andy at openmoko.com
Mon Feb 4 10:18:29 CET 2008
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Somebody in the thread at some point said:
> Dear all: After my search, I found out GSM leakage voltage problem.
> We can't just set the GPH0-3( TX_MODEM,RX_MODEM,CTS_MODEM,RTS_MODEM)
> to input and I try to set these GPIO to output low. The VBAT( GSM
> power) is almost zero. Therefore, I suggest a new GPIO configure in
> the attached file. The file is just for testing S32C2442's part
> current and not for any power mode. Best Wishes~
I didn't understand how the input mode can leak the current to allow 2V
on GSM VDD? It makes me worry that by setting to 0V level, instead you
allow current to flow into the 0V GPIO, hiding the problem. This is why
VBAT shows "almost zero", current is in fact flowing through it into the
0V GPIO pins.
This proposed bad current path would be like this:
(Secret Evil High Pin) --> [ GSM VDD ] --> ( 0V GPIO pins now )
You can confirm if my worry is correct by measuring the change in
overall current -- you will find it is either no different or higher
current is lost if my worry is correct -- in that case you didn't find
the real problem yet -- "Secret Evil High Pin".
Of course if the overall current is lower, congratulations instead!
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