connecting multiple keypads 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&amp;ie=UTF8&amp;qid=1504376458&amp;sr=1-19&amp;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.
As far as I know, you can connect multiple keypads of this type to a single set of 8 pins.  However, it seems like a lot of wire needs to be strung to get this to work, for each switch, 8 wires for the keypad, and two, or more, for power control.

Were I to do this project.  I would likely handle each switch independently, embedding a Pro Mini in each switch box along with an HC-12, or some such.  This means no wires are needed, any pad could control any switch, and expansion is much easier. 

Of course, this is only what I would do, and you understand your own requirements far better than I.