Hardware Button

The pull-up resistor is very common and you’ll see it in digital circuits all the time. It’s just a resistor connected from an input up to VCC, the positive supply of the circuit.

Pull-up resistors are used to make sure you have a HIGH state on the input pin when the button is not pushed. Without one, your input will be floating, and you risk that the input randomly changes between HIGH and LOW as it picks up noise in the air.

Luciferin uses GPIO 0 as default INPUT_PULLUP for the hardware button.