Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Tue, 6 Jan 2009 09:31:17 -0700

FWIW, if you change MAX_STRING_SIZE there are two CA related consequences to
consider.
1) You will create a new CA protocol that is incompatible with any CA
protocol with a different MAX_STRING_SIZE.
2) Padding overhead for sending small strings over this new CA protocol
increases.

BTW, I do see this MAX_STRING_SIZE limit, as an issue that needs to be
fixed.

Jeff

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> On Behalf Of Dalesio, Leo
> Sent: Sunday, December 28, 2008 8:03 AM
> To: Ilya V. Kitaev; Kalantari Babak
> Cc: [email protected]
> Subject: RE: How to implement simple control algorithm (one more question)
> 
> 
> YOu can make the strings as long as you like. You just can't set or get
> them through channel access then - a 40 character limit. I'm not sure that
> it handles this properly. Jeff or someone else should comment on that.
> Bob
> 
> -----Original Message-----
> From: [email protected] on behalf of Ilya V. Kitaev
> Sent: Fri 12/5/2008 3:29 AM
> To: Kalantari Babak
> Cc: [email protected]
> Subject: Re: How to implement simple control algorithm (one more question)
> 
> Hi,
> Thank you for your answer.
> I'd like to ask one more question:
> Is it ok to break 40 chars limit in CALC field( or another text fields
> like DESC) ?
> I've changed this limit  to 200 in calcoutRecord.dbd, db_access.c and
> epicsTypes.h (MAX_STRING_SIZE define) and it works ok.
> 
> 2008/12/3, Kalantari Babak <[email protected]>:
> > Hi,
> >
> > You do not need to write your own CA application for that.
> >
> > Monitor alarm status of your "ai" with a "calcout" record and write to
> > your "bo" upon occurrence of the conditions.
> > This can be done for example as the following:
> >
> > record(calcout, "$(ALGORITHM)")
> > {
> >         field(INPA,"$(YOUR_AI_REC).STAT CP") # monitoring
> >         field(INPB,"$(YOUR_BO_REC).VAL NPP")
> >         field(CALC, "A=3?1:A=5?0:B")
> >         field(OOPT, "On Change")
> >         field(OUT,"$(YOUR_BO_REC) PP")
> > }
> >
> > Alarm status value for HIHI is 3 and for LOLO is 5.
> >
> > HTH,
> > Babak

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System