// define pins for the ultrasonic sensor
const int trigPin = 9;
const int echoPin = 10;

// variables for duration and distance
long duration;
int distance;

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

void loop() {
  // trigger a pulse to the ultrasonic sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // measure the duration of the pulse
  duration = pulseIn(echoPin, HIGH);
  
  // calculate the distance in centimeters
  distance = duration * 0.034 / 2;
  
  // print the distance to the serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  
  // wait for a short period before taking the next measurement
  delay(500);
}