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 [email protected]

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