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Output NMEA to a VHF
#1
Initial situation : I have an USB GPS receiver connected to openCPC via this openCPN connection :
Network, Input, Signal K, localhost, 3000, 1. And it works OK !
I need to send the position to the VHF NMEA RS232 input. What I did :
  • I plugged an RS232 USB COM port in my USB2.0 HUB ;
  • in SERIAL, I  gave an alias (vhfrs232) to the detected USB port and established a 4800 Baud connection to Signal K ;
  • In Signal K, I can see the connection,  without any activity (no 'pumping')
  • In openCPN i created a connection :
    Network, UDP, 0.0.0.0, 10118, opencpnOUT, Transmit GLL.
  • In SK, I created a connection opencpnOUT
    UDP, 10118, nmea1data (?), Ignored GLL.
  • finally I edited the device connection :
    vhfrs232, Serial, , 4800, Output Events nmea0183out (?), Ignored GLL
I am not sure of what I marked (?), so I need some confirmation. I attach screenshot of my inputs :

   
   


Attached Files Image(s)
   
Cordialement
Didier B
Pi4, SSD USB3, OP 2.6.2, OC  5.2.4




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#2
Another option...
https://github.com/SignalK/signalk-serve...tting-Data
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#3
Hi Didier,

Considering that position input to a VHF is most likely to be useful in an emergency situation, wouldn't you like to have a solution with less complexity involved? A simple standalone GPS with builtin NMEA output would be much more failsafe for this purpose.

Regards
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#4
(2021-03-12, 01:38 PM)Knoet Wrote: Hi Didier,

Considering that position input to a VHF is most likely to be useful in an emergency situation, wouldn't you like to have a solution with less complexity involved? A simple standalone GPS with builtin NMEA output would be much more failsafe for this purpose.

Regards

You are 100 % right, all this set of connections looks like a gas refinery (in french : une usine à gaz !). Consequently, I have dramatically simplified the design :
Use of one RS232 NMEA GPS connected to the VHF GPS input;
Redirection in the VHF of position sentences towards the AIS output (a smart option of some recent VHFs) ;
Connection RS232 from the VHF to COM/USB port on the RPi.
RPi will receive both position and AIVDM and send them to Signal K and OCPN;

If the VHF cannot redirect the position to the AIS output then it is possible to connect the GPS TX to both VHF and RPi RXs : in RS2132 one talker can talk to 2 listeners simultaneously !
It is anyway a safe idea to prepare and test this link in case of failure of the VHF, or to save battery on passage making ...

Thanks a lot to have pushed me towards this simplification !
Cordialement
Didier B
Pi4, SSD USB3, OP 2.6.2, OC  5.2.4




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#5
That sounds good, this way you get the shortest data path to the VHF that is the most important listener. One caveat, if the AIS is a transponder that also outputs SOG and COG data (VDO and/or RMC) you may get some strange effects in OpenCPN if those are not exactly the same as the GPS output. If so, some filtering might be needed.
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#6
In OpenCPN you are outputting just GLL? And then on the input of SignalK you are ignoring GLL on that input? That doesn't sound right...
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