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

#define DHTPIN 15      // DHT22 data pin
#define DHTTYPE DHT22
#define MQ135_PIN 34   // MQ-135 sensor analog output

DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C Address 0x27 for 16x2 LCD

void setup() {
    Serial.begin(115200);
    
    dht.begin();
    lcd.begin(16,2);
    lcd.backlight();

    pinMode(MQ135_PIN, INPUT);

    lcd.setCursor(0, 0);
    lcd.print("Air Quality Mon.");
    delay(2000);
    lcd.clear();
}

void loop() {
    float temperature = dht.readTemperature();
    float humidity = dht.readHumidity();
    int air_quality = analogRead(MQ135_PIN); // Read from MQ-135

    // Check for errors
    if (isnan(temperature) || isnan(humidity)) {
        Serial.println("Failed to read from DHT sensor!");
        return;
    }

    // Display on Serial Monitor
    Serial.print("Temp: ");
    Serial.print(temperature);
    Serial.print(" °C, Hum: ");
    Serial.print(humidity);
    Serial.print("%, Air Quality: ");
    Serial.println(air_quality);

    // Display on LCD
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Temp: ");
    lcd.print(temperature);
    lcd.print(" C");

    lcd.setCursor(0, 1);
    lcd.print("AQ: ");
    lcd.print(air_quality);

    delay(2000); // Update every 2 seconds
}