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Old 11 December 2015, 17:15   #1
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On the subject of NMEA

Not wishing to teach Granny how to suck eggs but here's a little about NMEA.
Most modern GPS/ plotters support both NMEA 2000 & the older 0183. Whilst 2000 is quicker & designed to operate with more instrumentation the add ons tend to be expensive, for example you need a backbone wiring loom then connectors for everything you want to add
I prefer to use 0183, here's an example:
If you imagine your GPS/ Plotter as your core device, It is capable of talking to & listening to multiple others. Your DSC radio listens ie it receives position data from the GPS, it doesn't need to talk back. Autopilot also listens to the GPS telling it where to steer, it also doesn't need to talk back. whereas your Fish-finder/ depth gauge talks to the GPS, it doesn't need to listen.
With that said wiring becomes much easier.
If it's a listening device connect it to your GPS NMEA out or TX + & -
If it's a talking device connect it to your GPS NMEA in or RX+ & -
If it's a talking & listening device then use both.
If it talks incessantly, it's my ex wife !
You never know someone might find it this usefull
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Old 11 December 2015, 17:27   #2
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.......Your DSC radio listens ie it receives position data from the GPS, it doesn't need to talk back.......

Unless you want to display DSC targets on your plotter (MOB, distress etc) chuck AIS into the mix & it gets a whole lot more complex. 0183 is a "legacy" protocol & will gradually disappear. Even Nmea2000 has new protocols champing at its heels.
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Old 11 December 2015, 18:31   #3
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Couldn't agree more, I was just trying to keep it simple !
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Old 15 December 2015, 11:45   #4
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Couple of other things to consider:

NMEA 0183 allows, at one time on the bus, one talker, but multiple listeners. For multiple units sending data, the second has to wait until the bus is clear before trying to put data out. It operates at 4800 bps, using standard ASCII serial communication (similar to your old dial up computer modem.)

NMEA 2000 allows multiple sending units to put data on the bus (part of the receive protocol sorts out what's what.) It operates at 250Kbps (50 times faster than NMEA 0183.) In addition the coding for 2000 uses a compact binary word format, rather than discrete ASCII characters, which further increases network efficiency.

While both transfer data, the newer 2000 format will do so much faster, in more directions, with less network congestion. It does add cost and (to a degree) complexity in design, though.

Bottom line: If you have a lot of data, from multiple sources to multiple places, try to use 2000. If it's simple data transfer (say, GPS coords), go 0183.

jky
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Old 15 December 2015, 15:22   #5
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Quote:
Originally Posted by DavidMarten View Post
Not wishing to teach Granny how to suck eggs but here's a little about NMEA.
Most modern GPS/ plotters support both NMEA 2000 & the older 0183. Whilst 2000 is quicker & designed to operate with more instrumentation the add ons tend to be expensive, for example you need a backbone wiring loom then connectors for everything you want to add
I prefer to use 0183, here's an example:
If you imagine your GPS/ Plotter as your core device, It is capable of talking to & listening to multiple others. Your DSC radio listens ie it receives position data from the GPS, it doesn't need to talk back. Autopilot also listens to the GPS telling it where to steer, it also doesn't need to talk back. whereas your Fish-finder/ depth gauge talks to the GPS, it doesn't need to listen.
With that said wiring becomes much easier.
If it's a listening device connect it to your GPS NMEA out or TX + & -
If it's a talking device connect it to your GPS NMEA in or RX+ & -
If it's a talking & listening device then use both.
If it talks incessantly, it's my ex wife !
You never know someone might find it this usefull
I have coupled both the TX & RX up as per the diagram so the DSC only listening that part of the wiring has no use but won't do any harm?
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Old 15 December 2015, 17:41   #6
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Can't think of any reason that's going to be a problem. Turn it on & see if your GPS position appears on the VHF screen. Have you insurted your MMSI number into the VHF.
Regards, David.
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Old 16 December 2015, 02:59   #7
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Can't think of any reason that's going to be a problem. Turn it on & see if your GPS position appears on the VHF screen. Have you insurted your MMSI number into the VHF.
Regards, David.
not tried it as yet David still in the process of fitting out but will post results when i do, quite confident as one of the other guys on here has same set up and he kindly gave me the wiring info, also it all ties in lowrence had said only to wire GPS to radio, being a novice in this all makes sence now and yours and others input very valuble.

cheers
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Old 16 December 2015, 03:23   #8
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You are welcome. I know 0183 is an old protocol but it works fine for me and it's quick enough to run the autopilot on my Winga 25. I used it on a trip from Denmark to Norway without a problem.
Good luck. Regards David.
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