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Connecting NMEA 0183


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I’m trying to link my B&G H5000 CPU to my H2000 20/20 displays via NMEA 0183 (either via the performance processor or the NMEA FFD).

My H5000 CPUS has ….

#1:                       TX_A (-)

#2:                       TX_B (+)  

h5000.PNG

 

H2000 Performance processor has …

(#21:                   “Ground”)

#26:                    ”Input return”

#27:                    ”Input signal”

 perf.PNG

 

Alternatively NMEA FFD has ….

Brown:               “NMEA Input Signal”

Blue:                   “NEMA Input Return”

(Black:                “Ground”)

 nmeaFFD.PNG

 

 

I’m guessing the H5000 is NMEA 0183 v2.x or 3.x but H2000 is only NMEA 0183 v1.x (with the signal/ground connection rather than the newer +/- connection)

From what I understand I should connect "NMEA +/A" to "In" and "Shield" to "G", but nothing in the above manuals really corresponds to that.

nmea2to1.PNG

What is the correct way to wire these together? All I get from H2000 is Err.3 “Syntax or parity error on received NMEA data.” 

I’m simply sending VTG (Track made good and speed over ground) at 1hz 4800 Baud from H5000 trying to show SOG or COG on the display – but all I get is Error. 

I’ve tried both input 1 and 2 on the performance processor, calibrating NMEA MDE accordingly and using the NMEA FFD for the connection.

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Your problem might be the missing checksum in the NMEA0183  1.x protocol. If you cannot disable the checksum check on the receiving side (H5000) you won't succeed. Do yourself a favour and get some Garmin GNX120 mast displays directly connected to the NMEA2000 backbone...

   

 

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1 minute ago, chriggel said:

Your problem might be the missing checksum in the NMEA0183  1.x protocol. If you cannot disable the checksum check on the receiving side (H5000) you won't succeed. Do yourself a favour and get some Garmin GNX120 mast displays directly connected to the NMEA2000 backbone...

   

 

Thanks, the H5000 is the sending side, not the the receiving one. I dont think there is a setting for checksum for NMEA 0183 in nor H2000 nor H5000 though. Garmin looks really nice, but I'd prefer to get B&G displays to be able to display targets/polar data etc. out of my H5000 Performance CPU and not rely only on Expedition to feed Garmin with data. Using my old 2020 displays would be a "temporary" fix to invest step by step .... 

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The NMEA input consists of an optocoupler.  See it as a LED  shining on a transistor to get galvanic isolation.

The Signal return is simply the cathode of the LED and NOT gnd or B-. So you  connect that to the  TX-.

The A and B thing often creates misunderstandings, as the A/B from the RS422 point is opposite to the A/B of NMEA0183.

The pair is always eachothers compliment, so both of them can be +5V and 0V  but never at the same time. If you dont get it working, first thing is to reverse polarization. The LED inside the optocoupler will flash either way, but only one is readable.

 

/LC

 

 

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1 hour ago, LeCanard said:

The NMEA input consists of an optocoupler.  See it as a LED  shining on a transistor to get galvanic isolation.

The Signal return is simply the cathode of the LED and NOT gnd or B-. So you  connect that to the  TX-.

The A and B thing often creates misunderstandings, as the A/B from the RS422 point is opposite to the A/B of NMEA0183.

The pair is always eachothers compliment, so both of them can be +5V and 0V  but never at the same time. If you dont get it working, first thing is to reverse polarization. The LED inside the optocoupler will flash either way, but only one is readable.

 

/LC

 

 

Thanks @LeCanard am I reading you correct that  TX_A (-) and TX_B (+) should be connected to Input signal and return and if not working - try the other way around? I've tried both -  TX_B (+) to Signal and  TX_A (-) to Return looks like some kind of connection established, but I still get a syntax/parity error. 

Could it be related to H5000 sending a checksum and H2000 not understanding what a checksum is?

 

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I very much doubt the checksum is the problem. More likely to be something like the valid flag in the later versions of VTG. But I need to drag my test h2000 out from its dusty corner of the workshop and hook it up to a terminal so I can send different versions to it, to verify this.

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  • 2 weeks later...

In my (fumbling) efforts to get AIS sending to my chartplotter, and chartplotter sending to wheel-pilot, I learned that the labels the manufacturers use for their inputs and outputs is.... inconsistent and non-intuitive.  Even though they're working against the same spec.

I had "assumed" that "out (+)" would connect to "RX", and that "out ( - )" would connect to "TX", to complete a circuit between the devices.

Wrong.

In my case, to get the (Vesper) AIS to send targets to the (Garmin) chartplotter involved
-- AIS "out (+)" to chartplotter "RX"
-- AIS "out ( - ) to boat ground.

To get the (Garmin) chartplotter to send steering course/waypoint data to the (RayMarine) wheel-pilot involved
-- chartplotter "TX" to wheel-pilot "NMEA IN (+)"
-- wheel-pilot "NMEA IN ( - )" to boat ground

In other words, the devices that have a "TX" or "RX" channel only need one wire, the device itself uses boat ground.  The devices that have an "___ (+)" or "___ ( - )" expect to send or receive signal through the "(+)", and need the "( - )" connected to boat ground.

Note, I had to mess with baud-rates, too, to get everything talking correctly.  AIS to chartplotter worked fine at "NMEA high speed" (38,400 baud), the chart-plotter to wheel-pilot connection needed to be set at "NMEA standard" (4800 baud) 

You can check to see if the sending device is delivering signal to the wire with a multimeter - you should see a ~3V spike on the wire about once a second.  If the sending device is delivering the signal, from there it should be a simple (?) matter to get that signal into the right "RX" or "IN (+)" channel on the receiving device.  Just be sure to connect the corresponding "( - )" to boat-ground.

This may be obvious and well-known to you, but just in case it's useful....

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