the echo pin
  duration = pulseIn(echoPin, HIGH);

  // calculate the distance in centimeters
  distance = duration / 58.2;

  // print out the distance in centimeters
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(500); // wait for 500ms before measuring again
}