signalk-openwrt

SignalK plugin that connects to an OpenWrt 4G/5G router via SSH, auto-discovers modems via ModemManager (mmcli -L), 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).

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>.operator	Mobile operator name	string
environment.outside.cellular.<index>.connected	Modem connection status	boolean

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

Requirements

On the OpenWrt router

• ModemManager must be installed and running:

  opkg update
  opkg install modemmanager
  /etc/init.d/modemmanager enable
  /etc/init.d/modemmanager start

• SSH access must be enabled (enabled by default on OpenWrt)
• Signal polling must be enabled on each modem:

  mmcli -m 0 --signal-setup=30

On the SignalK server

No additional dependencies — ssh2 is installed automatically.

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
SSH port	SSH port	22
Username	SSH username	root
Password	SSH password (leave empty to use key auth)	—
SSH private key path	Path to private key file (if no password)	—
Poll interval	Seconds between polls	30

SSH key authentication (recommended)

Instead of storing a password, you can use SSH key authentication:

1. Generate a key pair on the SignalK server (if not already done):

   ssh-keygen -t ed25519 -f ~/.ssh/id_signalk_openwrt

2. Copy the public key to the router:

   ssh-copy-id -i ~/.ssh/id_signalk_openwrt.pub root@192.168.1.1

3. In the plugin config, leave Password empty and set SSH private key path to /home/node/.ssh/id_signalk_openwrt

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

0.4.0

• Dynamic modem auto-discovery via mmcli -L — no manual modem configuration required
• Modems indexed by their ModemManager index in SignalK paths

0.3.0

• Multi-modem support with configurable path id per modem

0.2.0

• Switched from ubus JSON-RPC to SSH + mmcli for broader compatibility
• Added SSH key authentication support
• Auto-detection of best available technology (5G, LTE, UMTS, GSM)

0.1.0

• Initial release (ubus JSON-RPC, experimental)

License

MIT — Jean-Laurent Girod