modemmanager-meig-asr

ModemManager plugins for ASR-based MeiG modems, packaged for Raspberry Pi OS. They make the Teltonika TRM200 USB LTE modem (MeiG SLM770A inside) work with ModemManager and NetworkManager: the modem is detected correctly, connects via a normal NetworkManager gsm connection, and reconnects on its own.

Target system

OS	Raspberry Pi OS (64-bit) trixie (Debian 13), tested with Raspberry Pi OS Lite, release 2026-09-15 (2026-09-15-raspios-trixie-arm64-lite.img.xz)
Architecture	arm64 only
ModemManager	modemmanager 1.24.0-1+deb13u1 from Debian trixie (also what Raspberry Pi OS trixie installs)

The package adds plugins to ModemManager's plugin directory. Debian's modemmanager package stays unchanged. Because the plugins use ModemManager-internal symbols, each release works with exactly one modemmanager version, see Compatibility and updates.

Supported devices

USB ID	Device	Plugin
2dee:4d57	MeiG SLM770A, RNDIS mode (AT+SER=3), e.g. Teltonika TRM200 as shipped	meig-asr
2dee:4d58	MeiG SLM770A, ECM mode (AT+SER=2)	meig-asr
1d12:0102	Teltonika ALA440 (untested)	teltonika-meig-asr

Installation

Download the .deb for your release from the releases page and install it with apt, which also installs ModemManager if it isn't installed yet:

sudo apt install ./modemmanager-meig-asr_<version>_arm64.deb

The package reloads the udev rules and restarts ModemManager. Re-plug the modem (or reboot) so it's picked up with the new udev rules.

Check that the plugin handles the modem:

mmcli -L                      # [MEIG INCORPORATED] SLM770A
mmcli -m any | grep plugin    # plugin: meig-asr

Then create a NetworkManager connection with your SIM's APN:

sudo nmcli connection add type gsm ifname '*' con-name cellular apn <your-apn>

NetworkManager connects automatically. The modem's network interface (usb0) gets an address by DHCP.

Important

The plugin changes the modem's stored configuration. It turns the modem's auto-dial off (AT+DIALMODE=1). A factory-new TRM200 dials on its own at power-on; after the plugin has run, it no longer does, even after this package is removed or the modem is used on another host. To restore auto-dial, send AT+DIALMODE=0. See docs/TRM200.md.

In image builds

The package can be installed in a chroot, e.g. with pi-gen or pimod. Without a running systemd, the package scripts do nothing. Example for a pimod Pifile:

MM_MEIG_ASR_VERSION=1.24.0-1
RUN sh -c "curl -fsSL -o /tmp/modemmanager-meig-asr.deb https://github.com/trackIT-Systems/modemmanager-meig-asr/releases/download/${MM_MEIG_ASR_VERSION}/modemmanager-meig-asr_${MM_MEIG_ASR_VERSION}_arm64.deb"
RUN apt-get install -y /tmp/modemmanager-meig-asr.deb
RUN rm /tmp/modemmanager-meig-asr.deb

apt-get install fails the build if the image's modemmanager isn't the version the release was built for.

Compatibility and updates

The package depends on the exact modemmanager and libmm-glib0 version it was built against, e.g. modemmanager (= 1.24.0-1+deb13u1). apt refuses to install it next to any other ModemManager version, and the plugins can't end up loaded into a ModemManager they don't fit.

When Debian publishes a new modemmanager for trixie:

• apt upgrade holds the new modemmanager back.
• apt full-upgrade would remove this package to install it.

Wait for a release of this repository for the new version, or build one (see Maintenance). Check the installed version with apt-cache policy modemmanager.

