romant
New Member
Please, let me advise how to show OpenCPN VMG data on an external display?
thanx, Roman
thanx, Roman
VMG: OPenCPN -> Display?
- Thread starter romant
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Yngmar
Well-Known Member
What external display do you have, and how is it connected?
romant
New Member
Below is a list of current equipment on my sailboat that is already working well:
-two B&G Triton2 instruments; DST800 Depth, Speed and Temperature Transducer; 608 Wind Sensor all connected on N2k bus,
-magnetic compass; u-blox GPS; attached to Arduino based bridge that provides NMEA messages: GPS data and heading for OpenCPN COM port,
-the bridge is attached also n2K bus and is able to transform available N2k sentences in NMEA messages (for OpenCPN or autopilot) and vice-versa (for Triton Displays). It can generate, e.g. NMEA0183 HDG obtained from magnetic compass and transform it in N2kPGN127250 for B&G display. Same is done for GPS data (e.g. with N2kPGN129026 Rapid Update, etc.). The bridge can also generate NMEA0183 APB (using N2k wind data) that is needed for the autopilot but not available from existing sensors or from OpenCPN.
From the above equipment, I would need the "Waypoint Closing Velocity - WCV" which is available in OpenCPN as VMG if a route is activated. A plan was to get VMG from OpenCPN and generate N2kPGN129284 Navigation Data for B&G display. However, it seems that VMG is not directly available from OpenCPN.
An alternative was NMEA RMB message (WCV is in field 12), but RMB is present as an output on a separate COM port for autopilot and therefore not easily available for the bridge. I hope that there is a simple solution, because WCV is a crucial parameter in sailing that must be visible from cockpit.
Any ideas/solutions are appreciated.
-two B&G Triton2 instruments; DST800 Depth, Speed and Temperature Transducer; 608 Wind Sensor all connected on N2k bus,
-magnetic compass; u-blox GPS; attached to Arduino based bridge that provides NMEA messages: GPS data and heading for OpenCPN COM port,
-the bridge is attached also n2K bus and is able to transform available N2k sentences in NMEA messages (for OpenCPN or autopilot) and vice-versa (for Triton Displays). It can generate, e.g. NMEA0183 HDG obtained from magnetic compass and transform it in N2kPGN127250 for B&G display. Same is done for GPS data (e.g. with N2kPGN129026 Rapid Update, etc.). The bridge can also generate NMEA0183 APB (using N2k wind data) that is needed for the autopilot but not available from existing sensors or from OpenCPN.
From the above equipment, I would need the "Waypoint Closing Velocity - WCV" which is available in OpenCPN as VMG if a route is activated. A plan was to get VMG from OpenCPN and generate N2kPGN129284 Navigation Data for B&G display. However, it seems that VMG is not directly available from OpenCPN.
An alternative was NMEA RMB message (WCV is in field 12), but RMB is present as an output on a separate COM port for autopilot and therefore not easily available for the bridge. I hope that there is a simple solution, because WCV is a crucial parameter in sailing that must be visible from cockpit.
Any ideas/solutions are appreciated.
Yngmar
Well-Known Member
Well, that's a bit more to go on that your rather terse first question 
The way to get the VMG to waypoint out of OpenCPN is indeed the RMB sentence it sends to autopilot ports. OpenCPN can output on multiple connections, so you can just add another one, also configure it as output, and grab the VMG from that RMB sentence and send it wherever you need it.
Alternatively, you can use kplex to multiplex the data from OpenCPN's autopilot output and send it to autopilot and the N2k bridge. Although this is needlessly complicated compared to the solution above.
The way to get the VMG to waypoint out of OpenCPN is indeed the RMB sentence it sends to autopilot ports. OpenCPN can output on multiple connections, so you can just add another one, also configure it as output, and grab the VMG from that RMB sentence and send it wherever you need it.
Alternatively, you can use kplex to multiplex the data from OpenCPN's autopilot output and send it to autopilot and the N2k bridge. Although this is needlessly complicated compared to the solution above.
romant
New Member
Thank you for your prompt advice. I will start with implementation of the first option and output RMB to an alternative COM port. It is not clear to me how to grab the RMB? Actually I have set the OpenCPN input port to COM6 (which is the output of NMEA-N2k bridge). COM7 is used as output for autopilot. I can add a new output port for a copy of the RMB. But I have to grab the RMB by NMEA-N2k bridge, probably through a new RxTx port on the bridge, and then set N2kPGN129284 and push it to CANbus. Do you know for a simpler solution, with no extra hardware? Any idea, how the external WCV is shown in commercial systems, just by moving the navigator computer to the cockpit?
I will inform you about the progress.
I will inform you about the progress.
romant
New Member
How to show VMG from OpenCPN route window into the Dashboard. Which variables is actually shown under VMG in the Dashboard? UNtil now, I can just get ---.
Thanks for any advice.
Thanks for any advice.
