shr- GPS howto?

Al Johnson openmoko at
Mon Jan 26 17:40:12 CET 2009

On Monday 26 January 2009, Helge Hafting wrote:
> arne anka wrote:
> >> slot. If it isn't there, then your phone have this problem.
> >
> > not necessarily. in fact, if you really have this problem you didn't
> > update your kernel a very long time.
> > the gps/sd card fix is in all kernels available for a very long time now,
> > the hw fix is not necessary.
> Really? The problem was noise from the SDcard electronics disturbing the
> gps receiver.  The software fix was to turn the sdcard clock off while
> the card isn't actively used.  But that don't help at all if the card
> _is_ in use most of the time - for example if you're running your linux
> distribution from the card. Or are playing songs stored on the card. Or
> have your map tiles on the card.

That is only half the software fix. The other half reduces the default drive 
strength on all the SD signal lines. This is similar in effect to putting a 
capacitor on all the signal lines, not just the clock line that is affected 
by the hardware mod. I have no difference in GPS performance if rootfs is in 
NAND or on SD, and I have no hardware mod.

> The capacitor makes the SDcard less noisy - even when it is being used
> all the time. I can get a fix and use the gps while listening to music,
> for example.

So can I, but I don't have the hardware mod ;-)

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