Invalid GPS data to ICOM M506 from Garmin Chartplotter

Captain Crash · 06 July 2015, 19:26

I have a new Icom M506 connected via NMEA 2000 to a five-year-old Garmin 551s chartplotter/sounder. The NMEA2000 hardware is all new Garmin stuff and there are only these 2 devices on the network at the moment.

The chartplotter and the radio can "see" each other on the network and I was able to go into the radio's menu to enable the chartplotter as the specific NMEA2000 GPS source. The chartplotter gets all the AIS data from the radio without any configuration - AIS contacts are displayed on the chartplotter instantly the radio is turned on and all the functionality of CPA alarms etc etc is there.

The problem however is that the radio says it's getting invalid GPS info from the chartplotter (indicated by a flashing satellite icon and ??? displayed in these fields on the radio screen).

I've updated the chartplotter's firmware all the way from v2.5 to v4.6 via a download from Garmin onto an SD card. This has made some nice improvements to the chartplotter but did not fix the invalid GPS data.

I hooked up the NMEA0183 feed from the chartplotter to the radio, and went into the radio's menus to set the NMEA 2000 GPS source to "none". Hey presto the radio immediately started receiving a valid GPS position and time from the chartplotter. The AIS feed continues to work fine via NMEA2000.

So I do have a fully-working system BUT it's annoying that something as simple as the GPS position won't work over NMEA2000. It doesn't give me much confidence to add more gizmos to the NMEA2000 network!

Does anyone have any idea what is going wrong? Must admit I haven't tried contacting Garmin or Icom yet (suspect they will blame each other). Any suggestions gratefully received.

Pikey Dave · 06 July 2015, 19:40

I had exactly the same problem with a 506 connected to my Lowrance HDS. Try tightening the all the nmea2000 cable connection & "T" s, that's all I did & it sorted itself out, I'm not convinced that's what the problem was but it hasn't reappeared. I suspect that there was a bad connection in the input data line to the radio, the radio was outputting ok, so the head unit saw the radio on the network & the data from the radio was going onto the bus, but the radio wasn't receiving data off the bus.

.....sh1t happens.......

Captain Crash · 06 July 2015, 21:52

Wow I would never have thought of that but it sounds very logical. Will give it a try tomorrow!

willk · 06 July 2015, 22:27

Wired one of these recently to a Lowrance NMEA2000 network - 100% plug and play. I'm liking Pikey's plan as an easy check.

Captain Crash · 07 July 2015, 18:00

Well I had a good go at cleaning and tightening all the connections today. Also dismantled the whole NMEA 2000 network and swapped the cables and Ts round in different combinations so that different ones connected to the radio, GPS and power. (I thought this might reveal a bad cable or T.)

No joy - every combination resulted in AIS working but GPS not.

Guess I have to assume that either my radio has a bad data input or my GPS has a bad data output.

Pikey Dave · 08 July 2015, 08:03

Iirc, you can go into the menu on the radio & set the source for the GPS, I think it's in the nmea2000 menu.

.....sh1t happens.......

Captain Crash · 08 July 2015, 08:51

Quote:

Originally Posted by Pikey Dave

Iirc, you can go into the menu on the radio & set the source for the GPS, I think it's in the nmea2000 menu.

.....sh1t happens.......

Yep that's right. If I set it to Garmin 551s, the M506 complains of invalid gps data (flashing satellite icon). If I set it to none, the NMEA0183 feed takes over and the M506 is happy (solid satellite icon and gps position displayed on the radio screen).

I can leave it like this but it's just annoying that there's a glitch somewhere in my NMEA2000 system.

Pikey Dave · 08 July 2015, 14:29

Are there any settings on the garmin to output the GPS data to the nmea2000 bus?

.....sh1t happens.......

Captain Crash · 08 July 2015, 23:52

No settings on the Garmin when it was running v2.5 firmware.

Now that I've upgraded to the latest firmware v4.6, there is a NMEA2000 config screen for the M506. However the only setting that's there is to input your MMSI number. Not sure why this is needed, I'm guessing it's something to do with the AIS/DSC integration.

Didn't make any difference, GPS position via NMEA2000 reads as invalid on the M506 both before and after the firmware upgrade.

willk · 09 July 2015, 00:40

Just a random thought - but have you tried changing the GPS format - i.e. is it in digital format?

