Experimental Physics and
Industrial Control System

Hinko Kocevar via Tech-talk <[email protected]> · Sun, 2 Jun 2019 17:53:39 +0000

Thank you all for the input.

I understand that adding new records to the IOC database is the "EPICS" way of doing it, and I've done it so far for IOCs under my control, with success. The thing is that there are not enough bodies, with EPICS knowledge and free time, for this to happen on all IOCs at ESS, leading such low priority requirements being forgotten.

I've never used the base filters before - this looks like a good opportunity to look into that!
The PVs that need throttling are mainly scalars, but in some cases, even more critical PVs as waveforms. I would imagine that "deadband" filter might not play well with those. In any case, deadband filter looks promising, but at the end of the day, I'm after simple decimation of PV update rate, not depending on the value change itself.
(How) can filters be used with python client (pyepics3)?

The periodic polling, sounds like to most straightforward approach, for sure.
In python, there might be unwanted delays introduced to the "caget" if the PV is not accessible/reachable at the time of the poll. And then the rest of the PV updates (in a single thread) suffer from not being updated in timely fashion. Someone will say, use threads; but I can have +50 PVs to look at on this slow monitoring client hence each PV would need to get its own thread? Or would the use of PV instead of caget in pyepics3 lead to better experience?

Thanks,
Hinko
________________________________________
From: William Layne <[email protected]>
Sent: Thursday, May 30, 2019 7:19:24 PM
To: Hinko Kocevar
Cc: [email protected]; Emanuele Laface
Subject: Re: Camonitor with client dictated update rate

Oops forgot to CC tech-talk

--------- Forwarded message ---------
From: William Layne <[email protected]<mailto:[email protected]>>
Date: Wed, May 29, 2019, 5:08 PM
Subject: Re: Camonitor with client dictated update rate
To: Hinko Kocevar <[email protected]<mailto:[email protected]>>

You could create a record, with a 1hz scan rate, that has the input field linked to the desired PV. Then have your user monitor the subsampled PV.

On Wed, May 29, 2019, 1:21 PM Hinko Kocevar via Tech-talk <[email protected]<mailto:[email protected]>> wrote:
This might sound like a silly motion, but you are probably used to those from me by now.

A non-EPICS person at my facility wonders if EPICS could support camonitor like PV monitoring, but with CA client dictating the rate of value updates. Imagine 1s update rate, that certain slow client would use, while the PV would update much faster, and the rest of existing CA clients just use regular camonitor’ing.

I can see answers like, just use caget like approach and poll or define a new (set) of PVs for that slow rate, but that is IOC material. My use case revolves around very, very busy IOC devs that have no time to support crazy ideas of individuals who want slow updates.

Any insights appreciated!

Thanks (and have a nice weekend to those living in Sweden),
Hinko

On Wed, May 29, 2019, 1:21 PM Hinko Kocevar via Tech-talk <[email protected]<mailto:[email protected]>> wrote:
This might sound like a silly motion, but you are probably used to those from me by now.

A non-EPICS person at my facility wonders if EPICS could support camonitor like PV monitoring, but with CA client dictating the rate of value updates. Imagine 1s update rate, that certain slow client would use, while the PV would update much faster, and the rest of existing CA clients just use regular camonitor’ing.

I can see answers like, just use caget like approach and poll or define a new (set) of PVs for that slow rate, but that is IOC material. My use case revolves around very, very busy IOC devs that have no time to support crazy ideas of individuals who want slow updates.

Any insights appreciated!

Thanks (and have a nice weekend to those living in Sweden),
Hinko

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System