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<== Date ==> <== Thread ==>

Subject: Re: Change input links run-time in a db
From: Luedeke Andreas <[email protected]>
To: "Pedersen, UK (Ulrik)" <[email protected]>
Cc: [email protected]
Date: Thu, 08 May 2008 16:35:35 +0200
Hi Ulrik,
the problem seems to arise from the fact, that the scalcout writes its VAL field instead of its SVAL field.
I get the error message on the console:


   Illegal Database Request Type PV: result.INP error detected in
   routine: dbPut - database request type is 0

This looks to me like a bug (sorry: undesired feature) of the scalcout record.

I found a strange workaround, maybe some EPICS guru can explains why it works:

   record(scalcout, select) {
     field(DTYP, "Soft Channel")
     field(INPA, "1")
     field(CALC, "PRINTF('wave%d PP',A)")
     field(OOPT, "Every Time")
     field(OUT,  "result.INP CA")
     field(DOPT, "Use CALC")
     field(FLNK, "result.PROC CA")
   }

I just made the OUT link a channel access link and added an FLNK to process the modified waveform record, again an CA is required.
This works, but don't ask me why :)


Of course an INLINK can be as well a DOUBLE (constant) or a string (PV), it's up to the record to decide on what type of data to write.
But I found the same behaviour when first writing to an stringout records VAL field:
it only works if I use CA type OUTLINK _and_ FLNK.



Cheers Andreas

Pedersen, UK (Ulrik) wrote:
Hello,

I'm trying to write a database where a waveform record (DTYP soft) can
have it's INP field changed at run-time to switch between one of two
other waveform records.


Basically I need a sort of multiplexing functionality to let one
waveform record collect the data from one of several other waveform
records. This can be done by changing the INP field of the resulting
waveform record to point to any one of the other waveforms.

When changing the waveform INP field with a dbpf command on the IOC
shell, things work Ok... When changing the INP field with a caput
(client side) in Linux shell, things work Ok...

However, I need to do the switching directly in the database. For this
purpose I am using an sCalcout record to create the string - using the
OUT field of the sCalcout to write to the waveform INP field... - This
doesn't work and I can't figure out why.

Does anyone know what could be the problem with my database (see below)
or have any suggestions how to program this kind of functionality in a
database? (not using genSub records or snl programs...)


record(waveform, wave1) { field(PINI, "YES") field(DTYP, "Soft Channel") field(NELM, "10") field(FTVL, "DOUBLE") }

record(waveform, wave2) {
  field(PINI, "YES")
  field(DTYP, "Soft Channel")
  field(NELM, "10")
  field(FTVL, "DOUBLE")
}

record(scalcout, select) {
  field(DTYP, "Soft Channel")
  field(CALC, "PRINTF('wave%d PP',A)")
  field(OOPT, "Every Time")
  field(OUT, "result.INP PP")
  field(DOPT, "Use CALC")
}

record(waveform, result) {
  field(DTYP, "Soft Channel")
  field(NELM, "10")
  field(FTVL, "DOUBLE")
}


Appriciate any help or suggestions. Thanks.


Ulrik

--------------------------------------------------------------------

  Ulrik Pedersen               phone: +44(0)1235-778580
  Software Engineer            email: [email protected]

      Diamond Light Source Ltd.
      Rutherford Appleton Laboratory,
      Chilton, Didcot
      OxfordShire OX11 0DE

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RE: Change input links run-time in a db Pedersen, UK (Ulrik)
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