Not entirely sure where to begin as I am not familiar with Garmin Marine/NMEA boating equipment, but hoping someone here can give me some pointers. I have a friend with a boat equipped with Garmin navigation hardware including a blackbox with an AIS module, a chart plotter and some addition displays and sensors including wind speed/direction sensors like the Garmin GNX Wired Sail Pack.
My goal is to connect to this onboard equipment in some way (e.g. Wifi, Bluetooth) and extract the wind direction and speed somehow from a laptop/mobile phone.
There is a Wifi network on board that Garmin creates (I guess the blackbox does that) and when I connect my laptop to that Wifi network, I see that several services are published through mDNS:
$ dns-sd -B _services._dns-sd._udp
Browsing for _services._dns-sd._udp
17:29:17.011 ...STARTING...
Timestamp A/R Flags if Domain Service Type Instance Name
[...]
17:29:17.218 Add 3 6 . _tcp.local. _garmin-ota-updt
17:29:17.218 Add 3 6 . _tcp.local. _garmin-mrn-stng
17:29:17.218 Add 3 6 . _udp.local. _garmin-ds-sink
17:29:17.218 Add 3 6 . _tcp.local. _garmin-swifi
17:29:17.218 Add 3 6 . _tcp.local. _garmin-mrn-card
17:29:17.218 Add 3 6 . _tcp.local. _garmin-gvs
17:29:17.218 Add 3 6 . _tcp.local. _garmin-helm
17:29:17.218 Add 3 6 . _tcp.local. _garmin-vssl-inv
17:29:17.218 Add 3 6 . _tcp.local. _garmin-bl-id
17:29:17.218 Add 3 6 . _tcp.local. _garmin-sn-sink
17:29:17.218 Add 3 6 . _tcp.local. _garmin-updt-tst
17:29:17.218 Add 3 6 . _tcp.local. _garmin-wx-rx
17:29:17.218 Add 3 6 . _tcp.local. _garmin-bcm
I've looked but I cant find any documentation on these services and what they provide. I understand that in the past Garmin published a Marine SDK but it seems that it is no longer available. I've reached out to Garmin support but they were not able help me either. Can anyone point me in the direction of what service/port I should connect to and which protocol top use? I read that some newer devices provide a protocol called Signal K that seems to expose data in JSON format. Does Garmin expose that in some way?
Alternatively, I see that the Garmin equipment also supports bluetooth connections. Does anyone know if it is possible to obtain that data through bluetooth? If so, I think I would prefer that even over Wifi.
If anyone has some documentation available or even tips that could help me in any way that would be really great!
Thanks!
