MC7455 on Rasp Pi 3

Aleksander Morgado aleksander at
Tue Sep 19 16:07:08 UTC 2017


>> How are you managing the connection? Are you getting any specific error?
> I'm using the built-in debian/Raspbian network start/stop scripts. The
> card shows up as wwan0 automatically and I have the start/stop scripts
> set to run mbim-network start/stop appropriately and set the static
> IP.
> There's a check script that runs in cron to check the connection and
> if it's not up (I can't ping some outside addresses), it'll bounce the
> interface and wait to see if it comes back. After doing that about 5
> times, if the Internet connection doesn't come back, it reboots the
> RPi.

Does the bounce of the WWAN imply mbim-network is re-executed?

> I don't really have it set up to grab any diags or logs before I
> bounce the interface in my check script. What would I look for?

You could run the "mbim-proxy" manually to dump logs to a log file, e.g.:
$ /usr/libexec/mbim-proxy --verbose > /var/log/mbim-proxy.log 2>&1

And once the proxy is running, run mbim-network as you were (but with
the PROXY=yes in the mbim-network profile). This will dump all MBIM
communications to a file, and we can check later on which kind of
errors you got that forced the connection to get disconnected.

>> In general I'd advise to use ModemManager along with NetworkManager,
>> as that allows for automatic reconnections by configuring the
>> connection settings to autoconnect in NM, and NM also knows exactly
>> what needs to be done to get the setup connected.
> I'm not familiar with MM and NM. Are they cli based? There's no gui,
> this is purely an embedded device.

Yes, MM and NM are daemons and they have CLIs. There's no GUI
required, although multiple GUIs support NM and MM.

>> You can also use mbim-network but you need to consider that the IP
>> settings may need to be set manually in the network interface if DHCP
>> doesn't work. Also, this won't do automatic reconnections for you.
> Currently, I have the RPi setup to run mbim-network start/stop and
> also sets the static IP:
> # cat /etc/network/interfaces
> auto wwan0
> iface wwan0 inet static
>         pre-up mbim-network /dev/cdc-wdm0 start
>         pre-down mbim-network /dev/cdc-wdm0 stop
>         address 24.221.x.x
>         netmask
>         gateway 24.221.x.x
>         dns-nameservers


>> Setting up an autoconnect profile in the modem may also be an option,
>> if there isn't one already. Although that isn't support via MBIM, you
>> would need to use QMI over MBIM and --wds-set-autoconnect-settings in
>> qmicli operations.
> I'm not familiar with the autoconnect profile, is it set up through AT commands?

There probably is some AT command to do that, but I was really
referring to the QMI command, i.e.:
$ qmicli -d /dev/cdc-wdm0 --wds-set-autoconnect-settings="enabled,home-only"

> I'm not really sure if I should have a more elaborate start/stop
> script to change other settings or just go with the mbim-network
> start/stop? If you think MM and NM would be the better way to go and
> they're cli based, I'd be happy to give it a try.

Well, NM and MM are autonomous daemons that will actively manage the
connections; that means reconnecting if needed and such. The
"lightweight" solution is probably the mbim-network based one,
although it would also be more limited.


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