Backup battery discharged -> GTA01 and GTA02 dead
rod at whitby.id.au
Mon Jul 21 13:32:26 CEST 2008
Werner Almesberger wrote:
> Rod Whitby wrote:
>> but never as a result of the normal NOR boot sequence.
> Has it ever booted from NOR (before it started to act strangely) ?
Yes, for a number of weeks after I got it, it worked fine. I could do
NAND and NOR boots with no problems. I went overseas for a couple of
weeks, during which it discharged both main and backup battery
completely, and when I returned it wouldn't boot. It hasn't booted
since until I left it overnight to recharge the backup battery, and then
I started to get the very rare booting condition.
>> *Never* have I been able to get it to boot twice in a row.
> That sounds bad :-( I've seen systems behaves like yours, but they
> were usually afflicted with some hardware problem. Normally, it's
> the VB_SYS cap Andy mentioned.
> Just to check: is this GTA02 a mass-production device or a preview
> model ? Could you please mail the serial number ?
Serial number is 8B8313262. This is a preview model, but looked like it
came off the mass-production line (it was in the final box with all
accessories, and is in no way marked like a prototype).
>> I'm monitoring the nRESET line at various points in the sequence above,
>> and I've never seen it go above 0V.
> That would be consistent with the capacitor problem. (But could be
> a number of other things as well.) I guess you don't have an
> oscilloscope you could attach to watch it continuously for you ?
I do have a scope probe for a 16650 logic analyser at work, and will
look at setting it up in the next few days to see if there are any
pulses on nRESET - is that what I should be looking for? What other
signals should I be using as a trigger or tracing alongside nRESET?
>> Knowing that the batteries and usb charger are fine, and that nRESET is
>> still low, what's the next level of debugging I can try - how do I work
>> back from the nRESET test point to the PMU pins to find out what's going
> Hmm, that's the point where I'd start watching voltage levels with
> a scope, and maybe have look the the capacitors under the shield ...
I'm happy to keep probing here to find the problem, but I don't have SMT
rework equipment to fix anything serious. If it's a missing cap that
could be scavenged from a GTA01 (I have two of those that don't work
either) then I'm up to trying to solder that on (I have a temp
controlled station with a 1mm tip and a steady hand).
Which shield do I start lifting ;-)
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