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Adding an auxiliary/portable display?

Old 10-02-2014, 05:27 AM
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Default Adding an auxiliary/portable display?

Just curious about the NMEA2000 connectivity with displays. I've pretty much figured up going with the Garmin 800 series, but what about adding a second display to it for viewing the screen (sounder in a different location, for example)? Do I need a more capable display to "process" the signal from the sounder? Is there any display that can simply act as an "external monitor" and show exactly what is on the parent screen, without the "processing"
Old 10-03-2014, 05:25 PM
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I've done a little bit of research in to NMEA2000 and am a bit lost.

I understand the backbone cable, terminators, and how the power and accessory connections are made. I also think I understand the "sharing" between devices on the network - a chart chip in one chart plotter, for example, can be viewed and run on a second display, as well as tracks, waypoints, etc.

So what I think I am not understanding is that the combo units have built in sounders. If I had 2 MFD's and a NMEA2000 sounder the sounder would be connected over the network and available to both MFD's, correct? So, then, a combo plotter/sounder has the sounder portion built in - it does not connect to the sounder over the network. Since it is built in to the display is a second display, in the case of my question, required to run the sounder over the network (just like the MFD example)? Or, since the sounder is already processed by the display of which it is internal to, can the result of that processing be "viewed" remotely via the network, as opposed to running the sounder remotely from that second display over the network?

I am familiar with the ISO 11783 standard (CAN networks on Ag equipment). NMEA2000 is CAN = controller area network = all devices on the network have addresses and all displays/interfaces are Universal Terminals*. So does that mean the combo units are two parts (for simple terms) of the network - both the UT and the address of the sounder controller?

*Universal Terminal, used to be Virtual Terminal, is just a "display". Maybe on NMEA2000 it is MFD (multifunction display?). I haven't found a specific reference for correct terminology here.

In ISO 11783 you have different "task controller" functionalities (TC-BAS, TC-GEO, TC-SC), among other functionalities. Devices can meet the "standard" and be considered "ISO compatible", but because of looseness in the ISO standards spelling out the specific parts of the standard a device can meet the standard and still not be "compatible". That incompatibility comes back to the fuctionalities (like the task controllers mentioned above). This is fairly prevalent with interconnectivity between manufacturers, but those functionalities that are part of the standard are the "languages" that different types of data are sent (GPS positioning, speed, device feedback, device control, etc).

It sounds like the NMEA2000 standard is very similar. If you have a stand-alone sounder on the network and you have a UT that speaks that "language", thus making that "functionality", it works. If your UT does not speak that language it can not make that functionality.

The old NMEA 0183 protocols are similar - VGA, VTG, RTC, RTM, etc - they are all parts of the overall standard and communicate a specific type of information.

So the sounder included in a combination display/sounder unit has the CAN/NMEA2000 messaging, I assume, all within the same box. At that point, though, it really would be pointless having two units in the same box talking on a CAN. Since the processing of the sounder to be displayed on a screen has already been done does the auxiliary UT have to be able to read the sounder protocol over the NMEA2000 network, just as if that sounder was a separate box and not a combo?

Or is it simply that the sounder information is part of the incompatibility of the NMEA connectivity/sharing because it is not, and can not, be a controller on the CAN? Would that, then, mean that the NMEA2000 functionality is "limited", as is the Garmin Marine Network functionality on the GPSMap800 series (and all other Garmin combos as far as I know)?

Last edited by KC8QVO; 10-03-2014 at 05:36 PM.
Old 10-03-2014, 08:56 PM
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some plotters have video out. you just run it to any screen (tv, computer screen, mini screen etc) and it'll mirror what ever is on the plotter.

the nmea 2000 screens will just give you data numbers. depth 20ft, speed, cog, pos, wind etc. no graphics, just values but you could scroll through and change them etc.

where as the video screen you'd have to change the plotter to change what's on the 2nd screen, and they'd always be the same.

if you want a 2nd screen to show different things, like depth sounder on one and chart on the 2nd. you need 2 networkable chart plotters.
Old 10-04-2014, 06:21 AM
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Hrmmm.

None of the 800 or 1000 series combos or chart plotters have video out. It looks like that starts at the 4208 chart plotter. Yet, at $2000 I'd be ahead just going with a whole second smaller 4" or so screen combo with a second transducer. And that $2k doesn't include a networked sounder/transducer for the unit, so add another $1000+. Doesn't make much sense.

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