The function reports the state of the Flame sensor connected to the selected pin. The function returns 1 when it is HIGH (or 3.3V) or 0 when it is LOW (or 0V).
There are lots of pins to which the sensor can be connected:
- Digital Pin: D1, D2 or D3
- Analog Pins: A1 and A2
- Servo Pins: S1 or S2