Connecting NMEA 0183 GPS data to ICOM M330 VHF

[earthbm]

I have spent hours, following the instructions, and no result. My ICOM M330 does not have its own GPS antenna, so needs to be connected to a NMEA 0183 GPS source (for emergencies and to make it stop beeping periodically to say that there is no location set).

The nearest, and possibly only, NMEA 0183 source is the Simrad NAIS-400 class-B AIS. When I connect my laptop to it I see that GPS data is being transmitted:


The NAIS-400 NMEA output settings:


The ICOM M330 connection page:


The NAIS-400 connections page:


I’ve tried these combinations:
NAIS-400 to ICOM m330:
Brown to Yellow
Pink to Green

I think these are what I’m supposed to connect.
(Same polarity, Transmit to Listen, same data rate)

ICOM is not clear whether H is high baud rate (38400) and L is low (4800), but I assume it’s the case. I also tried switching NAIS-400 to sending 9600 over the pink wire.

At the end of my sanity here… any tips/pointers?

[Statistical]

The wires have to be done in pairs.
So for low birate out of of the NAIS it is Pink AND Purple. For high bitrate it is Brown AND Blue. NMEA uses differential signally to reduce noise/interference so it will always be 2 wires for NMEA 1083 for one way communication and 4 wires for two way communication.

Now if you should use the high speed or low speed pair I am not sure but that should narrow down the possibilities.

I would start with Purple to Yellow & Pink to Green.

[wholybee]

The correct connection should be:
Green to Pink, and Yellow to Purple.

The high speed 38,400 connection is normally only used with AIS data. Since you are only interested in GPS, the 4800 is the normal speed to use.

There are 2 wires required, a high(or +) and a low(or-). The transmit pair of wires from the AIS connects to the receive pair on the VHF.

[earthbm]

Nope. Tried
Green-Pink
Yellow-Purple

NO POSITION. NO DATE.

[Statistical]

Originally Posted by earthbm

Nope. Tried
Green-Pink
Yellow-Purple

NO POSITION. NO DATE.

Did you change back the data rate you previously changed to non-standard rate?

[earthbm]

I did, back to 4800.

The NMEA 0183 cable connected to NAIS-400 is used to supply power to it (red and black) and to activate a silent mode switch (light green and orange), both of which function as intended. So I think the source is good.

The problem is likely at the ICOM M330 side.

If my assumption that terms Data-L and Data-H in the manual refer to the low and high transmission rates (4800 and 38400) then connecting both green (Listener B, Data L, GPS In -) and yellow (Listener A, Data H, GPS In +) just duplicates the same thing on two different channels.

[Kelkara]

I don't think you have it right ... the data channel has two phases on the two wires ... you need to connect in+ and in- wires (data input) to the appropriate connections on the gps ... Data-h and data-l is just another way of labelling it.

The other two wires out+ and out- are an output channel for getting dsc data out from the radio to a plotter.

[Statistical]

Originally Posted by earthbm

I did, back to 4800.
If my assumption that terms Data-L and Data-H in the manual refer to the low and high transmission rates (4800 and 38400) then connecting both green (Listener B, Data L, GPS In -) and yellow (Listener A, Data H, GPS In +) just duplicates the same thing on two different channels.

It does not. "+", "A" or "Data-H" is one half and "-", "B" or "Data-L" is the other half. They are just synonyms for the same thing.

Normally pointless EE details most people never know because when they connect it, it just works but now might help avoid confusion:

Data-H & Data-L are used together in this case they mean Low & High signal not speed. NMEA like canbus uses differential signals. The same data is transmitted on both wires but one with a positive deflection (Data-HIGH or + or A) and one one with a negative deflection (Data-LOW or - or B). This helps to prevent interference from noise because we don't care about the exact value only the difference so interference which pushes the voltage higher will do so on both lines meaning the difference is still the same. The receiver will take both lines mux them and pull the difference as a method of noise correction.



Now most places just call it + and - although that is a "white lie". Icom is trying to be correct in naming and just created confusion.

I don't know why it isn't working if you wired it as described but one wire by itself however will never work for any NMEA 0183 (or NMEA 2000 or canbus or ethernet) device.

[Moo]

It should be

--AIS -- --Radio--
Pink ------> Green (Data-L)
Purple ----> Yellow (Data-H)

[earthbm]

Originally Posted by Moo

It should be



--AIS -- --Radio--

Pink ------> Green (Data-L)

Purple ----> Yellow (Data-H)

With three people consistently suggesting this connection, and still with no data I now can only assume it’s ICOM’s malfunction?

