Basic NMEA sanity check

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lampshuk

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Hi, I am trying to connect NMEA data to my Cobra 55 DSC radio. I have wired it up using my own 2.5mm mono jackplug (recommended elsewhere) and what I think are the correct connections (inner = NMEA+, Outer = GND).

No joy.

I don't have any other NMEA devices to use as a test of the output, but is there a basic check I can perform with a multimeter to see if I've even got data on the NMEA wires from the sending device?

(which is a Vesper XB8000, by the way: lovely bit of kit and a doddle to install standalone and connect with my iPad. Now I need to plumb it in to the radio and get virtual ports working on my PC for the wireless GPS link)

Thanks for any suggestions,

Martin.
 
What speed is the NMEA output from the Vesper? I can't find any information from a quick look at their site, but the fact that it's an AIS device makes me suspect it's probably 38400bps rather than the older 4800bps which your Cobra (and pretty much any other VHF) will be expecting. Looks like the Vesper is configured via a PC program - is there anything in there to alter the NMEA 0183 speed?

Pete
 
Yes, I dialled it down to 4800 (at which point it only generates GPS, not AIS, which is OK for my current use).
Problem is I don't know if there's anything coming out at all, whether I have failed to connect the plug correctly, or whether the Cobra's inputs are working etc.
My only diagnostic check is the lat/lon readout on the VHF. When it says something other than 99.99.9999 I will know it's at least reading something. So far it has not flickered.

I have been assuming that the Cobra uses (+) for the tip connection and (-) for the shaft. In the manual it just refers to red and black wires (for their supplied cable) so I am hoping that they connect them in the same way any sane human being would.
 
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prv said:
What speed is the NMEA output from the Vesper? I can't find any information from a quick look at their site, but the fact that it's an AIS device makes me suspect it's probably 38400bps rather than the older 4800bps which your Cobra (and pretty much any other VHF) will be expecting. Looks like the Vesper is configured via a PC program - is there anything in there to alter the NMEA 0183 speed?

Pete
Click to expand...

Yes, you can configure the 0183 speed from the software. You can choose what data you want to transmit via NMEA but if you want to transmit AIS data by NMEA you have to select the 38400.

Richard

Too late - points totally covered by Martin!
 
As you might have gathered, the multimeter will not see the data..

One good test is to connect a laptop with a known good serial input connection. Run some terminal emulation (or similar software on it ) and you will easily see if any data is there and at what speed. You could use the

Did you manage to connect a laptop to the Vesper and configure the output for NMEA at 4800 baud?

Whereabouts are you in the Solent..? If near Southsea I'd be happy to call round with the necessary laptop and serial cables to check.

I assume you have used the Yellow and Gray cables from the Vesper to (as you say) the Red and Black NMEA cables on the VHF.

http://downloads.vespermarine.com/xb/XB_InstallGuide_20140609-web.pdf
 
This is something that comes up quite frequently.

You can take NMEA0183 direct into a PC & look at the text sentences. Of course as PCs have improved, this kind of useful thing has become more complex. If you have an old laptop that has a 9-pin serial socket & is running XP or older, it's easy. Comment the NMEA data line or NMEA+ to pin 2 & then ground or NMEA- to pin 5 of the 9-pin connector. Fire up Hyperterminal & set it up for a direct serial connection with the appropriate baud rate & you should see the NMEA data. It's just text.

If you only have USB but still have XP, then you can simply use a USB to serial converter.

If you have W7 or above, then it doesn't come with XP. You should be able to use something like PuTTY which is a free terminal program. I still have an old lappy that I use for this occasionally so haven't tried a newer one with PuTTY.

Most systems squirt out data only 1 or 2 times a sec. So, a very simple test that just indicates if something's going on is to use a multimeter. When there's a data burst, you should see a twitch in the voltage which should idle at around 12V wen there's no data burst. But that's about all you can do with a multimeter.
 
Martin_J said:
As you might have gathered, the multimeter will not see the data..
Click to expand...

Oh. That's disappointing. After all, it is a digital multimeter

;)

Seriously, though: thanks for your troubleshooting offer. We are at Hythe, so a bit of a trek.

I was wondering if I should be able to see anything with the meter - even an average voltage or occasional pulse of 5V to show it's actually putting something on the GPS plug. As I mentioned, I made my own connection to the Cobra, so the only question is whether red is indeed the inner (tip) and black the outer of the jack plug. I guess I can just try transposing them. What's the worst that could happen? Well, OK. Apart from frying the transponder and setting fire to my boat, what's the next worst thing that could happen?

Yep, I can connect to the Vesper with USB or wifi and config this that and the other.

Part of the problem with not being down at the boat to try this out is that I find myself getting half way through a post asking for advice and then realise that I should try this or that for myself before posting. But, not being able to try it out, I go ahead and post anyway. So: thankyou all for your patience. I have contacted Vesper support and they are being helpful, so far just confirming what others have said about configs etc.

(Thanks, Martin_J - I have downloaded the firmware. Just need to pluck up courage to update when I am down there next)

When (not if!) I get this stuff working I will post a blow-by-blow account of how. I do like what I have seen so far.

Cheers, all.

Martin.
 
