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Old 04-03-2014, 21:25   #1
mub
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Confused by lack of GPS 'lock' and status

In an attempt to tidy up the wires i 'worked' on my system and it no longer 'works'.

Before - Trimble NavTRAC GPS, Standard Horizon GX2150
OpenCPN 3.3.1419 on Ubuntu 13.10
OpenCPN was acting as the NMEA0183 multiplexer to get the GPS position to the VHF.

I added a Shipmodul Miniplex-2Wi using the WiFi as the link to OpenCPN
OpenCPN process the stream showing all the AIS targets BUT the black ship never goes red. It also dances around in a circle till I turn on the compass.

From this I think that the 'communication' is good. and the green messages in the NMEA debug window - the AIS targets and the ship orientation seem to support this

There is nothing suspicious in the log file about why this might be an issue.

Here is a GGA and GXP message that I grabbed.

$GPGGA,040241,4738.8586,N,12220.7092,W,1,4,001,,,, *4C

$GPGXP,040241,4738.859,N,12220.709,W,*73


They look valid to me.

All suggestions very welcome as I have reached

Mub
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Old 05-03-2014, 05:48   #2
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Re: Confused by lack of GPS 'lock' and status

Mub....

1. I see a bug in the GGA processing code in 3.3.1419. But it has been there forever. Easy fix for next Beta. Probably would cause your problem if GGA is to used for positioning.

2. OCPN does not process GXP.

3. Where is RMC? That is a more "normal" position sentence.

4. Is the VHF getting position OK?

Good Luck
Dave
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Old 05-03-2014, 10:58   #3
mub
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Re: Confused by lack of GPS 'lock' and status

Fistly I should say that 3.3.1419 was working as as were the previous beta versions before the wiring change.
May be there is a difference between the way the network stream is presented to the way a USB uart stream is presented?

To answer your questions.

The GPS does not output RMC - I have checked it's documented list of sentences and checked it's output. Yes I know that is odd and it is old but seems reliable.

Both the VHF and autopilot ( on the GPS's second 0183 output ) display GPS position with never a question.

And THANKS for all of the hard work.

Quote:
Originally Posted by bdbcat View Post
Mub....

1. I see a bug in the GGA processing code in 3.3.1419. But it has been there forever. Easy fix for next Beta. Probably would cause your problem if GGA is to used for positioning.

2. OCPN does not process GXP.

3. Where is RMC? That is a more "normal" position sentence.

4. Is the VHF getting position OK?

Good Luck
Dave
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Old 10-03-2014, 16:50   #4
mub
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Re: Confused by lack of GPS 'lock' and status

Quote:
Originally Posted by bdbcat View Post
Mub....

1. I see a bug in the GGA processing code in 3.3.1419. But it has been there forever. Easy fix for next Beta. Probably would cause your problem if GGA is to used for positioning.

Good Luck
Dave

Dave

Sounds like the bug is well understood - at first glance I couldn't see anything in the bug list or the code.

Since I find myself with a little more time on my hands and my C++ needs some exercise - I was planning on making an engine monitor plugin.. but I think I will work through the code NMEA codae and see what I see..

I am in the process of setting up the dev environment and personal bugs are always a good place to start.

Brian
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Old 10-03-2014, 17:40   #5
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Re: Confused by lack of GPS 'lock' and status

Brian...

The GGA bug:

Code:
@ -7278,7 +7278,7 @@ void MyFrame::OnEvtOCPN_NMEA( OCPN_DataStreamEvent & event )
  {
       if( m_NMEA0183.Gga.GPSQuality > 0 )
           {
-                if( !wxIsNaN(m_NMEA0183.Gll.Position.Latitude.Latitude) )
+               if( !wxIsNaN(m_NMEA0183.Gga.Position.Latitude.Latitude) )
                    {
                          double llt = m_NMEA0183.Gga.Position.Latitude.Latitude;
                          int lat_deg_int = (int) ( llt / 100 );
Will be in github very soon.

Around this area would be a good place to put some breakpoints and look at the data as it comes in real-time.

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