#define CO2_SENSOR_PIN 36  // Analog pin connected to MG811 AOUT

// Calibration constants
#define ZERO_POINT_VOLTAGE 0.4  // Voltage at 400 ppm CO2
#define CO2_SCALING_FACTOR 0.02 // Voltage change per ppm (approximate)

void setup() {
  Serial.begin(115200); // For debugging
  analogReadResolution(12); // Set ADC resolution to 12-bit
  Serial.println("MG811 CO2 Sensor Initialized");
}

void loop() {
  int adcValue = analogRead(CO2_SENSOR_PIN); // Read raw ADC value
  float sensorVoltage = adcValue * (3.3 / 4095.0); // Convert to voltage (3.3V ADC reference)

  // Calculate CO2 concentration (ppm) using the voltage difference
  float co2Concentration = calculateCO2(sensorVoltage);

  // Print sensor readings
  Serial.print("Sensor Voltage: ");
  Serial.print(sensorVoltage);
  Serial.print(" V | CO2 Concentration: ");
  Serial.print(co2Concentration);
  Serial.println(" ppm");

  delay(2000); // Delay for stability
}

// Function to calculate CO2 concentration from voltage
float calculateCO2(float voltage) {
  if (voltage < ZERO_POINT_VOLTAGE) {
    return 400; // Minimum ppm (ambient level)
  }
  return 400 + ((voltage - ZERO_POINT_VOLTAGE) / CO2_SCALING_FACTOR);
}