I had a similar diagnostic problem trying to work out if the DSC Vhf was kaput or the GPS was no longer sending a signal.
I put a multimeter on the GPS +/- and could see regular voltage pulses, less than 5v, sure enough the VHF was the culprit.
I'm sure I read using a multimeter on here or somewhere on the tinterweb.
Good luck with it and let us know how you get on.
 
wooslehunter said:
This is something that comes up quite frequently.

Most systems squirt out data only 1 or 2 times a sec. So, a very simple test that just indicates if something's going on is to use a multimeter. When there's a data burst, you should see a twitch in the voltage which should idle at around 12V wen there's no data burst. But that's about all you can do with a multimeter.
Click to expand...

Thanks, Mister Hunter. That's exactly what I'm after (though I have also just ordered one of Nigel's logic probes).
I think I've got a ser-USB converter kicking around somewhere. I need to look for it.

Now: enough of this displacement activity. Need to get some work done to pay for all this gubbins.

Cheers,
Martin.
 
although if you're into gadgets and really want to see the data then consider having an oscilloscope on board if you wish to see the quality vs noise of the data stream... Useful for checking shielding and interference.

http://www.sainsmart.com/sainsmart-arm-dso203-nano-4-channel-mini-v2-quad-pocket-digital-oscillo-scope.html

Multiple uses as well.. My last use for this oscilloscope was in checking if it was the rev. counter that was not working, whether the cabling was at fault or was the alternator just not sending pulses...

The aluminium cased version and supplied probes do seem to be well made.
 
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lampshuk said:
I was wondering if I should be able to see anything with the meter - even an average voltage or occasional pulse of 5V to show it's actually putting something on the GPS plug
Click to expand...

I have an analogue multimeter on board. It's a long time since I needed to test any NMEA, but I think when I did the needle waggled around in a fairly distinctive way.

Pete
 
lampshuk said:
(Thanks, Martin_J - I have downloaded the firmware. Just need to pluck up courage to update when I am down there next)

When (not if!) I get this stuff working I will post a blow-by-blow account of how. I do like what I have seen so far.

Cheers, all.

Martin.
Click to expand...

That firmware update was over a year ago and would have affected XB8000s bought in late 2012 I think.

The firmware update is easy to do and must be done over wifi rather than USB cable, so you don't even have to remove any panels to access the XB8000 (if it's mounted behind a panel like mine).

The firmware update issued last quarter of July 2014 was problematic and solved one problem whilst creating another. I emailed Carl at Vespermarine as soon as I realised the problem and he promised a new update which was posted on the VM website a week or so later. This is a good update and solves the new problem without resurrecting the old one. Just make sure you get the very latest updates from the VM site - there are two files in the one package which should be 2.01.8549 and 5.09.8473.

Richard
 
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lampshuk said:
Oh. That's disappointing. After all, it is a digital multimeter

;)

Seriously, though: thanks for your troubleshooting offer. We are at Hythe, so a bit of a trek.

I was wondering if I should be able to see anything with the meter - even an average voltage or occasional pulse of 5V to show it's actually putting something on the GPS plug. As I mentioned, I made my own connection to the Cobra, so the only question is whether red is indeed the inner (tip) and black the outer of the jack plug. I guess I can just try transposing them. What's the worst that could happen? Well, OK. Apart from frying the transponder and setting fire to my boat, what's the next worst thing that could happen?

Yep, I can connect to the Vesper with USB or wifi and config this that and the other.

Part of the problem with not being down at the boat to try this out is that I find myself getting half way through a post asking for advice and then realise that I should try this or that for myself before posting. But, not being able to try it out, I go ahead and post anyway. So: thankyou all for your patience. I have contacted Vesper support and they are being helpful, so far just confirming what others have said about configs etc.

(Thanks, Martin_J - I have downloaded the firmware. Just need to pluck up courage to update when I am down there next)

When (not if!) I get this stuff working I will post a blow-by-blow account of how. I do like what I have seen so far.

Cheers, all.

Martin.
Click to expand...

Possibly a long shot but are you absolutely sure you have plugged your NMEA jack into the right socket on the back of the Cobra. There are two, one for the NMEA and one for the external speaker, and they are labelled the wrong way round in some editions of the manual. Previous owner of my boat had dutifully wired the radio as required by the manual and it took me ages to track why neither the NMEA feed nor the cockpit speaker worked.

If that's not the problem then the issue lies further up the line (or the radio is broken) as I think you have got your jack wiring (+ve to tip) correct.

Don't know why you wouldn't see data bursts with a multimeter.

Cheers
 
Martin_J said:
although if you're into gadgets and really want to see the data then consider having an oscilloscope on board ...
Click to expand...
Now you are talking serious gadgets. I've got two of these, one at home and one on the boat:
ScopeMeter without AC power pack http://amzn.to/1q2hI3T
ScopeMeter with power pack: http://amzn.to/1gC1h4R

It's an excellent multimeter as well as an oscilloscope, so very handy when tracing problems. If you want to know more than "is there a signal" a 'scope can't be beaten. I got the version with the power pack (it has a strange plug) and made an isolated 12V to 6V power supply for it. It will of course run on batteries.
 
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nigelmercier said:
I'll It's an excellent multimeter as well as an oscilloscope, so very handy when tracing problems. If you want to know more than "is there a signal" a 'scope can't be beaten. I got the version with the power pack (it has a strange plug) and made an isolated 12V to 6V power supply for it. It will of course run on batteries.
Click to expand...

Ooerr. Now I feel totally outgunned in the gadget department.
 

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