GTA02 GPS rework for SD card interference issue

[Stefan Fröbe]

Hi guys,

as I wrote before ( but the message did apparently not hit the list since I
used a different email address ) I had the hardware fix applied on friday
but used a 0603 cap instead, which fit quite nicely.

After further testing I can only congratulate the OM-team for their quick
and easy fix: whether inside at the window, in a moving train or in narrow
streets, the FR is aquiring a Fix consistenly within about 120s from cold
start under the most difficult conditions, and of course even faster at
consecutive tries ( warm start ).  Under normal conditions, a TTFF of 40s
seems to be the maximum needed even for a cold start, which in my opinion is
exceptionally good!

The SD-Card (4GB) still works as expected by this RF only fix, and there is
no need to unmount it ...

Btw, this was all done with the mwester-andy kernel from 080716...

Big thumbs up to everyone at OM, now let the mapping begin ;-)

Stefan

On Fri, Jul 18, 2008 at 1:26 PM, Stefan Fröbe <frobiac at googlemail.com>
wrote:
Great work, and I can confirm this to be working just fine !!!

That's an advantage of working in a company in the semiconductor business:
enough people with the skills and tools able to try this modification out on
a lunchbreak - now I get a TTFF from cold boot of 150s under most difficult
conditions:  Clouds / Mist, and  high buildings on two sides.

The previous software-only improvements were of mixed results: only once did
a fix occur, and by far not as fast as the 34s  I got without SD-Card.

Will keep you updated on further results this weekend, but so far it is
great news to see a fix this quickly!

Keep up the great work and spirit,
Cheers,
Stefan


On Sun, Jul 20, 2008 at 6:25 PM, Yaroslav Halchenko <site-openmoko.org@
onerussian.com> wrote:

> hm... or alter clocking pulse sufficiently for unstable SD performance
> with some (or all) SDs... how could we know for sure unless verified
> empirically...  (noone could guess that having SD impacts GPS for quite
> a while, right?)
>
> I am not yet planing to do this hw mod on my phone, thus I can't really
> compare, and it would be great if anyone having such modded phone (I
> guess OM people) do such a simple test (basic IO testing of SD card
> similar to the ones which were posted to this list before).
>
> NB It would be really pathetic if then after new 'fixed' units are
> shipped, and new owners start complain that 50% of SD cards do not work
> or get significant performance reduction, right? So why not to make sure
> (I bet they already did smth like that thus it is just for someone from
> OM give results with numbers)
>
> On Sat, 19 Jul 2008, Michael Kluge wrote:
>
> > This additional capacitor has been added between clock and GND for the
> > SD card. So it is most probably just there to filter frequencies higher
> > than the clock rate itself.
>
> > Michael
> --
> Yaroslav Halchenko
> Research Assistant, Psychology Department, Rutgers-Newark
> Student  Ph.D. @ CS Dept. NJIT
> Office: (973) 353-5440x263 | FWD: 82823 | Fax: (973) 353-1171
>        101 Warren Str, Smith Hall, Rm 4-105, Newark NJ 07102
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