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<== Date ==> <== Thread ==>
Subject: Re: Sequencer seem to skip states with EPICS 3.16.1
From: Ralph Lange <[email protected]>
To: EPICS Tech Talk <[email protected]>
Date: Tue, 30 Jan 2018 21:00:25 +0100
On Tue, Jan 30, 2018 at 5:25 PM, Simon Reiter <[email protected]> wrote:
Hi all,

I ran into another problem.
Using the sequencer (2.2.4) for a state machine was working well. With the upgrade to EPICS 3.16.1,
some states seem to be skipped. Normally, it would go like READY -> STARTING -> RUNNING.
I added log messages to verify these states. This is fine.

But using camonitor only show READY -> RUNNING.
The same happens for external software, which uses a channel subscription.
This problem also happens in EPICS7.

Any idea, how I can solve this without implementing some delay workaround.

What record type do you use to represent your state?

In the CA server, updates for strings are handled using a reference (pointer) in the queue, while numerical type updates put their value in the queue.
If your record has a string value, two fast subsequent writes to it may actually lead to the first string never being sent, if it gets overwritten while the event with the pointer to it is still in the outgoing queue. In that case, it might be better to use an mbbi or mbbo (enum type) record, because an enum's natural type is numerical, while it still has nice string representations for its states.

Cheers,
~Ralph

References:
Sequencer seem to skip states with EPICS 3.16.1 Simon Reiter
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