Litetouch bus protocol

Does anyone know what Litetouch/Savant uses for communication between the controller and keypads/modules?  I'm guessing it's RS-485.  Also, is the protocol they use over it documented anywhere?
 
I have an aging Litetouch system, and I was going to experiment with an Arduino touchscreen to see how tough it would be to replace the keypads with something a bit more modern looking.

Are you going to have the Arduino use the same 4 wires? 
 
I was looking at just replacing the switches with something else that talks with a PC and the PC sends commands to the litetouch LC5000 controller to control modules / groups, but I didn't find anything cheap enough that supports a multidrop rs485.  You need to have 2 wires for power and 2 for comm  port (3 if you use the ground). 
 
What Arduino touch screen system are you planning on using?

AnotherOne said:

Are you going to have the Arduino use the same 4 wires? 
 
I was looking at just replacing the switches with something else that talks with a PC and the PC sends commands to the litetouch LC5000 controller to control modules / groups, but I didn't find anything cheap enough that supports a multidrop rs485.  You need to have 2 wires for power and 2 for comm  port (3 if you use the ground). 
 
What Arduino touch screen system are you planning on using?

Click to expand...

 
 
Well, I just looked at the system tonight, and it's actually 5 wires per bus.  
 
PS - "+" and "-"
SW - "+" , "-" , and "D"
 
My guess is that it's 3-wire RS485 or RS422.  I'll probably need to take apart a keypad and look at the chips on it to figure it out.
 
As for the touchscreens, I saw an Arduino Uno with a TFT capacitive touchscreen on Ebay for $44 or so.  As a test, I'll probably just use a nano with a couple of buttons attached to see if this is even feasible.

The PS "+" and "-" is an input from your litetouch power supply, the SW "+", "-", and "D" are the 3 wires that run too al the switches (getting the power from the power supply).