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