Re: Tips for doing conditional logic in EPICS records

["Mooney, Tim M. via Tech-talk" <tech-talk@aps.anl.gov>]

Hi Mark,

One way to do conditional execution in an EPICS database is by using the SELM and SELN fields of a seq record.  Set SELM to "Specified", and write a number to the SELN field. If you want more than one of several things to happen, you can write "Mask" to SELM, and write a bitmap value to SELN, specifying which things to do.

Tim Mooney (mooney@anl.gov) (630)252-5417
Beamline Controls Group (www.aps.anl.gov)
Advanced Photon Source, Argonne National Lab

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From: Tech-talk <tech-talk-bounces@aps.anl.gov> on behalf of Mark Davis via Tech-talk <tech-talk@aps.anl.gov>
Sent: Monday, April 27, 2020 10:05 AM
To: tech-talk@aps.anl.gov <tech-talk@aps.anl.gov>; John Priller <priller@nscl.msu.edu>
Subject: Tips for doing conditional logic in EPICS records

 

Hi all,

I am looking for some tips on the best way to implement logic such as
the following using EPICS records:


flag = 1;
for (each new set of readings)  {
     if (readbackA == fixedVal1)   flag = 1;  else
     if (flag == 1)  setVal = readbackB;  else
     if (readBackC == fixedVal2)  setVal = readbackD;
     flag = 0;
}


For the initial setting I figured simply a record that includes the
initial value in the VAL field (and PINI set to "Yes"?).

The for "loop" would be simply an FLNK in the record (or last in a
sequence of records) that gets the new readings, triggering the
processing of the the record that handles the 1st if condition (in this
case, I have one record that gets them all at once).

At that point how to best to proceed is not obvious to me, and there are
probably  lots of possibilities (A sequence of calcout or scalcout
records?  Maybe a transform record?)

Suggestions?

--
Mark Davis
NSCL/FRIB Control Systems Software Engineer
davism50@msu.edu