Pikey Dave · 09 July 2015, 08:34

Quote:

Originally Posted by Captain Crash

No settings on the Garmin when it was running v2.5 firmware.

Now that I've upgraded to the latest firmware v4.6, there is a NMEA2000 config screen for the M506. However the only setting that's there is to input your MMSI number. Not sure why this is needed, I'm guessing it's something to do with the AIS/DSC integration.

Didn't make any difference, GPS position via NMEA2000 reads as invalid on the M506 both before and after the firmware upgrade.

You need to input your mmsi number into the Garmin so it doesn't see itself as a dangerous target. I ignores your own mmsi. Have you inputted your mmsi into the VHF?

Captain Crash · 10 July 2015, 12:32

No haven't tried that, not sure if I can change it. Also I figure that if the M506 recognises the format over NMEA 0183 than it should also be ok over NMEA 2000.

I'm planning to get a B&G Triton display unit in the near future - that should tell me which unit is at fault.

Pikey Dave · 20 September 2015, 17:10

Update to this

Since fitting my Icom M506 I've had intermittent issues with the VHF losing position & time info similar to the op. I thought I had sorted it by tightening the nmea 2000 connections. I visited the Icom stand at the boatshow, explained the issue & got a "ah! We might know about that" kind of response. There is an issue with Garmin plotters & the V1.001 firmware in the M506. They are now on V1.004 firmware. Just checked mine & it's V1.002. As I was at the stand, another bloke turned up with exactly the same problem. I'm going to get my firmware upgraded over the winter. Unfortunately it can only be done by Icom either on site by their field tech. Or at a service centre.

.....sh1t happens.......

jyasaki · 21 September 2015, 16:21

Quote:

Originally Posted by Captain Crash

Also I figure that if the M506 recognises the format over NMEA 0183 than it should also be ok over NMEA 2000.

I believe this is incorrect. While the two systems are similar in operation (both serial multiplexed communication), I believe the actual "language" used (the one and zero combinations that make up the actual words) are fairly different.

If you're getting any data transmitted correctly either from the GPS to the NMEA 2000 bus or from the bus to the GPS, that implies that the fault is likely how the GPS data is being formatted (rather than a GPS talking to the NMEA2K bus type problem.) As far as what exactly that might be, I can't really help.

jky

Pikey Dave · 21 September 2015, 17:02

Further info. I've been in communication with Icom UK again today & the answer is....wait for it..........NMEA0183

The absolute, genuine, no money back guaranteed way to make it work is to use NMEA0183 for position & time data into the VHF. Still use NMEA2000 for DSC & AIS info out of the VHF, but NMEA for data in. Apparently there is a conflict (bug) in the Icom NMEA2000 implementation, they have already resolved this with Raymarine & Garmin by modifying software in the plotters, they can't guarantee that the new firmware for the VHF will resolve the issue with Lowrance etc. So it looks like the soldering iron is coming out tomorrow. Slightly p1ssed off, as the main driver for buying the M506 was the "plug & play" NMEA2000, yeah right

willk · 21 September 2015, 17:28

Mine works just fine with NMEA 2000 & Lowrance HDS2 :-P

Pikey Dave · 21 September 2015, 17:33

Quote:

Originally Posted by willk

Mine works just fine with NMEA 2000 & Lowrance HDS2 :-P

Well, aren't you the lucky boy

It works fine radio to HDS, it's the radio that keeps losing its data. You don't realise it until you look at the VHF & it says "No position or time"

willk · 21 September 2015, 17:35

Quote:

Originally Posted by Pikey Dave

Well, aren't you the lucky boy

It works fine radio to HDS, it's the radio that keeps losing its data. You don't realise it until you look at the VHF & it says "No position or time"

It works just fine at that too! I'd have noticed the constant beeping. That would drive me mad. I bet you're raging....

Pikey Dave · 21 September 2015, 17:37

Quote:

Originally Posted by willk

It works just fine at that too! I'd have noticed the constant beeping. That would drive me mad. I bet you're raging....

Beeping????

willk · 21 September 2015, 18:26

Quote:

Originally Posted by Pikey Dave

Beeping????

It beeps and displays your message if I turn the plotters off