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GSM connection

We have started our development task using GM 47. As the first step in our task for integrating system, I had tried to setup a demo system which comprises of 2 work-stations; one is connected to (an HAYES compatible modem with normal PSTN line) and 2nd station with the GM47 unit. The intention is to get both of them connected.

From the 1st station, we invoked the dial-out command (ATDT ..) and we can observe the 2nd station receiving RING. When we issue the ATA command (used to anwer a call) from the 2nd station, it returns OK indicating the command has been executed BUT the dialer(1st station) still could not establish communication. Usually, upon dialing out and being answered by ATA, the caller shall establish the connection and prompt messages CONNECT 9600 etc.

I believe that other possible faults have been eliminated since the replacement of the GSM module with (an HAYES compatible modem with normal PSTN line)works fine. Further, dialing through voice (normal telephone)is successful.

I would appreciate if you can provide suggestions regarding this issue. Thanks
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njega
Asked:
njega
1 Solution
 
MeffCommented:
Your problem is a standard problem. ATD can start a voice call or a data call. May you did mix it. Please find a standard message to new clients from AWP as below:

Some tips from Advanced Wireless Planet

1. Modem cable
Please be sure that you use a modem cable and not a null modem cable.
2. Power supplies
Aware a peak current of 2 ampere if the module will connect to the GSM network. If your power supply is not able to support the peak current, then you will get a reset of the GSM module
3. SIM card
Be sure that your SIM card support SMS, data call or GPRS if you would like to use this services. If you miss the services then contact your GSM operator.
4. First step (very short version)
We explain the use of the GSM module with terminal software.  Have a look that the modem cable is connected to your PC, the power is connected to your board, the antenna is connected and a SIM card is in the SIM card reader.
The device comes with autobauding. More about autobauding in the Software User Guide chapter 2.5.1. Send the command AT. If you get the answer OK, then your connect to the module is well. The recommended speed is 38.400 8,N,1. Next step should be to send the PIN number with the command AT+CPIN (chapter 2.5.2.2) and if this was successful, you could use the command AT+CREG to check the status. If you use a SIM card that supports voice calls as well, then you could use the command ATD 123456789; to start a voice call to the phone on your desktop or your mobile handset. Please do not the ";" on the end of the number! Without ";" you start a data call; a analogue PSTN phone will ring, a ISDN phone will may be not ring, because with your dialling the kind of the call will be transmitted. An ISDN phone that is coded as a voice device will not ring and you will get an error code as an answer from the device. The level of the error codes depends on the settings of the commands AT+CMEE. If the phone rings you can pick up the phone. Without headset connected to your board, you cannot hear anything, but you can be sure that all is well for further steps.

A lot of technical stuff you will find on www.gsm-modem.de as well
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