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Old 19-05-2015, 19:28   #1
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openCPN to VHF for DSC

I new to the forum.

I'm looking to connect my laptop that is on OpenCPN to my VHF for GPS coordinate info. My VHF has only 2 wires and it describes connecting them to NMEA. So I guess I need to go USB to NMEA. Any help is much appreciated.
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Old 19-05-2015, 20:30   #2
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Re: openCPN to VHF for DSC

You can connect a USB to RS-232 serial converter to the OpenCPN computer. The OpenCPN manual describes how to configure a serial port as an output port for NMEA repeater. There is a host of features where you can filter out certain NMEA sentences. But this may not be necessary as the VHF will ignore anything it doesn't care about. Set the BAUD rate for 4800. Tell OpenCPN which serial port number matches the USB adapter.

On the serial port adapter there will be a 9 pin male connector. Using a female 9-pin connector connect pin 3 (TXD) to the NMEA data wire on the VHF. Connect pin 5 (GND) to the GND wire on the VHF.

Please be aware that USB to serial adapters sometimes change their port number under Windows. If you keep the USB adapter plugged in all the time it should stay as the same port number but if you unplug it then the port number may change.
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Old 20-05-2015, 18:53   #3
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Re: openCPN to VHF for DSC

Thank you very much.

So I need something like this
http://www.amazon.com/TRENDnet-USB-RS-232-Serial-Converter/dp/B0007T27H8

I am then confused how to convert the serial to wires. What type of converter do I need there?

Sorry if you already answered this. I'm not really techy. Thanks again!
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Old 20-05-2015, 18:58   #4
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Re: openCPN to VHF for DSC

Am I going laptop - out usb - to serial - to another converter that splits serial? I just want to make sure I am following you.

Thanks again
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Old 20-05-2015, 20:28   #5
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Re: openCPN to VHF for DSC

What operating system does your laptop run?
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Old 21-05-2015, 04:45   #6
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Re: openCPN to VHF for DSC

Windows XP
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Old 21-05-2015, 05:26   #7
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Re: openCPN to VHF for DSC

Note that NMEA 0183 is actually RS422, not RS232. It's sort of compatible, but not always. See: Electric Marine Discussions: Interfacing Equipment using NMEA 0183

It's a good idea to look for a USB adapter which is specifically compatible with RS422, like this one: USB2-F-6001 | USB to 1-port RS422

If you want to be totally sure and don't mind spending a little more money, you can use the Actisense NGW-1-USB. The NGW-1 is also opto-isolated which eliminates ground loop problems which occur sometimes.

I use an el-cheapo Chinese RS422 adapter, however, which works perfectly in my particular application.
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Old 21-05-2015, 05:36   #8
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Re: openCPN to VHF for DSC

For Windows XP I recommend only using the USB devices with FTDI chipset. This is the best one I know:

Amazon.com: GearMo® USB RS-232 Serial Adapter with LED Indicators Win 8 , 7, Vista, XP, 2000 Support: Computers & Accessories

Then you only need a 9-pin female connector like this:

Amazon.com: StarTech.com Assembled DB9 Female Solder D-SUB Connector with Plastic Backshell (C9PSF): Computers & Accessories

This connector can be used to connect the 2 wires from your VHF to the adapter.

Please tell us the exact model of VHF you have. I may be able to tell if there is any issue with the RS-232 interface.
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Old 21-05-2015, 05:39   #9
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Re: openCPN to VHF for DSC

Thank you.

I'm still confused. If I get the usb to RS422 how do I connect it to the VHF? I need another adapter right?

Id rather go cheaper if possible. What two adapters would you recommend?

Would this work? https://www.google.com/shopping/product/18027578715266038687?q=usb+to+RS422&client=safari& hl=en&biw=320&bih=460&prds=paur:ClkAsKraXylPEodOnK ytVgOqSpkDnDlVq1BSvVL4CSy7D47_sVJ9acu8-wPWqRN9HQ85pTLmBolzLJlCP8-IkVKuMRSxHhSrJWh5SWc4abVi93KawE6HyIyxXRIZAFPVH712A JkN3s59coCrndKdnAzX-Jh10g&ved=0CBEQpis&ei=6cJdVb3YJO61sAS3xYGIAw
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Old 21-05-2015, 05:45   #10
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Re: openCPN to VHF for DSC

It's a Cobra MRF55BD VHF.

The cobra adapter splits to two wires.

The manual says:

"Bond the nmea out negative wire to The black wire on the GPS interface cable "

"Bond the Nmea out positive wire to the red wire on the GPS interface cable "
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Old 21-05-2015, 09:14   #11
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Re: openCPN to VHF for DSC

Use the 2 adapters I already mentioned above. Connect the red wire to pin 3 of the DB9 female plug. Connect the black wire to pin 5. Plug the DB9 female into the USB adapter. It should work.
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Old 21-05-2015, 10:14   #12
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Re: openCPN to VHF for DSC

Quote:
Originally Posted by transmitterdan View Post
Use the 2 adapters I already mentioned above. Connect the red wire to pin 3 of the DB9 female plug. Connect the black wire to pin 5. Plug the DB9 female into the USB adapter. It should work.
I got it now. Sorry about that. I'm on my mobile phone and it's hard to tell text from links.

I'll buy both of those and connect the VHF wires to the empty serial connector.

The RTS connection shows at pin 3 and the TDX pos and negatives are pins one and two. I'm going by the diagram on this site. http://www.brainboxes.com/product/us-324/1-port-rs422-485-usb-to-serial-adapter

Is this the incorrect diagram? Thanks again! You guys are awesome. I would have never been able to fiqure this out.
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Old 21-05-2015, 14:52   #13
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Re: openCPN to VHF for DSC

Quote:
Originally Posted by liberty22 View Post
I got it now. Sorry about that. I'm on my mobile phone and it's hard to tell text from links.

I'll buy both of those and connect the VHF wires to the empty serial connector.

The RTS connection shows at pin 3 and the TDX pos and negatives are pins one and two. I'm going by the diagram on this site. 1 Port RS422/485 USB to Serial Adapter - US-324 - Brainboxes - RS422/485 RS232 Serial Cards

Is this the incorrect diagram? Thanks again! You guys are awesome. I would have never been able to fiqure this out.
The device I recommended to you is a cheaper RS232 device. In that case the pinout I gave is correct. If you buy a more expensive RS422 device those pins 1 and 2 you mention are correct.

Do not worry about RTS. It is not needed. You only need to connect TXD signal from the adapter to the VHF.
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Old 21-05-2015, 17:41   #14
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Re: openCPN to VHF for DSC

Just ordered everything. I'll keep you posted. Thank you very much!!
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Old 28-05-2015, 18:59   #15
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Re: openCPN to VHF for DSC

Got all my wires in. I'll keep you posted how I do. Thank you again!!!
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