Hi Radu,

are you shure that the level of the Siemens in input is TTL? I suppose that
should be CMOS level, and probably you  need a level converter. I think that
the two diode and the resistor is not sufficient,  but if you say sometimes
work...

Do you have the same ground for the PIC and the telephone?

Ciao




esday, July 31, 2002 6:03 PM
> Subject: PICBASIC-L 16F877 and SIEMENS C35 and the "rain dance"
>
>
>
> Hi PBP friends,
> I need your help for a strange problem that happens connecting the 16F877
> to an GSM C35 of Siemens.
> This telephone have an internal modem driven directly (I suppose TTL) as
it is
> powered by  3.5 volt of its battery I have connecter the transmit pin of
> the PIC  powered at 5 volt, trought two diodes to reduce the upper level a
resistor
> of 1K to  limit the current, but the connection is unstable and
unreliable.
> Sometimes works and  sometimes not apparently without reasons.
>  Also I have tried to remove the diode and the resistor but the problem
> remain the same.
> Do you have idea what i made wrong?
> Do you know the exact level to comunicate with this GSM telephone?
> For sending data I use the RC6 (pin 25) and for receiveng I use RB3 (pin
36).
>
> Please help me because I'm near to became crazy... I have make also the
> "rain dance"  without result :-)
>
> Regards
>
>
> Do You Yahoo!?
> Yahoo! Health - Feel better, live better
>

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