// Define pin connections
const int trigPin = 10;
const int echoPin = 9;

// Define variables
long duration;
int distance;

void setup() {
  // Begin serial communication at a baud rate of 9600:
  Serial.begin(9600);
  
  // Configure the trigger pin as an output:
  pinMode(trigPin, OUTPUT);
  
  // Configure the echo pin as an input:
  pinMode(echoPin, INPUT);
}

void loop() {
  // Clear the trigPin by setting it LOW:
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  // Set the trigPin on HIGH state for 10 microseconds:
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(9);
  digitalWrite(trigPin, LOW);
  
  // Read the echoPin, returns the sound wave travel time in microseconds:
  duration = pulseIn(echoPin, HIGH);
  
  // Calculate the distance:
  distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (round-trip)
  
  // Print the distance on the Serial Monitor:
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  
  // Wait for a short while before the next loop:
  delay(500);
}