Not reading all sentences for autopilot

[mcm]

See screen chot, the output sentences are not all there when viewing nema data ?

[stevead]

Do you have an active route ?

[mcm]

No, dockside, this occured earlier in the week, setting up autopilot after update, and steering to w.p. was erratic in the extreme, Comnav suggests autopilot not getting all its data.
Have 3 seperate gps receivers and all 3 read identical for all intents.

[stevead]

No, dockside

To the best of my knowledge XTE, APB and RMB sentences are only generated when there is an active route.

[mcm]

Was the same data during the weeks test run with a waypoint activated and data sent to autopilot com port. would not steer to the point.

[Hakan]

mcm..
How to activate a route is described here: https://opencpn.org/wiki/dokuwiki/do..._route_console
You can also point a desired position, right click -> "Navigate to here" to make a (temporary) route from your position to the mark created.

[mcm]

The problem is, activating a route or steering to a waypoint requires gps data to be received by the autopilot, if not receiving the proper sentences then the pilot cannot steer to the w.p
If the sentences are not even being received by opencpn as per the readout then they cannot of course go to the autopilot.
Am wondering if I should do a reinstall of opencpn but worried I may lose chart data ?

[Dsanduril]

Originally Posted by mcm

...If the sentences are not even being received by opencpn as per the readout then they cannot of course go to the autopilot.
...

From where are you expecting to receive route/waypoint data into OpenCPN? A description of your overall system might help. The screen shot shows you are receiving GGA/GSA/RMC from a GPS device, that provides only position/speed/fix information. Do you set your route on the GPS and expect to receive route information from it? In that case, what GPS?

Or, are you expecting OpenCPN to do the route work? That's how it seems because the output filtering is set to allow "EC" sentences, which come from OpenCPN. But, in that case, as noted above, you need an active route in OpenCPN, it simply won't generate the sentences if there is no active route (if there is no active route then OpenCPN has no idea where you want to go). Even the $GPRMC sentence with SOG/COG isn't making it out (presumably to the AP) because you only allow $ECRMC.

[mcm]

Ok, will do another sea trial , I assume if I enter a temp. waypoint and instruct the system to send to gps and with the proper sentences set in the com port then it should steer to that point even though it is not really a route being only one location.

[mcm]

Noticed that setting a input port does not show the ecrmc sentences etc none of the sentences have the EC prefix except on the output setting ? if not received, how can they be transmitted ?

[Dsanduril]

You don't really need to get underway to see if the NMEA works, just set a route active and it will start computing the required information. Just because the boat isn't going anywhere doesn't mean the values can't be computed.

The first two letters of a five-letter NMEA sentence are the "talker ID". GP=GPS, EC=Electronic Chart System, in this case OpenCPN. OpenCPN receives GPS information from the GP, and if you have an active route it will then calculate the bearing to waypoint (BTW), distance to waypoint (DTW), cross-track error (XTE) and a number of other parameters. It then creates the "EC" sentences and will transmit these (if told to do so), but only if it is calculating them, and that only happens if it has an active route.

You could modify your transmit sentences and change "ECRMC" to "GPRMC", that would tell OpenCPN to pass through the RMC received from the GPS on the output side. Then the AP would have position and SOG/COG information. Still wouldn't help with the track mode going to a waypoint, but may satisfy some of the AP needs when no route is active.

[Hakan]

mcm..
What says the manual for your AP about NMEA0183 sentences it react to and need to allow switching into NAV/TRACK mode?
The "talker", e.g "EC" or "GP, is normally not interpreted. But again you've to consult the specifications in the manual.

[mcm]

OK, looks like we are good to go...
a query, when drop mark here is activated and used to nav to here, send to gps com 4 ,
the gps says ok transmitted, the mark does not change to a "activated" type mark and thus does not get navigted to ?

[bdbcat]

mcm...
"I assume if I enter a temp. waypoint and instruct the system to send to gps and with the proper sentences set in the com port then it should steer to that point even though it is not really a route being only one location."


Pardon me for being simplistic, but I think that there is a basic misunderstanding here.


1. If you send a waypoint to some GPS receiver, and somehow instruct the autopilot to steer to that point, then OCPN will not involved in the autopilot data-flow at all.
2. In order to use OCPN to control the autopilot, then OCPN must be following an "active route", which has been created in OCPN GUI, and "activated" by right - click.


Can we agree on that?
Dave

[stevead]

mcm....
I think as Dave points out that you have a misunderstanding of how OpenCPN works. Amidst Covid lockdowns and with too much time on my hands, here's an explanation.

When you right-click on a waypoint and select "Send to GPS", all you are doing is sending the waypoint information to the GPS device. The assumption here is that the GPS device is not just a simple GPS sensor, but something like a Garmin handheld GPS or even a full blown Chartplotter. The NMEA 183 sentence sent is something like:

$ECWPL,3802.329,S,14439.596,E,End*08

Similarly if you right-click on a route and select "Send to GPS", you are sending the route and the waypoints that comprise it to the GPS device.

$ECWPL,3804.946,S,14434.753,E,Start*04
$ECWPL,3802.329,S,14439.596,E,End*08
$ECRTE,1,1,c,Test Route,Start,End*66

On receipt of these sentences, the GPS may store the waypoints and routes in its internal storage. You are not telling the GPS to start navigating, nor are you telling an Autopilot to begin navigating. If your GPS is connected to your Autopilot, you will need to push whatever buttons are on your GPS to control the Autopilot.

If on the other hand your Autopilot is connected to OpenCPN, you can either select a waypoint, right-click "Navigate to Here" or select a route and right-click "Activate". On screen, OpenCPN will provide a visual indication that a route is active by highlighting the route and next waypoint and by displaying the navigation panel showing cross track error, range, bearing etc. (see attached pictures). Open CPN will then control the autopilot by sending something like:

$ECRMB,A,0.000,L,,Start,3804.946,S,14434.753,E,0.084,71.565,0.000,V,A*18
$ECRMC,042657,A,3804.973,S,14434.652,E,0.000,0.000,210821,11.708,E,A*27
$ECAPB,A,A,0.000,L,N,V,V,71.565,T,Start,71.565,T,71.565,T*73
$ECXTE,A,A,0.000,L,N*4F

Note that you have to engage your autopilot and set its mode of operation for it to actually do anything. OpenCPN does not switch an autopilot on nor select its mode of operation.