const int TRIG_PIN = 6;
const int ECHO_PIN = 7;
const int LED_PIN = 3;
const int DISTANCE_THRESHOLD_1 = 50;
const int DISTANCE_THRESHOLD_2 = 150;
const int DISTANCE_THRESHOLD_3 = 250;
const int DISTANCE_THRESHOLD_4 = 350;

float duration_us, distance_cm;
unsigned long previousMillis = 0;
int blinkInterval = 1000;

void setup() {
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  duration_us = pulseIn(ECHO_PIN, HIGH);
  distance_cm = 0.017 * duration_us;

  if (distance_cm <= DISTANCE_THRESHOLD_1) {
    blinkInterval = 200; // Kurang dari atau sama dengan 50 cm, berkedip selama 0.2 detik
  } else if (distance_cm <= DISTANCE_THRESHOLD_2) {
    blinkInterval = 1000; // 50 cm hingga 150 cm, berkedip selama 1 detik
  } else if (distance_cm <= DISTANCE_THRESHOLD_3) {
    blinkInterval = 1500; // 150 cm hingga 250 cm, berkedip selama 1.5 detik
  } else if (distance_cm <= DISTANCE_THRESHOLD_4) {
    blinkInterval = 2000; // 250 cm hingga 350 cm, berkedip selama 2 detik
  } else {
    blinkInterval = 0; // Jarak di atas 350 cm, LED dimatikan
  }

  if (blinkInterval > 0) {
    if (currentMillis - previousMillis >= blinkInterval) {
      previousMillis = currentMillis;
      if (digitalRead(LED_PIN) == LOW) {
        digitalWrite(LED_PIN, HIGH);
      } else {
        digitalWrite(LED_PIN, LOW);
      }
    }
  } else {
    digitalWrite(LED_PIN, LOW);
  }

  Serial.print("distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

  delay(100);
}