#define MQ2_ANA A1
#define MQ2_DIG 2
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);
const int G_LED = 4;
const int Buzzer = 5;

void setup() {
  lcd.init();
  lcd.backlight();
  Serial.begin(9200);
  pinMode(MQ2_ANA, INPUT);
  pinMode(MQ2_DIG, INPUT);
  pinMode(G_LED, OUTPUT);
  pinMode(Buzzer, OUTPUT);
}

void loop() {
  lcd.setCursor(2,0);
  lcd.print("Smoke = ");
  lcd.setCursor(10,0);
  lcd.print(analogRead(MQ2_ANA));
  if (analogRead(MQ2_ANA) > 400) {
    tone(Buzzer, 200);
    digitalWrite(G_LED, HIGH); 
    lcd.setCursor(0,1);
    lcd.print("GAS Detectee !");
  }
  else
  {
    noTone(Buzzer);
    digitalWrite(G_LED, LOW);
    lcd.setCursor(0,1);
    lcd.print("aucune GAS Detectee !");
  }
}