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Old 03-02-2015, 16:04   #31
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Re: OCPN support VHF DSC Position NMEA sentences?

I did further tests of DSC emulation with the E120W "Cancel Distress Call Type 16" msg and actual tests to OCPN and E120W with my VHF radio.

First on the E120W -

Emulation of the Cancel Distress msg with 16 as the Call Type (field 2) and 12 as Category (f4) = This does NOT cancel a Distress msg or a Position msg which is already displayed on the screen. If there is no existing msg on the screen the 'Cancel Distress' creates a new Distress popo-up.

Same msg as above but changing f4 to be 16 instead of 12 = same results as above.

Other reactions noted:
A Distress msg will over-ride a Position pop-up already on the screen.
A Position msg will over-ride a Distress pop-up already on the screen.

Now to REAL tests with my radio. It is a GME DX600D manufactured 2013 and specified as 'Class D'.

I used the DSC call 'POSITION REQUEST' and received an auto response from 2 different vessels. The replies were clearly seen on the VHF radio screen and data was sent to the connected plotter, but neither OCPN or the E120W reacted to the DSC data.

I captured the data and found my radio was outputting $CVDSC instead of the expected $CDDSC. Here is a capture of the data:

$CVDSC,20,5037233000,08,21,26,2335015110,8888,,,B, E*67<CR><LF>
$CVDSE,1,1,A,5037233000,00,78009300*00<CR><LF>

So it appears both OCPN and the E120W are 'fussy' about the Talker ID being specifically $CD for these messages. I always imagined NMEA listener devices were quite 'broad-minded' about talker IDs so long as they started with $ and were 3 chr total since there is often overlap of NMEA msgs from different types of instruments/devices.

PjotrC can you confirm that OCPN needs to see $CD exclusively as the talker ID. Any chance that can be opened up to accept other ID's such as $CV?

I have emailed GME asking why they use $CV instead of $CD and if it can be changed, but no reply yet. I have seen $CV listed as a Talker ID for VHF radios but the same list shows $CD for DSC talkers.

It also seems Raymarine requires the $CD ID exclusively too. I have emailed them to ask if they accept other talker IDs for their DSC msgs but no reply from them either.

I wonder if anyone else out there knows of VHF-DSC radios which use talker IDs other than $CD?

When/if I get replies from GME or RM I will report back.

In the meantime, all this testing is very interesting but it looks like I have a radio and 2 navigation plotter which don't want to talk!
Ray
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Old 04-02-2015, 02:17   #32
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Re: OCPN support VHF DSC Position NMEA sentences?

Quote:
Originally Posted by Gypsy23 View Post
PjotrC can you confirm that OCPN needs to see $CD exclusively as the talker ID. Any chance that can be opened up to accept other ID's such as $CV?
Ray,

You are doing a great job of testing an area that is seldom addressed with live data... important and interesting indeed.

I do not know the 4.0 code but in 2.5 I looked only at CD talkers. It is not too difficult to expand this to include all other radio equipment. You certainly might want to enter a request for this into Flyspray. What is not quite trivial is to make sure that DSC-DSE pairs are not mixed up between talkers, if simultaneous messages are received...

Now, why people seem to look just at CD and not CV, CT and CX? I guess mostly from the numerous examples widely published and included in manufacturer's documentation. I re-read now the NMEA183 spec I used originally, and it is definitely not clear, what the equipment will send to the plotter. In section 6 Table 4 (talkers mnemonic codes list) VHF radio is shown as CV, but in the examples (section 7) the VHF radio is addressed as CD... if not for this one example it is easy to get an impression that CD is for all DSC received, and all the other mnemonics are for addressing specific equipment functions.

Please enter your request for change, I think there is no harm in accepting CV (and maybe CT and CX). And do continue testing... great job.

Thanks,

Piotr

PS. Maybe CT and CX can safely be dropped from a pleasure craft network... Assuming there is just one type of VHF radio connected to OCPN on a given boat (a reasonable assumption, I think) there will always be either CD or CV received. Makes programming much easier.
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Old 07-02-2015, 21:55   #33
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Re: OCPN support VHF DSC Position NMEA sentences?

Piotr
Tks for the Ack and further comment on the talker names.

I have not heard back from either Raymarine or GME but I did do some more testing and my face is a little Pink! It turns out the E120W DOES respond to the $CV talker DSC messages, but not those from my GME radio. So it is a bit broad-minded than I gave it credit for and when I sort out the hardware interface with my radio, I should be OK.

It turns out the "NMEA" output from the GME is not RS422, not even RS232. It gets loaded down by the E120W NMEA input impedance (abt 600ohms) such that the signal is only -0.25V to +2.5V (viewed on a scope). All other "NMEA" signal sources into the E120W are at least -4V to +5V when plugged in to the E120W.

