Experimental Physics and
Industrial Control System

Hi Patrick,

 

The standard asyn device support for output records will do that if you set the info tag asyn:READBACK=1.  If you write an asyn driver then you can use this standard asyn device support, and not have to worry about how to do it.  If you are not using an asyn driver then you can use this code as an example (e.g. asyn/devEpics/devAsynInt32.c).

 

This support is documented here:

https://epics.anl.gov/modules/soft/asyn/R4-32/asynDriver.html

 

It says:

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Callback updates for output records

Beginning in asyn R4-26 support was added for updating output records from driver interrupt callbacks. This feature allows output records to reflect changes in the underlying hardware that are caused by manual front-panel operation, changes caused by another output record, etc.

By default output records do not update when a driver does interrupt callbacks. However, if the following info tag is added for a record in the database file then callbacks will be enabled and the output record will be updated whenever the driver does a callback for that value.
info(asyn:READBACK, "1")
If the value of the info tag is 0 or if the info tag is not present then updates of output records on interrupt callbacks are disabled.

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Cheers,

Mark