RE: CA and data acquisition array with variable length in waveform record)

["Mark Rivers" <rivers@cars.uchicago.edu>]

One way to do this is to use caget(), which can explicitly read a limited amount of data.
 
This is what I have used for reading image data in my new areaDetector software client.
 
There are 3 ancillary PVs.  xSize, ySize, and frameCounter.  When frameCounter increments (new data available) the client does a caget to read (xSize*ySize) pixels.
 
Mark
 

________________________________

From: tech-talk-bounces@aps.anl.gov on behalf of Liyu, Andrei V
Sent: Wed 10/29/2008 7:54 PM
To: tech-talk@aps.anl.gov
Subject: CA and data acquisition array with variable length in waveform record)



Hi, 

I would like to use EPICS for one system but there is one problem where I can't come to correct solution. 
Data acquisition system gets data array. Array length always changes. For example, first measurement has 2000 length array. Next measurement has 50000 length array. Then 2002, 1500, 51000, and so on. 

I can create waveform record with 100000 length that will satisfy max points in array. When client subscribes it must set counts of data array. And I, definitely, don't want to transfer 100000 data array each time.

Have anyone solved this? 

Thanks, Andrei.