GPIO testing

[Zygmunt Krynicki]

Hey

I found an interesting way to test GPIO that is used by the CI20
project (the mips development board). Basically it involves pairing
two identical products (whatever they are) and using one to test the
other. I suspect a loopback variant might work in some cases as well
(except when the number of pins is odd) but I suspect this one is
safer across reset where the state of those pins is uncertain (so that
current and voltage limits are not exceeded).

Still, if you're interested have a look [1]. The link includes
interesting photos and screenshots from logic analyzers. As a bonus
there's some portable high-level code that we can just reuse for our
testing experiments.

[1] http://elinux.org/CI20_HW_test

Best regards
ZK