Suspended mode

Mon Feb 4 10:41:41 CET 2008

Hi Andy:

>>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!

I know what you worry, and I also know this possibility.
I try to test some thing in u-boot, because I can change GPIO setting in U-boot. I remove B1701 (GSM power path) and the GSM does not have any power source .I set GPIO( TX, RX,CTS,RTS,INT0,IO1) to input mode. I still found VBAT ( GSM power) have 1.0Voltage. I check all GSM's pins connect to any chip (S3C2442,Audio Codec, download buffer).I start measuring these pins and I found the RX has 1.8V voltage.
It is more than VBAT. Therefore, I just assume the RX is the source and I set these GPIO to low. The VBAT change to 0.001 V. 
I don't sure it is right.
I already request Matt give me a suspend image to test it and I will check it again in suspend mode.

Thanks for you point it.

  Best Wishes~


Allen Chang ( 張 吉 隆 )

First International Computer Inc.
7F, No.300, Yang Guang St., NeiHu, Taipei, 114, Taiwan
Tel: +886-2-8751-8751 Ext: 6171

Fax: +886-2-8751-8739

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