My project is to use an Arduino to control the lighting of a small apartment. My preferred option is to replace each wall light switch with a 4x4 membrane keypad (https://www.amazon.co.uk/Mirocle-Matrix-Membrane-Keyboard-Arduino/dp/B01LMU6OPG/ref=sr_1_19?s=electronics&ie=UTF8&qid=1504376458&sr=1-19&keywords=membrane+keypad). The UX would allow any keypad to control any light, eg. pressing 1-4 will set light 1 to brightness 4.
The problem I have is this will result require 4 x 8 = 32 pins, so I'm looking for alternatives.
So my questions:-
1/ Is there a simple pll to serial converter that I should be using to interface the keypads?
2/ Can I wire multiple keypads onto the same set of 8 pins? Only one keypad will ever be touched at one time.
3/ Are there simple serial versions of the classic membrane keypad.