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Subject: Re: Questions about channel access C API programming
From: Wang Xiaoqiang via Tech-talk <tech-talk@aps.anl.gov>
To: Abdalla Ahmad <abdalla.ahmad@sesame.org.jo>, "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Tue, 5 Mar 2019 17:01:53 +0100
Hi,

Call ca_flush_io after ca_put.

1. ca_task_initialize is the old API, and creates a non-preemptive context.
2. DBR is for request and DBF is for field type. But plain DBR_XXX has the same value as DBF_XXX.

Best
Xiaoqiang

On 3/5/19 3:08 PM, Abdalla Ahmad via Tech-talk wrote:
Hi

The attached C file is a snippet from a Qt project. In the project there was a function that writes values to many PVs in a loop. What was happening is that some PVs do not get their new value updated immediately but after 3 or 4 seconds. The code shows a similar behavior, two consecutive "ca_put" calls, and the same behavior occurs. I double-checked the database (included in the comments) but there is nothing wrong. I tried to use ca_context_ or ca_task_ but the project crashes maybe because the QE framework is already handling low-level CA. What am I missing here?

Another two questions came up:

1.What is the difference between ca_task_initialize and ca_context_create?

2.What is the difference between request types (DBR_) and field types (DBF_)?

P.S.: We are using Base 3.15.6

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 <http://www.sesame.org.jo/>


References:
Questions about channel access C API programming Abdalla Ahmad via Tech-talk

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