Extract a column of data from 2D Waveform Record

[Peter Milne <peter.milne@d-tacq.com>]

The ACQ196 multi-channel digitizer includes an embedded microprocessor 
and EPICS IOC, and in normal operation outputs a Waveform Record per 
channel on a relaxed schedule, 1Hz typical.

The data from the hardware is a 2D array in [sample][channel] order, and 
embedded software takes care of extracting ("channelizing") the data so 
that each waveform record is a 1D array   eg CH01[sample].

Now we have a requirement to run this at higher pulse rates, up to 60Hz. 
The embedded software will not be able to channelize the raw data at 
this rate, although it should be possible to present a single Waveform 
Record per pulse containing the 2D data.

My question is how to handle this 2D record in a client and/or soft IOC 
running on another host?.

The client software needs to be able to take a slice [:][ch].

Maybe it's quite easy to do this outside the IOC (eg with Python Channel 
access), but ideally it would happen inside an IOC so that it's 
completely transparent to a client. The Subarray record is an obvious 
choice, but it appears to take a contiguous block of data, there doesn't 
seem to be a concept of a stride value.

eg assuming the Waveform Record refers to data
[samples][channels] with dimension (typical) [1024][96], the extract 
routine needs to run through the data set with a stride of 96.

It looks like subarray could be used to extract [sample-N][:] but not 
the required [:][channel].

Any suggestions welcome.

Thanks


Peter.




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Peter Milne			Peter.Milne@d-tacq.com
D-TACQ Solutions Ltd		www.d-tacq.com