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

Subject: Re: AsynDriver with delayed and async communication
From: Eric Norum via Tech-talk <tech-talk@aps.anl.gov>
To: Joao Afonso <joao.afonso@cern.ch>
Cc: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Wed, 30 Jan 2019 11:13:07 -0800
I have implemented such support using an extra readback thread for devices that send out of order or unsolicited responses.  I’ve not used the callbackRequestDelayed mechanism that you mention — instead the records are set to SCAN=“I/O Intr” and the reader thread just pushes values into the records using the asyn xxxInterrupt->callback() support.


On Jan 30, 2019, at 9:09 AM, Joao Afonso via Tech-talk <tech-talk@aps.anl.gov> wrote:

2) Use asynDriver:
 - From what I understood, it is possible to stop a callback and send it back to the queue using the 'callbackRequestDelayed()' EPICS function. This, with the help of a state machine, would allow the callback to be executed in two steps, and not block callbacks from other users. It seems to be similar to the approach taken on the asynDriver '<top>/testApp'.
 - In this case, a separate thread would receive all the results, and store them in a place where the callbacks would read later.
 - However, I don't know if it is fully compatible with asynDriver, or if asynDriver provides a better mechanism for this type of interaction. Is there a better approach?


References:
AsynDriver with delayed and async communication Joao Afonso via Tech-talk

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