Hardware notes

• Raspberry Pi 5 power: with a power supply that doesn't negotiate 5 A, the Pi 5 limits all USB ports together to 600 mA. Under data load the USB power switch then trips (over-current change on all ports in the kernel log) and the modem re-enumerates. ModemManager and NetworkManager recover on their own within ~40 s, but the connection drops each time. Use the 5 A (27 W) supply (the USB limit is then lifted automatically, usb_max_current_enable=1) or a powered USB hub.
• RNDIS or ECM: the TRM200 ships in RNDIS mode (rndis_host), which works out of the box. Switching to ECM (cdc_ether) is persistent and reboots the modem: AT+SER=2,1 for ECM, AT+SER=3,1 back to RNDIS. The kernel's option driver only knows the RNDIS ID; for ECM, the package's udev rule 70-meig-slm770a-ecm-option.rules adds 2dee:4d58 so the AT ports come up.
• Port layout (both modes): interface 2 ASR diagnostics (ignored), interface 3 primary AT port, interface 4 secondary AT port, interface 5 GPS.
• Addresses: the modem's DHCP server identifies itself as 169.254.0.1, but the router it hands out is in the carrier network (e.g. a /29), so it doesn't clash with link-local setups on other interfaces.

More hardware and firmware details (USB boot stage, dial settings, +ECMDUP quirks, unsupported AT commands, how to test a change) are in docs/TRM200.md.

Background

Stock ModemManager 1.24 handles the SLM770A with its generic plugin, which can't connect:

• AT+WS46=? returns ERROR, so ModemManager thinks the modem has no LTE, never queries +CEREG, and reports the packet service as detached on LTE.
• ATZ returns ERROR, so enabling fails whenever the modem was already attached when ModemManager started (e.g. at boot).
• The generic plugin can't bring up the RNDIS/ECM network interface.

The ASR, MeiG and Teltonika plugins come from ModemManager MR !1502. patches/ backports them to ModemManager 1.24.0 and fixes what testing on a TRM200 turned up:

Patch	Source
0001–0004	MR !1502 ("Add support for Teltonika -> MeiG -> ASR modems", by lvoegl, commit 0076a216), backported from main to 1.24.0
0005	plugin-private copy of mm_3gpp_normalize_address(), which only exists in ModemManager main and isn't exported by the 1.24 daemon
0006	adds the RNDIS variant 2dee:4d57 (TRM200)
0007	MM_DEFINE_SHARED for shared-asr/shared-meig. The MR lacks it, so these modules don't load unless plugins are built into the daemon
0008	skips the ATZ init, which the modem answers with ERROR
0009	MeiG modems dial and hang up with +ECMDUP and report the connection status from +ECMDUP?

Why +ECMDUP instead of +CGACT (as in the MR), tested on firmware SLM770A_A.57.3_EQ102:

• A context activated with +CGACT isn't routed to the network interface. NetworkManager reported a connection with a valid DHCP lease, but no traffic passed.
• +ECMDUP=<cid>,1,<pdp type>,"<apn>" activates the context itself and connects it. Activating it with +CGACT first makes the following +ECMDUP fail.
• +ECMDUP=<cid>,0 disconnects the interface; the LTE default bearer stays active, so +CGACT? can't show a dropped connection, while +ECMDUP? can.

build.sh also makes libmm-shared-meig.so depend on libmm-shared-asr.so (DT_NEEDED + RUNPATH=$ORIGIN): ModemManager opens shared modules in directory order with immediate binding, so shared-meig would otherwise fail whenever it happens to be opened first.

The backport leaves daemon code untouched; only src/plugins/ and the build files change. Debian's 1.24.0-1+deb13u1 only patches the Fibocom plugin, so upstream 1.24.0 is ABI-identical to it.

The MeiG SLM770A AT command manual is published by Teltonika.

Status

Tested on a Teltonika TRM200 (firmware SLM770A_A.57.3_EQ102) on a Raspberry Pi 5 running Raspberry Pi OS Lite 2026-09-15 (arm64) with modemmanager 1.24.0-1+deb13u1:

• The meig-asr plugin claims the modem in both RNDIS and ECM mode. The modem reports LTE, the packet service is attached, and NetworkManager connects with a gsm connection that only sets the APN.
• IPv4 traffic works (ping, HTTPS). A 2 MB download ran at ~4.7 Mbit/s over ECM and ~3.8 Mbit/s over RNDIS (single samples, LTE Cat 1, roaming).
• With data checked after each step: 5 of 5 NetworkManager disconnect/reconnect cycles, a ModemManager restart and a USB re-plug (RNDIS mode).
• A connection dropped by the modem was detected within ~10 s; NetworkManager reconnected and data flowed again ~15 s after the drop.
• Enabling works at hot-plug, at boot, after a ModemManager restart and after inhibition.

