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Old 31-01-2020, 06:02   #1
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OpenCPN, NMEA2000 and Autopilots

Given some of the discussion on the Signal K Implementation thread, I thought it may be appropriate to have a separate thread focused purely on communicating with autopilots using NMEA2000.

It is reasonable to assume that the three major autopilot manufacturers: Raymarine, Garmin & Navico (Simrad, B&G) are loathe to publish what NMEA2000 Parameter Group Numbers (PGN's) are used to control their autopilots. In addition to the "documented" PGN's they may also use proprietary messages.

I hope that we can prevail on the OpenCPN user community to log NMEA 2000 traffic to and from their MFD's and autopilots so that we can learn how to control these devices.

From my perspective I'm not fussed what log formats are supplied, I'm happy with candump (Linux utility), EBL (Actisense), VDR (Yacht Devices Voyage Recorder), Canboat (kees verruijt's utility) or even the raw format from TwoCan.

Thanks in advance.
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Old 31-01-2020, 06:51   #2
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Re: OpenCPN, NMEA2000 and Autopilots

Can someone please explain why the autopilot must be controlled from OpenCPN?
When I arrive at next waypoint I don't want the autopilot changes course setting automatically. I better do it myself.
When my autopilot lost his settings and the boat drifted away then the autopilot beeps and I get also an alarm with OpenCPN grace to some plugins.
Are there any other situations where the autopilot is better controlled by OpenCPN as by its own electronics?
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Old 31-01-2020, 08:00   #3
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Re: OpenCPN, NMEA2000 and Autopilots

Autopilot systems usually consist of the following components:
1. a drive unit to control the rudder
2. a rudder feedback unit to sense the rudder angle
3. an autopilot computer to control the drive unit
4. a compass
5. an autopilot keypad (on/off/standby, left/right, autopilot mode) to command the computer to follow a compass heading or wind angle (assuming there is a wind sensor)
6. an optional multi-function display or chartplotter to additionally command the computer to steer to a waypoint/route, follow a depth contour or some of the new fangled options such as "dock to dock auto-routing"

The benefit of integrating OpenCPN with the autopilot is that some users may not have a chartplotter on board, or may not have one that is compatible with their brand of autopilot and they may wish to use OpenCPN with their autopilot to steer to a waypoint or follow a route.

Today OpenCPN is capable of controlling autopilots that use NMEA 183 communcations, however integration of OpenCPN with the newer NMEA 2000 communications standard is not yet supported.

I fully agree with your observation that good seamanship is not solely reliant on a single source of navigation data and that the prudent sailor keeps a good watch on their vessel using all available means.
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Old 31-01-2020, 08:14   #4
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Re: OpenCPN, NMEA2000 and Autopilots

Quote:
Originally Posted by CarCode View Post
Can someone please explain why the autopilot must be controlled from OpenCPN?
When I arrive at next waypoint I don't want the autopilot changes course setting automatically. I better do it myself.
When my autopilot lost his settings and the boat drifted away then the autopilot beeps and I get also an alarm with OpenCPN grace to some plugins.
Are there any other situations where the autopilot is better controlled by OpenCPN as by its own electronics?

Not certain which AP or other electronics you are talking about, but the tiny pilot (pypilot) for example, doesn't necessarily need to go through OCPN to work. In this basic set up, its working in compass mode (or possibly wind mode if added).

Only when you interface w/gps then you can do waypoints. If you do a single waypoint (go to here) in OCPN it will get you beep then turn off (if I remember correctly). If you set up a series of waypoints it will then steer those waypoints.

On their own most APs will be point and shoot w/o gps or a chartplotter interface. For sailboats, this is probably the most used function in openwater. For entering restricted areas (river, channels), then waypoints through OCPN may be very useful aid to help steer.


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Old 31-01-2020, 08:22   #5
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Re: OpenCPN, NMEA2000 and Autopilots

So it seems nobody can answer to my question:
Quote:
Are there any other situations where the autopilot is better controlled by OpenCPN as by its own electronics?
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Old 31-01-2020, 08:49   #6
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Re: OpenCPN, NMEA2000 and Autopilots

Thought it was evident by the responses that the AP alone typically will not be able to do GPS or waypoint interface.
So yes, if you want to steer by waypoint or gps it is better to interface w/OCPN or other chartplotter/gps than the stand alone AP electronic head.
There are probably some other apps/programs in OCPN that are also helpful like in watchdog that will provide different alarms if you go off course or make landfall that aren't available in your AP head.
Is there some other specific situation that you are having that needs a different answer?


