Reason for GPS problems found!

Al Johnson openmoko at
Tue Jul 15 22:10:41 CEST 2008

On Tuesday 15 July 2008, Kalle Happonen wrote:
> Yaroslav Halchenko wrote:
> > indeed, especially since I see possibility for it to be twofold: if it
> > is not purely an issue of SD card in place putting physical stress on
> > the board somehow (would be worth checking with dummy plastic
> > insert instead of real SD card), it means that
> I just ran three tests. Without SD card, with SD card with tape over the
> contacts, and SD card normally. This doesn't seem to be mechanical,
> since the first two cases got fixes in ~45 seconds, and with the SD card
> actually in and working I stopped waiting after 10 minutes.

I did the same test with the same conclusion - physical presence of card with 
contacts covered gives the same result as no card - in my case fix in 135s 
with about 5s variation either side, 7 sats in view from a location indoors 
near a window. Uncovering the contacts found time and 2 sats after ~200s but 
no more before I gave up a couple of minutes later.

I was looking for something 
under /sys/devices/platform/glamo3362.0/glamo-mci.0/mmc_host to power the 
interface down and try it that way. Not spotted anything that looks like the 
bluetooth or gps power interfaces though :-( Perhaps I'm looking for the 
wrong thing...

> It'll be interesting to see what removing the SD card does to the
> battery life, if anything.
> > 1. either SD card is powered all the time (which afaik is not needed for
> > the flash memory ;-)), thus leading to power drain without need
> >
> > 2. some component on the way (e.g. capacitor) is noisy
> > and emitting EM noise/interference, thus again consuming power without
> > need.
> >
> > Could anyone verify that power consumption is not changed considerably
> > whenever SD card is in but not engaged, in comparison to whenever there
> > is no SD card?
> >
> > On Tue, 15 Jul 2008, Jay Vaughan wrote:
> >>> 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.
> >>
> >> oh man, if this is true, its not good news.
> >>
> >>
> >>
> >>
> >> ;
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