AT Command Tester – Can’t connect to GSM/GPRS TTL UART MODEM-SIM900

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This topic contains 1 reply, has 2 voices, and was last updated by  Stuart Llewellyn 1 year, 1 month ago.

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  • #11813

    Nishant

    The modem is registered on the network as indicated by the LEDs.

    However I can’t get it to connect using AT Command Tester. Keep getting Invalid or no response from the device. Please check the modem port and the baud rate.Disconnecting port COM7.

    Baud rate: 9600

    #11819

    Admin
    Keymaster

    Hi Nishant,
    It is possible that the baudrate is incorrect.. Have you tried connecting at other baudrates?
    Also you may want to check if your connecting to the command port of the modem. If you physical conenction to the modem is through USB, generally multiple serial ports are enumerated for the modem. You need to connect to the command port of the modem.

    Just to eliminate any AT Command Tester specifc connection issues, you can also check the serial conenction through another tool called Putty,

    http://m2msupport.net/m2msupport/check-serial-connection-using-putty/

    Tks

    #11983

    Stuart Llewellyn

    I too have this problem. The SIM900 GSM shield is connected to an Arduino Uno. Its blinking every 3 seconds ssaying to me it sregistered on the network.

    I’ve followed each step in the tourbleshooting. Tried all the different baud rates with AT Command Tester cannot connect.

    Tried using Putty, set up for serial my COM port (5) baud rate of 19200, have some sample code that on recieving the command s will send a text message ot my phone. This works when I type s I get an sms from my arduino to my phone. But in Putty if I type AT I go no response….

    If I can get a text message through Putty surely that means my baud rate is correct? Yet I still cannot connect to GSM shield through the AT Command Tester. And something is not right, if putty will not give me an OK after giving an AT command…. yet in the same window I can type s, and my code will run and send me a message through Putty.

    I’m also able to connect with another terminal Bray: https://sites.google.com/site/terminalbpp/

    But struggling to use this terminal. However I can connect and get a OK response from an AT command.

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