Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Fri, 10 Feb 2023 08:38:29 -0800

On 2/9/23 11:09, Ignacio Arriagada via Tech-talk wrote:

Hello everyone!
I'm currently working on an EPICS system that would greatly benefit from using PVAccess, pva2pva/QSRV. The talk, examples and VM used in the EPICS Collab last year have been a great resource so far (thank you Kay Kasemir!!!) and have gotten me far into my prototype.

Moving forward with my work, I was wondering the following:

  * Are there examples of applications using JSON files within a QSRV implementation. It is mentioned here -> https://docs.epics-controls.org/projects/pva2pva/en/latest/doxygen/qsrv_page.html#qsrv_config <https://docs.epics-controls.org/projects/pva2pva/en/latest/doxygen/qsrv_page.html#qsrv_config> but I can't figure out how to actually include the .db in my prototype build.

The "iocimagedemo" example includes creation of two equivalent group PVs
from the same set of records.  One from database info tags in "image.db",
and a the other from a separate "image.json" file.

  * Is there a PVAccess reference manual (a la CA <https://epics.anl.gov/base/R3-14/12-docs/CAref.html>)? I have been trying to use the protocol specification page in github, but it would be great if there was something covering PVAccess from a higher level perspective.

The protocol spec. is likely the opposite of a user friendly introduction
to configuration.

The CAref document is one reasonable place to start as user configuration
for PVA and CA are very similar (by design).  In most cases substituting
EPICS_PVA_ for EPICS_CA_ in environment variable names will work.

I'm working to develop better documentation as part of the PVXS module.

https://mdavidsaver.github.io/pvxs/netconfig.html

Obviously "better" is subjective, and I'm certain that what I write won't
speak to everyone all the time.  I'm certain that much of it reads like
something written by an expert for an expert, because it was.  I need a
reference manual myself!  Writing for "new users" is hard for me in no
small part because I am not "new" to EPICS, and haven't been for quite
some time.

Personally, I feel that the best introductory documentation is written
by someone who has just figured it out for the first time.  Someone who
isn't familiar with the assumptions and conventions which warp the minds
of those who regularly work with EPICS (or any big piece of software).

As a note.  If you interested in diving into the deep details of the
PVA or CA protocols.  Beyond what most users need to know.  You might
find this useful.

https://github.com/mdavidsaver/cashark

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System