connect DSC radio to a gps being used on PC using Opencpn nav software

2 radios of interest have DSC
Cobra Electronics MR F45-D
ICOM IC-M402S

Someone told me I need a USB to RS485 RS422 adapter to send NEMA data into the radio.
maybe this
https://www.ebay.com/itm/DTECH-4ft-...740289?hash=item1cd6cb6d41:g:4tcAAOSwug5dReC9

Then the GPS data can be sent to the radio?

Anyone familiar with what I want to do?

Yes. You want to download the manuals. NEMA connections will be found within

I'm pretty sure the serial adapter is a RS232 to USB

If your PC has a serial port, you don't need the USB adapter. The one linked is good, don't use an adapter with a Prolific chip, they're flakey. The FTDI chip is reliable, won't give you a problem.



The VHF manual should give you the color codes for the RX- and RX+.
Typical use is getting GPS position from the chartplotter to the VHF. You'll need to enable the PC's COM port at 4800 baud, you may need to tell the software which sentences to transmit. The VHF manual will indicate which sentences it will recognize. Usually VTG (course/speed), GLL (lat-lon), ZDA (time/date), RMC (min recommended nav data), perhaps other GPS detail data (satellites & signal, etc).

There's so little utility in DSC data output by the radio that the DSC-out is rarely connected. But it's just 2 additional wires if the radio supports it.



It's used for transmitting coordinates of a received DSC call to the chartplotter, and for polling a DSC station's position. If you buddy boat, you can check your buddy's location with his MMSI #. If you can figure out how to do the 22 button presses in the proper sequence.

Desktops still may use serial port but pretty much all laptops in the last 10 years have USB.

If you just want the radio to receive GPS data, on ours I just splice it into the the same nema output line that goes to our laptop since they are both just listeners

It is a desktop with serial port, I dont need the adapter. But lots of new ATX MB, they eliminated the serial port just like laptops.

I actually tore apart an old steel ATX case and created a PC so it would fit in the space, its dry, behind the salon cabin wall below the top deck. I can mount any ATX motherboard in there.

I run HDMI long cable to the monitor and use USB extension cable with the hub up at the helm.

https://www.westmarine.com/buy/west-marine--vhf595-fixed-mount-radio-white--18114512?recordNum=55
I am finding out DSC is not all the same.?
This WM VHF advertises these DSC features

Advanced DSC Features: The following DSC features are supported: Individual Call, Group Call, All Ships Call, Position Request, Position Send, Test Call, Name and MMSI Directory, Standby Mode and Received Call Log.

Click to expand...

Does this radio not do all that?
https://www.cobra.com/products/mrf45d#
Manual
https://cdn.shopify.com/s/files/1/2203/2035/files/MRF45D_US_MANUAL_ENG_vF.pdf?60628816433846715

AND, the MMSI number is not easily changed, they kinda lock out end users changing the number, which makes me know want to buy a used vhf.

Standard-Horizon GX1850 VHF Marine Band DSC Radio - CONTINUOUSWAVE
This radio you can reset the MMSI code without sending it back, so I assume its not going to cost $100 to do this.

MMSI RESET
The owner's manual mentions that the MMSI of the DSC radio can be reset by the user after contacting the factory to obtain a reset code. Standard-Horizon has already used this method on the HX870 hand held radio. This is a significant improvement over the usual situation where the radio was required to be shipped to the factory or an authorized service center for any change of the maritime mobile service identity.

Click to expand...

What are you using to feed the GPS data to the PC? Please forgive me if I'm stating the obvious, but both of those VHF's only receive GPS data via NMEA for the DSC functionality but they don't have their own GPS antenna & chip to acquire position data on their own. I'm just asking to clarify that you aren't trying to pull this data from the radios.

Gdavid said:

What are you using to feed the GPS data to the PC? Please forgive me if I'm stating the obvious, but both of those VHF's only receive GPS data via NMEA for the DSC functionality but they don't have their own GPS antenna & chip to acquire position data on their own. I'm just asking to clarify that you aren't trying to pull this data from the radios.