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Old 06-02-2020, 15:04   #7
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Re: OpenCPN, NMEA2000 and Autopilots

I have spent the winter integrating OpenCPN into a large NMEA2k network and I'm not sure why there would be an impression that OC couldn't send the proper autopilot guidance commands thru its serial/network connections. Mind you, you can't interact with N2K NATIVELY from OC, regardless of whether you're sending or receiving. You need a gateway between OC and N2K, but once you have that established, the gateway takes the PGN's from the N2K network and converts them to 0183 sentences, and likewise, takes 0183 sentences sent from OC, and converts them back to PGN's. I have my system happily talking both ways without issue. I will be interfacing a Robertson AP11 autopilot into the system this spring (once I'm back on the boat again...this is all happening on the benchtop currently). The Robertson only has 0183 inputs, so I'll likely send those commands over serial directly to the AP instead of going 0183->N2K->0183. For a native N2K AP, you just need the gateway. I've had great luck with the Yacht Devices hardware (and their support is FANTASTIC).

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Old 07-02-2020, 00:37   #8
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Re: OpenCPN, NMEA2000 and Autopilots

Just another example of working integration between 'OpenCpn, NMEA 2000 and an Autopilot' is the Garmin GHC20 having both N2K and RS-422 interfaces.
I've converted the RS-422 into RS-232 using a FTDI converter and have a fully working setup although the GHC 20 does not convert external PGN's between N2K and RS-422.
I'm also having an N2K Airmar DT800 depth/temperature instrument so I've added the TwoCan plugin and a USBtin 'CAN-bus to usb' converter giving me all required information from the N2K network.
/LennartG
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Old 09-02-2020, 03:31   #9
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Re: OpenCPN, NMEA2000 and Autopilots

Quote:
Originally Posted by CarCode View Post
So it seems nobody can answer to my question:

I have two reasons to control the autopilot from my computer, and specifically from OpenCPN. My arguments apply specifically to my Raymarine Evolution pilot, communicating with Raytalk ng which is NMEA2000.
  1. I want a remote control with the possibility to set the autopilot to Auto/Standby and to adjust the heading set. The wireless remote control that Raymarine provides is too expensive and rather old fashioned, connected through the old Seatalk with a converter that caused all kinds of problems.
  2. The Track function on the autopilot is difficult or impossible to use with OpenCPN. It needs data from O, but whatever you send it, after some time it switches off with a “No data” message. I have the impression it requires a Raymarine display to function.
  3. When the Raymarine track function does work, it behaves very erratically at startup, steering crazy headings for some minutes, then stabilizing on the right track. Further it requires confirmation at every waypoint, which is not practical when you have routes with hundreds of waypoints often very close together.
To do a better job one needs to control the autopilot for at least the following functions: set heading, set auto/standby. I have decoded the communication of the autopilot with the pilot head and deciphered the proprietary pgn's that perform these functions. With this I have build a plugin for O that provides a remote control for the autopilot and a route following function. The plugin is using a Actisense NGT-1 for the communication with the NMEA2000 network of Raymarine. The plugin is also monitoring the keystrokes on the Raymarine P70 pilot head and acts on that to activate the route following. The current version of the plugin does however not function (yet) with the released version of O, it needs a higher version of the plugin API in O which is already in O master, coming out in next release. Further details on this plugin: https://www.cruisersforum.com/forums...ts-225322.html. I will have a updated version of this plugin available before summer.


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Old 09-02-2020, 06:16   #10
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Re: OpenCPN, NMEA2000 and Autopilots

Quote:
Originally Posted by Douwe Fokkema View Post
I have two reasons to control the autopilot from my computer, and specifically from OpenCPN. My arguments apply specifically to my Raymarine Evolution pilot, communicating with Raytalk ng which is NMEA2000.
  1. I want a remote control with the possibility to set the autopilot to Auto/Standby and to adjust the heading set. The wireless remote control that Raymarine provides is too expensive and rather old fashioned, connected through the old Seatalk with a converter that caused all kinds of problems.
  2. The Track function on the autopilot is difficult or impossible to use with OpenCPN. It needs data from O, but whatever you send it, after some time it switches off with a “No data” message. I have the impression it requires a Raymarine display to function.
  3. When the Raymarine track function does work, it behaves very erratically at startup, steering crazy headings for some minutes, then stabilizing on the right track. Further it requires confirmation at every waypoint, which is not practical when you have routes with hundreds of waypoints often very close together.
To do a better job one needs to control the autopilot for at least the following functions: set heading, set auto/standby. I have decoded the communication of the autopilot with the pilot head and deciphered the proprietary pgn's that perform these functions. With this I have build a plugin for O that provides a remote control for the autopilot and a route following function. The plugin is using a Actisense NGT-1 for the communication with the NMEA2000 network of Raymarine. The plugin is also monitoring the keystrokes on the Raymarine P70 pilot head and acts on that to activate the route following. The current version of the plugin does however not function (yet) with the released version of O, it needs a higher version of the plugin API in O which is already in O master, coming out in next release. Further details on this plugin: https://www.cruisersforum.com/forums...ts-225322.html. I will have a updated version of this plugin available before summer.
Douwe Fokkema
I understand. But I do not need a remote control nor a track function.
I am lucky to have the old Neco NM692 autopilot which is sadly not manufactured anymore. I have never had such a nice unit before. Even in bad weather with heavy wind and weaves from the back when any other autopilot failed quickly it works like a charm. All instrumentations and controls are in the cockpit which I don't leave during bad weather. In an area with very big traffic I better stearing by hand. So a remote control is useless for me.
Tracking is displayed and followed only by OpenCPN. That is the navigation system I need. The Neco is mostly operating analogous. At the time of its fabrication there was no digitalization.
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Old 09-02-2020, 06:47   #11
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Re: OpenCPN, NMEA2000 and Autopilots

