Bug #1024 (oscillating re-camping), the story goes on...

Dieter Spaar spaar at openmoko.org
Wed Apr 1 18:02:50 CEST 2009


here is some more information about the 32kHz oscillator
instability/interference theory as the cause for bug

I have added a way to easily change the setting for the
32kHz oscillator current to the firmware as suggested
by Joerg. However here with my devices, it does not
change anything. This does not mean a lot, it could
be that the documentation for this register is wrong,
there is only one place in the documentation which
mentions this register and the firmware does not use
it so I have no reference. I can measure (or better,
estimate ;-) a difference of about 1 uA in the total
current of the GSM modem if I change the register
setting between highest and lowest oscillator
current. I don't know what one could expect here if
the setting is correct.

There is something else I tried: With one of my GSM Test
equipment (HP 8922) I can tune the reference oscillator
of the simulated cell. If I change the timing (so far
I changed it by 5ppm) in the deep sleep period between
receiving the PCH, I get a similar behavior: the error
flag is set and it stays set until the phone re-synchronizes.
Its not exactly re-camping, but this could come from the fact
that my HP 8922 does not have the encryption option and
the actual camping to the HP 8922 test cell  is a very simple
procedure. So maybe this explains the difference.

Still, this all is no evidence for anything...

Best regards,

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