Experimental Physics and
Industrial Control System

 

On Mar 5, 2021, at 7:39 PM, Wang, Andrew via Tech-talk <tech-talk at aps.anl.gov> wrote:

So I have a waveform record that allows four numbers to be stored. I tried to use the subArray record to get the ith element from the array. I set the MALM, NELM and INDX fields to be 1, 1, and 2 respectively. However, when I process the subArray record, I get the first element of the array, rather than the third element.

If this is not a viable way to go about it, are there other potential ways to store a scalar from an array in a record aside from using an asub record?

If you don’t need the index to change, there is a simpler way to extract a specific element from an array, and the latest EPICS release 7.0.5 makes that even better. The array channel filter lets you specify the subarray as part of a PV name; prior to 7.0.5 you had to explicitly use the CA protocol for it, but in 7.0.5 this syntax now works with DB links as well. 

An ai record retrieving the 2nd element from a waveform record named wf would have have an INP field something like this:

field(INP, "wf.[1] CA")

In 7.0.5 that can become this:

HTH,

- Andrew