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
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
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: aqzf13@dsl.pipex.com My low-cost Philips LPC210x ARM development system: http://www.geocities.com/leon_heller/lpc2104.html
"sampei" wrote
Have you crossed the signals over, that is Rx --> Tx and Tx --> Rx?
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
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
microcontroller
ATE1 and ATE0.
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