For completeness, this video suggested something different, with the green wire going to ground??? Anyway, I tried that too, no result.
https://youtu.be/uvuOtGTgs3Q

Tried grounding the radio to the house battery negative too.

[Moo]

Originally Posted by earthbm

With three people consistently suggesting this connection, and still with no data I now can only assume it’s ICOM’s malfunction?

For completeness, this video suggested something different, with the green wire going to ground??? Anyway, I tried that too, no result.
https://youtu.be/uvuOtGTgs3Q

Tried grounding the radio to the house battery negative too.

How are you physically making the connections?
Can you see the data on the output from the AIS (put a multimeter on it set to dc Volts and you should see a changing voltage between 0 and +/- 3)?
Have you set up the radio to receive from the NMEA input?

[wholybee]

Originally Posted by earthbm

With three people consistently suggesting this connection, and still with no data I now can only assume it’s ICOM’s malfunction?

For completeness, this video suggested something different, with the green wire going to ground??? Anyway, I tried that too, no result.
https://youtu.be/uvuOtGTgs3Q

Tried grounding the radio to the house battery negative too.

Anything to ground is absolutely incorrect. That would be a different system (rs232)

The two possible issues, make sure the settings in both devices are correct. Often in the sending device (in this case the AIS) there is a selection of what NMEA sentences to send. Some raymarine AIS units will not send GPS data for some stupid reason. You need to make sure the correct sentences are being sent. And on both devices, you need to make sure the bps rate is set correctly, in this case to 4800. My Standard Horizon has a an internal/external GPS setting that needs to be set to external. I'm not sure what you have.

The other thing is that I have seen companies that mix up labeling on H/L and +/-, so reversing polarity might fix it. I have seen this quite often, surprisingly.

Purple to Green
Pink to Yellow


I have an RS422 to USB adapter that I keep with my laptop, that allows me to test the signal, identify the wires correctly, the bit rate, and know that the sentences are correct. That would be helpful here, but is a whole nother level of testing.

[earthbm]

Originally Posted by wholybee

The two possible issues, make sure the settings in both devices are correct. Often in the sending device (in this case the AIS) there is a selection of what NMEA sentences to send. Some raymarine AIS units will not send GPS data for some stupid reason. You need to make sure the correct sentences are being sent. And on both devices, you need to make sure the bps rate is set correctly, in this case to 4800.



The other thing is that I have seen companies that mix up labeling on H/L and +/-, so reversing polarity might fix it. I have seen this quite often, surprisingly.



Purple to Green

Pink to Yellow

Flipping purple and pink didn’t work.

The sending device, Simrad NAIS-400, is controlled by connecting a laptop with ProAIS2. It has the checkboxes for the sentences, in the screenshot of my original post above. I don’t see a command to enable sending data. I assume that, being a screen less AIS box, it kind of has to send it?

…However:

Originally Posted by Moo

How are you physically making the connections?

Can you see the data on the output from the AIS (put a multimeter on it set to dc Volts and you should see a changing voltage between 0 and +/- 3)?

Have you set up the radio to receive from the NMEA input?

I’m twisting the wires by hand, with an intermediate cable.

Measuring the voltage on the NMEA 0183 output wires, it’s only between 0-0.5v. I assume the multimeter is averaging it switching between 0 and 5v?

ICOM m330 doesn’t seem to have a switch to receive. I assume it always wants to receive.

[wholybee]

At this point my only suggestion would be to use an RS422 to USB adapter and PuTTY software to confirm the output of the AIS. Then, once confirmed then you can work on getting the ICOM to recognize it. But if you have not performed such a test, it could be as difficult or more difficult than getting this to work.

You could try the 38400 output. I looked at the ICOM manual, and it is terrible. It doesn't say anything about expected data rate, or how to change it (apparently you can't?) But it does say that with an AIS connected you can make a DSC call by the AIS ships name. That would require 38400 to get the AIS data.

[CatLove]

try to connect the wires as follows:
- purple with yellow
- grey with white
- pink, green, yellow and brown all to GND (black power wire)
This converts the differential to single ended and works perfectly fine if cables are not very long , 10ft ok, 100ft not ok.
In addition both devices need to be set to the same baud rate and the correct sentences need to be selected the same on both devices.