const int mq135Pin = A0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(mq135Pin);

  // Convert to voltage (RP2040 ADC is 12-bit: 0–4095)
  float voltage = sensorValue * (3.3 / 4095.0);

  Serial.print("Gas Level: ");
  Serial.print(sensorValue);
  Serial.print(" | Voltage: ");
  Serial.println(voltage);

  delay(1000);
}