Click to expand...

I have a usb gps device plugged into the usb hub by the helm. That feeds GPS data into the PC. On the OpenCPN forum, I was told GPS data can be sent from the PC to the radio by NMEA by way of the serial port.
I did read on a forum Standard Horizon will do the MMSI change for free, you have to pay shipping.

I need to study DSC some more, not that i would use any advanced DSC features.

Yes, that adapter is what you need. NMEA-0183 uses the RS-422 (EIA-422) standard. Just connect the two wires to the screw down terminals on the DB9 and you should be good to go.

That adapter goes USB into the computer and DB-9 Female terminal block, plug that terminal block into the DB9 male connector at one end of the cable and plug the other end into an available USB port. The drivers should auto install, but if not you can download them or they probably come on a CD or USB.

To the folks who mentioned serial ports: I'm guess you noticed the old-school DB-9 connectors and were concerned that it might be an RS-232 (EAI-232) standard serial port. This isn't the case. It is RS-422/485. It just happens that they used a DB-9 connector to terminal the cable and connect to the terminal block.

An 1850G has the gps in it.
https://www.amazon.com/Standard-Hor...coding=UTF8&psc=1&refRID=MGP956A362F93PJ0SRP4

This site says their 1850 has the gps in it, but if its not a 'g' model, it wont.
it is cheaper than the Amazon one. I may contact them to ask about the gps and model they are selling, I think they screwed up their features listing for this model.

https://www.thegpsstore.com/Standard-Horizon-GX1850-Explorer-VHF-White-P5887.aspx
"25W Output Power with Internal GPS"

And they do sell the 1850g in white or black.
https://www.thegpsstore.com/Standard-Horizon-GX1850G-Explorer-VHF-with-GPS-White-P5874.aspx

But its a lot more money than say the WM radio. Although I wonder would the WM radio accept gps data from the PC? It does, I just read manual.
It may be a Uniden radio
https://www.westmarine.com/buy/west-marine--vhf595-fixed-mount-radio-white--18114512?recordNum=55

gkesden said:

Yes, that adapter is what you need. NMEA-0183 uses the RS-422 (EIA-422) standard. Just connect the two wires to the screw down terminals on the DB9 and you should be good to go.

That adapter goes USB into the computer and DB-9 Female terminal block, plug that terminal block into the DB9 male connector at one end of the cable and plug the other end into an available USB port. The drivers should auto install, but if not you can download them or they probably come on a CD or USB.

To the folks who mentioned serial ports: I'm guess you noticed the old-school DB-9 connectors and were concerned that it might be an RS-232 (EAI-232) standard serial port. This isn't the case. It is RS-422/485. It just happens that they used a DB-9 connector to terminal the cable and connect to the terminal block.

Click to expand...

Would my PC motherboard's serial port 9 pin, work or do I have to get the usb adapter?

Your mother board's serial port is most likely RS-232 vs RS-422. These are technically different standards. Among other things, RS-422 uses differential signaling and is multi-drop.

Having said that, when RS-422 is used single drop, as it is in your case, it isn't very far from RS-232. And, many people have connected NMEA-0183 stuff to RS-232 ports and reported good reliability. Having said that, others have reported things not working or reliability issues. Success likely depends, in part, upon the type, length, shielding, and quality of the cable as well as the quality of the power and electrical noise.

So, I guess what I'm saying is that you can try connecting the NMEA-0183 directly to that serial port. It might work, or it might not. (Hint: Check my assumption about it being RS-232 -- it if it is RS-422 or RS-485, it is compatible).

But, if it were me -- and when it was me -- I bought the adapter cable to guarantee a reliable, correct interface. It wasn't very expensive.

gkesden said:

Your mother board's serial port is most likely RS-232 vs RS-422. These are technically different standards. Among other things, RS-422 uses differential signaling and is multi-drop.