When I send captured data $CVDSC/DSE msgs back to the E120W from my PC with a USB-Serial cable which provides signals of -5 to +5, it responds correctly, the same as it did to $CDDSC/DSE. Unfortunately, it still doesn't work with OCPN.

I will have to take this further with GME or build a small interface circuit which presents a higher impedance to the GME radio.

Meanwhile, back to OpenCPN and it's view of DSC/DSE msgs. I do think it would be beneficial for OCPN to recognise DSC/DSE msgs from talkers other than $CD or even $CV. Whilst it may be good practice to wire the VHF talker directly to a PC or plotter, it could easily be sent via a router or other Nav intrument which could have it's own talker ID replace the radio's $CD and then the same problem would arise.

I will generate a request for a change in Flyspray. Your point about ensuring DCE/DSE message pairs are kept true is important, all the samples I have seen so far are generated in two lines sequentially. Only the CRLF at the end of the DSC message and then again at the end of the DSE.

Thanks for your encouragement. It is a time consuming process to test without a 'buddy' DSC radio to bounce off. I have to 'scavenge' for active radios by looking for MMSI's on my AIS then calling them!!

Rgds
Ray
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Old 18-02-2015, 02:47   #34
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Re: OCPN support VHF DSC Position NMEA sentences?

Quote:
Originally Posted by rgleason View Post
Shouldn't some of this find its way into the wiki if it is not covered in some areas? Just to make wiki clearer?
Attached are some more samples of DSC/DSE sentences, including various distress relays and acknowledgements. Some of this is purely theoretical, if and how a specific sentence is generated can depend on specific equipment. I did not find any real example of relay/ack...

When connecting a DSC radio to OCPN users would benefit greatly from checking the manufacturers specs, and trying out a few scenarios, to get a feeling of how they are handled. Clearly, this is not the same support as expected from a typical Class D equipment.

I would recommend again the steps suggested a little earlier in this thread ( OCPN support VHF DSC Position NMEA sentences? ), plus

5. excluding the DSC targets (especially Distress) from distance filtering in the AIS Target List.
Attached Files
File Type: pdf dscdse_samples.7z.pdf (1.0 KB, 50 views)
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Old 27-02-2015, 10:48   #35
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Re: OCPN support VHF DSC Position NMEA sentences?

PjotrC--Please check the file you uploaded as a PDF file. I can't open it with any sort of PDF reader. The ".7z" suggests it is some sort of compression archive.

I was able to get to the payload, but it took a lot of extra steps.
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Old 27-02-2015, 11:08   #36
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Re: OCPN support VHF DSC Position NMEA sentences?

Just strip the .pdf off and unzip the file. 7zip is the unpacker of your choice.
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Old 27-02-2015, 15:58   #37
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Re: OCPN support VHF DSC Position NMEA sentences?

Pjotr,

Added to
OpenCPN Beta File Thingie rguser rgpass
Nmea Folder
  • dscdse-vhf-samples-f....7z
  • dsc-vhf.txt
For those who would like to test OpenCPN with sample VHF DSC using the Voyage Data Recorder plugin -"VDR_pi" [Play Function]

I have read your notes, do you think we should add the text in your link to "Comments" in the Wiki?

"I would recommend again the steps suggested a little earlier in this thread ( OCPN support VHF DSC Position NMEA sentences? ), plus
.. adding your item #5
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Old 28-02-2015, 23:14   #38
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Re: OCPN support VHF DSC Position NMEA sentences?

Quote:
Originally Posted by PjotrC View Post
Attached are some more samples of DSC/DSE sentences, including various distress relays and acknowledgements. Some of this is purely theoretical, if and how a specific sentence is generated can depend on specific equipment. I did not find any real example of relay/ack...

When connecting a DSC radio to OCPN users would benefit greatly from checking the manufacturers specs, and trying out a few scenarios, to get a feeling of how they are handled. Clearly, this is not the same support as expected from a typical Class D equipment.

I would recommend again the steps suggested a little earlier in this thread ( OCPN support VHF DSC Position NMEA sentences? ), plus

5. excluding the DSC targets (especially Distress) from distance filtering in the AIS Target List.
I tested the sample sentences you provided in both OCPN and with my Raymarine E120W.

Here's what happened:

Response to PjotrC Sample DSC/DSE messages 1Mar2015


File OCPN E120W dsc_distress_unspec Distress Distress dsc_selfposrep Position
Distress dsc_coastrelay_allships Position Distress dsc_coastrelay_individual Position Distress dsc_coastrelay_area Position
--- dsc_pollposrep Position --- dsc_coastack Position --- dsc_distress Distress Distress dsc_selfcancel Position ---
As you can see, both systems responded correctly to the Distress msgs (with leading data field "12") but they each react differently to the other samples.

