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

// Initialize the LCD, adjust address (0x27) if needed
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Define MQ-135 sensor pins
const int mq135_before = A0;
const int mq135_after = A1;

void setup() {
  // Initialize LCD
  lcd.begin(16,2);
  lcd.backlight();
  
  // Initialize serial communication
  Serial.begin(9600);
  
  lcd.setCursor(0, 0);
  lcd.print("Air Quality");
  lcd.setCursor(0, 1);
  lcd.print("Monitoring...");
  delay(2000);
  lcd.clear();
}

void loop() {
  // Read sensor values
  int sensorValueBefore = analogRead(mq135_before);
  int sensorValueAfter = analogRead(mq135_after);

  // Convert sensor values to PPM
  float ppmBefore = sensorValueBefore * (5.0 / 1023.0) * 100; // Adjust multiplier for calibration
  float ppmAfter = sensorValueAfter * (5.0 / 1023.0) * 100;   // Adjust multiplier for calibration

  // Display on LCD
  lcd.setCursor(0, 0);
  lcd.print("Before: ");
  lcd.print(ppmBefore);
  lcd.print(" PPM");

  lcd.setCursor(0, 1);
  lcd.print("After: ");
  lcd.print(ppmAfter);
  lcd.print(" PPM");

  // Print to Serial Monitor
  Serial.print("PPM Before: ");
  Serial.print(ppmBefore, 2);
  Serial.print(" | PPM After: ");
  Serial.println(ppmAfter, 2);

  delay(1000); // Update every second
}