I have an old touchphone with keys 0 to 10, which I need to connect to raspberry at certain distance.
So it's as if there are 10 pushbuttons. However I don't want to use a 10-wire cable, but would rather use 4 (or 2.. serial?)
I wonder what kind of circuit can combile 10 bits and pack them into single digital value, which I can
then send to Raspberry IO ?
10 bit Analog-to-Digtal converter ?
or maybe use some old USB keyboard circuit ?