Having said that, when RS-422 is used single drop, as it is in your case, it isn't very far from RS-232. And, many people have connected NMEA-0183 stuff to RS-232 ports and reported good reliability. Having said that, others have reported things not working or reliability issues. Success likely depends, in part, upon the type, length, shielding, and quality of the cable as well as the quality of the power and electrical noise.

So, I guess what I'm saying is that you can try connecting the NMEA-0183 directly to that serial port. It might work, or it might not. (Hint: Check my assumption about it being RS-232 -- it if it is RS-422 or RS-485, it is compatible).

But, if it were me -- and when it was me -- I bought the adapter cable to guarantee a reliable, correct interface. It wasn't very expensive.

Click to expand...

I got this, the price looked good to me at $83 and I checked the manual and seems to do all the DSC features and hook up to my GPS off the motherboard.
It actually looks to be the MRF45D and I dont know why Amazon is selling these at this price, maybe clearance them out.

https://www.amazon.com/gp/offer-listing/B004HSND3M/ref=dp_olp_new_mbc?ie=UTF8&condition=new

This one for $100 also looked interesting, looks like the WM one selling for $130, except no controls on the mic.
https://www.amazon.com/Uniden-UM385...=B076DPJZ9L&psc=1&refRID=0YN71SDMMTZ0PTMX2099

I dont need a super expensive fancy radio, I almost never use the vhf except for weather. It has weather alerts, so it will play the weather report if an alert occurs.. The DSC stuff looks interesting if you were going to privately call someone or get in trouble. Except lets say you request a private call, dont you then use the public radio to talk?

http://www.ab4oj.com/icom/ic7700/7700hw_sw_setups.pdf
I will try my serial port first before buying the USB adapter to serial cable.
I have a serial cable I can cut open.
I would suppose that pin 3 and pin 5 is what I would need to take gps data from the PC to the radio?

 For connecting to COM ports, RS-232 cables use a connector having 9 pins. There are Male
and Female versions. COM ports on PC’s are DB-9 Male.
 Pins are functionally designated. Those listed here most often appear in software setups.
o RXD, pin 2 typically receives data in to PC. Used by CI-V.
o TXD, pin 3, typically transmits data out of the PC. Used by CI-V.
o DTR, pin 4, typically transmits commands.
o GND, pin 5 is signal ground.
o RTS, pin 7 typically transmits commands.

I think, Yes:

Looking at the ICOM M402S manual (https://www.icomamerica.com/en/downloads/DownloadDocument.aspx?Document=86), page 23:
RS-232 DB-9 GND (Pin 5) to NMEA-0183 - (outside of coaxial connection)
RS-232 DB-9 TXD (Pin 3) to NMEA-0183 RX (center of coaxial connection)

Note: The manual you linked to seemed to be a HAM radio versus the VHF-DSC radio you initially inquired about. My answer applies to the VHF-DSC radio.

More generally..

If the NMEA-0183 is labelled with A/B nomenclature, the solution is commonly:
RS-232 DB-9 GND (Pin 5) to NMEA-0183 Shield Ground
RS-232 DB-9 TXD (Pin 3) to NMEA-0183 RX-A
RS-232 DB9 RXD (Pin 2) to NMEA-0183 TX-A
Unconnected: NMEA-0183 RX-B
Unconnected: NMEA-0183 TX-B

If the NMEA-0183 is labelled with +/- nomenclature, the solution is commonly
RS-232 DB-9 GND (Pin 5) to NMEA-0183 -
RS-232 DB-9 TXD (Pin 3) to NMEA-0183 RX
RS-232 DB9 RXD (Pin 2) to NMEA-0183 TX

gkesden said:

I think, Yes:

Looking at the ICOM M402S manual (https://www.icomamerica.com/en/downloads/DownloadDocument.aspx?Document=86), page 23:
RS-232 DB-9 GND (Pin 5) to NMEA-0183 - (outside of coaxial connection)
RS-232 DB-9 TXD (Pin 3) to NMEA-0183 RX (center of coaxial connection)

Note: The manual you linked to seemed to be a HAM radio versus the VHF-DSC radio you initially inquired about. My answer applies to the VHF-DSC radio.

