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So this is an alternative to NMEA (which is a variant of CANbus / SAE J1939)?

* https://en.wikipedia.org/wiki/National_Marine_Electronics_As...

* https://en.wikipedia.org/wiki/NMEA_2000

* https://en.wikipedia.org/wiki/NMEA_0183

It's not an alternative to NMEA, thought it definitely started as an open source replacement of NMEA. Cooler heads prevailed and the NMEA body opened some of the IP to SignalK developers. So instead of the opensource hardware that used SignalK as originally envisioned we have the same NMEA based proprietary hardware that SignalK ingest and convert to JSON.

Just an FYI, the first link (NMEA OneNet) sounds great, but isn't actually used by any of the major manufacturers yet sadly.

Also, only NMEA2000 is based on CANbus, NMEA0183 is not.

Indeed.

NMEA2000 is essentially a Marine Electronics version of CANBUS with their own agreed upon PGNs.

NMEA0183 is pretty close to RS-232 (and/or RS-422), usually at 4800 baud, but there's a "High Speed" variant at 38,400 baud.

Minor nitpick: NMEA0183 is a text format (based on "sentences"), it's at the protocol layer, RS-422 is the most common transport layer but we often carry it over UDP or TCP too. SignalK can convert and output your data in NMEA0183 on TCP port 10110, for instance.

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