Sending RMC to GX2200

[RoryG]

I want to send RMC sentences to a Standard Horizon GX2200 so that the GPS COG line on my OpenCpn display is corrected for magnetic variation.
My equipment is as follows:
Windows 10 PC running OpenCpn Ver. 5.2.4


GX2200 connected to the windows 10 PC using a ftdi rs232 cable.



Raymarine EV100 Wheel Pilot, connected to the PC via a Yacht Devices NMEA 2000 USB Gateway


The radio is connected to the PC like this: This sends GPS, AIS and DSC info to the PC from the radio.



I'm hoping that the compass info from the Raymarine (or maybe just the var from WMM) unit can be sent to the GX2200. I'm not sure which wires to connect or how exacly the OpenCpn ports should be configured.

[Hakan]

RoryG..
If I understand you correct: The very first thing would be the GPS part of the VHF would do it right and send a correct variation. If the firmware is old the WMM table is outdated and therefor gives a false variation. Correct?
1. Could you update the firmware on the VHF?
2. If not. Try to set it so the transmitted variation is 0.0 degr. Check the setting for your GPS part of the VHF. If the GPS on the VHF will report variation 0.0 OpenCPN's WMM plugin will kick in and take care of the variation and your COG will be correct.

Håkan

[RoryG]

The VHF will not handle Variation on it's own


From the Manual:
"NOTE Setting to “Magnetic” is effective only when the RMC sentences with magnetic data are input from external devices such as a GPS receiver. It is ineffective when using the internal GPS of the GX2200."


From the Manual:

NMEA 0183 Input (4800 baud)GGA, GLL, GNS, RMC, GSA, & GSV
NMEA 0183 Output (4800 baud)DSC, DSE, GGA, GLL, GNS, RMC, GSA & GSV




NMEA 0183-HS Input (38400 baud)GGA, GLL, GNS, RMC, GSA, & GSV
NMEA 0183-HS Output (38400 baud)DSC, DSE, GGA, GLL, GNS, RMC, GSA, GSV & VDM


So, if the radio does not internally correct for Magnetic Variation without an external device sending it that info, It seems I must send it from the PC to the radio. I think the RMC sentance is the only one that the radio will accept that has variation data in the stream.
Once the RMC with the variation data is received by the radio, it should add that info to its outgoing RMC sentance, allowing my GPS COG to display with the mag correction. I hope

[Hakan]

- OCPN is not made to produce a RMC containing variation, in field 10, only.

- If your goal is to have a variation corrected COG in OpenCPN and the GPS don't transmit that it would be no problem if you've plugin WMM activated.
But to be sure where we are: Please check what's in the RMC from the GPS. Use the Toolbar->Options->Connections-> [] NMEA Debug window and see what's coming in. If you're unsure copy the received GPRMC or GNRMC message and show it here. (You know in the NMEA Debug window you can filter for example "RMC"?)

Here's my example
<GREEN>09:07:02 (TCP:192.168.10.229:10110) $GPRMC,,A,5743.7320,N,1139.9532,E,9.700,331.394,23 0394,,W*70<0x0D><0x0A>
As you can see field 10 is empty. ( ,,W*)

[smac999]

So you want to send gps data from the pc to the 2200 so that the 2200 will send Correct gps data back to the pc?...,

The pc would already have that correct gps info in the first place.... making the whole thing unesassary.


The compass or autopilot has nothing to do with it.

The gps will provide true cog data. And the gps will have mag variation based on its world location , date, and a built in table. At which point you just change units back and forth in the settings to get true or mag cog.

The compass Can then get mag variation info from the gps. And now it can also change heading units back and forth. That would require getting gps data into the stng network. Or manually setting the variation in the pilot compass menu.

The compass needs the mag variation data from the gps. The compass does not provide that to the gps. You have that backwards.

[RoryG]

Thanks for the help guys. I'll look at my settings further.