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Old 19-01-2019, 06:04   #1
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Multiplexer NMEA incompatible with Repeater NMEA

Hello All,
First , Thanks for this very good software. I use it for 10 years with pleasure.

I have just buy a CLipper GPS (Repeater Nmea of Nasa marine) to replace my dead cockpit GPS.
It seems that the NMEA multiplexer of opencpn doesn't work fine for this repeater.

OpenCpn send ECRMC and ECRMB to Repeater (I'am using 4.8.8 release).

The issue comes from the NMEA sentences. OpenCPN send:
ECRMB
ECRMC
ECRMC
ECRMC
ECRMB ect...

The repeater need to receive :
ECRMB
ECRMC
ECRMB
ECRMC

So, when repeater don't receive ECRMB just after ECRMC, he displays: "No RMB"

In conclusion, my repeater is OK one second then KO one second, ect...

Why OpenCPn send the same sentence few times ?


Thanks for your help.
Laurent
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Old 20-01-2019, 11:37   #2
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Hello dev team,
I think that I have found the issue in the code.
In routeman.cpp, line 601, the comment precise : //Send all known Autopilot messages upstream.
It seems that there are 4 possibilities : RMB,RMC,APB,XTE
For each case, the code ends by : g_pMUX->SendNMEAMessage( snt.Sentence );
so, it looks like 4 sentences are sent everytime.
In my case, the first one is RMB, the second one RMC. I don't want to send APB and XTE, but the snt variable is always seted by RMC for the third and fourth.

What do you think of that?

Regards
laurent
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Old 20-01-2019, 13:03   #3
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Please read
https://opencpn.org/wiki/dokuwiki/do...s_nasa_clipper
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Old 20-01-2019, 13:23   #4
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Quote:
Originally Posted by cagney View Post
Thanks Cagney.
I known this topic. But for me, fix a software bug by an hardware solution (Arduino) is not the good solution.
Futhermore, I beleive that most of bugs related in this topic are already fixed in the last release.

We are not far to be able to use Nasa-Marine Clipper GPS Repeater with OpenCpn.

Regards
Laurent
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Old 20-01-2019, 14:27   #5
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Quote:
Originally Posted by Cocody56 View Post
Hello dev team,
............
In my case, the first one is RMB, the second one RMC. I don't want to send APB and XTE, but the snt variable is always seted by RMC for the third and fourth.
laurent

You could try to filter APB and XTE if you don't wont them to be sent.
In Options->Connections edit the connections outgoing sentences to specify what messages to send, like ECRMB, ECRMC
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Old 20-01-2019, 18:05   #6
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Re: Multiplexer NMEA incompatible with Repeater NMEA

cocody56...


Just FYI, the OpenCPN dev team considers the Nasa Clipper GPS Repeater device to be broken in many ways. Workarounds for that specific device are low priority, just now.


Feel free to pass this opinion on to Nasa.


Thanks
Dave
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Old 21-01-2019, 00:32   #7
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Quote:
Originally Posted by Hakan View Post
You could try to filter APB and XTE if you don't wont them to be sent.
In Options->Connections edit the connections outgoing sentences to specify what messages to send, like ECRMB, ECRMC
Hello Hakan,

Yes, sure, I am using "output filtering".
OpenCpn send only ECRMC and ECRMB, this filtering is correct.

The issue comes from the x4 sentences. OpenCPn sends eachtime 4 sentences.

If you filter in order to send only ECRMB. OpenCPN will send 4 sentences of ECRMB by cycle.
If you filter in order to send only ECRMB and ECRMC. OpenCPN will send 4 sentences by cycle as bellow:
ECRMB
ECRMC
ECRMC
ECRMC.

Whatever you select, 4 sentences will be sent.

Regards
Laurent
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Old 21-01-2019, 00:45   #8
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Quote:
Originally Posted by bdbcat View Post
cocody56...


Just FYI, the OpenCPN dev team considers the Nasa Clipper GPS Repeater device to be broken in many ways. Workarounds for that specific device are low priority, just now.


Feel free to pass this opinion on to Nasa.


Thanks
Dave
Hello bdbcat,
Ok, I understand that it is not a priority for the dev team.
I am going to try to fix this bug myself.
Could you just confirm me that my analyse is good please ?
I mean in routeman.cpp, g_pMUX->SendNMEAMessage( snt.Sentence ); is running 4 times without any conditions.

Thanks in advance
Regards
Laurent
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Old 21-01-2019, 01:31   #9
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Laurent
I'd a check on my Win10 by Wireshark: (NMEA Debug window is not always reliable. Sometimes sentences are duplicated. O has more prioritized work than print Debug perfect?)
While in navigation mode and filter to send only ECRMB and ECRMC:
Every second four sentences are sent, correct.
The order is though:
ECRMB
ECRMC
ECRMB
ECRMC
3 msec between each. One full second to next sequence.
So based on your post above this would be what you asked for?
There's a but: To be able to use Wireshark I used UDP IP and not a serial port. It could be a serial buffer may slightly change the time sequence?

Håkan
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Old 21-01-2019, 02:49   #10
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Hakan,
I have just tested with UDP connection.
I don't see any differences...
I think that you should trust NMEA debug windows.
Thanks for your help
Regards
Laurent
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Old 21-01-2019, 11:28   #11
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Hi Laurent

I am successfully using the NASA GPS Repeater with OpenCPN.

It took a while to figure out but it works perfectly for me now.

See this thread for more info: OpenCPN Magnetic Variation Reversed?
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Old 22-01-2019, 01:08   #12
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Re: Multiplexer NMEA incompatible with Repeater NMEA

Quote:
Originally Posted by gchead View Post
Hi Laurent

I am successfully using the NASA GPS Repeater with OpenCPN.

It took a while to figure out but it works perfectly for me now.

See this thread for more info: OpenCPN Magnetic Variation Reversed?
Hi gchead,

It sounds good !

But, I have one questions:

The Repeater NMEA of Nasa Marine can be used with and without Route activated in Opencpn.
Does it work without Route activated in your solution ? I mean , in order to display SOG and COG only.

I read that you are using OpenCPn 4.99.0 so I have to install it in order to test again.

Regards
Laurent
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Old 22-01-2019, 02:20   #13
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Re: Multiplexer NMEA incompatible with Repeater NMEA

It only works fully when Route is Activated.

Yes, you need to install patched OpenCPn 4.99.0 until the new version is released.
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