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at-commandmodem

Recover modem from AT+CEER 388

CEER 388 Issue

We are using an Lara R211 modem an are experiencing issues where calls start to fail after some time due to the following CEER error:

AT+CEER?

+CEER: "CC setup error", 388, "CS connection release triggered by MM"

We tried to change the carrier but that does not work anymore (AT+COPS). The only way to recover the modem seems to be resetting it (via pin).

Questions

  1. What is the proper way to recover from CEER 388? Is there anything we try to do or is resetting the modem the appropriate approach here?
  2. What is the actual root cause for this failure?
Solution

  • We were never able to fully fixed the underlaying issue but have been able to find a workaround that mitigates the issues we were facing:

    • We switched from a python-modem fork to using modem-manager.
    • Using modem-manager allowed us to reset the modem much faster (i.e. for CEER 388).
    • We added a retry mechanism for unsuccessful calls (for selected CEERs).