[Openec] fail-safe startup code?

[Frieder Ferlemann]

Hi,

starting a new thread from one of the topics in the thread "openec plans".

Frieder Ferlemann schrieb:
> We should have a fail safe startup code which allows the XO
> to recover no matter what we do. (With the help of only an
> external USB keyboard).
>
> So (RFC) the boot vector would point to a routine which
> pulls down KEY_OUT1 and then checks if all KEY_IN1..3 are low.
> If this is the case it would set its IO Ports so that the
> XO has a chance to boot (and then it would sit in a loop
> checking if KEY_UP_L is pressed).
> Otherwise the routine would jump into SDCC generated code.

the openec repository now has a first go at this kind of routine at:
http://dev.laptop.org/git.do?p=projects/openec;a=blob;f=main.c;hb=c6492dfd4ab6eae7b9d4c58750ea43b26a4a9e46

Line 80 and following.
It will not be functional yet. So noone without
debricking equipment should try.

It would be great if this routine would get some review
and then finally some testing.

To make a start: I'm not sure whether proposing
to pick KEY_OUT_1 was a good choice because that pin
has an alternate function (ISP_EN#).
Should KEY_OUT_2 have been used instead?

Greetings,

Frieder