[Voyage-linux] Best Alix 13C2 GPIO Setup For Reading Open/Close Circuit on Shutdowns Controller?

[mgrollman]

I am a long-time Voyage user (started at 0.2, currently on 0.5 for most 
systems) that wants to do some new GPIO stuff with the Alix 3C2 board.  
The goal here is to have a way to turn the Alix off in an semi-elegant 
way a short period of time (10 minutes) after ignition is turned off for 
a mobile Alix solution.

For this new application, we'd like to integrate Alix 3C2 (or perhaps a 
nearby model Alix) with a shutdown controller in a vehicle (similar to: 
http://www.mpegbox.com/microsdc/index.html).  In order to interface with 
this unit, we'd like to read a signal from the shutdown controller that 
is either open or shorts to ground, depending on what the shutdown 
controller sees on the ignition line high or not.

I am none-too-clever with circuit design, and would prefer not to build 
something that lets out the white smoke from a bunch of Alix boards.  
But I assume there is a small circuit that would be build here that is 
pretty fail-safe for reading such an open or closed input?

There is an alternate line on the shutdown controller which sends 
momentary connect to ground but is otherwise open -- not sure that'd be 
any easier to read, though.

Anyone have some good suggestions on best way to do this, both from an 
electronics point of view, as well as a GPIO driver point of view?  I 
see there are a few different driver solutions now in GPIO-land, but not 
sure which is best for for this kind of simple task.

Cheers,

- Michael