// Pin Definitions
const int TRIG_PIN = 10;
const int ECHO_PIN = 9;

void setup() {
  // Set up pins and serial communication
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  Serial.begin(9600); 
}

void loop() {
  long duration_us; // Time in microseconds
  float distance_cm; // Distance in centimeters
  
  // 1. CLEAR the Trig pin
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  // 2. SEND the 10us ultrasonic pulse
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // 3. MEASURE the echo pulse duration
  duration_us = pulseIn(ECHO_PIN, HIGH);

  // 4. CALCULATE distance
  // Speed of sound = 0.034 cm/us. We divide by 2 for one-way trip.
  distance_cm = duration_us * 0.034 / 2; 

  // 5. PRINT result
  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

  // Wait before next measurement
  delay(5000); 
}