#define TRIG_PIN 9  
#define ECHO_PIN 10  

long duration;       
int distance;      

void setup() {
  Serial.begin(9600);       
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT); 

  Serial.println("=== Ultrasonic Distance Sensor ===");
}

void loop() {
  // Send a short HIGH pulse to trigger the sensor
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Measure how long the echo pin stays HIGH
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance (speed of sound = 343 m/s)
  distance = duration * 0.034 / 2;

  // Print the distance
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(500);  
}