#define TRIG_PIN 3
#define ECHO_PIN 4 // Make sure to define ECHO_PIN

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}

float readDistanceCM() {
  // Trigger the ultrasonic pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Measure the duration of the echo
  int duration = pulseIn(ECHO_PIN, HIGH);

  // Convert duration to distance in centimeters
  return duration * 0.034 / 2;
}

void loop() {
  // Read the distance from the ultrasonic sensor
  float distance = readDistanceCM();

  // Check if an object is within 100 cm
  bool isNearby = distance < 100;

  // Turn the LED on or off based on proximity
  digitalWrite(LED_BUILTIN, isNearby ? HIGH : LOW);

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

  // Small delay to prevent spamming the Serial Monitor
  delay(100);
}