Isolating GPS noise source was Re: Reason for GPS problems found!

Simon Matthews s.matthews at karrak.id.au
Tue Jul 15 18:03:04 CEST 2008


Is the noise from the SD card itself, most likely or from pcb
signal/power lines going to/from the SD card?

I should have my Freerunner by now so i could do some tests, but it is
still stuck in China!

Here are some ideas. 
If you mask off all the data and clock with sticky tape, but leave the
power pads on the SD card unmasked and see if this makes any difference.
The SD card pinouts are


    ------------------
   /  1 2 3 4 5 6 7 8 |
   |9                 |
   |                  |
   |                  |
   |                  |
   |                  |
    ------------------

1 CD/DAT3
2 CMD
3 VSS
4 VDD
5 CLK
6 VSS
7 DAT0
8 DAT1
9 DAT2

So mask off 1,2,5,7,8,9

Maybe soldering a 0.1uF decoupling cap between VDD and VSS as close to
the SD connector as possible may help.

Trying to shield the GPS connector might help or more radical surgery
like cutting the connector off and patching it directly into the antenna
mux and chopping the tracks to the internal antenna plug.

I don't think this wouldn't be good for the warranty though.

I must say i don't like the position of the internal antenna plug. 


Simon 


On Tue, 2008-07-15 at 16:37 +0200, Yorick Moko wrote:
> they know about it now
> (joerg even replied in this thread, he's a member)






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