I have a simple 4 button keypad. I've been working with this on my little breadboard. I have 4 inputs going to pins 14-17 (A0-A3 in DIO mode.)
Today I blew 2 of the inputs. Nothing special, they just quit working. No "aw crap" action on my part. The others seem to be floating and I get random keypresses. It's been hot and dry, and I'm guessing some static electricity got these.
If I use the Bounce library or the Keypad library, should I have pulldowns on the all the pins? I put some 20K resistors to ground on the pins and it seems to work, but I'm curious. Would this protect against pins just going away? Will the pulldowns interfere with the debouncing or with the matrix keypad code?