FiPy + LTE CAT M1: Problem when stablishing a connection



  • I have been working for a week on defining a sequence of AT commands to connect a Fipy to a LTE CAT M1 testing cell. I have achieved some progresses but I have not been able to connect the device to the cell yet. Unfortunately, so far, the only way I have for testing new sequences of AT commands is to modify the specific lines of the source code and recompile the whole firmware which takes about 10 minutes per test :S (too slow).

    In my testing environment it is neccesary to configure the band (20) and channel (6400) as well as a specific APN. When I switch on the radio (AT+FUNC=1) and read the avilable cells which are scanned by the Fipy (AT+COPS=?), the Fipy returns the right testing cell. However, when I try to attach to the cell (AT+COPS=1,2,"21407") the result is unsuccesful. Below, you can see the sequence of AT commands and their results:


    AT COMMAND: [AT..] -> AT RESPONSE: [..OK..]
    AT COMMAND: [ATZ..] -> AT RESPONSE: [..OK..]
    AT COMMAND: [AT+CMEE=2..] -> AT RESPONSE: [..OK..]
    AT COMMAND: [AT+CGDCONT=1,"IP","APN_id"..] -> AT RESPONSE: [..OK ..]
    AT COMMAND: [AT!="addscanfreq band=20 dl-earfcn=6400"..] -> AT RESPONSE: [....OK ..]
    AT COMMAND: [AT+CFUN=1..] -> AT RESPONSE: [..OK..]
    AT COMMAND: [AT+COPS=?..] -> AT RESPONSE: [..+COPS: (1,"provider_id","provider_id","21407",7),,(0,1,2,3,4),(0,1,2)....OK..]
    AT COMMAND: [AT+COPS=1,2,"21407"..] -> AT RESPONSE: [..+CEREG: 2....+CEREG: 0..]
    AT COMMAND: [AT+CEREG?..] -> AT BAD RESPONSE: [..+CEREG: 2,4....OK..]
    restarting...
    AT COMMAND: [AT+CEREG?..] -> AT BAD RESPONSE: [..+CEREG: 2,4....OK..]
    restarting...


    I have doubts about the result of AT+COPS=1,2,"21407" (+CEREG: 2....+CEREG: 0). Actually, this result seems to be composed of two sub-results ("+CEREG: 2" and "+CEREG:0"). According to the Sequans Monarch manual, those status codes means the following:

    2: "not registered, but MT is currently trying to attach or searching an operator to
    register to"

    0: "not registered, MT is not currently searching an operator to register to"

    Could you clue me in on how to solve this issue and achieve a IP connection over LTE-M1?



  • @brotherdust thanks for your proposal. It seems the best way to speed up any connection test with the LTE modem.

    Regarding AT commands, can you suggest me a sequence that worked under same (or similar) technical conditions?



  • @icorredor You might try bypassing the ESP32 and connecting to the LTE modem directly over UART so you can just type in the AT commands manually. I was able to do it without too much trouble and it sped up my troubleshooting time considerably. Here's the thread: https://forum.pycom.io/topic/2496/gpy-readiness/20


 

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