Testing Start button

[WillMunns]

The start button is a input to the PI GPIO, when "off" the input should read 3.3v WRT ground.

The value of the resistor used is not critical but its chosen to protect the PI if 12v is put on the pin by an willful idiot, or if a software but drives it as an output.

The PI uses an internal pull up to drive make this pin high - this is in the region of 50k, along with our own current limiting resistor (IIRC 10k) we could test our resistor by using a burden resistor (as in the GPIO test) but the PI value is not well characterized and I don't think we would be able to tell the difference of 1k vs 10k.

I think the best we can do check there is 3.3v on the pin and that shorting it to ground is detected by the PI.