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).

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 SSH sessions 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>.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

0.4.3

• Preserve zero-valued signal metrics instead of treating them as missing
• Detect network technology from any available numeric signal field
• Skip overlapping polls when a previous poll is still running

0.4.2

• Synced package metadata with the npm release

0.4.1

• Added a built-in Node test suite covering modem discovery, publishing, and error handling

0.4.0

• Dynamic modem auto-discovery via mmcli -L — no manual 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