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

Subject: Proposed change in asyn - request for comments
From: Mark Rivers <rivers@cars.uchicago.edu>
To: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Cc: Eric Norum <eric@norum.ca>
Date: Mon, 28 May 2012 16:40:20 +0000
Folks,

Eric Norum and I are proposing a change to asyn to enable standard asyn device support to set record timestamps based on time stamp information from an asyn driver.  The change is backwards compatible.  Here is the proposal:

- Add a timeStamp field to the asynUser structure

- Drivers can optionally set the timestamp field in the asynUser that is passed in interface read() operations and in callbacks to device support for input records.

- asyn device support sets the record timestamps based on pasynUser->timeStamp if the following are both true:
  - The record TSE field is set to epicsTimeEventDeviceTime (-2)
  - pasynUser->timeStamp is non-zero

The idea is that the asyn driver can determine the time stamp very close to the time that the I/O operation completed.  The record timestamp can thus be set much closer to the "true" time than if the time is determined with recGblGetTimeStamp later on when the record processes.

Before we commit this change I'd like to hear if this would be useful to others.  I'm particularly interested if this would help the LCLS and other FEL folks who want to timestamp areaDetector and other asyn driver records with the pulse identification.  Are there changes to the proposal that would make it more useful, but still general?

Cheers,
Mark



Replies:
Re: Proposed change in asyn - request for comments Ernest L. Williams Jr.
Re: Proposed change in asyn - request for comments Michael Davidsaver
Re: Proposed change in asyn - request for comments Bruce Hill

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