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Author Topic:   Garmin 740 to Simrad NSS8 NMEA Network Bridging
bluewaterpirate posted 02-09-2012 08:06 PM ET (US)   Profile for bluewaterpirate   Send Email to bluewaterpirate  
For you guys that like to look at all the nuts and bolts of an install, here's a good example of the NMEA 0183 data [from a GARMIN GA30 GPS receiver connected by NMEA-0183 to a GARMIN GPSmap 740] being shared over a NMEA-2000 network using the network bridging functionality of the Garmin GPSmap 740. The Simrad NSS8 is able to use the Garmin's GPS receiver data for positional information.

A NMEA 2000 network gives you a lot of options for sharing information between vendor equipment.

Screen shot of the Garmin GPS antenna being used by the Simrad NSS8

Screen shot of the Garmin 740's GPS Sky View Display showing the same screen data as the Simrad NSS8

There you go--Tom

jimh posted 02-10-2012 09:09 AM ET (US)     Profile for jimh  Send Email to jimh     
Tom--Thank you for contributing those screen capture images. I find them very interesting. As you point out, on a NMEA-2000 network you can have more than one GPS receiver, and you can configure the various chart plotters to use a particular GPS receiver from the network. However, I also noticed a couple of additional features that your screen captures show.

I see that that sky-view display on the SIMRAD is very similar to the sky-view display on the Lowrance HDS series. The presentation is almost identical, except that the graphic elements have a different style and color scheme. But, aside from the presentation graphics, I notice that the location of the WAAS source is referenced by its NMEA satellite ID instead of its PRN code number. The two are related as follows: NMEA satellite ID is the PRN code minus 87.


GPS: PRN Codes and NMEA Satellite ID

for more on that topic.

Here is the sky-view of a Lowrance HDS device for comparison:

The similarity is remarkable. More about the sky-view presentation can be found here:

Lowrance HDS GPS Data Display

Also, I think you have annotated the screen captures. The blue text in the SIMRAD screen capture does not appear on the actual screen, nor does the red text in the GARMIIN screen capture. Is that right?

bluewaterpirate posted 02-10-2012 09:31 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Jim .....

The Simrad is using the Garmin GPS antenna so the Simrads Sky View Display replicates the Garmin Sky View Display. If the Simrad was using it's embedded or GS 15 GPS antennas then it would be the same as the Lowrance.

You are correct, I annotated those screen shoots with colored text.

My geriatric mind just remembered your question in regards to PRN 133 in an earlier post. My Simrad display showed the satellite being out of place in the eastern sky. Answer, PFM (pure freaking magic) I have no idea why it was displayed due east when in fact it's located to the southwest.


jimh posted 02-10-2012 01:13 PM ET (US)     Profile for jimh  Send Email to jimh     
What happens in the configuration Tom describes is not a bridging of the NMEA-0183 and NMEA-2000 networks in the usual sense of a network bridge. Rather, the data contained in the NMEA-0183 datagrams or packets from the external GARMIN GPS receiver are being processed by the GARMIN GPSmap 740 and resent in a new form--the appropriate parameter group form for GNSS navigation data in the NMEA-2000 protocol. If the "bridge" between the networks just transported the data, the data would not be in the proper form on the foreign network. The NMEA-0183 data has to be received, processed, and retransmitted in a new form on the NMEA-2000 network in order for it to be useful.

It is very likely that the internal GPS receiver in a multi-function device like a SIMRAD NSS8 or a LOWRANCE HDS8 is really a NMEA-0183 device. Most GPS receiver chips are designed with NMEA-0183 as a standard data output. The receiver sends digital serial data on its output port in the NMEA-0183 format. Internal to the LOWRANCE HDS8 or SIMRAD NSS8, that data from that GPS receiver is converted from NMEA-0183 protocol to NMEA-2000 protocol, and then transmitted on the NMEA-2000 network. I am just about certain that this occurs because:

--I have not seen any GPS receiver chips where the chip manufacturer has included a full NMEA-2000 interface; they all seem to be NMEA-0183 protocol outputs; and,

--I have seen the internal GPS in my Lowrance HDS8 send data to other devices on the NMEA-2000 network. For example, the GPS receiver sends data to my ICON gauges, which display the boat speed over ground and use that parameter to compute miles-per-gallon fuel economy.

There are some GPS receiver devices sold as NMEA-2000 GPS receivers, but I suspect that in those devices there is a GPS receiver chip putting out NMEA-0183 and some additional circuitry to convert the data to NMEA-2000. The device contains a certified NMEA-2000 port, and sends the navigation data from the GPS receiver to the NMEA-2000 network using the appropriate parameter groups.

bluewaterpirate posted 02-10-2012 02:52 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
I did some experimenting over lunch and here are the results.

Garmin N2k Device List Simrad%20Garmin%20Network%20Bridging/10FEB12_1251_00-1.gif?t=1328902872

Garmin 740 Output Bridging Control Simrad%20Garmin%20Network%20Bridging/10FEB12_1251_02-1.gif?t=1328903372


bluewaterpirate posted 02-11-2012 01:06 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
A couple more pictures .... you can see turning off newtork bridging on the Garim 740 terminates access to the Garmin GA30 GPS antenna date. Simrad%20Garmin%20Network%20Bridging/shot20-1.png?t=1328983170 Simrad%20Garmin%20Network%20Bridging/shot19-1.png?t=1328983360


jimh posted 02-11-2012 01:31 PM ET (US)     Profile for jimh  Send Email to jimh     
This boat networking is getting more complicated than computer LAN's!
bluewaterpirate posted 02-11-2012 06:20 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
I've been really taking a hard look at all the NSS8 functionalities and displays. There is a wealth of info availbale to the user.

My next project is installing my SonicHub then a G4 Broadband radar. Really having to use my imagination making install space. Here's what's being passed over my Garmin N2k network (N2k and NMEA0183 Data). Simrad%20Garmin%20Network%20Bridging/shot1-1-1.png?t=1329001607 Simrad%20Garmin%20Network%20Bridging/shot2-1.png?t=1328982889 Simrad%20Garmin%20Network%20Bridging/shot3-1.png?t=1328982889

This is the data the Simrad is receiving on the Garmin N2k newtork from the Garmin 740 and GA30 GPS antenna. Simrad%20Garmin%20Network%20Bridging/shot5-1.png?t=1328982890 Simrad%20Garmin%20Network%20Bridging/shot6-2.png?t=1328982891

I would think your Lowrance units can probably veiw the same information


jimh posted 02-12-2012 11:15 AM ET (US)     Profile for jimh  Send Email to jimh     
At first glance, to me it looks like the SIMRAD has more sophisticated tools for analyzing and describing the network devices and data than the Lowrance HDS series, although I will have to qualify that by saying that I have not spent a lot of time trying to dig into the Lowrance menus nor have I had too many other devices connected to it. I think the SIMRAD system is probably intended for more sophisticated installations, and it has been equipped to handle them well with those tools.

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