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-   -   GPS USB connector to VHF (http://www.sailnet.com/forums/electronics/56115-gps-usb-connector-vhf.html)

macsailor 07-11-2009 10:27 PM

GPS USB connector to VHF
 
I want to connect a GPS with a USB connector to a Raymarine 55 VHF. The manual for the Ray55 just shows a NMEA bare two wire connection for input and a two wire NMEA output connection. How do you interface the VHF with a GPS that has a cable with a USB connector ?

I have a Garmin Map76Cx. Can this gps display position data for a received DSC call if the 2 NMEA out wires are connected to the GPS ?

I would really like to just connect a puck type of GPS with this radio what is available ? any I have seen have a USB connector. Would a MS streets&trips GPS work ?

Thanks

sailingdog 07-15-2009 10:49 PM

You can't connect a USB based GPS to an NMEA 0183 device like a Ray55 VHF. NMEA 0183 is based on either a RS-422 or RS-232 serial protocol, with a data rate of 4800 baud, 8 bits, 1 stop bit and No parity. USB is a high speed serial protocol and is not compatible with either RS-422 or RS-232.

However, the GPSMap 76Cx has an NMEA 0183 four-pin serial/power port on the back and can be connected to the radio for DSC position data to the VHF. However, I don't believe it supports NMEA 0183 input to display the position of INCOMING DSC CALLS.

ottos 07-16-2009 02:22 PM

Quote:

Originally Posted by sailingdog (Post 505748)
You can't connect a USB based GPS to an NMEA 0183 device like a Ray55 VHF. NMEA 0183 is based on either a RS-422 or RS-232 serial protocol, with a data rate of 4800 baud, 8 bits, 1 stop bit and No parity. USB is a high speed serial protocol and is not compatible with either RS-422 or RS-232.

I don't have any experience with NMEA, but I do know for a fact (and use professionally) a USB - serial data converter which is not much more than a cable. Some electronics are built into one of the molded connectors. That said, YMMV :rolleyes:

sailingdog 07-17-2009 12:48 AM

Yes, but those devices go from an RS-232 DEVICE TO USB HOST, which is not what is required in this situation—which is USB DEVICE to RS-232 HOST. Also, I'd point out that those devices require a DEVICE DRIVER to be recognized by the computer properly.... something which isn't an option with either the VHF or the GPS.

Quote:

Originally Posted by ottos (Post 505897)
I don't have any experience with NMEA, but I do know for a fact (and use professionally) a USB - serial data converter which is not much more than a cable. Some electronics are built into one of the molded connectors. That said, YMMV :rolleyes:


macsailor 07-17-2009 07:27 AM

thanks for the information
 
I also have my old Map76, it has a cable with an small connector on the end, DB9 (?). What you are saying is this cable should plug into the the Map76Cx and provide the signal required for the VHF.
It is too bad someone does not produce a GPS puck for this application, it could sit near the VHF and be a dedicated GPS just for this purpose.

thanks again, Bob

sailortjk1 07-17-2009 09:24 AM

Quote:

Originally Posted by macsailor (Post 506095)
It is too bad someone does not produce a GPS puck for this application, it could sit near the VHF and be a dedicated GPS just for this purpose.

thanks again, Bob

I have no idea about the tech stuff like the Dog does, but what I do know is that I use a puck style USB/GPS with software on a laptop. The USB/GPS is powered by the laptop computer. I'm not sure how you would power up the GPS in the scenerio you describe. Would you somehow power it via the VHF? or perhaps run a seperate power supply? Not sure how that would work. Some others might have better explanations for you.

sailingdog 07-17-2009 12:34 PM

I'd point out that Garmin, Raymarine, and several other vendors make standalone GPS antenna that output NMEA 0183 data. The Garmin GPS17 is one of them. The Raymarine RayStar 125 is another.

sailingdog 07-17-2009 12:37 PM

Yes, the NMEA IN + wire from the VHF should connect to one pin (3 IIRC) and the NMEA OUT + wire from the VHF should connect to pin 2. The NMEA IN - and OUT - wires should connect to Pin 5.

Quote:

Originally Posted by macsailor (Post 506095)
I also have my old Map76, it has a cable with an small connector on the end, DB9 (?). What you are saying is this cable should plug into the the Map76Cx and provide the signal required for the VHF.
It is too bad someone does not produce a GPS puck for this application, it could sit near the VHF and be a dedicated GPS just for this purpose.

thanks again, Bob


ottos 07-17-2009 01:14 PM

Quote:

Originally Posted by sailingdog (Post 506061)
Yes, but those devices go from an RS-232 DEVICE TO USB HOST, which is not what is required in this situation—which is USB DEVICE to RS-232 HOST. Also, I'd point out that those devices require a DEVICE DRIVER to be recognized by the computer properly.... something which isn't an option with either the VHF or the GPS.

You're right, of course. And based on the little bit I read today - even if they were compatible at the Physical and Data Link levels, you'd need something to translate the higher level protocol to the NMEA sentences. There is some interesting information here Peter Bennett's GPS and NMEA Site although some looks older.

macsailor 07-18-2009 08:46 PM

thanks !
 
I like the idea of the standalone Garmin GPS17. I see this model is discontinued but new ones are still available on Ebay for $175. It is more than the USB "puck" types but it is a much better more reliable unit I guess. It would work as a backup GPS system as well.
Bob


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