Connecting NMEA 0183 GPS data to ICOM M330 VHF

[Moo]

Originally Posted by earthbm

Flipping purple and pink didn’t work.




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.

0 to 0.5 is too low there is something wrong there, or your meter is bad. Check your intermediate cable. Measure the output with nothing connected.

Check the port configuration on the radio. You are not looking for a "switch" on the radio to change the input but a menu selection in the configuration menu. It says that external input has priority over the internal GPS Rx, but check anyway.

Again measure the tx pair from the AIS with nothing connected and also connected to the radio.

[Sheetbender]

I have the same problem with my Icom m424g. Connected my 424g to my quark A027 multiplexer and "NO POSITION". Followed the instructions from both devices to the letter.
Using a usb to rs422 adapter, I saw that the quark is sending gps data to OpenCPN in Windows 11. Two wires for receive. No ground needed. if a ground is needed then your using rs232. Tried 4800 baud to 38400 from the multiplexer.
The vhf has no baud setting. Icom has no 0183 receive switch, only a transmit switch. Manual says that external gps overrides internal gps.

I will be tying to get some technical help from Icom. Wish me luck.


P.S. I wouldn't be needing external gps if the Icom has a better internal gps receiver. It sometimes takes 20 to 60 minutes to get a fix. then the lat and long wanders a great deal, not accurate at all. Mounted below deck is the reason of course. I figured on just using external, big mistake!

[Sheetbender]

Reversed the wires and bam, instant position. Is it my Quark multiplexer or the Icom that has the polarity reversed? Hmmm

[nohal]

It is likely you connecting the wires wrong, not any of the devices being designed wrong. This is not your electrical connection where you connect positive to positive and ground to ground, it is differential RS-422 signalling where you connect TX on one side to RX on the other and vice versa.

[wholybee]

Originally Posted by Sheetbender

Reversed the wires and bam, instant position. Is it my Quark multiplexer or the Icom that has the polarity reversed? Hmmm

Is it possible one device was RS232, and the other RS422? Connection between the two works, but isn't what you would expect. Normally you should buy a converter, but read this:

https://stratusengineering.com/rs232...tronics-power/

I have seen devices get the polarity wrong, however. Usually its the cheap RS422 to USB devices.

[Tin Tin]

I was under the impression AIS GPS signals are only applicable to the AIS device. I tried and failed with a Ray AIS 650 and Ray VHF. I then connected the VHF to the autopilot NMEA out put and it worked just fine.

[Sheetbender]

Icom tech support said swap the connections. Neg to pos. Still keeping the same connections on each end, tx to rx. I did not have connections wrong and it is rs422 on both ends.
Icom did not admit their polarity is wrong, it could be my multiplexer.
Proper connections for rs422 are neg to neg, pos to pos. That did not work.

[svmobert]

Okay, first let's start with some facts here..

1.) M330(G) supports ONLY 4800 baud
2.) M330(G) requires one of the following sentences for GPS data (RMC, GGA, GNS, or GLL and VTG)
3.) M330(G) Green is GPS-In(-) and "Data-L" and "Listener-B"
4.) M330(G) Yellow is GPS-In(+) and 'Data-H" and "Listener-A"
(and note that the Icom manual shows all 3 naming conventions so it's pretty clear)
5.) NAIS-400 can output on either NMEA output port. But in this case we want port 2 - low-speed, 4800 baud.
6.) NAIS-400 Pink is Transmit(-) (aka Talker-B and Data-Out-L)
7.) NAIS-400 Purple is Transmit(+) (aka Talker-A and Data-Out-H)
8.) listeners connect to talkers
9.) NMEA wiring is (-,L,B) to (-,L,B) and (+,H,A) to (+,H,A)

So.. Based on that info. the correct wiring must be..

NAIS400 Pink -> M330(G) Green
NAIS400 Puple -> M330(G) Yellow

And we know that the M330(G) only supports 4800 baud, so the NAIS400 Port 2 setting in ProAIS2 must be 4800 baud to match.

Next, we need to ensure that the NAIS400 is outputing sentences that the M330(G) supports.. I noticed in the first screenshot that only RMC was showing in the ProAIS2 output log, and in another shot of ProAIS2, that RMC, GLL, and GGA are all enabled.

So first problem to investigate here is why aren't GLL and GGA also showing in the log? Maybe the settings were changed after the screenshot of the log was taken.. but if not, then the AIS is not doing what ProAIS2's configuration is showing it should be doing. ProAIS2 is generic software covering many brands and models of AIS units. It's possible that the NAIS400 doesn't actually support those sentences... or that the firmware version installed on the unit doesn't support them.

Do you have the latest firmware (2.02) on the NAIS400? If not, upgrade it before you go any further.

We know that the radio should support RMC, but if the NMEA0183 sentences aren't all working properly, it's also possible that the RMC sentence itself is not quite right for the M330(G) to process.

I would also try disabling RMC on the AIS and leaving the other 3 enabled, check the log and see if they show up at all. And see if the radio starts getting position.

Next, if you have an M330G and not a standard M330.. Did you try using the external GPS antenna puck attached to the radio's GPS antenn port? This may solve your problem with the internal GPS not being reliable..

[wholybee]

Originally Posted by Sheetbender

Icom tech support said swap the connections. Neg to pos. Still keeping the same connections on each end, tx to rx. I did not have connections wrong and it is rs422 on both ends.
Icom did not admit their polarity is wrong, it could be my multiplexer.
Proper connections for rs422 are neg to neg, pos to pos. That did not work.

To make sure I understand, You connected TX+ to RX-? (etc. for all wires)
That is supposed to be incorrect, but I have seen it before. I have seen it often enough that I always test with temporary connections.

Regarding the naming of NMEA connections. RS422 uses TX and RX to identify the signals. NMEA invented it's own vocabulary, but as NMEA0183 is an RS422 connection ultimately using RX and TX for the signals is normal.

[Tin Tin]

Just as a trial on your ProAIS2 set the NMEA1 to 4800 as well. Then try with both of the AIS outputs. You must disconnect your USB when you do these trials.

[nigel1]

Originally Posted by Sheetbender

Reversed the wires and bam, instant position. Is it my Quark multiplexer or the Icom that has the polarity reversed? Hmmm

I would say it was the Quark Multiplexor. I had the same situation, in theory, I connected the wires correctly, but nothing worked. So then swapped the wires around on the quark, and everything worked.
Have left a note on the multiplexor to the effect that the connections labled +ve are in fact -ve, and vice versa.