Signal K Implementation

[verkerkbr]

Originally Posted by boat_alexandra

Is it correct that currently the only signalk message for opencpn to output is the nmea0183 APB equivalent? This is converted to either n2k or nmea0183 to control actual autopilots by sk node?

How about messages for manual control? Will this work with other autopilots over n2k? What messages are currently converted related to autopilots that opencpn can support in a generic way?

What about messages for informing the autopilot how narrow the channel is based on the chart or active route "area" this would allow the autopilot to trade efficiency for accuracy in some cases.

The pypilot plugin already sends a lot of different messages to configure the autopilot gains, calibrate sensors, set current/temperature limits and much more. It would be interesting to see what settings are similar to other autopilots supported through signalk.

In my opinion there is not so much need to get data from OpenCPN. Only for routing and info about heading to, and distance to a waypoint.

And a route is in principal only more waypoints 1 2 3 .....etc.

It must be easy to translate this to SignalK.

It can then be shown in MXTommy or other future instrument sets.

The corrections and settings plus remote control can be done in software like Sean's Pypilot.

Pypilot is a autopilot in itself.

The outcome is only a switch with plus, minus or neutral for a tillerpilot motor or an electric motor can be used for a present autopilot or hydraulic systeem with only use of the motor.

In this way it is very easy to have an autopilot using a simple "autohelm" motordrive with the advanced Pypilot options with the use of SignalK.

The next stage is a SignalK/canboat translation to NMEA2K.


Bram

[LennartG]

Bram, either we do something that is working for external autopilots or we do a dedicated interface requiring the user to use pypilot. The latter is, in my opinion, a bad choice (nothing bad with pypilot).
Whatever interface there is: It must be open and allowing today's autopilots to be interfaced using the commonly used commands/PGN's.
Please do not start by limiting the options, we need the frequently used translations and that includes the APB (PGN's 127237, 129283, 129284) translation. It is then up to SK to ensure these translations are being implemented.

/Lennart

[verkerkbr]

Originally Posted by LennartG

Bram, either we do something that is working for external autopilots or we do a dedicated interface requiring the user to use pypilot. The latter is, in my opinion, a bad choice (nothing bad with pypilot).
Whatever interface there is: It must be open and allowing today's autopilots to be interfaced using the commonly used commands/PGN's.
Please do not start by limiting the options, we need the frequently used translations and that includes the APB (PGN's 127237, 129283, 129284) translation. It is then up to SK to ensure these translations are being implemented.

/Lennart

Hi Lennart,

I fully agree with you. But it takes perhaps some time to get the APB translation from Canboat/signalk to NMEA2K ready.

In the meantime and also for users who like to make there own autopilot. Pypilot is an advanced autopilot system with an emu to compensate the boat movements.

In the SignalK options there is also:

signalk-raymarine-autopilot
Plugin that controls a Raymarine autopilot by scott@scottbender.netVersion
1.3.

Don't know what this does.


Bram

[bcn]

Discussing with a others about messages generated by OpenCPN another category came up: Alarms.


MOB. The corresponding N2K PGN is 127233 "Man Overboard Notification (MOB)"
The description here:
https://www.nmea.org/Assets/20130906...0amendment.pdf

[teppokurki]

Originally Posted by bcn

Discussing with a others about messages generated by OpenCPN another category came up: Alarms.


MOB. The corresponding N2K PGN is 127233 "Man Overboard Notification (MOB)"

This would be handled as a SK notification, O sending the SK message over the same data connection. I created an issue for this in signalk-to-nmea2000 plugin https://github.com/SignalK/signalk-t...2000/issues/35, please feel free to comment there.

Other notifications and alarms in the same vein.

Also the other way: would notifications in O be handled by the core or some plugin? For example N2K alarms are now available in SK.

[teppokurki]

Originally Posted by LennartG

...that includes the APB (PGN's 127237, 129283, 129284) translation. It is then up to SK to ensure these translations are being implemented.

First: please, don't talk about SK in the third person. There is no "SK who it is up to ensure something". It is people, not an entity bestowed upon us that has a will of its own.

Second: I had time to look at this and started the implementation, see https://github.com/SignalK/signalk-t...s/autopilot.js

There you can see how SK paths map to PGN fields. Quite a lot of fields in those pgns.

So if we continue on this route O could send one delta with the different paths over to SK side and it would result in those PGNs going out.

Now the question is: which fields are actually the minimal set for each autopilot? Do the different autopilots use these PGNs in a consistent manner, and are there any proprietary PGNs to add or needed? Data captures from real world would go a long work to make the armchair coding result in something that works.

So, any people in the audience who have N2K autopilots and could provide data captures to help in checking how things work? Or friends who have friends who...

