Note: the 3x4 keypad is a 12 digit keypad with 7 pins (I know it is multiplexed already but I was looking to increase the number of free pins on the arduino)
What about using the 74HC595? Looks like that would get it down to 3 pins.
What about it? How would you use a 74HC595 to multiplex inputs?
Citing an "instructable" - and that one is clearly no exception - is considered akin to swearing here.
You can charlieplex it
You can charlieplex it:-
@tcox8, you could add 4 of your other switches into the same matrix as your keypad, making it 4x4, and save even more pins.