connecting 8051 to cellular

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Hallo,
I'm doing a project (for a university exam) based on a 8051 microcontroller
that
comands with at commands a siemens cellular using 8051 serial port.
Siemens cellular is connected to 8051 through its data cable,but:
1)if i send at commands to cellular with hyper terminal,it' ok
2)if i send at commands from micro to pc,it's ok
3)if i send at commands from micro to cellular,it doesn't responds.
what can i do?
thanks




Re: connecting 8051 to cellular

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I'd check the signal levels coming out of the serial port on the
micro, to make sure their OK for the cellphone.

Is it meant to be RS-232? If, so, you may well find that the PC will
quite happily read serial data at TTL logic levels, but the cellphone
is requiring "true" RS-232 levels (-10V marking , +10V spacing).
Are you using a suitable level converter (Maxim MAX232 series are
common for this)?

--
  Max

Re: connecting 8051 to cellular


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It might be the handshaking on the phone RS-232. You might need to tie
some lines appropriately. I think I had to do something like this when
using a Siemens M20.

Leon
--
Leon Heller, G1HSM
Email: snipped-for-privacy@dsl.pipex.com
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Re: connecting 8051 to cellular

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Have you crossed the signals over, that is Rx --> Tx and Tx --> Rx?
http://www.airborn.com.au/serial/rs232.html



Re: connecting 8051 to cellular

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The GSM Modules often have a full modem serial implimentation.
Int other words you must make sure of the CTS, DTR etc. signals
as well.

Regards
  Anton Erasmus




Re: connecting 8051 to cellular
A guy at work had the same problem.  It turned out that the cellphone was
echoing the incoming
AT commands and he wasn't prepared to parse them.  Evidently, there is some
way to turn off
echoing.

--Anthony


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microcontroller



Re: connecting 8051 to cellular
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ATE1 and ATE0.

Please do not toppost.

--
Chuck F ( snipped-for-privacy@yahoo.com) ( snipped-for-privacy@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
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