If you're using Overo with the 40-pin header a safe bet for your two input lines is:

Pin 27 - gpio146
Pin 29 - gpio147

Per the first section of the wiki:

1)Export them to userspace
2)Set direction to "in"
3)Verify state with "echo"

These two pins are floating, so pull them low to get "0".   Pin 1 can be used as a ground.

Apply 1.8V to get "1". 

Greg






From: Nick Starzicki <nick2501@gmail.com>
To: General mailing list for gumstix users. <gumstix-users@lists.sourceforge.net>; Greg Kogut <gkogut@yahoo.com>
Sent: Tuesday, December 6, 2011 12:11 PM
Subject: Re: [Gumstix-users] GPIO

And how do i know the port numbers which are available as input?
בתאריך 2011 12 6 21:30, מאת