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<== Date ==> <== Thread ==>

Subject: Re: [Fwd: LabView/EPICS]
From: "Dale L. Brewe" <[email protected]>
To: Ned Arnold <[email protected]>, APS tech-talk <[email protected]>
Date: Tue, 09 Mar 2004 14:29:37 -0600
We've used LabVIEW for quite some time for a variety of tasks on the PNC-CAT beamlines at the APS. For our primary interface we use a LabVIEW application that is primarily a CA client for iocs running modified versions of the synApps distribution. It also provides additional client-side control such as scripting-like automation of tasks, hiding of PV names from users by use of user-defined names for PVs, etc. Non-epics devices are integrated into the same user interface. CA uses the SCA library for Win32 from Chris Timossi at LBNL, and in my opinion functions quite well. Users typically have quite a few front panels open controlling several motors, scalers, scans, multielement detectors, and so on, connecting to dozens if not hundreds of PVs, and LabVIEW functions adequately in terms of performance and stability. The application does take quite a bit of RAM, but 512MB is sufficient for our beamline computers. It's flexible enough that we use the same executable for both beamlines and use ini files at run time to specify PV names and control which modules are loaded to account for hardware differences. We've generally had quite positive comments from users. Many are familiar w/ LabVIEW both in terms of use and program development, and we've collaborated w/ users to develop tomography and surface diffraction applications.
Another LabVIEW application provides feedback control of our monochromator, using the NI PID toolkit. It runs two feedback channels at 500Hz with performance up to our requirements. We haven't tested it at higher speeds but I don't see a reason it couldn't be pushed faster.
Non-epics devices at the beamline are controlled by a server using the NI datasocket protocol. It performs well enough but an epics interface would be more convenient to integrate scanning of positioners (e.g. slit positions), and recording of detectors during scans. I've looked into the ActiveX epics interface others have mentioned but haven't gotten to the point of trying to use it.
In terms of future needs on the client end, LabVIEW w/ SCA/Win32 works about as well as I would want. At the server end, as I mentioned, a CA interface would be nice as far as integrating positioners and detectors controlled by LabVIEW into our beamline software. The main requirement I can think of for a future CA interface is that it be more scalable than datasocket. With datasocket, one has to wait for client writes to individual datasocket items with a separate element on the diagram for each datasocket item. This makes it difficult to scale up to a large number of datasocket items. I've resorted to combining individual related variables into an array or LabVIEW "cluster" and sending/receiving the whole thing at once even if only a single element changes.


dale brewe

At 10:11 AM 3/8/2004, Ned Arnold wrote:

I recently had a discussion with the Product Manager of LabView
Realtime/Embedded about possibly implementing a tightly-coupled EPICS
interface to LabView. They have heard alot about EPICS from their
customers and would like to investigate what would be involved in providing this capability in an integrated way.


The first question for us to answer is "what do we want?". So, I would
like to hear people's experience with the EPICS/LabView interfaces that
are currently available. I know of two major ones:

  - Active-X interfaces (for clients and server)
  - Shared-memory interface to standard EPICS records (3.14)

Please contribute your experiences, comments, ideas, wishes, etc with
these solutions or let us know of any others that have been done. For those of you familiar with LabView, what other capabilities/features/performance requirements would you like to see?


The goal would be to develop a list of requirements for the
"out-of-the-box" LabView/EPICS solution.

Please reply by March 12.


Ned




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dale L. Brewe PNC-CAT/U. of Washington
ph: 630 252 0582 fax: 630 252 0580
Mail:
Argonne National Laboratory
Bldg 435E sector 20
9700 S. Cass Ave.
Argonne, IL 60439
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



References:
[Fwd: LabView/EPICS] Ned Arnold

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