signalk-garmin-race-timer-plugin

Signal K server plugin that decodes Garmin Race Timer broadcasts from NMEA 2000 (PGN 126720, manufacturer code 229) and publishes them as Signal K racing data.

Note: This plugin is read-only. It decodes race timer data broadcast by a physical Garmin race timer device over NMEA 2000. The device operator must start and control the race countdown on the hardware — this plugin cannot initiate or modify the timer.

Signal K Paths

| Path | Type | Units | Description | |---|---|---|---| | navigation.racing.timeToStart | number | s | Countdown time remaining. 0 after race start. | | navigation.racing.elapsedTime | number | null | s | Elapsed race time since start. null during countdown. | | navigation.racing.startTime | string | null | ISO 8601 | Predicted start time during countdown, locked to actual time after start. | | navigation.racing.finishTime | string | null | ISO 8601 | Captured when timer is stopped during race. Cleared if race resumes. | | navigation.racing.status | string | - | countdown, racing, countdownPaused, raceFinished |

Notifications

| Path | Trigger | Cleared when | |---|---|---| | notifications.navigation.racing.raceStart | Countdown-to-race transition (race begins) | Race finishes or new countdown starts | | notifications.navigation.racing.raceFinish | Race-to-finished transition (timer stopped during race). Includes elapsed time in message. | Race resumes or new countdown starts |

NMEA 2000 Data

The plugin registers a custom canboatjs definition for PGN 126720 (Garmin proprietary, manufacturer code 229). It listens for 39-byte "data exchange" messages (command byte 0xFE) with message type 0x0002 (timer data), broadcast at 1 Hz by the race timer device.

Relevant fields extracted from each message:

| Field | Bits | Description | |---|---|---| | Command | 8 | 0xFE — data exchange (filtered; heartbeat 0xE7 and others are ignored) | | Message Type | 16 | 0x0002 — timer data (filtered; keepalive 0x0007 and others are ignored) | | Timer Data Type | 8 | 0x05 — time data | | Timer Value | 32 | Milliseconds — countdown remaining or elapsed race time, depending on status | | Timer Status | 8 | 0 = race running, 1 = countdown running, 2 = race paused (finished), 3 = countdown paused |

The full field layout is defined in src/pgns.js.

REST API

GET /plugins/signalk-garmin-race-timer/state returns the current timer state as JSON.

Development

npm run build    # compile TypeScript
npm run watch    # compile on change
npm test         # run tests

Disclaimer

This project is not affiliated with, endorsed by, or associated with Garmin or its subsidiaries. "Garmin" is a registered trademark of Garmin. This plugin is an independent, unofficial project provided for demonstration purposes only. Use at your own risk.

License

Apache-2.0