SIM Reconnection Issues (Modem Manager 1.20.4)

Armand Daussà adaussa at
Tue Mar 5 13:21:13 UTC 2024

Hello everyone,

Recently I have encountered an issue related to reconnecting cellular.

*OS*: Raspian OS Lite (32 bits) -> Linux panells3 6.1.0-rpi7-rpi-v8 #1 SMP
PREEMPT Debian 1:6.1.63-1+rpt1 (2023-11-24) aarch64 GNU/Linux
*Modem*: SIM7600G-H

The SIM is active. Using mmcli I can see that the state is connected. I
then proceed to de-activate the SIM remotly. This is where the logs start
(Feb 29 13:00:00).
The logs then show a constant change in state where *enabled -> searching*
and *searching -> enabled* is constantly logged.
All the night is spent like this, switching the state. What I am trying to
test is that upon remot activation of the SIM, the connection is resumed
without problems.
So, fast forward to Mar 01, I activate the SIM remotely and nothing
happens. I end up reseting the modem with "mmcli -m 0 --reset" and then a
restart of the ModemManager.service and finally the connection is
established correctly.

I am not sure what could be the issue. It is also worth noting that we have
tested this in other boards that have the same modem, and the behaviour is
not the same for every board.

Thank you in advance!
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