More generally..

If the NMEA-0183 is labelled with A/B nomenclature, the solution is commonly:
RS-232 DB-9 GND (Pin 5) to NMEA-0183 Shield Ground
RS-232 DB-9 TXD (Pin 3) to NMEA-0183 RX-A
RS-232 DB9 RXD (Pin 2) to NMEA-0183 TX-A
Unconnected: NMEA-0183 RX-B
Unconnected: NMEA-0183 TX-B

If the NMEA-0183 is labelled with +/- nomenclature, the solution is commonly
RS-232 DB-9 GND (Pin 5) to NMEA-0183 -
RS-232 DB-9 TXD (Pin 3) to NMEA-0183 RX
RS-232 DB9 RXD (Pin 2) to NMEA-0183 TX

Click to expand...

I did get the MRF45D vhf Cobra radio from Amazon.

The instructions are simply this,
To Install A GPS Device:
1. Install the GPS device in a convenient location
according to its manufacturer’s directions.
2. Bond the NMEA out negative wire to the black
wire of the GPS interface cable.
3. Bond the NMEA out positive wire to the red
wire of the GPS interface cable.

So seems like pin 3 (positive to red)and pin 5 (negative to black) is used.
https://cdn.shopify.com/s/files/1/2203/2035/files/MRF45D_US_MANUAL_ENG_vF.pdf?60628816433846715

I have a serial port double ended cable, I plan to snip off the 25 pin end. And I will trace the wires using my ohmmeter. I have had that cable for at least 20 years and never used it.

I also recall some centronics printer ports could be set to function as serial ports in a PC bios setup page.

I also have an old Xircom usb to db9 serial port adapter, it has no windows drivers, but it does work in Linux.

I found the mb manual online, the serial port says this...

Serial Port Connector: JCOM1 This connector is a 16550A high speed communication port that sends/receives 16 bytes FIFOs. You can attach a serial device to it.
Would that be just rs232?

https://www.aliexpress.com/item/328...chweb0_0,searchweb201602_4,searchweb201603_52

Another option, buy a gps like this.
Has to have power, ground, then green is tx and white is rx.
On the radio the black I suppose would also be black on the gps and the red on the radio would be green on the gps?

or do you use the green and white to the radio from the gps?
Which ones go where?

Advantage of this GPS is PC does not have to be on, however where to get DC power to run gps. Need a converter circuit to create 3.3 to 5vdc.

Technically speaking, the UART is the component that takes the parallel data from the computer and makes it serial and vice-versa. It normally includes buffering (FIFOs). RS-232 is the physical layer protocol that carries this data on the serial bus. So, a UART could be used with RS-422 or RS-485. But, in practice, a 16550 series UART is typically associated with RS-232 and isn't a great choice for RS-422. So, yes, I think that find strongly supports the idea that it is an RS-232 port.

I'm a little surprised that you have a 25-pin ("DB25") RS-232 connector. I haven't seen one of those for years. But, it is what it is. RS-232 delivered via DB-9 is the same as RS-232 delivered via DB-25. The only differences are that a bunch of pins that aren't commonly used are left off of the DB-9 connector and the pin-out is different. Not the different ways pins 2 and 3 are used as compared to my earlier post.

RXD - Pin 3
TXD - Pin 2
GND - Pin 7

So, to hook up your radio to a DB-252 RS-232 port, you'd connect:


GPS NMEA-0183 + (or A) ---- Computer DB-25 RXD (Pin 3)
GPS NMEA-0183 - or GND ---- Computer DB-25 (Pin 7)
If the GPS has a "B" NMEA wire, it should be left disconnected.

