Reason for GPS problems found!
joerg at openmoko.org
Tue Jul 15 23:29:17 CEST 2008
Am Di 15. Juli 2008 schrieb thomasg:
> Hi ppl,
> I write this to community, not to devel or owners because everyone should
> *sbeh*, one of the people in #neo1973-germany IRC-channel found the reason
> for the GPS problems.
> The problem only occurs if a SD card is set in. Doesn't matter if it's
> mounted or in use, it just has to sit in the socket.
> The TTFF went from no fix at all to TTFF 120 seconds indoor(!!!), and about
> 40 seconds outdoor.
> Two other people could verify this with about the same results.
> We'll do more tests later, but for now we surely know what's causing the
> problem (and it seems to be a EMC problem).
> First results show at the same devices, even outdoor, that there is no fix
> in over 400 seconds with SD card, the signal seems to be at least 10 to 20
> dB worse (so bad, that most satellites don't even appear).
> Testresults from other people appreciated.
So we can assume this is pretty confirmed by quite some reports now.
Thanks to community for the awesome help on this!
Special thanks to *sbeh* for finding this. Please mail me directly ;-)!!
We did quite some tests on this as fast as we could (and I never assumed we
could be *that* fast), and it seems we found the root cause of the problem.
ALL THIS IS PRELIMINARY INFO! Due to further tests to confirm.
Just to let you all know we're on it, and please stop thinking about shielding
the SDcard with tin foil or relocating internal gps-antenna. It won't
The good news: *IF* all pans out, there's (or soon will be) a new kernel at
Andy branch that stops SD-card clock when SDcard is idle. We hope this will
almost cure the problem, at least reduce it to sth like "you can't GPS while
watching video from SD" or the like (hope you can cope with that ;).
We're about to verify a hw-fix so you could even watch video and still have
GPS positioning during that.
Please stay tuned and be patient, we'll come up with news *really soon*.
And *please* don't try weird reworks and maybe break your FR by doing so
;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-)
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