[time-nuts] Timelab, two SR620s and losing samples

Attila Kinali attila at kinali.ch
Sun Jan 17 09:54:18 UTC 2016

Guete Morge!

On Sun, 17 Jan 2016 07:24:32 +0100
Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> >> Have you tried swapping "role" of the SR620?
> >
> > Yes, I've done that. Both SR620's lose some samples, but only one of
> > them loses significantly more than the other.
> OK. So, the dropping follows the counter rather than the role?

> >> Have you tried grabbing data in the Linux environment?
> >
> > Nope. I couldn't find any tool for linux that worked.
> > I also tried to run Timelabs in Wine, but that segfaults on start.
> > Do you have any recommendation for a tool?
> You don't need anything fancy. A small program to talk to the serial 
> port should do it. If you could use talk only, I would just pipe it to a 
> file and compare them later.

Hmm.. good idea.

> I really wish TimeLab existed directly on Linux. Last time I tried 
> running it under Wine, it worked but didn't draw things properly for me.

It's like Lady Heather, it needs to be ported to Qt ;-)
> >> Have you tried feeding timelab two streams generated on the linux side?
> >
> > What do you mean by that?
> If you generate data that looks like real data and then mock the serial 
> ports to make TimeLab beleive it is real counters, you can now see if 
> the dataflow themselves causes issues over the Linux/Windows border and 
> into TimeLab.

Ah.. unfortunately this would need a bit more fiddling and tool building
than I have time for. I'm only here for another week and have to spend
most of the time learning how to do ASICs.
> > Due to the problems I had with the SR620s and what the group at the TU Vienna
> > experienced (I am currently using their equipment), we started to ponder
> > whether we should build our own, multi-input TICs. Especially considering
> > that we are about to design some ASICs which we expect to be synced up
> > better than 100ps (somewhere around 20-50ps, limited by the delay uncertainty
> > of the cables).
> Well, building your own TIC would naturally be interesting, but adds 
> another aspect in that you will have to verifiy them extensively. It 
> will be another factor of uncertainty to consider.

Yes. It wouldn't be something that is done fast. I expect it to take
at least half a year with a couple of highly motivated people as a team.
A year would be probably more realistic. And after that, comes a whole
lot of verification and qualification. But that could probably be done
together with PTB or CERN.

			Attila Kinali
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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