Known issues:

• The +ECMDUP dialing (patch 0009) was only tested in RNDIS mode; ECM mode was tested with the earlier +CGACT dialing.
• The GPS port is reported as unhandled; there's no location support yet.
• No global IPv6 address on the network interface with an ipv4v6 connection (tested with one carrier only).

Maintenance

Building

On Raspberry Pi OS or Debian trixie, arm64 (or in a debian:trixie container):

apt-get install --no-install-recommends \
  build-essential ca-certificates dpkg-dev git gettext \
  meson ninja-build pkg-config patchelf python3 xsltproc \
  libdbus-1-dev libglib2.0-dev libgudev-1.0-dev \
  libmbim-glib-dev libqmi-glib-dev libqrtr-glib-dev \
  libpolkit-gobject-1-dev libsystemd-dev systemd-dev modemmanager
./build.sh
./check-symbols.sh

build.sh fetches the ModemManager release pinned in versions.env, applies patches/, builds only the plugin targets and packages dist/modemmanager-meig-asr_<version>_arm64.deb with:

usr/lib/aarch64-linux-gnu/ModemManager/libmm-plugin-meig-asr.so
usr/lib/aarch64-linux-gnu/ModemManager/libmm-plugin-teltonika-meig-asr.so
usr/lib/aarch64-linux-gnu/ModemManager/libmm-shared-asr.so
usr/lib/aarch64-linux-gnu/ModemManager/libmm-shared-meig.so
usr/lib/udev/rules.d/70-meig-slm770a-ecm-option.rules
usr/lib/udev/rules.d/77-mm-meig-port-types.rules
usr/lib/udev/rules.d/77-mm-teltonika-port-types.rules
usr/share/doc/modemmanager-meig-asr/{README.md,TRM200.md,copyright,changelog.Debian.gz}

It refuses to run if build/ exists; remove it for a fresh build.

check-symbols.sh verifies that every ModemManager symbol the plugins import is exported by the installed modemmanager/libmm-glib0, and that the modules export what ModemManager's loader requires. CI runs it on every build and test-installs the package on Debian trixie with the Raspberry Pi OS archive (archive.raspberrypi.com) enabled, i.e. the package set of Raspberry Pi OS trixie.

When Debian updates ModemManager

1. Update MM_TAG, MM_COMMIT and MM_DEBIAN_VERSION in versions.env. Check debian/patches of the new Debian version for changes outside src/plugins/.
2. Rebase patches/ if needed (git am onto the new tag, then git format-patch -N --zero-commit --no-signature <tag>..HEAD).
3. Build, test on hardware, and release (see below).

Once MR !1502 is merged and shipped by Debian, this repository is obsolete.

Versioning

Releases are tagged <ModemManager version>-<revision>, like Debian package revisions. The tag is also the package version:

1.24.0-1   first release for ModemManager 1.24.0
1.24.0-2   our own changes (fixes, new USB IDs, ...) or a Debian-only update
           of ModemManager 1.24.0 (e.g. +deb13u2), still for 1.24.0
1.26.0-1   rebuilt for ModemManager 1.26.0, revision starts again at 1

The exact Debian ModemManager version is in versions.env and in the package's Depends. Tags have no v prefix.

Untagged builds (CI on main, local builds) get <ModemManager version>-0~git<date>.<commit count>.<commit>, e.g. 1.24.0-0~git20261007.10.e814430, which apt sorts before the first release. Builds are only distinguishable by version once committed: rebuilding with uncommitted changes reuses the version, and apt won't reinstall it.

Releasing

Add a ## [<tag>] section to CHANGELOG.md, then push the tag. CI builds the arm64 .deb and attaches it to a GitHub (pre)release.

License

GPL-2.0-or-later, like ModemManager's plugins.