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Old 28-06-2013, 08:26   #1
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OpenCPN not accepting NMEA data from NEXUS server

I cannot get OpenCPN to accept NMEA data from the NEXUS server on my boat.

Below is a portion of an input stream collected using Hypertext:

$IIHDM,233,M
$IIHDT,233,T
$IIMWD,241.85,T,241.85,M,13.19,N,06.79,M
$IIMTW,21,C
$IIMWV,012,R,13.99,N,A
$IIVDR,117.29,T,117.29,M,0.06,N
$IIVHW,233,T,233,M,00.00,N,00.00,K
$IIVWT,014,R,14.20,N,07.31,M,,
$IIZDA,000956,,,,00,
$IIVWR,015,R,13.82,N,07.11,M,,
$IIVWR,012,R,12.49,N,06.43,M,,
$IIDBT,008.56,f,002.61,M,001.41,F
$IIGLL,3856.936,N,07454.509,W,000958,A
$IIHDM,233,M
$IIHDT,233,T
$IIMWD,246.72,T,246.72,M,11.06,N,05.69,M
$IIMTW,21,C
$IIMWV,019,R,09.87,N,A
$IIVDR,117.29,T,117.29,M,0.06,N
$IIVHW,233,T,233,M,00.00,N,00.00,K
$IIVWT,021,R,09.60,N,04.94,M,,
$IIZDA,000959,,,,00,
$IIVWR,018,R,10.57,N,05.44,M,,
$IIVWR,016,R,11.89,N,06.12,M,,
$IIDBT,008.62,f,002.63,M,001.42,F
$IIGLL,3856.936,N,07454.509,W,001000,A
$IIHDM,233,M
$IIHDT,232,T
$IIMWD,245.65,T,245.65,M,11.52,N,05.93,M
$IIMTW,21,C
$IIMWV,012,R,11.27,N,A
$IIVDR,117.29,T,117.29,M,0.06,N
$IIVHW,232,T,232,M,00.00,N,00.00,K

I don't know why the "II"s are there and they may be the cause of the problem.

Does anyone have any ideas one what's wrong and how I fix it?

Thanks,

Coleman Blake
Tayana 37
Traveler
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Old 28-06-2013, 08:41   #2
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Re: OpenCPN not accepting NMEA data from NEXUS server

Coleman...
I have no idea what a nexus server is, but the "NMEA" stream it produces does not contain a single valid sentence - all of them are missing the checksum part at the end...
The II is a talker Id and really does not matter.

Pavel
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Old 28-06-2013, 08:59   #3
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Re: OpenCPN not accepting NMEA data from NEXUS server

Pavel,

NEXUS is a brand of navigation/instrument server. It collect data from transducers and GPS and displays the data on displays. It also outputs the collected data on an NMEA 0183 stream.

The one I have is pretty old and that may account for the lack of checksums. However, NavMonPC accepts the data stream and correctly displays the data.

The control checksum option will allow invalid checksums, but apparently won't pass sentences with no checksum.

Coleman
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Old 28-06-2013, 09:22   #4
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Re: OpenCPN not accepting NMEA data from NEXUS server

Coleman...
Any chance the unit can be set to obey the NMEA standard? Or can NavMonPC add the checksums and be used as a router? I really know neither... The question is how broken the message can be to consider it usable. Having it wrong can get a bit dangerous...

Pavel
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Old 28-06-2013, 09:59   #5
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Re: OpenCPN not accepting NMEA data from NEXUS server

Playing the nmea stream in #1, with the VDR plugin, I get own ship position and true heading.

Thomas
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Old 28-06-2013, 12:12   #6
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Re: OpenCPN not accepting NMEA data from NEXUS server

Tom,

Is it possible that the VDR plugin only interprets the sentences for position and true heading and it interprets my data as valid?

Coleman
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Old 28-06-2013, 16:04   #7
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Re: OpenCPN not accepting NMEA data from NEXUS server

Problem solved. I unchecked the "control checksum" box on the connection setting and the data is accepted.
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