Quote:
Originally Posted by Douwe Fokkema View Post
I have two reasons to control the autopilot from my computer, and specifically from OpenCPN. My arguments apply specifically to my Raymarine Evolution pilot, communicating with Raytalk ng which is NMEA2000.
  1. I want a remote control with the possibility to set the autopilot to Auto/Standby and to adjust the heading set. The wireless remote control that Raymarine provides is too expensive and rather old fashioned, connected through the old Seatalk with a converter that caused all kinds of problems.
  2. The Track function on the autopilot is difficult or impossible to use with OpenCPN. It needs data from O, but whatever you send it, after some time it switches off with a “No data” message. I have the impression it requires a Raymarine display to function.
  3. When the Raymarine track function does work, it behaves very erratically at startup, steering crazy headings for some minutes, then stabilizing on the right track. Further it requires confirmation at every waypoint, which is not practical when you have routes with hundreds of waypoints often very close together.
To do a better job one needs to control the autopilot for at least the following functions: set heading, set auto/standby. I have decoded the communication of the autopilot with the pilot head and deciphered the proprietary pgn's that perform these functions. With this I have build a plugin for O that provides a remote control for the autopilot and a route following function. The plugin is using a Actisense NGT-1 for the communication with the NMEA2000 network of Raymarine. The plugin is also monitoring the keystrokes on the Raymarine P70 pilot head and acts on that to activate the route following. The current version of the plugin does however not function (yet) with the released version of O, it needs a higher version of the plugin API in O which is already in O master, coming out in next release. Further details on this plugin: https://www.cruisersforum.com/forums...ts-225322.html. I will have a updated version of this plugin available before summer.


Douwe Fokkema

Beste Douwe,

the latest OpenCPN beta version has SignalK input. The route made in O can be transfered back in NMEA183 to SignalK format.

GPS data from NMEA2K is coming via my canbus board to SignalK.

All the info can be displayed in the MXTommy SignalK display. All this is working on the SignalK server.

There is plugin for SignalK to NMEA2K but there are some PGN's still missing that are needed by an NMEA2K autopilot.

If this is solved I think you can use a route made in OpenCPN and use it on an NMEA2K autopilot.There is also Pypilot with movement sensing. If all this things are combined, then you have perfect software to control an autopilot.


Regards,


Bram
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Old 09-02-2020, 06:53   #12
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Re: OpenCPN, NMEA2000 and Autopilots

Douwe's beta plugin is in the wiki AutoTrackRaymarine
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Old 09-02-2020, 07:02   #13
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Re: OpenCPN, NMEA2000 and Autopilots

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Douwe's beta plugin is in the wiki AutoTrackRaymarine

Then I get this message:


This topic does not exist yet
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Old 09-02-2020, 07:18   #14
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Re: OpenCPN, NMEA2000 and Autopilots

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Originally Posted by verkerkbr View Post
Beste Douwe,

the latest OpenCPN beta version has SignalK input. The route made in O can be transfered back in NMEA183 to SignalK format.

GPS data from NMEA2K is coming via my canbus board to SignalK.

All the info can be displayed in the MXTommy SignalK display. All this is working on the SignalK server.

There is plugin for SignalK to NMEA2K but there are some PGN's still missing that are needed by an NMEA2K autopilot.

If this is solved I think you can use a route made in OpenCPN and use it on an NMEA2K autopilot.There is also Pypilot with movement sensing. If all this things are combined, then you have perfect software to control an autopilot.

Regards,

Bram
Hi Bram,

The PGN's I am using to control the Raymarine pilot are proprietary and don't have nmea183 equivalents. So I don not see how a SignalK server can do a conversion. Further I have no need of a conversion, my plugin is working and tested during a full sailing season.
To follow a route I do not need the full route in the plugin. I just use the DTW, BTW and XTE for the current leg, that is sufficient to steer on track. Reason I needed an update in O is that the accuracy of the XTE in the nmea183 message lacks precision. I want to steer within meters from the track, limited only by the accuracy provided by the GPS.

Greetings, Douwe
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Old 09-02-2020, 07:35   #15
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Re: OpenCPN, NMEA2000 and Autopilots

Sorry that link was wrong, too late to correct AutoTrackRaymarine Wiki
https://opencpn.org/wiki/dokuwiki/do...trackraymarine
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