Re: Timing in seq record

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

Hi Freddie,

Thanks for pointing out that issue.

That issue was closed on March 12, 2021, saying there has been a pull request.

7.0.6 was release on July 3, 2021, and 7.0.6.1 on October 6, 2021.  But I don't see anything about this issue in the release notes for either of these.

Is there a release of base that fixes this fairly serious issue?

Mark

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From: Freddie Akeroyd - STFC UKRI <freddie.akeroyd at stfc.ac.uk>
Sent: Wednesday, March 2, 2022 7:54 PM
To: Mark Rivers <rivers at cars.uchicago.edu>
Subject: RE: Timing in seq record

 

Hi Mark,

 

This might be related to Timers expire early · Issue #106 · epics-base/epics-base (github.com) as I think it may use timers for the delay

 

Freddie

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Mark Rivers via Tech-talk
Sent: 03 March 2022 00:35
To: Mark Rivers <rivers at cars.uchicago.edu>
Cc: tech-talk at aps.anl.gov
Subject: RE: Timing in seq record

 

I see the same thing with base 7.0.5.

 

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Mark Rivers via Tech-talk
Sent: Wednesday, March 2, 2022 6:31 PM
To: tech-talk at aps.anl.gov
Subject: Timing in seq record

 

I have the following simple database with a seq record which just writes 1 and 0 to the Shutter record.  There is a delay of $(DELAY) before writing 1 and before writing 0.

 

record(seq,"$(P)OpenCloseShutter") {

    field(PINI, "YES")

    field(DLY0,"$(DELAY)")

    field(DOL0,"1")

    field(LNK0,"$(P)Shutter PP MS")

    field(DLY1,"$(DELAY)")

    field(DOL1,"0")

    field(LNK1,"$(P)Shutter PP MS")

    field(FLNK,"$(P)OpenCloseShutter.PROC CA")

}

 

record(bo, "$(P)Shutter") {

    field(ZNAM, "Done")

    field(ONAM, "Moving")

}

 

If DELAY is 0.1 I see the following with camonitor on Shutter:

 

 

Test:Shutter                   2022-03-02 18:22:24.997849 Moving

Test:Shutter                   2022-03-02 18:22:25.092984 Done

Test:Shutter                   2022-03-02 18:22:25.188102 Moving

Test:Shutter                   2022-03-02 18:22:25.283205 Done

Test:Shutter                   2022-03-02 18:22:25.378332 Moving

Test:Shutter                   2022-03-02 18:22:25.473436 Done

Test:Shutter                   2022-03-02 18:22:25.568547 Moving

Test:Shutter                   2022-03-02 18:22:25.663681 Done

Test:Shutter                   2022-03-02 18:22:25.758885 Moving

Test:Shutter                   2022-03-02 18:22:25.854026 Done

Test:Shutter                   2022-03-02 18:22:25.949228 Moving

 

The period is about 190 ms rather than the expected 200 ms, but not too far off.

 

However, if I set DELAY=0.01 then I see this:

 

Test:Shutter                   2022-03-02 18:25:44.341923 Done

Test:Shutter                   2022-03-02 18:25:44.347055 Moving

Test:Shutter                   2022-03-02 18:25:44.352186 Done

Test:Shutter                   2022-03-02 18:25:44.357367 Moving

Test:Shutter                   2022-03-02 18:25:44.362523 Done

Test:Shutter                   2022-03-02 18:25:44.367682 Moving

Test:Shutter                   2022-03-02 18:25:44.372816 Done

Test:Shutter                   2022-03-02 18:25:44.377965 Moving

Test:Shutter                   2022-03-02 18:25:44.383104 Done

Test:Shutter                   2022-03-02 18:25:44.388263 Moving

Test:Shutter                   2022-03-02 18:25:44.393372 Done

Test:Shutter                   2022-03-02 18:25:44.398496 Moving

Test:Shutter                   2022-03-02 18:25:44.403633 Done

 

The period is 10 ms when it should be 20 ms.  The DELAY appears to be 5 ms, not 10 ms.

 

If I set DELAY=.005 then the Shutter PV has no monitor events.

 

Something seems wrong here, since I know that epicsThreadSleep on Linux is capable of good accuracy down to 100 microseconds or so.

 

This is base 7.0.4 on Centos 7.  Is this expected?

 

Mark

 

 

 

 

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