Begin forwarded message:
From: Werner Almesberger <[EMAIL PROTECTED]>
Date: April 16, 2008 7:36:22 PM GMT+08:00
To: gta02 <[EMAIL PROTECTED]>
Subject: [gta02] u-boot boot menu regression ?
Miles keeps on telling me about troubles with the factory and the boot
menu, but I can't quite figure out what's going on. Can anyone please
help ?
The problems seem to be related to the latest change where I reduced
the time u-boot spends sampling the buttons by one second. Now, while
this could theoretically create a very small window in which AUX has
to be pressed, all the delays u-boot incurs before even getting to
that loop should leave more than enough time.
Let me repeat the procedure for invoking the boot menu:
- Press and hold POWER
- give u-boot a few milliseconds (let's be generous and make this
100ms)
to load itself and move out of harm's way
- Press and hold AUX
- Continue holding POWER and AUX until the boot menu comes up
- Release POWER and AUX in any order
The red LED (underneath AUX) can be used as an indicator for the
deadline to press AUX. The LED flashes briefly when the device is
turned on.
If AUX is pressed and held by the time the LED flashes, u-boot will
enter the boot menu. If AUX is not pressed and held until more than
one second after the LED flashes, u-boot will not enter the boot menu.
If AUX is pressed at time 0s < t < 1s after the LED flashes, the boot
menu will be entered with probability (1s-t)*100%.
So to make sure to enter the boot menu, just press AUX before the
LED flashes. There should be about 1-2 seconds between pressing
POWER and the LED flashing, so it should be very easy to get this
right.
Here's a timing diagram:
http://svn.openmoko.org/developers/werner/bm.pdf
If there is still a problem, I need to know what exactly is going
wrong. Have you encountered a case where the timing is vastly
different ? Is there something at the factory that prevents the
use of the correct timing ? Does u-boot fail to bring up the menu
despite following the correct timing ?
Thanks !
Cheers, Werner
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