Bug #1024 (oscillating re-camping), the latest news.
spaar at openmoko.org
Mon May 11 19:49:34 CEST 2009
Leonti Bielski wrote:
> Did you measure the capacitor on other "normal" phones?
> If on the phones without the problem capacitor measures around 10uF as
> supposed than we have our solution :)
I did not measure them yet (its some effort to remove the capacitor without
breaking anything and I don't have a huge pile of phones for experiments).
But even if the capacity of "good" phones is know, this does not mean
a lot. Till now its not 100% clear what effect the larger capacitor has.
It could be that it reduces voltage drops if the Calypso chip wakes
up. But it could also be that it reduces noise which comes from the
rest of the system. I can imagine that there are a lot of parameters
which determine how noise from the outside of the GSM modem
can disturb the affected supply voltage of the Calypso and most
certainly there are differences between the phones . I don't have
the hardware equipment to make detailed enough measurements
to find out which of the above is true (if not something else or a
mixture of several different things).
And finally we don't have the documentation of the details inside
the Calypso. So we can only speculate what can cause the
problems. We know that there is a PLL inside the Calypso
and that this PLL seems to be rather sensible, but we don't
know what exactly happens when the Calypso is sent into
"Deep Sleep" and when it wakes up again. During those
transitions there is a switch from the main clock to the 32 kHz
clock, but again, we don't have the details.
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