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

// Inisialisasi LCD (alamat 0x27, 16 kolom, 2 baris)
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Pin sensor dan output
#define GAS_PIN 34
#define LED_PIN 26
#define buzzer 25

// Ambang batas gas (dalam persen)
#define GAS_THRESHOLD 60.0

void setup() {
  Wire.begin(21, 22);
  lcd.init();
  lcd.backlight();
  Serial.begin(115200);

  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  lcd.setCursor(0, 0);
  lcd.print("Monitoring Gas");
  tone(buzzer, 1000);
  delay(225);
  tone(buzzer, 1500);
  delay(225);
  tone(buzzer, 2000);
  delay(225);
  noTone(buzzer);
  delay(275);
  lcd.clear();
}

void loop() {
  int gasValue = analogRead(GAS_PIN);
  float gasPercent = (gasValue / 4095.0) * 100.0;

  Serial.print("Gas Value: ");
  Serial.print(gasValue);
  Serial.print(" (");
  Serial.print(gasPercent, 1);
  Serial.println("%)");

  lcd.setCursor(0, 0);
  lcd.print("Gas: ");
  lcd.print(gasPercent, 1);
  lcd.print(" %");

  if (gasPercent >= GAS_THRESHOLD) {
    // LED berkedip
    digitalWrite(LED_PIN, HIGH);
    tone(buzzer, 2000);
    delay(300); 

    digitalWrite(LED_PIN, LOW);
    tone(buzzer, 1000);
    delay(300);
  } else {
    digitalWrite(LED_PIN, LOW);
    noTone(buzzer);
    delay(1000); // delay lebih lama saat aman
  }
}