#include <Wire.h>
#include <LiquidCrystal_I2C.h>

#define TRIG_PIN   9
#define ECHO_PIN   10
#define LED_PIN    7
#define BUZZER_PIN 8

LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  Wire.begin();
  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Sistem Siap...");
  delay(1500);
  lcd.clear();
}

long bacaJarak() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  long durasi = pulseIn(ECHO_PIN, HIGH, 30000);
  if (durasi == 0) return 999;
  return durasi * 0.034 / 2;
}

void loop() {
  long jarak = bacaJarak();

  if (jarak < 100) {
    // LED ON
    digitalWrite(LED_PIN, HIGH);

    // LCD: nada dihidupkan
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("nada dihidupkan");
    lcd.setCursor(0, 1);
    lcd.print("Jarak:");
    lcd.print(jarak);
    lcd.print("cm");

    // Buzzer nada 400 Hz, delay 500ms
    tone(BUZZER_PIN, 400);
    delay(500);
    noTone(BUZZER_PIN);

    // Buzzer nada 500 Hz, delay 500ms
    tone(BUZZER_PIN, 500);
    delay(500);
    noTone(BUZZER_PIN);

  } else {
    // LED OFF
    digitalWrite(LED_PIN, LOW);
    noTone(BUZZER_PIN);

    // LCD: nada 500 (mati)
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("nada 500");
    lcd.setCursor(0, 1);
    lcd.print("Jarak:");
    lcd.print(jarak);
    lcd.print("cm");

    delay(300);
  }
}