Nexus bus (or FDX) protocol?

[hka]

Hello,

Has anyone come across a project related to tapping into classic Nexus Bus (or FDX) via RS485-USB adapter or similar? I have a boat with a set of Nexus NX instruments and it would be great to feed the data stream directly to the SignalK server (RasPi) on board. RS485 converter costs only few $ (vs $100+ for GND10 or 100s of $ for NX2 server).

Thanks,

Harri

[jjjaaa]

I share the interest.

In particular, I would be interested in the bus that controls the transducers. I'd like to build a bridge to connect non-nexus transducer(s) directly to the existing system. In particularly I am interested on how the wind transducer connects to nexus NX2.

- JA

[barnakiel]

I think Garmin sells a Nexus bridge now. Garmin bought Nexus.

b.

[gjorgensen]

Originally Posted by barnakiel

I think Garmin sells a Nexus bridge now. Garmin bought Nexus.

b.

Yup, the GND10. It bridges to NMEA2k. Other than that, the protocol has always been proprietary and I haven't heard of anyone substantially reverse engineering it.

I still have classic Nexus (not NX2) on my boat, but will be replacing them with NMEA2k stuff soon since they're so obsolete.

[masterov]

Can someone on this thread confirm that GND10 box can be used to bring the data from the Nexus Server Classic to an NMEA2000 bus?

[gjorgensen]

Having installed one to convert their new NMEA2k wind transducer to FDX bus (to replace a wind transducer) I can only 100% say it works in that direction. But given that, I think it's high likelihood it works the other direction as well.

While Nexus were great in the day, I have to say I'm looking forward to just being NMEA2k for everything on the new boat.

[masterov]

I've ordered one. Will report back after I install it.

[masterov]

Hey @gjorgensen

I connected the GND10 to the Nexus Bus. It looks like the data in flowing from NMEA2K side over to the Nexus network, however, not only the data doesn't flow in the opposite direction (Nexus --> NMEA), plugging GND10 into the Nexus network caused all the data to disappear from the instruments.

For example, instead of wind speed I now see this:

Screen Shot 2017-07-07 at 9.43.13 PM.jpg Views: 305 Size: 218.7 KB ID: 151425" style="margin: 2px" />

If I unplug it, the instrument shows wind correctly:

Screen Shot 2017-07-07 at 9.43.44 PM.jpg Views: 223 Size: 272.3 KB ID: 151426" style="margin: 2px" />

Would you be so kind and share details (and perhaps photos) of your setup?

Thank you!

[gjorgensen]

Well, we've since since sold our boat and our new one has all new B&G on it, so I may be of limited help going forward. But it turns out I helped the new owner of the boat with something similar.

Long story short, I replaced the wind transducer as he bought the boat, with the new Garmin version that includes a converter cable. I had naively hooked that up to the WIND input on the server but hadn't had any real time to test it before he bought the boat. He called me for help because it was reporting things like 400 MPH wind speeds and the entire server seemed to be acting weird.

We eventually figured out that the WND10 converter does NOT convert from NMEA2k to FDX, but instead to NMEA0183. It didn't come with any documentation so that was pretty unclear. So you need to hook the WND10 output to a network port. In the case of our old boat the GPS was hooked to the network port already, but Achilles at Chicago Marine Electronics pointed out that there's another network port on the autopilot computer and they're networked together. If that wasn't there he would have needed a multiplexer. We moved the WND10 line to there and it seemed to work fine.

Now, in your case there need to be two lines. I think the network port on the server has two NMEA0183 connections, one in and one out. Both need to be hooked to the WND10. I still have no idea if it converts outbound, but that should at least get the inbound side working.

Hopefully this helps.

[masterov]

Hi gjorgensen,

Thanks for your reply.

I do not actually have a WND10 instrument.
I have a Classic Nexus server and a GND10 bridge.

My problem is that when I plug in the GND10 into the nexus network, the readings on my instruments disappear. I suspect that GND10 starts transmitting (non-existent) data from the NMEA side, therefore supressing the data coming from the Nexus server.

Have you experienced anything like it when you first installed the GND10 black box?

Did your old boat have NX2 or Nexus Classic?

[gjorgensen]

Sorry - no experience with the GND10 bridge, so I'm of no real help there. My best guesses would either be what you suggested - that the GND10 is putting some odd data out there - or that there's too much information being sent by the GND10 and that's clogging up the bus or the server. If you have an AIS on the NMEA2000 side I'd unplug that and see if it helps. FYI, ours was a classic server.

Garmin seems to have killed all the Nexus support from what I can tell, and no one there seems to know anything about it. My only other suggestion would be to contact a guy named Achilles at Chicago Marine Electronics (Support). He is very knowledgeable about Nexus setups and has helped me in the past. If anyone knows what to do it's him.

[masterov]

Thanks, gjorgensen

I thought you said earlier in the threat that you've "installed one [GND10] to convert their new NMEA2k wind transducer to FDX bus". May be I misunderstood? If you had it installed, all I want is a confirmation that it worked properly, and did not jam your Nexus bus. At least I would know that it is possible to configure it correctly.

Already talking to Achillefs. He is convinced the GND10 is compatible with the Nexus Classic.

I will update the thread if I find a solution.

[gjorgensen]

It was the WND10, not the GND10, sorry about that.

[masterov]

Just to update here. I was able to solve the problem. Achillefs from Chicago Marine Electronics connected to my computer remotely and was able to configure the system, so now it works properly. This guy knows garmin systems better than garmin tech support folks

So I can confirm that GND10+Nexus Classic server work together well.

The trick was to get the latest version of the Nexus Race software, and then do what is described in this document: The GND10

[gjorgensen]

Thanks Masterov, that's good info. And that makes sense - by default it wants to use NMEA2k transducers for all data sources instead of FDX. So I would assume reconfiguring the sources fixed it?