Connect Openplotter to NASA Clipper Repeater.

[Jodel]

I know this issue has been dealt with in some depth in:

https://opencpn.org/wiki/dokuwiki/doku.p...sa_clipper

It seemed that a lot of interfacing electronics was required.

However, I just tried connecting the NASA Repeater to a NMEA to USB interface in the Pi running Openplotter.  I filtered out all the NMEA other than the three Sentences that it requires and up popped Lat and Long on the display.  When I selected a waypoint to go-to in opencpn I could see that the RMB sentences were being outputted  and the repeater started to display Bearing and distance  to waypoint  etc.
All is well so far!  Just one small glitch.  after a few seconds the display flashes "No RMB" for about half a second and then back to displaying the correct data for about a second.  The flashing between the correct data and no RMB continues and never stops.
If I switch to the position display, Lat and Long are steady - just the normal changes in the last digit as the GPS position moves minutely.
The NMEA debug window shows the RMB sentence being output to the port every second or so with no errors.

Any suggestions as to the cause of this issue?

Jodel

[Jodel]

Having worked on the problem for the last few hours I have a working solution and am closer to the cause of the problem.
If I set the outgoing filter to only send ECRMC and ECRMB the repeater works fine as long as a route is active.  If the route is de- activated Opencpn stops sending BOTH sentences and the repeater reports no GPS position.
This is not really a problem as the main function of the repeater is to show route data, and the lack of a lat and long display when no route is active is not much of an issue.
As well as ECRMC, opencpn also has GPRMC which is available all the time, even when a route is not active.
I then tried sending only GPRMC and ECRMB.  This gives a position on the repeater whether a route is selected or not.  However, when a route is active and openpcpn sends the ECRMB and the screen for displaying bearing and distance starts flashing again.

I have noticed in the NMEA debug screen that there is a difference at the end of the sentence between ECRMC and GPRMC.
It looks like a check sum issue?
I'll do some more research and report back on progress.
By the way GSA seem not to be needed ( even though the instructions with the repeater says to send it)
Jodel

[PaddyB]

I had similar issues, the repeater would only display if it received both rmb & rmc sentences. Rmc alone didn't do anything