I am not sure what it all means other than it confirms that their is not a uniform implementation of response to the DSC/DSE msgs.

Ray
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Old 01-03-2015, 01:23   #39
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Re: OCPN support VHF DSC Position NMEA sentences?

Quote:
Originally Posted by PjotrC View Post
Attached are some more samples of DSC/DSE sentences, including various distress relays and acknowledgements. Some of this is purely theoretical, if and how a specific sentence is generated can depend on specific equipment. I did not find any real example of relay/ack...

When connecting a DSC radio to OCPN users would benefit greatly from checking the manufacturers specs, and trying out a few scenarios, to get a feeling of how they are handled. Clearly, this is not the same support as expected from a typical Class D equipment.

I would recommend again the steps suggested a little earlier in this thread ( OCPN support VHF DSC Position NMEA sentences? ), plus

5. excluding the DSC targets (especially Distress) from distance filtering in the AIS Target List.
I tested the sample sentences you provided in both OCPN and with my Raymarine E120W.

Here's what happened:

Response to PjotrC Sample DSC/DSE messages 1Mar2015


File OCPN E120W
dsc_distress_unspec Distress Distress
dsc_selfposrep Position Distress
dsc_coastrelay_allships Position Distress
dsc_coastrelay_individual Position Distress
dsc_coastrelay_area Position No response
dsc_pollposrep Position No response
dsc_coastack Position No response
dsc_distress Distress Distress
dsc_selfcancel Position No response

As you can see, both systems responded correctly to the Distress msgs (with leading data field "12") but they each react differently to the other samples.

I am not sure what it all means other than it confirms that there is not a uniform implementation of response to the DSC/DSE msgs.

Sorry, having problems creating a table of these results.

Ray
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Old 01-03-2015, 08:49   #40
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Re: OCPN support VHF DSC Position NMEA sentences?

Now with PjotrC's List and test file and Gypsy 23 test results we can have a meaningful report and operational confirmation in the Wiki!

From there it can be adjusted, expanded and improved over time.

You deserve a Thank you from all users.
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Old 01-03-2015, 17:20   #41
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Re: OCPN support VHF DSC Position NMEA sentences?

I rechecked my results with OCPN and have found that the 'Self Cance' msg DOES cancel a Distress message. I think I only tested it after a Position msg yesterday. To be specific:

'dsc_distress' drops a red Distress mark AND a Distress pop-up message.

if the Distress is still active and:

'dsc_selfcancel' is Rx the Distress mark and pop-up are removed.

if there is no active Distress, 'dsc_selfcancel' drops a green Position mark.

This means the table of results is:



File OCPN E120W
dsc_distress_unspec Distress Distress
dsc_selfposrep Position Distress
dsc_coastrelay_allships Position Distress
dsc_coastrelay_individual Position Distress
dsc_coastrelay_area Position No response
dsc_pollposrep Position No response
dsc_coastack Position No response
dsc_distress Distress Distress
dsc_selfcancel (after Dist) CancelsDist Retest needed
dsc_selfcancel (No Distress) Position No response

More info for Wiki
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Old 01-03-2015, 19:04   #42
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Re: OCPN support VHF DSC Position NMEA sentences?

Pro-tip. Use [ CODE ] [ / CODE ] tags to maintain spacing.
I copied your text to clipboard to get the spacing.

Quote:
Originally Posted by Gypsy23 View Post

This means the table of results is:

Code:
File                            OCPN              E120W 
dsc_distress_unspec             Distress          Distress       
dsc_selfposrep                  Position          Distress       
dsc_coastrelay_allships         Position          Distress       
dsc_coastrelay_individual       Position          Distress       
dsc_coastrelay_area             Position          No response       
dsc_pollposrep                  Position          No response       
dsc_coastack                    Position          No response       
dsc_distress                    Distress          Distress        
dsc_selfcancel (after Dist)     CancelsDist       Retest needed   
dsc_selfcancel (No Distress)    Position          No response
More info for Wiki
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Old 01-03-2015, 19:54   #43
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Re: OCPN support VHF DSC Position NMEA sentences?

Tks for the layout tip and the cleaned up table - I hope I remember it.
Ray
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Old 01-03-2015, 21:12   #44
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Re: OCPN support VHF DSC Position NMEA sentences?

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Originally Posted by bcn View Post
Just strip the .pdf off and unzip the file. 7zip is the unpacker of your choice.
I already extracted the payload. I just want to let you know how much of a chore you made it.
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Old 02-03-2015, 08:00   #45
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Re: OCPN support VHF DSC Position NMEA sentences?

Off topic, but thought I would bring it up while people are testing.

Is any of the equipment being tested here capable of setting up a DSC call over NMEA0183 ?

Can this be documented so that functionality can eventually be added to OpenCPN ?

Cheers,
JM.
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