Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Mon, 10 Jul 2023 09:23:50 -0700

On 6/23/23 14:23, Evans, Richard K. (GRC-H000) via Tech-talk wrote:

Hello,

What software tools/components would best enable an EPICS system to render real-time frequency plots (fft/psd) of single channels of data as it is being recorded? Is that possible within CSS/Phoebus? I can't find any mention in the CSS documentation about displaying live frequency plots).

(I somehow overlooked this post last month...)

Usual design practice with EPICS would have computationally
expensive operations like an FFT done once in an IOC instead
of repeated in every client.  The assumption being that there
will always be more than one client.

I know of, and have been responsible for, a number for drivers
include include FFT calculations.  I have found that there is
just enough variation to prevent easy generalization.  cf.
differences like complex vs. real inputs.  Windowing or other
filtering.  Log vs. linear output.  Whether to include 0Hz.
Phase "unwrapping".  etc...

As a case in point.  The FEED driver for the LBL Marble board
includes FFT calculation (added by Sonya Hoobler @SLAC).
Of course, that code was created for RF applications, and  might
need some need some adaption for yours.

Elaine Chandler's User meeting talk on April 25th, 2023 at Fermilab, titled: "C2 Data Viewer: Visualization tool for EPICS7 Data Streaming" [1] describes a DAQ "scope" application that I would like to consider using, but I was told that this capability also exists in other tools as well and I should learn about all the tools that do this before deciding how to implement this. Is this (real-time spectral display of data) a common capability? What does the community recommend? Thanks!

(Assume the underlying EPICS system is acquiring data using an FMC IOC with fast ADCs -  i.e. Marble [2] and Zest [3] at 50 kSPS)

Thanks!
/Rich

[1] https://indico.fnal.gov/event/58280/contributions/264784/
[2] https://github.com/BerkeleyLab/Marble
[3] https://github.com/BerkeleyLab/Zest

- Richard Evans, NASA GRC - Armstrong Test Facility
   Data and Information Systems Management
   Public URI: https://www.linkedin.com/in/rkevans
   Agency URI: https://wiki.grc.nasa.gov/pbgeneral/User:Rkevans

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System