Reason for GPS problems found! / more patches

Andy Green andy at
Mon Jul 21 09:35:02 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| On Mon, 21 Jul 2008 02:11:38 +0200, Andy Green <andy at> wrote:
|> Just a heads-up there is also another relevant patch on stable tonight.
|> ~ It gives another interesting knob to twiddle about GPS performance.
| What does “strength” mean in this context? Voltage?

No, it will refer to the amount of current allowed to the drive the
output transistors in the Glamo's SD-related IO cells.  If they are
starved of current, it affects the rise and fall time of the output, it
is the sharpness of the edges that creates the higher frequency energy
that makes trouble at 1.5GHz we suspect.

Running at strength 0 worked fine here on the SD Card we ship and should
significantly affect those high harmonics.  I eyeballed the clock signal
that results and it's not so degraded.

Basically stopping the clock when idle attacks it the bulk of the time
when we don't talk to the device and the strength setting attacks it
even when we are talking to the SD Card.

- -Andy
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