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<== Date ==>		<== Thread ==>

Subject:	RE: Simple channel access write program within Qt
From:	"Abdalla Ahmad" <[email protected]>
To:	"Kasemir, Kay" <[email protected]>
Cc:	"[email protected]" <[email protected]>
Date:	Sun, 8 Apr 2018 05:36:38 +0000

Thank you Kay, that explains a lot.

Abdalla.

From: Kasemir, Kay [mailto:[email protected]]
Sent: Tuesday, April 03, 2018 4:08 PM
To: Abdalla Ahmad <[email protected]>
Subject: Re: Simple channel access write program within Qt

Hi:

I assume you have multiple threads.

Some 'main' thread that starts everything up,

the UI thread that handles button presses etc. from the UI,

and then another worker thread in which you write, since you wouldn't want to delay the UI with such work.

--> See the section on using CA from multiple threads in the CA manual, https://epics.anl.gov/base/R3-14/8-docs/CAref.html#Client2

-Kay

From: [email protected] <[email protected]> on behalf of Abdalla Ahmad <[email protected]>
Sent: Tuesday, April 03, 2018 3:36 AM
To: [email protected]
Subject: Simple channel access write program within Qt

As part of experimenting with EPICS Qt with EPICS Base 3.14.12.3, I came to the need to write a function that writes values to PVs. Here is my attempt:

int status;

chid id;

CA_SYNC_GID gid;

ca_search(name, &id);

status = ca_pend_io(1); // Already checking if status != ECA_NORMAL

ca_put(type, id, &value); // type can be DBF_STRING, DBF_DOUBLE, etc.

This is already working fine but I have some questions:

1. I used to have ca_task_initialize and ca_task_exit but my Qt application always crashes on executing the function, the value is written but the app crashes. I thought since CA is already initialized and cleaned-up within EPICS Qt I removed both functions and the app works fine. Is this a correct behavior?

2. When do I really need the synchronous group version of ca_put(the ca_sg_put)?

Best Regards,

Abdalla Ahmad

Control Engineer

SESAME

Allan, Jordan.

Tel: (+962-5) 3511348 , ext. 265

Fax: (+962-5) 3511423

Mob: (+962-7)88183296

www.sesame.org.jo