Fast trigger over Ethernet

[bobausttex]

Good Day,

This may not be the place for this question.  My system is not "real-time" but my need is.

I need to send a trigger over the LAN/ethernet jacks to another part of the building but the trigger has to be fast and more important low or no jitter.  Has anyone found a way to sync to systems over the common network that has low jitter?

[MarkCG]

how much jitter is tolerable? Regular ethernet is not really designed for realtime/ low jitter -- if you are talking a millisecond that may not work. 

[bobausttex]

Using a dedicated second port on the embedded computer and sending the *TRG command to the waveform generator I am getting about 6ms of delay and 1ms of jitter.  I would like 10 times better but could live with half that.

I was wondering how much better UDP might work on this privet LAN?  I am trying to test that but I am still learning about UPD. 

Perhaps some solution that sends a trigger over the wire without disturbing the net traffic?   

I just don't want to have to run BNC from one system to the other when they can be moved, often, around this large building and forklift could cut the cable.  I only want to hook power and net cable and go to the office and run it.  Trigger is the holdup.

[nanocyte]

Time Sensitive Networks might be of interest:

http://www.ni.com/white-paper/54730/en/

Yes, UDP should have better performance.

Switches could be a problem in a traditional LAN network as they could prioritize other traffic over yours.

[MarkCG]

sounds like you are controlling an instrument, usually those want a TCP connection but maybe it will do UDP as well?? I think running the cable might be the easiest thing to do, setting up time sensitive networking may not be worth it. 

Just spitballing here...but maybe some kind of optical or wireless transmission? If you have line of sight you might rig up something with a photocell and an IR emitter to trigger, with simple electronics. Or maybe a radio transmitter and receiver like a garage door opener. 

[MarkCG]

actually, check out radio controlled switches

https://www.pololu.com/category/142/rc-switches

[bobausttex]

Thanks for the input.

At this point the lab does not allow any wireless connections.  It is stupid but it is what it is.  I also can not ensure line of sight or passage of radio through the metal walls.

Since this will be in use for years and across many different setups spending the time now may be worth it in the end.

[bobausttex]

No real solution yet but I have not gotten UDP to work so I can test. 

I did consider using the gps pulse per second.  The signal is low enough jitter but I would have to get a repeater for inside each building or run  an antenna outside the building from both ends.  I am trying to get rid of the wires not add.