Experimental Physics and
Industrial Control System

Peter Milne <[email protected]> · Wed, 28 Mar 2012 10:47:11 +0100

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			[email protected]
D-TACQ Solutions Ltd		www.d-tacq.com