#define TRIG_PIN 9
#define ECHO_PIN 10
#define LED_PIN 13     // Optional LED
#define BUZZER_PIN 12  // Optional Buzzer
#define SAFE_DISTANCE 20  // Distance threshold in cm for obstacle detection

void setup() {
  // Initialize serial communication:
  Serial.begin(9600);

  // Set the trigger pin as output and echo pin as input
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  
  // Set LED and Buzzer pins as output (if used)
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
}

void loop() {
  // Send a pulse to the TRIG pin to start measuring distance
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);  // Wait for a short time
  digitalWrite(TRIG_PIN, HIGH);  // Send a pulse
  delayMicroseconds(10);  // Pulse duration
  digitalWrite(TRIG_PIN, LOW);  // Stop sending pulse

  // Measure the pulse duration on the ECHO pin
  long duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate the distance (in cm)
  long distance = (duration / 2) / 29.1;  // Speed of sound is 343 m/s

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

  // Check if the distance is below the threshold (obstacle detected)
  if (distance < SAFE_DISTANCE) {
    // Turn on LED and Buzzer if obstacle is detected
    digitalWrite(LED_PIN, HIGH);
    digitalWrite(BUZZER_PIN, HIGH);
  } else {
    // Turn off LED and Buzzer if no obstacle is detected
    digitalWrite(LED_PIN, LOW);
    digitalWrite(BUZZER_PIN, LOW);
  }

  // Wait for a short period before the next reading
  delay(500);
}