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General help wanted on multiplexing
#1
Hi all,

first I am new to openplotter so apologies if this is covered elsewhere but I did not find any general information.

I want to have my openplotter set up to be used in two ways:

1. headless in the wheelhouse with AIS+NMEA from legacy equipment over USB

2. on a TV in the saloon for monitoring while at anchor and for general planning, in this case AIS+NMEA from legacy equipment over wifi.

My question is a general one. With multiple inputs/outputs of NMEA data is there a way to ensure you do not get data loops, where sentences go out and come back via different routes? Left unchecked this could very quickly flood the system. I say this as on my Raymarine autopilot it says any input on the NMEA input will go out over the sea talk bus "unless that data is already on the bus". I assume it keeps a table of what source/sentences it sees on the bus and matches any input with that prior to output. Does anything like this happen in openplotter?
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#2
This is the data routing, if you follow it you should not have problems. Be careful with outputs, do not send them to any kplex/signal k input.

[Image: assets%2F-L9g5MoJ9GSCaNGq_yjb%2F-LMX8_h7...b0ccf36fdf]
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#3
(09-16-2018, 07:07 AM)Newt2u Wrote: Hi all,

first I am new to openplotter so apologies if this is covered elsewhere but I did not find any general information.

I want to have my openplotter set up to be used in two ways:

1. headless in the wheelhouse with AIS+NMEA from legacy equipment over USB

2. on a TV in the saloon for monitoring while at anchor and for general planning, in this case AIS+NMEA from legacy equipment over wifi.

My question is a general one. With multiple inputs/outputs of NMEA data is there a way to ensure you do not get data loops, where sentences go out and come back via different routes? Left unchecked this could very quickly flood the system. I say this as on my Raymarine autopilot it says any input on the NMEA input will go out over the sea talk bus "unless that data is already on the bus". I assume it keeps a table of what source/sentences it sees on the bus and matches any input with that prior to output. Does anything like this happen in openplotter?

you should only need either 1 or 2 not both if it gets data usb serial there is no need for wireless.. it can be hdmi in saloon and still be accessed as if headless vnc or send data to opencpn on android device.
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#4
Kplex can manage this when it is setup correctly.
On kplex page you can select any device. A click on diagnostic will show which sentence get in and which get out.
You can directly reduce traffic if you filter (block) input sentences.( typical when there are more than one GPS).
The output diagnostic does show how much bandwidth your data needs. You can reduce this with filter settings.
New in openplotter 1.2 is that you can filter system and signalk.
For low speed communication (4800) use "Accept only sentences:" otherwise you will flood your device.

You typically create loops when you have systems as opencpn which get all available sentences!
If opencpn (or any other chartplotter with nmea0183) creates a RMB sentence for the autopilot and sends it to kplex this sentence is available for all. And that means it will be send back to opencpn. It is part of the input stream to opencpn.
That's the loop. You can block it if you create another output device which has the filter Ignore sentences RMB.
Another typical loop is if you create nmea0183 sentences from Signal K or and they went from kplex into signalk to nmea0183->signalk converter. You can easilly add an ignore filter for these sentences.

In other words: Every device which uses input and output invites you to create loops.
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#5
(09-16-2018, 07:55 AM)jim321 Wrote: you should only need either 1 or 2 not both if it gets data usb serial there is no need for wireless.

The two options are to avoid a very long usb cable from wheelhouse to saloon where the monitor is located.

(09-16-2018, 08:12 AM)e-sailing Wrote: In other words: Every device which uses input and output invites you to create loops.

Thanks that was useful, the plan I have is as follows, there may not be problems but with what you say I can probably avoid them.

Ooops, I am having problems uploading images to the forum but the image is uploaded here:

https://www.dropbox.com/s/ls15xxxjlrrpvl...p.png?dl=0
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