#define TRIG 5       // Ultrasonic TRIG pin
#define ECHO 18      // Ultrasonic ECHO pin
#define LED_PIN 19   // LED pin (simulating vibration motor)

void setup() {
  pinMode(TRIG, OUTPUT);   // Tell ESP32 TRIG is output
  pinMode(ECHO, INPUT);    // Tell ESP32 ECHO is input
  pinMode(LED_PIN, OUTPUT);// LED output
  Serial.begin(115200);    // For monitoring distance
}

void loop() {
  long duration, distance;

  // Send pulse to ultrasonic sensor
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  // Read echo (time it took for signal to return)
  duration = pulseIn(ECHO, HIGH);

  // Convert time to distance in cm
  distance = (duration * 0.0343) / 2;

  // Check if obstacle is close
  if(distance < 50){       // threshold = 50 cm
    digitalWrite(LED_PIN, HIGH);  // LED ON → obstacle detected
  } else {
    digitalWrite(LED_PIN, LOW);   // LED OFF → no obstacle
  }

  // Print distance for monitoring
  Serial.print("Distance: ");
  Serial.println(distance);

  delay(100); // small delay
}