VHF radio issue?

[Captain Larry-DH]

Another note: standard Ethernet patch cables are great wire for connecting NMEA0183. Just cut the ends.

 

[Craig Cook]

Uhhhh, wow...........first of all, thanks Larry. Second, I feel very confident saying the radio/chartplotter would never function together if I had to figure this out on my own. I'm headed down to the boat tomorrow so will pull everything aprt and follow your instructions. I will post here when completed.

wow................

 

[genec]

References: Page 16 (section 6.4) of the GX1300 manual, and Pages 3 and 4 of the Garmin Installation Instructions http://static.garmin.com/pumac/GPS-echoMAP_500-700-50-70_INST_EN-US.pdf
The Garmin manual is confusing because of the terminology it uses. For example, it says the Garmin function is TX and corresponds to the "NMEA device wire function" of Receive + . So is it send or receive? It's send, and must be connected to the OTHER device's receive:
Pin 3 is Black or shield and ground (or "-") it is used as a reference level for the signal and must be connected to the radio's GREEN and BROWN NMEA "-". If you have both black and shield wires from the GPS, connect them together with the Green and Brown from the radio. (Don't worry that the radio has a separate green and brown for input and output "minus", they are the same, because all "plus" signals reference "signal ground" which should be the same as "common ground" and not "float" at different voltages. The Garmin manual has a note that says the two port grounds don't need to be combined, but it doesn't say they shouldn't be, and it will simplify/stabilize the installation if you do connect them all together.)
Pin 4 is the blue wire and is Garmin Port 1 Transmit. It should be connected to the Yellow GPS Receive wire from the radio. This will enable the radio to send position info.
Pin 5 is the Brown wire and is Port 1 receive. It should be connected to the White DSC Send wire from the radio. This should enable the Garmin CP to display position info sent by other senders of DSC distress calls.
It gets interesting, because the Garmin CP has two NMEA 0183 ports, but the GX1300 radio has one GPS port. So the GX1300 radio will receive GPS info but send DSC info to the CP, all on one port. You will need to assign this through software in the CP. This is all the time I have tonight and haven't looked up the Garmin settings you need. But I hope this helps.

Ahhhh yes, the ambiguity of RS-232 in another format: NMEA 0183. Actually it is more like RS-422, which if I recall is just differential RS-232, and meant for long distance or "noisy environments."

Good work Larry.

 

[Captain Larry-DH]

Thanks Gene. This is something I know about that's not common knowledge anymore, because it's old technology, like me It's kind of like solving a puzzle and it's sort of fun to sort through the ambiguity of the documentation. As an EE you're probably very familiar with these things too.

The simple thing about RS-232 and RS-422 is that the chips have discrete "drivers" (talkers or senders) and "receivers" (listeners) on each signal lead, so (just like people) there is no successful communications if you try to connect talkers to talkers, or listeners to listeners. It seems like every product manual ever written has trouble clarifying what they mean by send/receive, in/out, transmit/receive, or in the days of computer dumb terminals (when this was considered current technology) computer ports and discrete analog modems; it used to be Data Terminal Equipment / Data Communications Equipment DTE/DCE. I'm showing my age to those who know.

This documentation issue always stems from the issue of perspective. Just as using the terms right and left are confusing on a boat (and using port/starboard solve the problem) the electronics industry never made up proper words to address which type of device is the universal reference for "goes-inta" and "goes-outa".

 

[genec]

Thanks Gene. This is something I know about that's not common knowledge anymore, because it's old technology, like me It's kind of like solving a puzzle and it's sort of fun to sort through the ambiguity of the documentation. As an EE you're probably very familiar with these things too.

The simple thing about RS-232 and RS-422 is that the chips have discrete "drivers" (talkers or senders) and "receivers" (listeners) on each signal lead, so (just like people) there is no successful communications if you try to connect talkers to talkers, or listeners to listeners. It seems like every product manual ever written has trouble clarifying what they mean by send/receive, in/out, transmit/receive, or in the days of computer dumb terminals (when this was considered current technology) computer ports and discrete analog modems; it used to be Data Terminal Equipment / Data Communications Equipment DTE/DCE. I'm showing my age to those who know.

This documentation issue always stems from the issue of perspective. Just as using the terms right and left are confusing on a boat (and using port/starboard solve the problem) the electronics industry never made up proper words to address which type of device is the universal reference for "goes-inta" and "goes-outa".

Agreed... and having designed products that used those chips... I fully agree.

The ambiguity is in the documentation... if you ever get a chance to read the RS-232 standard... you'll understand... it was all things to everyone, and no "point of view" was offered... which meant that the same "aimless" sort of language went right into manuals and other documents. The bi-directional nature of some of the designs makes it even more ambiguous.

I really liked that you tied all the grounds together... that really gives the signals a non-confusing reference. And over the distances used on a boat, there isn't likely to be any sort of a ground loop problem. (just bolt it all to the darn engine block) GRIN

 

[Captain Larry-DH]

Craig - I just looked at the Garmin manual and don't see any settings to enable or disable ports. So I assume the CP always has both ports enabled. Save port 2 for an AIS device connection, if you have or plan to get one, or use NMEA 2000 for AIS.

There are a few settings to enable NMEA protocol features, so you should go through those. Here's the manual http://static.garmin.com/pumac/GPS_echoMAP_5_7_OM_EN.pdf

 

[Craig Cook]

Larry, I did not get this project going as I had hoped this past weekend. I am embarrassed to admit that my wife and I fell victims to a scam artist plumber this past week. We were tipped off but the plumber had already started doing damage. We have a new reputable plumber doing repairs but the boat sat unused. I hope I can get things resolved at the house and get down to the this coming weekend.

Thanks again for the explanations.

 

[Captain Larry-DH]

Sorry about the plumber - good luck with the project.

 

[Craig Cook]

Update:

Thanks for all the good advice everyone, turns out to be a moot point. The admiral hurt her back the last time we were out, exactly what her back guy said would happen if she didn't stop pulling ropes on a boat. Between the rope pulling and getting tossed around on the lake we have not been back out in 4 weeks. The boat went up for sale Saturday morning and looks like it may have sold this morning. Signing off...........Craig

 

[SFS]

That's really unfortunate. Health issues can really take away a lot of things. Best of luck as you move forward.

 

[Captain Larry-DH]

Sorry to hear that. Wishing you both good health and happy times ahead.