+C5GREG? does not report any output from mmcli

Aleksander Morgado aleksandermj at chromium.org
Fri Feb 3 09:30:30 UTC 2023

> I'm trying on MM 1.20.4 and noticing that AT+C5GREG? (and also AT+CREG?) do not report any output when called from mmcli.
> # mmcli -m 0 --command=AT+C5GREG?
> response: ''
> # mmcli -m 0 --command=AT+CREG?
> response: ''
> # mmcli -m 0 --command=AT+C5GREG=?
> response: '+C5GREG: (0-2)'
> +C5GREG? (or +CREG?) is correctly reported using minicom so modem does responding to these commands.
> Any idea what could be going wrong? I'm trying with Telit FN990 but looks like this is a generic issue.

ModemManager has a mechanism to process URCs coming in the AT response
flow. Your command response is being "eaten" by this mechanism, which
ModemManager processes as a URC.
This is a known limitation of --command; at the end ModemManager
cannot ensure that a real valid +C5GREG URC is interleaved between
your command and your response. I guess we could try to improve that,
but I'd prefer to suggest not using +C5GREG? in --command, because
attempting that would be tricky :D


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