// menentukan pin untuk sensor ultrasonik
const int trigPin = 9;
const int echoPin = 10;

// menentukan pin untuk LED
const int ledPin = 13;

// menentukan jarak ambang batas dalam cm
const int thresholdDistance = 10;

void setup() {
  // menginisiasi komunikasi serial
  Serial.begin(9600);
  
  // mengatur pin sebagai input atau output
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
  
  // Matikan LED terlebih dahulu
  digitalWrite(ledPin, LOW);
}

void loop() {
  // Send a 10us pulse to trigger the sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // Read the echo pin
  long duration = pulseIn(echoPin, HIGH);
  
  // Calculate the distance
  int distance = duration * 0.034 / 2;
  
  // Print the distance for debugging
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  
  // Turn on the LED if the object is within the threshold distance
  if (distance <= thresholdDistance) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
  
  // Small delay before the next measurement
  delay(100);
}