Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Fri, 25 Jul 2014 15:58:55 +0200

On Friday 25 July 2014 14:34:13 Dirk Zimoch wrote:
> Another alternative is to set default values DRVL=-Inf and DRVH=Inf.

I like this idea. It precisely captures the desired default behaviour
w/o imposing any artificial limitation. I guess the 'if (prec->drvh >
prec->drvl)' hack was from before +/-Inf was standardized.

BTW, does dbLoadRecords understand +/-Inf in a db file? Does
dbLoadDatabase in a record type field definition's "initial" property?

Cheers
Ben

> On 25.07.2014 14:05, Benjamin Franksen wrote:
> > On Thursday 24 July 2014 11:27:24 Andrew Johnson wrote:
> >> On 07/24/2014 04:47 AM, Benjamin Franksen wrote:
> >>> On Thursday 24 July 2014 11:15:56 Dirk Zimoch wrote:
> >>>> On 21.07.2014 12:41, Benjamin Franksen wrote:
> >>>>> Why don't you just set DRVL=DRVH=<the desired value>.
> >>>>>
> >>>>       /* check drive limits */
> >>>>       if (prec->drvh > prec->drvl) {
> >>>>
> >>>>           if (value > prec->drvh)
> >>>>
> >>>>               value = prec->drvh;
> >>>>
> >>>>           else if (value < prec->drvl)
> >>>>
> >>>>               value = prec->drvl;
> >>>>
> >>>>       }
> >>>>
> >>>> DRVL=DRVH => no check at all!
> >>>
> >>> Strange. Not intuitive to me. And contrary to the docs.
> >>
> >> That check predates the CVS history of the aoRecord.c file (1995).
> >> It
> >> makes perfect sense to me, there has to be a way to disable the
> >> clipping behaviour,
> >
> > Hm, yes, that makes sense.
> >
> >> and the assumption is that you would only create
> >> ao records for things that you want to be able to actually change.
> >
> > In general, yes, but there are exceptions. I have used ao or ai
> > records to hold physical constants as parameters for a calculation.
> > It would be nice if I could tell the database to fix the value and
> > not even allow a db or ca put to change them. (One solution could
> > be a simple record type for such parameters. Maybe I'll write one
> > when I have some leisure...)>
> >> If
> >> you want to stop changes for a while, disable record processing
> >> using
> >> SDIS & DISV.
> >
> > I don't think this will prevent the VAL from changing e.g. due to
> > put
> > operations, or does it?
> >
> >>> This is from the
> >>> RRM
> >>> (https://wiki-ext.aps.anl.gov/epics/index.php/RRM_3-14_Analog_Outp
> >>> u
> >>> t#Desired_Output_Parameters):
> >>>
> >>> """
> >>> The VAL field's value is forced to be within the limits specified
> >>> in
> >>> the fields DRVH and DRVL, which are configured by the designer:
> >>>
> >>> DRVL<=VAL<=DRVH
> >>>
> >>> Note: If nothing is entered for DRVH and DRVL, the output value
> >>> will
> >>> never change.
> >>> """
> >>
> >> Wiki page fixed to document existing code.
> >
> > Thanks.
> > Ben
> > --
> > "Make it so they have to reboot after every typo." â€• Scott Adams
> >
> >
> > ________________________________
> >
> > Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
> >
> > Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher
> > Forschungszentren e.V.
> >
> > Aufsichtsrat: Vorsitzender Prof. Dr. Dr. h.c. mult. Joachim Treusch,
> > stv. Vorsitzende Dr. Beatrix Vierkorn-Rudolph Geschäftsführung:
> > Prof. Dr. Anke Rita Kaysser-Pyzalla, Thomas Frederking
> >
> > Sitz Berlin, AG Charlottenburg, 89 HRB 5583
> >
> > Postadresse:
> > Hahn-Meitner-Platz 1
> > D-14109 Berlin
> >
> > http://www.helmholtz-berlin.de

--
"Make it so they have to reboot after every typo." â€• Scott Adams

________________________________

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.

Aufsichtsrat: Vorsitzender Prof. Dr. Dr. h.c. mult. Joachim Treusch, stv. Vorsitzende Dr. Beatrix Vierkorn-Rudolph
Geschäftsführung: Prof. Dr. Anke Rita Kaysser-Pyzalla, Thomas Frederking

Sitz Berlin, AG Charlottenburg, 89 HRB 5583

Postadresse:
Hahn-Meitner-Platz 1
D-14109 Berlin

http://www.helmholtz-berlin.de

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System