Experimental Physics and
Industrial Control System

"Szalata, Zenon M." <[email protected]> · Sun, 14 Oct 2007 18:07:08 -0700

Thanks Tim,
In this case, one more difficulty remains.  I think ao is not appropriate because the data to be output typically consists of 10 to 15 bytes of numeric data, 0 value being valid and could be anywhere in the array.  This I think, makes stringout not useful.  Can waveform be used to output array of bytes?  Quick look at the definition of the waveform record tells me that it can only be used for input, I see only INP link there.  What else is there that can handle writing an array of bytes to a device?  Thanks again,
Zen 

-----Original Message-----
From: Tim Mooney [mailto:[email protected]] 
Sent: Sunday, October 14, 2007 5:50 PM
To: Szalata, Zenon M.
Cc: EPICS tech-talk
Subject: Re: genSub

Szalata, Zenon M. wrote:

> I have successfully put together a soft IOC which consists of a number "Soft Channel" type of records.  These are mostly longin, one ot two bo and mbbo, and one genSub.  In the edm companion for this IOC, I have a number of text controls to put new values into all the records with the exception of the genSub record.  There is a Message Button in the edm program which is used to trigger processing of the genSub record,  When genSub is processed it takes the values from all the other records, performs some calculations, creates a string of numeric values and prints the results.  All works fine.
> Next step in the evolution of this learning exercise is to output the calculated result to a GPIB CAMAC crate controller (in this case KS3988).  I do not know how to do that.
> I am using asyn.
> 1. genSub is not part of EPICS nor asyn.  There is no DSET_xx type of definition
>    for it that I can find. 
> 2. In my case I do not need a gpibCmd for it, but it seems to me that I need to
>    have the device( genSub, GPIB_IO, devyyxxxx, "XXXXX") statement, so that I can
>    specify that the output is GPIB_IO...
> What do I need to do to accomplish that?
> I have tried a few combinations and either the IOC generates a linking error or crashes with segmentation fault when the IOC is initialized.  I guess, I need an example showing how to do that.  I see in "myExample" (chapter 2 in EPICS IOC Application Developer's Guide) how to add a use defined "Soft Channel" type record.

You can't use device support with the genSub record.  The record simply lacks the code required to use device support.  You'll have to get the genSub record to write to a record that can have device support, such as an ao record.

> Once I overcome the previous difficulty, I think I will have another problem to solve.  This is what I am worried about.
> 1. When I send a certain combination of numberic values to KS3988, it should be
>    ready to return some data.  That is, sending it some sequence of numbers
>    prepares the crate controller to return some numeric results.
> 2. I am thinking to have a forward link in the genSub record to a waveform record
>    which would be setup to read from the GPIB controller.  Is it guaranteed that
>    the waveform record is processed after the genSub record has sent the command
>    bytes to the controller?  If not, what should I do to assure properly timed
>    execution of the two records?

Yes, If you have an output record that writes to a device and forward links to an input record, the input record will not process until the output record has sent its data.

In view of previous comment, of course, you would in actual practice have the genSub record write (using a PP link) to an ao record (for example), and have the ao record forward link to the waveform record.

> Many thanks in advance,
> Zen

--
Tim Mooney ([email protected]) (630)252-5417 Beamline Controls & Data Acquisition Group Advanced Photon Source, Argonne National Lab.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System