(Again, I recommend using a RS422<->RS232 converter cable, but understand your request to do otherwise and am trying to be helpful).

But, since I'm really not used to seeing 25-pin serial ports these days, can you post a picture so I can make sure we're talking about the same thing? Also, may I know the computer make and model (so I can google it).

gkesden said:

Technically speaking, the UART is the component that takes the parallel data from the computer and makes it serial and vice-versa. It normally includes buffering (FIFOs). RS-232 is the physical layer protocol that carries this data on the serial bus. So, a UART could be used with RS-422 or RS-485. But, in practice, a 16550 series UART is typically associated with RS-232 and isn't a great choice for RS-422. So, yes, I think that find strongly supports the idea that it is an RS-232 port.

I'm a little surprised that you have a 25-pin ("DB25") RS-232 connector. I haven't seen one of those for years. But, it is what it is. RS-232 delivered via DB-9 is the same as RS-232 delivered via DB-25. The only differences are that a bunch of pins that aren't commonly used are left off of the DB-9 connector and the pin-out is different. Not the different ways pins 2 and 3 are used as compared to my earlier post.

RXD - Pin 3
TXD - Pin 2
GND - Pin 7

So, to hook up your radio to a DB-252 RS-232 port, you'd connect:


GPS NMEA-0183 + (or A) ---- Computer DB-25 RXD (Pin 3)
GPS NMEA-0183 - or GND ---- Computer DB-25 (Pin 7)
If the GPS has a "B" NMEA wire, it should be left disconnected.

(Again, I recommend using a RS422<->RS232 converter cable, but understand your request to do otherwise and am trying to be helpful).

But, since I'm really not used to seeing 25-pin serial ports these days, can you post a picture so I can make sure we're talking about the same thing? Also, may I know the computer make and model (so I can google it).

Click to expand...

Its the cable, one end is 25 pin female, other end is 9 pin female, the PC is 9 pin, so I would cut off the 25 pin end. It feels like a high quality thick cable.

How about the aliexpress gps wiring? I was thinking probably, red and black is 5vdc power, and the other 2 wires hook to radio?
And an easy 12v to 5v power converter, is a usb 12vdc charger, use that with a cut off usb cord to power the gps, I have a couple I got for free.

I can see the big advantage of using a seperate GPS for the radio. And for $15 not bad deal. I actually bought my PC USB GPS from aliexpress for $7 and it has been working great for over a year now.

NMEA Connections VHF - GPS [Archive] - Yachting and Boating World Forums
It just got too complicated.
I dont think that gps will work on my radio.
the negative of the radios power is joined to the black wire of the gps, so I need the 12v version of a gps. And on the gps I use the tx wire, the rx wire wont be used at all. Likely the rx wire on the gps is used to modify the gps parameters.
So I think I would need this one instead that already runs on 12v power.

https://www.aliexpress.com/item/329...chweb0_0,searchweb201602_4,searchweb201603_52

which then can go outside the boat, but I just wanted a small one to sit on the helm instead of some mushroom looking thing.

Unless you think this would work...,
wires coming from gps,
red goes to 5vdc positive power supply
black goes to 5vdc negative power supply
green tx goes to red on radio
white rx not used

That leaves the black nmea wire on radio left to connect
black nmea on radio goes to ground

Anyone know?

So, I might be losing track of the goal, so check me. As I now understand it, we want:
-- OpenCPN running on a PC
-- GPS available to each of that PC and the VHF-DSC


One thing you can do:
-- Get one USB GPS unit that emits NMEA sentences. Plug it into the PC. The PC is now good to go.
-- Get the unit you found that wants 12V and hook it up to your VHF-DSC as discussed above.

This is nice in that it gives each unit its own, independent GPS and requires no non-standard connections. And, these GPS units are very inexpensive and available from Amazon or AliExpress. This would probably be my choice.

