Experimental Physics and
Industrial Control System

Adam Jon DeGrush <[email protected]> · Wed, 30 Jan 2002 19:54:19 -0500 (EST)

Hello All,

I am relatively new to epics so I apologize if my question seems poorly
informed.

I am trying to monitor the connection of channels using
ca_change_connection_event from the client library and am having
difficulty getting it to work. I would like to do a group poll
(synchronous or asynchronously) of my channels at a certain frequency and
would like make sure that my channels are connected before I do this.  I
though I could just install a connection handler like in the example:

    for (pCurrent = pFirst; pCurrent != NULL; pCurrent = pCurrent->next){
       status=ca_change_connection_event(pCurrent->chan,
	                                myHandler);
       SEVCHK(status, "ca_change_connection_event:
			couldn't change handler");
       }
and then have something like:

while(1){
	ca_pend_event(POLL); //
	myGroupPoll();
	nanosleep(fiveseconds,NULL);
        }

and then have my handler either block or remove from my list those
channels that have been disconnected. Instead when I run it and disconnect
a channel there is a pause of about 5 seconds and then a segmentation
violation( although I think handler does get called).  The same thing
happens if I remove myGroupPoll().

In addition I seem the same behavior running the example code given at:

http://mesa53.lanl.gov/lansce8/Epics/ca/client/caX5Ftutor-6.html#HEADING6-0

Any help would be greatly appreciated.

Thanks,
Adam DeGrush

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System