Experimental Physics and
Industrial Control System

[email protected] · Wed, 27 Feb 2013 13:22:06 -0800 (PST)

Hi Benjamin,

Yes, I have been going through that guide. Mostly though I think my
trouble is with understanding the portable channel access server.

Thank you,
Patrick

> On Tuesday, February 26, 2013 10:17:12 [email protected] wrote:
>> Thank you for your reply. I have now disabled preemptive callback.
>
> Ok.
>
>> I am
>> using ca_poll to process the CA client and
FileDescriptorManager.process
>> to run the portable channel access server. These are called together in
a
>> single loop. However, once the CA client has attached to a number of
process variables, the CA background activity that runs due to the ca_poll
>> seems to delay the call to FileDescriptorManager.process too much. This
results in calls to caget for process variables in the portable channel
access server timing out. Is there another way to do this?
>
> Have you looked at
> http://lansce.lanl.gov/epicsdata/ca/client/caX5Ftutor-1.html yet? It
contains
> a lot of CA client examples and explains what calls to use in which
situation.
> You might be interested in chapter 4 "Monitoring a PV" and there
especially
> the section named "An Example Program" under which you'll find (among
else) a
> desciption of fdmgr, how it works and how it is used.
>
>> Also, is there
>> a way to avoid having the CA client search for process variables on the
portable channel access server, but still look for them on the
>> localhost?
>
> Set EPICS_CA_AUTO_ADDR_LIST to NO and EPICS_CA_ADDR_LIST so that the
gateway
> is excluded but localhost is included.
>
> Cheers
> Ben
>
> PS: The above link to the CA tutorial is not linked to from the EPICS
home
> page (or at least not in any prominent place). Could this be changed? I
found
> these pages extremely useful when trying to get my head around the CA
client
> API.
>
>> > On Monday, February 25, 2013 14:58:36 [email protected] wrote:
>> >> I think it turns out that the problem was
>> >> that I actually had preemptive callback enabled and I should not
>> have.
>> >
>> > Yes. If you use preemptive callback (i.e. multithreaded CA client)
>> don't
>> > create a FileDescriptorManager. It is only needed for single-threaded
clients
>> > and can be used to centralize the call to select in case the CA
client
>> is
>> > used
>> > together with other stuff that wants to call select (such as a GUI
library).
>> >
>> > Cheers
>> > --
>> > Ben Franksen
>> > ()  ascii ribbon campaign - against html e-mail
>> > /\  www.asciiribbon.org   - against proprietary attachments
>> >
>> >
>> > ________________________________
>> >
>> > 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
> --
> Ben Franksen
> ()  ascii ribbon campaign - against html e-mail
> /\  www.asciiribbon.org   - against proprietary attachments
>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System