SIMtrace phone-side VCC

This is merely a historical archive of years 2008-2021, before the migration to mailman3.

A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/simtrace@lists.osmocom.org/.

Tom Schouten tom at zwizwa.be
Fri Jul 26 21:19:29 UTC 2013


On 07/26/2013 05:05 PM, Kevin Redon wrote:
> Excerpts from Tom Schouten's message of 2013-07-26 22:55:32 +0200:
>> Hi folks,
>>
>> Seems not all phones use 3V signaling if the PHONE-side VCC pin is tied
>> to 3V.
>> This one insists on 1.8V : BLU SAMBA JR PLUS
> how does the phone behave?


if the at91 doesn't respond, the phone goes through the following 
power/reset sequence, about 1 second apart:

1.8V
3V
3V
1.8V

the at91 seems to mostly interpret the 1.8V serial line correctly, so 
the phone just starts talking at 1.8V until this eventually goes wrong.


>
>> Is this trick of tying VCC to 3V standard behavior?
> no, it is not standard. It just works (most of the time).
> And it should not damage the SIM nor the phone.
>
>> For future version of the board, it might be interesting to tie the VCC
>> pin to an ADC input, to detect different voltage levels so the firmware
>> can wait until phone decides to use 3V.
>>
> this will be done in the next board
>
good
( next to some GPIOs maybe ;)






More information about the simtrace mailing list