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Subject: Re: Undefined Timestamp on Motor Record
From: Torsten Bögershausen via Tech-talk <tech-talk@aps.anl.gov>
To: Dominic Oram - UKRI STFC <dominic.oram@stfc.ac.uk>, "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Fri, 16 Aug 2019 08:44:34 +0200


On 15/08/19 19:16, Dominic Oram - UKRI STFC via Tech-talk wrote:
Hello,

I'm in the process of writing a model 3 motor driver using version 6-11 of the motor record.

I have found some unexpected behaviour on initialisation if the driver has no device connected.

It appears the motor stays in the following state unless a parameter is updated at some point after initialisation (I'm not sure when):

caget -a MOTOR
MOTOR        <undefined> 0

If I have no device connected I set motorStatusCommsError_ to 1 on the first call to poll(). However, because all subsequent calls to poll() do not change any parameters I stay in the above state. I would instead expect to see something like:

caget -a MOTOR
MOTOR        2019-08-15 15:57:41.931650 0 COMM INVALID

as in the undefined timestamp situation it's not obvious to users that there is a comm error.

Setting motorStatusCommsError_ to 1 at some time after initialisation does give me the expected state.

Is this actually expected behaviour?
May be, may be not.
My understanding is, that all EPICS records stay in "undefined" state (UDF) until the device support is able to talk to the device.
In that sense the "undefined" state is OK.
(And this is what we do with motors here at ESS,
 never connected -> undefined.)

> Do other people see something similar?
Yes, fully reproducible here.
I think that easiest solution is to do a workaround like this:

  status = initialPollInternal();
  if (status != asynSuccess) {
    setIntegerParam(pC_->motorStatusCommsError_, 0);
    setIntegerParam(pC_->motorStatusCommsError_, 1);
  }


Thanks,

Dominic Oram
Senior Software Engineer
Experimental Controls
ISIS Neutron and Muon Source


Replies:
RE: Undefined Timestamp on Motor Record Dominic Oram - UKRI STFC via Tech-talk
References:
Undefined Timestamp on Motor Record Dominic Oram - UKRI STFC via Tech-talk

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