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Old 27-11-2012, 04:36   #1
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OpenCPN and CAN Bus PGN's

As more and more pleasure vessels get equiped with a CAN Bus architecture, are there plans to read and write PGN's in the future?

CeesH
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Old 27-11-2012, 23:52   #2
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Thumbs up Re: OpenCPN and CAN Bus PGN's

Quote:
Originally Posted by CeesH View Post
As more and more pleasure vessels get equiped with a CAN Bus architecture, are there plans to read and write PGN's in the future?

CeesH
2 years ago the answer to this question was negative as this would involve 3-party hardware and a license to use it. E.g. Actisense NGT NMEA2000 to usb converter.

Actually, I do not really understand why it needs a license to use the PGN's that are brought into my system by another hardware/software combination. This does not matter on CM93v2 because this charts come from Europe? Or how should I understand this?? And for every other data too, GPS for instance, it needs 3-party hardware.

I am glad you asked, lets hope the answer this time is more pleasing ;-)
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Old 28-11-2012, 00:30   #3
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Re: OpenCPN and CAN Bus PGN's

There are two different points to be observed in relation with CAN for vessels, better know as NMEA2000 or N2K:

- you need a piece of hardware/software like the mentioned Actisense gateway to be able to read (and write) to/from the bus

- the issue is the parsing and interpretation of the contents, the packets that are traveling on the bus, here referred as PGNs.
NMEA is asking a) for you to buy a licence to get their documentation that includes b) a non-disclosure scheme and makes it therefore invalid for an open source development.

Now the good notice:
some big progress has been made to re-engineer the PGNs here
Yacht Electronics

So what it takes now is to put the parts of the puzzle together.
I understand that the effort of revamping the communication part of OpenCPN is aiming to facilitate that way. So it looks that the solution is coming closer.

It is not that simple on the other hand. Within the architecture of N2K you might have several instances of the same PGN (two, three GPS, several sensors for ROT or Heading, more than one wind instrument, four sensors for fuel levels, seven or 254 temperature sensors, etc.) that will require different approaches to priorize information.

If there is an urgent need to have N2K data into OpenCPN there is a solution as well: take an Actisens N2K-->NMEA0183 gateway and you can get a good part of the N2K information converted into a simple 0183 data stream.

The Actisense stuff is used by a bunch of OEM manufacturers of N2K equipment in order to avoid licencing and to obtain a valid and correctly working N2K device, as it takes care for the correct communication on the bus level, as address claims, error correction, error treatment and things like that.

BCN
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Old 28-11-2012, 05:41   #4
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Re: OpenCPN and CAN Bus PGN's

My fellow country man from Yacht Electronics made his project OpenSource.

You can find it here; Yacht Electronics CanBoat

CeesH
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Old 28-11-2012, 05:53   #5
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Re: OpenCPN and CAN Bus PGN's

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............................It is not that simple on the other hand. Within the architecture of N2K you might have several instances of the same PGN (two, three GPS, several sensors for ROT or Heading, more than one wind instrument, four sensors for fuel levels, seven or 254 temperature sensors, etc.) that will require different approaches to priorize information.............................


BCN

This is a typical NMEA 0183 problem, in a N2K CAN system it's typical not a problem.

CeesH
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Old 28-11-2012, 08:19   #6
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Re: OpenCPN and CAN Bus PGN's

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Originally Posted by CeesH View Post
This is a typical NMEA 0183 problem, in a N2K CAN system it's typical not a problem.

CeesH
Yes indeed, N2K has no problem with multiple instances of a PGN. That has been included into the standard to overcome limitations of NMEA0183.

Nevertheless OpenCPN has to decide how to handle those on the application level.

There has been some discussion on this in the latest Beta 3.1.1105 thread with regard of getting for instance GPS data from different input streams - priorities, fallback strategies in the case of a missing stream, time outs.....

bcn
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Old 28-11-2012, 08:35   #7
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Re: OpenCPN and CAN Bus PGN's

@bcn,

Please keep this discussion clear to everybody. It's difficult enough for the amateur pleasure sailors to make a decision how to invest in these technologies.

I think that the way to go is for a modern communication system on board, eliminating hundreds of meter cable. NMEA 0183 is an out dated protocol.

OpenCPN must, in my opinion, take the step into this new century.

CeesH
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Old 28-11-2012, 08:46   #8
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Re: OpenCPN and CAN Bus PGN's

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Originally Posted by CeesH View Post
@bcn,

Please keep this discussion clear to everybody. It's difficult enough for the amateur pleasue sailors to make a decision how to invest in these technologees.

I think that the way to go is for a modern communication system on board, eliminating hundreds of meter cable. NMEA 0183 is an out dated protocol.

OpenCPN must, in my opinion, must take the step into this new century.

CeesH
Cees,

probably you are getting me wrong:

N2K is the way to go - I have it on my boat - and I would like to see it in OpenCPN.

And if somebody needs data from N2K badly today in OpenCPN, he can go the the gateway way.

I just wanted to point out, that implementing it into the program might be not that simple. And that's why I'm patiently waiting, and in the meanwhile getting my AIS and GPS data via USB - a solution that is an unstable mess.

But as I don't have the time/skills to program the N2K integration....


Hubert
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Old 28-11-2012, 09:04   #9
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Re: OpenCPN and CAN Bus PGN's

I only wanted to point out that CAN Bus technology is not space-craft technology.

