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I can not get the modem to respond to AT commands

Support request for GSM modem by email to me

I have hooked up my GSM modem to my PC and the SIM is registered on the network. But, I can not get the modem to respond to AT commands.  I wonder if it needs a null modem on the rs232? From my terminal I see this….

AT command problem with GSM modem

AT command problem with GSM modem

As you can see it echos back in red, but does not give the response from the modem I would expect. I think it is something simple, but cant figure what is wrong.

Answer on GSM modem support request

  • You do not need a null modem cable
  • Does your PC have a RS232 or do you use a USB to RS232 converter.
  • The first command I use always is “AT” and the answer will be “OK”.
  • You use “ATT” instead of “AT”.
  • The answers are the echo, but not the answer of the GSM modem. I have no idea which piece of hardware sent the echo. On “ATT” to the GSM modem you shall get “Error”, because it is a wrong command and on “AT” you can expect “OK”. For some reasons your and my GSM modem answer on “ATT” with “OK”.
  • Worst case the AT will be send to the landline modem in your laptop.
  • With AT+CREG you will detect if it your landline modem or a cellular modem.
  • The landline will answer with “Error” and the cellular modem will give a useful answer. The answer is described in the manual.

Updated: 2012-06-01 — 11:12 AM

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