Experimental Physics and
Industrial Control System

Patrick Thomas <[email protected]> · Fri, 21 Jan 2011 17:38:16 -0800

Do you mean calling ca_pend_event(0) in the main program, and

subscribing/unsubscribing in a separate thread? Is there an advantage to

this?

On 1/21/2011 5:34 PM, Jeff Hill wrote:

Hi Patrick,

The mechanism to start/stop a subscription is accessed via calls to
ca_create_subscription/ca_clear_susbscription. If you have a single threaded
application then you will need to start and stop the subscriptions from
within the main loop. Therefore, yes, that could be accomplished by calling
ca_pend_event with a finite timeout, deciding what subscriptions might be
needed, and calling ca_create_subscription/ca_clear_susbscription to start
stop the appropriate subscriptions - all of these actions in a loop. There
are of course many other, more complex, ways to schedule this including
changing to a preemptive callback mode application with multiple threads
(emphasis on complex) but of course a simple, minimal approach is often
just-a-fit for the design requirements.

Jeff
______________________________________________________
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-----Original Message-----
From: [email protected] [mailto:tech-talk-
[email protected]] On Behalf Of Patrick Thomas
Sent: Friday, January 21, 2011 6:01 PM
To: [email protected]
Subject: dynamic monitoring

Hi,

I was wondering what the best way is to dynamically monitor channels in
C. That is to start and stop monitoring channels at run time. I
currently have a program that connects to and attaches monitors to a
predefined list of channels and then goes into a ca_pend_event(0), which
blocks forever. Should I change this to a loop and specify a certain
time period, i.e. ca_pend_event(1) and add or remove channels in that
loop?

Thank you for your time,
Patrick

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System