Sending GPS info from OpenPlotter to VHF radio

[Kever]

I have taken the device I purchase, JBtek USB to RS485 Converter Adapter ch340T chip, and tested it on my laptop. It locks the cat /dev/ttyUSB0 output till unplugged. This is probably the problem.
I have ordered the following for it's replacement:https://www.amazon.ca/DTECH-RS485-RS422-Serial-Adapter/dp/B06WGQDV7Z

I have the Dtech one working on my system with a Garmin chartplotter and Raymarine Autopilot.  I did have to connect - to + and vice versa though, but I think that will depend on the VHF

Was that specific to send nmea GPS to the VHF radio?

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I have taken the device I purchase, JBtek USB to RS485 Converter Adapter ch340T chip, and tested it on my laptop. It locks the cat /dev/ttyUSB0 output till unplugged. This is probably the problem.
I have ordered the following for it's replacement:https://www.amazon.ca/DTECH-RS485-RS422-Serial-Adapter/dp/B06WGQDV7Z

I have the Dtech one working on my system with a Garmin chartplotter and Raymarine Autopilot.  I did have to connect - to + and vice versa though, but I think that will depend on the VHF

Was that specific to send nmea GPS to the VHF radio?

I did the first wiring diagram you posted with negative results. I will try the second one and hop it does the trick.

[Kever]

Thanks so much Techstyle;
That worked!

[burgoynebc@netscape.net]

Hi Kever:
Just wondering how you have made out. I just got back from a week on the boat and am catching up.
One thing I noticed and its probably not applicable but ... the baud rates dont match 38,400 and 4800. I've not got into Pi enough yet to know, but on my windows system I have to match the windows driver setting (device manager) for the gps input to my arduino and to my chartplotter. The NMEA specs say 4800 if I remember right, but my system does work OK at 9600, which is the default for one of my gps.
Richard
SV Zolanda

[Slovak]

it seems like manufacturers are not specific about polarity on the NMEA0183 connection so try:
PI            VHF
TX(+) --> RX(+)
TX(-) --> RX(-)
RX(+) --> TX(+)
RX(-) --> TX(-)

if that doesn't work, swap the polarity:
PI            VHF
TX(+) --> RX(-)
TX(-) --> RX(+)
RX(+) --> TX(-)
RX(-) --> TX(+)

this worked for me on both a Raymarine autopilot and a Garmin Chartplotter.

After about a week of beating my head against the wall with the PICAN-M HAT on my RPi4, I swapped the polarity per your suggestion and everything suddenly started to work. Interestingly, this is true for anemometer as well as VHF - which makes me wonder whether the board may be mislabeled or it's just general confusion amongst manufacturers. Either way, got it all working - thank you!

[Techstyle]

it seems like manufacturers are not specific about polarity on the NMEA0183 connection so try:
PI            VHF
TX(+) --> RX(+)
TX(-) --> RX(-)
RX(+) --> TX(+)
RX(-) --> TX(-)

if that doesn't work, swap the polarity:
PI            VHF
TX(+) --> RX(-)
TX(-) --> RX(+)
RX(+) --> TX(-)
RX(-) --> TX(+)

this worked for me on both a Raymarine autopilot and a Garmin Chartplotter.

After about a week of beating my head against the wall with the PICAN-M HAT on my RPi4, I swapped the polarity per your suggestion and everything suddenly started to work. Interestingly, this is true for anemometer as well as VHF - which makes me wonder whether the board may be mislabeled or it's just general confusion amongst manufacturers. Either way, got it all working - thank you!

No problem, this seems like a common thing which leads me to believe that it is a NMEA0183 vs RS422 issue rather than mislabeling.  My Seatalk 1 Autopilot and my Garmin communicate fine with the same polarity, it is the connection to the Pi (RS422) that is inverted.