Saturday, June 20, 2015

NMEA 2000 Weirdness Continues

This started out as a set of comments in the pilot house tour post, but I think it warrants it's own post since it's a good example of the problems one encounters with NMEA 2000 products, and how it can bankrupt a marine electronics installer and/or boat owner.

Carl E. said...
Hi Peter,

Thank you very much for the walk through and the commentary. Great also to see the whole package (I may have occasionally forgotten this stuff is meant to pilot a boat :)) in her element.

A previous post indicated there were still some gremlins on the N2K bus with regard to instancing, leading to the autopilot not getting a 10 Hz heading. Any improvement since then?

Finally, do you have some sort of concentrator for your video streams to interface them to the computer?
Peter Hayden said...
Hi Carl,

Glad you (and others) enjoyed the walk through.

I am still having some issues with N2K, but I don't recall any that interfere with getting 10hz heading to the pilot. But I'm probably just not remembering. The issue I'm working now is some interaction between Rose Point's N2K adapter and Furuno's NavPilot. The NavPilot is doing some things that make no sense and are disruptive on the bus, and perhaps even include a malformed PGN. Then, in the presence of the NavPilot misbehavior, the Rose Point adapter appears to misbehave as well. We will get it sorted out in time. Rose Point is all over it, as it typical of their attentiveness. Furuno is a little harder to rally, but as of today I have a new trace that pretty clearly shows the issues.

Carl E. said...
Hi Peter,

You mentioned the problem here:

More on NMEA 2000

Something about a bus storm every 10 seconds which occasionally prevented the heading information to propagate often enough?

Ahh, thanks.  Do you want to be my memory?

This actually is a good illustration of the problems an N2K user like myself encounter, and why people start tearing their hair out (yes, I am bald).  I still have the exact same underlying problem, namely the traffic storm.  But the symptoms are now different.  The pilot hasn't lost its heading source in months, but instead, an old symptom has returned.  Some time ago I mentioned that Coastal Explorer would occasionally show "No Fix" in place of the GPS status display.  This happens just for a second or two then the status display resumes normally.  There are no alarms and CE keeps working fine.

A while back someone, perhaps even you, asked if that problem had been resolved.  Or maybe you asked about the Fast Packer Errors since I suspected they might be the cause of the transient "no Fix" problem.  See there's that memory thing again!  Anyway I though the problem was gone but it came back.  Now I'm pretty sure it's a symptom of the address claim storms that I am still chasing.

Getting back to my point, anyone just operating my boat would have seen the No Fix problem, but then it went away.  Then they would have seen the NavPilot losing its heading source, but that problem went away too.  And now the No Fix problem has returned.  It's an exercise in chasing shadows, but there appears to be a single underlying cause.

Problems like this are killers for electronics installers and customers alike.  Chasing them down is hugely time consuming.  If the installer isn't charging for their time, they would lose their shirt.  And if the customer is paying to chase down these problems, they would be in the poor house.  I have been chasing this underlying address claim storm for going on 6 months now.

I have to admit that I am considering converting more of my system from N2K to NMEA 0183, and have started to sketch out what such a system would look like.  I've also considered segregating the Maretron monitoring systems from the navigation systems, but didn't go far with that idea.  Some of the navigation components also need to be monitored, so I would have to bring both N2K buses into the Maretron N2KView monitoring system, and I have no experience with how well that works, or if it's even possible.  Experience says it will be a new can of worms.  And besides, the interaction problem I have right now is between two navigation devices, so separate buses wouldn't solve the present problem.

The good news is that running the boat works fine, at least for now.  But having these odd problems is just real trouble waiting to happen, and that's not what I want on a boat.


  1. Hi Peter,

    The sight of me in a store having forgotten my shopping list...

    Six months sounds like a long slog, but good to hear you've pinpointed this. Out of curiosity, when selecting autopilots did you consider Comnav? They seem up to continuous heavy duty (Alaskan fishing boats, FPB's) and their Commander P2-model is exclusively NMEA0183. Having said that, your Furuno autopilot has NMEA0183-inputs as well?

  2. I looked very briefly at the Comnav pilots, but that's all. With N2K still prominent in the boat, an all 0183 pilot would have further complicated things. Plus, I had a number of very positive first hand reports about the NavPilot. I remain happy with the NavPilot decision even with this little problem, and I'm confident we will get it fixed.

  3. Hi Peter,

    I am seeing the same message "lost heading information" from my Furuno Navpilot installed last year. I acknowledge the alarm and the autopilot seems to carry on. It is very disconcerting to get these alarms and my electronics installer gets no clarity from Furuno. I like NMEA 2000 for the most part but it is certainly not bulletproof.

  4. Hi Ross,

    Sorry for the slow response, but we have been out of communications range for a while. What other equipment do you have on your N2K bus?


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