Another thing you can do...
-- Exactly as above, but, buy two USB of the 12V GPS units you found on AliExpress
-- Attach one to the radio and one to the computer's DB9 RS232 serial port as discussed earlier.

The above is nice in that you can buy two of the same thing.


Another thing you can do...
-- Exactly as above, but use the 3.3-5V unit for one or both of them.
-- To get the 3.3-5V DC, just go onto AliExpress or Amazon and get a DC-DC converter. They are often made to provide different voltages from a "cigarette lighter" port. This can provide the power for either or both

I don't like the, because why add a part? Once can buy 12V GPS units, so why by a 3-3V-5V unit just to need to convert it? It is more mess and more that can fail.


Another thing you can do:
-- Get a USB GPS that emits NMEA-0183 sentences from Amazon or Alibaba.
-- Plug that GPS directly into a USB port on your computer.
-- Connect your computer to the VHF-DSC as discussed, either via a USB port with a USB<->RS422 cable or with a RS232 DB9<-> RS422 cable, or directly from RS232 DB9 to the radio
-- In the OpenCPN Connections settings for the RS232 DB25 COM port, check the box "Output on this port (As autipilot or NMEA repeater"

The above should give you a nice, easy GPS connection to your computer and then use your computer to send it to the VHF-DSC radio. The down side to this is that if your computer is off or if OpenCPN isn't running -- no GPS for your VHF-DSC, which I wouldn't want for a VHF-DSC that you want to work reliably under all circumstances in an emergency.


And, another thing you can do:
-- Get a NMEA-0183 muliplexer.
-- Attach a NMEA-0183 GPS to that multiplexer
-- Connect the outputs of the multiplexer to each of the PC and the radio as we discussed above.

The above is nice in that it lets you share that GPS without the computer on, but not nice in that the GPS isn't redundant and the multiplexers are probably more expensive than the GPS. So, doing this as opposed to buying two GPSes is probably both less robust and more expensive. What I mean by less robust is, if you have two of the same GPSes, and one fails, you can decide if you want the remaining one to connect to just the computer, just the VHF-DSC, or to connect to the computer and then bridge to the VHF-DSC via OpenCPN (and change wiring accordingly). Those options don't exist if you use a multiplexer.


Again, as cheap as these GPSes are, I'd probably just get a USB one for the computer and a 12V 3-wire one for the radio and save the rest of the mess. I have 7 separate GPS receivers on my boat (2 internal two VHF-DSC radios, 1 internal to the Autopilot sensor core, 1 internal to an AIS radio, and 1 each on three plotters). They are generally not sent over the network -- but can be routed over the network if something fails, e.g. via the Miniplex-3 device or via either of the two OpenCPN plotters as described earlier.

When Nobeltec was shipping serial port cords with their PC navigation software (VNS) it had a RS 232 connector on one end and 3 bare wires coming out the other end.

The wires are:

Black - Data in
White - Data out
Green - Ground

Maybe it's not RS232, but I've been calling it that for nearly 30 years when I was a Nobeltec dealer.

The connector is plugged into a Serial to USB adapter. The one in the picture is a Triplyte and the other one I use is a Keyspan.

On my laptop, I use one serial cord for receiving GPS data and sending course information to the autopilot and the other serial cable receives AIS data.

Each is connected to it's own Serial to USB adapter.

If your PC has a common 9- or 25-pin serial port, it is probably RS232. When I spec'ed an all-in-one kiosk/industrial -style waterproof touchscreen PC specifically for OpenCPN, I spec'd it with (USB plus) DB9 RS422/485 ports. But, using RS422/485 isnt common except in industrial and marine settings.

Btw, if your radio supports it, you may want a connection such that the VHF-DSC /output/ of the radio goes to an /input/ on the OpenCPN PC.

The reason is that, if a nearby boat presses its DSC emergency button, your DSC radio, if it supports this feature as many if not most do, can send it to your OpenCPN, which will display the distress vessels location right on the chart, making it easier for you to find them, get there, and help.