I am running out of digital pins on my Pro Mini. However, I am not using any of the analog pins. Can anyone think of a reason why I could not use the analog pins for a keypad?
I can't think of any way to use them with a matrix keypad, but I should be able to connect up to 8 discrete buttons, no? Supply Vcc to one side of the button, and then read the analog input for voltage with a pulldown to pull the input low when the switch is open?
Or would it work better with pullups so the input is always in a known state (high when switch is open, low when it's closed)?
Yes, sorry, I forgot that some boards (Nano and Micro?) have eight analogue inputs A0 to A7, but the last two A6 and A7 can only be used as analogue inputs, whereas all the others can be used as analogue inputs or digital inputs or outputs.