Simtech plugin filtering out Waveshare Raspberry Pi 4G HAT

Scott Lemon slemon at
Wed Nov 17 16:22:22 UTC 2021

Just as a side note ... without the USB you'll never see the full bandwidth
possible with that modem.  I don't think you'll be able to push more than
Kb/s through the TTL serial connection reliably.

It is much neater, but there is a cost.

Scott C. Lemon
Principal IoT Solutions Engineer


Mobile: +1 (801) 336-4476
Email:   slemon at

On Wed, Nov 17, 2021 at 8:57 AM Aleksander Morgado <aleksander at>

> Hey,
> >
> > I've just bought one of these
> >
> >
> >
> > and I'm trying to get it to work with ModemManager using (at the moment)
> the default version available in Raspberry Pi OS (mm 1.14.12). I'm also
> having some trouble convincing meson to build the latest version to try
> making changes, but I think that's a separate problem entirely due to my
> lack of understanding of meson.
> >
> > ModemManager v1.14.12 works if I switch the jumpers around to "control
> the SIM7600 via USB to UART" and plug in an additional USB cable from the
> Pi to the HAT's onboard USB connection, but I'm trying to get it to work
> without this cable and in its default "Raspberry Pi control" jumper setting
> (mainly because it's neater, honestly).
> >
> > I believe that the Hat's serial port is being filtered out because the
> Simtech plugin expects the Hat to have a Vendor/Product ID. However, when
> plugged in via the GPIO header, I see only a serial (ttyS0) interface, and
> thus no Vendor/Product IDs can match.
> >
> > Can I force the Simtech plugin to be used, or would it make no sense
> because of the single serial port? Should it be claimed and usable by the
> AT plugin instead? I'm more than happy to change stuff on this, because it
> has no other use at the moment.
> >
> You should tag the ttyS0 interface with the "ID_MM_DEVICE_PROCESS"
> udev tag, so that MM can process the port.
> The Simtech plugin doesn't support non-USB modems, though, so you'll
> probably end up with the generic plugin managing the modem. If you do
> need the Simtech plugin, we could probably update it to have "vendor
> and product string filters" as some other plugins supporting RS232
> modems do (i.e. with MM_PLUGIN_ALLOWED_VENDOR_STRINGS).
> --
> Aleksander
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