Re: EPICS alarming on VAL != X

[Dirk Zimoch <dirk.zimoch@psi.ch>]

Does it make sense to change the code to:

if (prec->drvh >= prec->drvl)

And change the default values so that DRVL>DRVH (e.g. DRVL=0, DRVH=-1)

Then nothing would change if the db designer ignores the fields.

Another alternative is to set default values DRVL=-Inf and DRVH=Inf.

Dirk

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_Outpu
> > > 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." ― Scott Adams
>
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