Module loosing registration

  • Q: Type of module? A: GM862
    Q: Firmware version? A: Unknown
    Q: Type of starter kit you have? Custom
    (S1, S1B, S2, S3, S4, EVK1, EVK2, none, other)


    Latetly I have seen a strange behaviour on the GSM modules. I have had a telemetry system working non stop for the past 2 years but the last day I noticed it couldn't register to the network, so I powered off and then powered it up again. The module couldnt still register to the network, so I removed the SIM card and inserted it again and it successfully registered. I noticed this with another module as well, with the latest firmware. It is hard for me to replicate this at the lab. Removing the SIM card could be a hint of what could be the problem.

    Has anyone experienced this before? Any hints?


  • Hi,

    A new system was doing the same problem so I went to check it at the factory. This device had a GM862.
    When I went to check it, the status led on the modem was blinking so I thought it was something with the network. When I hooked up to my DEBUG output I noticed that it never got to the state machine where I check the registration (AT+CREG) but it was at the state where it checks if a pin is required by the SIM. Upon sending the command the module returned that it required a PIN but this SIM had the PIN disabled. I wrote some code to reset the module when in this condition. Once I updated my firmware it successfully reset the modem and the command returned that a PIN isnt required so it could now run and send data.

    Is there some bug in the modems with this command? It doesnt happen always and I noticed this happens more with the GM862.