#define TRIG_PIN 2    // Pin connected to the TRIG of HC-SR04
#define ECHO_PIN 4    // Pin connected to the ECHO of HC-SR04
#define LED_PIN 12    // Pin connected to the LED
#define BUZZER_PIN 13 // Pin connected to the Buzzer

void setup() {
  Serial.begin(115200);    // Initialize serial communication
  pinMode(TRIG_PIN, OUTPUT);  // Set TRIG pin as output
  pinMode(ECHO_PIN, INPUT);   // Set ECHO pin as input
  pinMode(LED_PIN, OUTPUT);   // Set LED pin as output
  pinMode(BUZZER_PIN, OUTPUT);// Set Buzzer pin as output
  
  digitalWrite(LED_PIN, LOW);   // Ensure LED is off initially
  digitalWrite(BUZZER_PIN, LOW);// Ensure Buzzer is off initially
}

void loop() {
  long duration, distance;
  
  // Clear the TRIG pin
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  // Set the TRIG pin HIGH for 10 microseconds to start the measurement
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read the ECHO pin duration
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate the distance in centimeters
  distance = (duration / 2) / 29.1; // Speed of sound: 29.1 us/cm

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

  // Trigger alarm if distance is less than a threshold (e.g., 10 cm)
  if (distance < 10) {
    Serial.println("Warning! Object detected close by!");
    
    // Turn on LED and Buzzer
    digitalWrite(LED_PIN, HIGH);
    digitalWrite(BUZZER_PIN, HIGH);
    
    delay(1000);  // Keep the alarm on for 1 second

    // Turn off LED and Buzzer
    digitalWrite(LED_PIN, LOW);
    digitalWrite(BUZZER_PIN, LOW);
  } else {
    // No alarm
    digitalWrite(LED_PIN, LOW);
    digitalWrite(BUZZER_PIN, LOW);
  }

  delay(500);  // Update every 500 milliseconds
}