Quectel EC25 bug - interaction between generic/3GPP and QMI connection methods

Tim Small tim at seoss.co.uk
Thu Apr 16 14:20:20 UTC 2020


We've got some EC25, and found the following bug...

On all tested EC25 firmware versions.

With ModemManager 1.10.0 and libqmi 1.22.0  and also with ModemManager
1.12.6 and libqmi 1.24.8.

Due to the QMI bug recently described on this list, these modems have
previously been occasionally running with the generic / 3GPP plugin, and
occasionally with the quectel / QMI plugin.

Things were working OK, up until the time that the modems were switched
to a different SIM card.

The modems continuously timed out during the "connecting" phase.

They appear to have retained the settings from the previous SIM card
(appears to be stored in non volatile memory), and that remembered
connection seems to stop the new connection (different SIM / APN).

The following workaround gets it to connect:


<< +CGDCONT: 1,"IPV4V6","EEM2M","",0,0,0,0
<< +CGDCONT: 2,"IP","giffgaff.com","",0,0,0,0
<< OK

>> AT+CGDCONT=1,"IP",""

<< OK


<< +CGDCONT: 1,"IP","","",0,0,0,0
<< +CGDCONT: 2,"IP","giffgaff.com","",0,0,0,0
<< OK

i.e. undefine the first PDP, and it will then connect via QMI.

Not sure if this is a modem firmware bug, or MM?  Any thoughts?



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