signalk-openwrt

SignalK plugin that connects to an OpenWrt 4G/5G router via ubus HTTP(S), auto-discovers modems via LuCI-authorized ModemManager mmcli calls, and publishes cellular signal metrics to SignalK paths.

Modems are discovered dynamically at each poll — no manual configuration required. If a modem is added or removed, the plugin adapts automatically.

Tested on GL.iNet GL-X300B (OpenWrt 24.10).

Polling behavior

At each poll, the plugin discovers currently available modems, reads their signal metrics, and publishes one SignalK update per modem.

If a poll is still running when the next interval fires, the new poll is skipped. This avoids overlapping ubus requests on slow or temporarily unresponsive routers.

Network technology is selected from the first available technology that exposes a numeric signal value, in this priority order: 5g, lte, umts, gsm. Numeric zero values (for example 0 dB SNR) are preserved and published.

SignalK paths published

For each discovered modem (indexed by its ModemManager index):

Path	Description	Unit
environment.outside.cellular.<index>.type	Network technology	string (lte, 5g, umts, gsm)
environment.outside.cellular.<index>.rssi	Received Signal Strength Indicator	dBm
environment.outside.cellular.<index>.rsrp	Reference Signal Received Power (LTE/5G)	dBm
environment.outside.cellular.<index>.rsrq	Reference Signal Received Quality (LTE/5G)	dB
environment.outside.cellular.<index>.snr	Signal-to-Noise Ratio / SINR (LTE/5G)	dB
environment.outside.cellular.<index>.signalQuality	ModemManager signal quality	ratio (0 to 1)
environment.outside.cellular.<index>.operator	Mobile operator name	string
environment.outside.cellular.<index>.connected	Whether ModemManager reports the modem state as connected	boolean

With a single modem (index 0), paths are: environment.outside.cellular.0.rssi, environment.outside.cellular.0.rsrp, etc.

The plugin also publishes Signal K metadata for each concrete modem path. The signalQuality path declares units: "ratio". Radio signal paths include their dB/dBm unit in the description because these units are not part of the standard Signal K unit preference definitions.

Requirements

On the OpenWrt router

• ModemManager must be installed and running:

  opkg update
  opkg install modemmanager luci-proto-modemmanager
  /etc/init.d/modemmanager enable
  /etc/init.d/modemmanager start

• LuCI/rpcd ubus access must be enabled over HTTP(S), typically provided by LuCI/uhttpd at /ubus.
• luci-proto-modemmanager must be installed, because this plugin intentionally uses the same mmcli ACLs as LuCI.
• Signal polling must be enabled on each modem:

  mmcli -m 0 --signal-setup=30

On the SignalK server

No additional npm dependencies.

Configuration

In SignalK: Server → Plugin Config → OpenWrt Cellular Signal

Option	Description	Default
Router address	IP or hostname of the OpenWrt router	192.168.1.1
ubus protocol	https or http	https
ubus HTTP(S) port	Router web port	protocol default
Username	LuCI/rpcd username	root
Password	LuCI/rpcd password, masked in the configuration UI	—
Allow self-signed HTTPS certificate	Accept the router's self-signed certificate	true
Poll interval	Seconds between polls	30

Installation

From npm

npm install --prefix ~/.signalk signalk-openwrt

From GitHub

npm install --prefix ~/.signalk https://github.com/macjl/signalk-openwrt.git

Restart SignalK after installation, then configure the plugin via Server → Plugin Config.

Changelog

See CHANGELOG.md.

License

MIT — Jean-Laurent Girod