Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Wed, 8 Aug 2018 11:36:40 +0200

Hello Ahmad,

StreamDevice can read variable length arrays. You need to set NELM to

the maximum number of elements. StreamDevice will set NORD to the number

of elements found. Modern EPICS versions are able to handle variable

length arrays when the client sets up a monitor using 0 for the

requested array length. It should then use the current NORD value.

However StreamDevice reads arrays in rows, not columns. If you have a

waveform record and use { separator=" "; in "%i"; }, stream device will

repeat the "%i" up to NELM times (or until end of line, until the

separator is not found any more or until the conversion fails).

But in your case it seems you have interlaced arrays:

a[0] b[0] c[0] d[0] e[0] f[0] g[0] h[0]
a[1] b[1] c[1] d[1] e[1] f[1] g[1] h[1]
a[2] b[2] c[2] d[2] e[2] f[2] g[2] h[2]

So StreamDevice will see the first elements of each array, not all

elements of one array.

StreamDevice would be able to read rows with variable length:

a[0] a[1] a[2] ...
b[0] b[1] b[2] ...
c[0] c[1] c[2] ...
d[0] d[1] d[2] ...
e[0] e[1] e[2] ...
f[0] f[1] f[2] ...
g[0] g[1] g[2] ...
h[0] h[1] h[2] ...

Also this will not help:
in "%i %*i %*i %*i %*i %*i %*i %*i";

Because the first %i reads all the elements in the row before even

parsing the first %*i.

I need a new syntax to specify interlaces arrays.

The only way I can think to at the moment is to pre-process the input

with a regsub which removed the "other" array elements from the input,

but I need to test that first. It may be quite inefficient. Thus if <N>

becomes huge (say >1000) parsing may be quite slow.

I will tell you soon if I can find a solution...

Dirk

On 08.08.2018 11:09, Abdalla  Ahmad wrote:

Hi

We are trying to implement an IOC for the Libera Spark BPM using stream

device, one of the tricky commands for example is TBT_IQ <N> which

returns a variable-length buffer of turn-by-turn data. An example:

TBT_IQ 3

22 -36  19 -38  16 -31  -3  -31

39 -212 29 -212 26 -163 -37 -150

39 -175 36 -176 27 -133 -21 -129

As you can see the output is an array of fixed columns (IQ parameters)

and variable rows (waveforms length). In a single line you can easily

parse and skip any value, but in this format we have two problems:

1.Is it possible to parse variable number of IN commands in the protocol

file?

2.Variable "IN" commands mean variable waveform length, is this possible

in EPICS?

Best Regards,

Abdalla Ahmad

Control Engineer

SESAME

Allan, Jordan.

Tel: (+962-5) 3511348 , ext. 265

Fax: (+962-5) 3511423

Mob: (+962-7)88183296

www.sesame.org.jo <http://www.sesame.org.jo/>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System