It's a dark area for a lot of sailors. But imagine,

Every truck uses a CAN Network,

It communicates with;

Brake CPU,
Transmission CPU,
Engine CPU,
Drive line CPU,
Dash CPU,
even open and closing windows runs trough a CPU.

The CAN Bus of a truck looks like a 6 lane commuter high way near a big city.

The CAN Bus of an average yacht looks like a dead-end street in a sleeping village at 12 o'clock at night.

Please stop all of this b@#!$ht about the difficulties of a yachts CAN Bus.

CeesH
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Old 28-11-2012, 10:38   #10
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Re: OpenCPN and CAN Bus PGN's

I think you're being too hash on bcn; his comments were based on the reality for most private boats.

1 NMEA have done themselves and the industry a great disservice by not making N2K open source. Even the major equipment manufacturers have their own proprietary versions to bypass the constraints

2 Most boats do not have N2K Canbus

3 Most boats currently sailing will never have N2K

4 There's not a lot of non-proprietary software that can handle multiple sensors.

You're suggesting OpenCPN could lead the field, but most boats don't have huge numbers of multiple sensors, especially N2K sensors. I have three GPSs but only one of everything else. It may be technically elegant to handle unlimited sensors and connectivity, but there are other higher priority features yet to be implemented in OpenCPN. No doubt N2K multiple sensor handling will come eventually, but it's just not important to most sailing people.
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Old 28-11-2012, 10:55   #11
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Re: OpenCPN and CAN Bus PGN's

I would strongly support hoolies remarks. There is no way I'm going to update all my boat electronics and anything I can afford to buy in future in that line will be second hand and assuredly NMEA 0183, which has worked fine for me for years.
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Old 28-11-2012, 11:03   #12
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Re: OpenCPN and CAN Bus PGN's

I am happy that some people think about this subject. I also hope that sailors understand that buying new equipment means they not only buy old technologie NMME 0183 but also state of the art CAN Bus technologie. Make your one dicsision how you want to go on.

My advice; look to the futere.........


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Old 28-11-2012, 12:16   #13
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Re: OpenCPN and CAN Bus PGN's

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Originally Posted by CeesH View Post
I am happy that some people think about this subject. I also hope that sailors understand that buying new equipment means they not only buy old technologie NMME 0183 but also state of the art CAN Bus technologie. Make your one dicsision how you want to go on.

My advice; look to the futere.........


CeesH
In spite of my seemingly negative remarks I'm thinking of upgrading my electronics. But due to NMEA's imposed restrictions, there's at least half a dozen variants on the N2K theme, even some with their own PGNs. Where do you start?

At least with nmea0183 it's a single standard that can be used to intermix different manufacturers' kit

CANBUS, as you have pointed out is a major industry standard, and has seemingly avoided this bu@@ers muddle by defining an open standard.
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Old 28-11-2012, 13:02   #14
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Re: OpenCPN and CAN Bus PGN's

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Originally Posted by hoolie View Post
In spite of my seemingly negative remarks I'm thinking of upgrading my electronics. But due to NMEA's imposed restrictions, there's at least half a dozen variants on the N2K theme, even some with their own PGNs. Where do you start?

At least with nmea0183 it's a single standard that can be used to intermix different manufacturers' kit

CANBUS, as you have pointed out is a major industry standard, and has seemingly avoided this bu@@ers muddle by defining an open standard.
N2K is pretty well standardized - very are few "private" PGNs and an effort is in place as well to keep up with new developments. Today it is a stable standard and in general a non-brainer to integrate between different vendors.

On the other hand NMEA wants to keep the hand on the standard - that is up to them but does not imply to keep documentation as "classified" (from a just logical point of view). NMEA insists to do so, so developers of open software are confronted with that situation. And are slowed down in their developments. Just a fact.

Back to OpenCPN: for navigation purposes the NMEA0183 stuff seems to cover what you need. N2K is more flexible, yes. No multiplexers. And easier in the layout of the wiring. Most probably. It's a bus, not a point to point protocol.
That's why OpenCPN should have it.

If your focus is presentation of data, monitoring or interaction (remote switches, light scenarios or what so ever, remote control - field of our IPAD and Android fans, battery management systems) then N2K is a different beast from NMEA0183. At a complete different level. Kees's (canboat) software does go in that direction.

bcn
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Old 28-11-2012, 13:36   #15
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Re: OpenCPN and CAN Bus PGN's

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... ... ...
Back to OpenCPN: for navigation purposes the NMEA0183 stuff seems to cover what you need. N2K is more flexible, yes. No multiplexers. And easier in the layout of the wiring. Most probably. It's a bus, not a point to point protocol.
That's why OpenCPN should have it.

I agree. And I suppose if the hardware interface is handled by a standard adaptor it wouldn't be too difficult to handle PGNs with the new "connections" interface.

If your focus is presentation of data, monitoring or interaction (remote switches, light scenarios or what so ever, remote control - field of our IPAD and Android fans, battery management systems) then N2K is a different beast from NMEA0183. At a complete different level. Kees's (canboat) software does go in that direction.

Controlling all sorts like lights, appliances, climatisation, engine control etc is of course what CANBUS is used for on cars.

bcn
CANBUS relies on distributed processing - a concept that at present doesn't get much coverage in boats. Certainly it's worth pursuing but I think it's for the long term.
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