[LennartG]

Teppokurki please, there was no insult intended, absolutely not!
I was just trying to keep the comment short and had no intention to make anybody feel bad or neglected. Sorry for that.
That is unfortunately what could happen if not being careful enough when trying to separate projects.
/Lennart

[LennartG]

Teppokurki,
I have a Garmin GHP20 but unfortunately, the boat is on dry land until mid May.
On top of that: The documentation from Garmin does not give much away regarding the 'essential' commands. The list includes almost any PGN that floats around in the NMEA2K network.
I currently communicate with the autopilot over RS-422 <-> RS 232 using NMEA 0183 sentences.
/Lennart

[verkerkbr]

Originally Posted by LennartG

Teppokurki,
I have a Garmin GHP20 but unfortunately, the boat is on dry land until mid May.
On top of that: The documentation from Garmin does not give much away regarding the 'essential' commands. The list includes almost any PGN that floats around in the NMEA2K network.
I currently communicate with the autopilot over RS-422 <-> RS 232 using NMEA 0183 sentences.
/Lennart

There is a list of NMEA2K PGN's which has something to do with waypoints and routes.

I expect that the other settings and controls are done in the computer of the autopilots.

Attached is the list of all the PGN's with reference to route etc. A number can certainly be removed for not needed or allready done in OpenCPN.

What is then left is probably the necessary data for the movement of the autopilot from the navigation software.

Bram

[verkerkbr]

Originally Posted by verkerkbr

There is a list of NMEA2K PGN's which has something to do with waypoints and routes.

I expect that the other settings and controls are done in the computer of the autopilots.

Attached is the list of all the PGN's with reference to route etc. A number can certainly be removed for not needed or allready done in OpenCPN.

What is then left is probably the necessary data for the movement of the autopilot from the navigation software.

Bram

I remember now some discussion about the actisense conversion to NMEA2K. Perhaps he can give more detailed information what is needed. (Email adress removed )
Timo Lappalainen

[bdbcat]

All..


Re N2K autopilot PGNs: Interesting discussion here...
https://www.coastalexplorer.net/foru...t/topics/76171


Dave

[LennartG]

Trying to achieve something I followed this path:
- Translated the 0183 sentences used into PGN's using the Actisense NGW-1 Gateway Conversion based on the MNEA 0183 commands used: APB, GGA, GLL, GSA, GSV, RMB, RMC
- I then filtered out those not listed as being received by Garmin GHC20 or its CCU, this is what remains:
127258 - Magnetic Variation
129025 - Position, Rapid Update
129026 - COG & SOG, Rapid Update
129029 - GNSS Position Data
129283 - Cross Track Error
129284 - Navigation Data

So these appears to be the 'important PGN's required' by Garmin Autopilot GHC20 or its CCU.
Just note that this is a 'paper product' FWIW.
/Lennart

[bcn]

Some more bits and pieces here (Chapter XI):
This one from Yacht Devices https://www.yachtd.com/downloads/ydnu02.pdf

[verkerkbr]

A lot of users with an Ais transponder have allready the NMEA2000 position data available. But most use instead the high speed NMEA183 connection for the purpose of OpenCPN. With a serial convertor to usb.

But with the SignalK input to OpenCPN via canbus adapter from NMEA2K, the use of the NMEA183 connection is no longer needed. I have used such a setup and it works. With one small problem. I had to switch on the network first and then the transponder.

The only thing that is missing for an NMEA2K autopilot, is an outgoing SignalK data stream from OpenCPN with the course and waypoints data and with a conversion to the right PGN's.

For users of an NMEA183 autopilot. Translation of SignalK to NMEA183 is allready available.

If you don't have a transponder, you can use an NMEA2K Gps antenna.
This is working here for a demo purpose.

There is one problem. These NMEA2K cables, connectors and gear are (much too) expensive.


Bram

[sbender]

Originally Posted by verkerkbr

Hi Lennart,

I fully agree with you. But it takes perhaps some time to get the APB translation from Canboat/signalk to NMEA2K ready.

In the meantime and also for users who like to make there own autopilot. Pypilot is an advanced autopilot system with an emu to compensate the boat movements.

In the SignalK options there is also:

signalk-raymarine-autopilot
Plugin that controls a Raymarine autopilot by scott@scottbender.netVersion
1.3.

Don't know what this does.


Bram

I am in the middle of reworking this to support other autopilot manufacturers.

https://github.com/SignalK/signalk-autopilot

In essence it will provide a common api for SignalK clients to use to control an autopilot. The api is described in the README. It allows clients to do things like engage the autopilot, change the target heading, etc.

I would appreciate any input you all have if it will be useful to you. (Please use github issues)