Experimental Physics and
Industrial Control System

Bruce Hill <[email protected]> · Fri, 16 Sep 2011 16:50:43 -0700

Hi Yong,
Thanks for the suggestions.   I was ok with converting my RMS to int for
this app, but now that I'm calculating other functions as well, I made
my RMS PV a  double.


Thanks also for the example, as I'd missed that aSub supports scalar

outputs.



waveProc looks interesting. It has stdDev instead of RMS, but it has

quite

a few other functions which our community may want, so I'll look into adding
that module to our system.

I still think we should either update the aSubRecord documentation to note

that the return value is treated as an error by the aSubRecord

processing routine,

or modify the source to change the behaviour.

Regards,
- Bruce

On 09/15/2011 06:59 AM, Hu, Yong wrote:

Hi Bruce,

If you look through aSubRecord.h, the data type of val field is
epicsInt32. I think RMS, mean, etc. are usually double. In this case,

'prec->val = do_sub(prec)' might not work well.



However, you don't need to make any change on aSubRecord.c. There're
many ways to process waveform/array data(RMS, Max, Min, Sum, data
fitting, FFT, etc.) using aSub record. As the wiki [1] says, aSub has
array-valued input and output fields. In your aSub record, you can use
one input link(i.e. INPA) for your waveform record, then use multiple
output fields (i.e. OUTA, OUTB, etc.) for the processed data(i.e. VALA
for average, VALB for Max, etc.). Here's one example from EPICS driver

for GE ICS-710 digitizer [2] I've been working on.



record(waveform,"${PREFIX}VoltWf-I")
{
   field(SCAN,"I/O Intr")
   field(DESC,"voltage waveform data")
   field(DTYP,"ics710")
   field(NELM,"${NELM}")
   field(FTVL,"DOUBLE")
   field(INP,"@C${CARD} S${CHANNEL} WVOL")
   field(PREC,"6")
   field(EGU,"V")
   #forward link to aSub record to process waveform data: mean, min,
max, rms, integral, std, etc. ;
   field(FLNK,"${PREFIX}VoltWf-aSub_")
}

#see ics710ProcessWfAsub.cpp: process the waveform record: mean, min,
max, integral(sum), std(RMS noise), etc. ;
record(aSub,"${PREFIX}VoltWf-aSub_")
{
    field (DESC,"process waveform data")
    field (INAM,"ics710InitWfAsub")
    field (SNAM,"ics710ProcessWfAsub")
    field (INPA, "${PREFIX}VoltWf-I")
    field (FTA, "DOUBLE")
    field (NOA, "${NELM}")
    field (OUTA, "${PREFIX}AveVolt-I PP")
    field (FTVA, "DOUBLE")
    field (NOVA, "1")
    field (OUTB, "${PREFIX}MaxVolt-I PP")
    field (FTVB, "DOUBLE")
    field (NOVB, "1")
    field (OUTC, "${PREFIX}MinVolt-I PP")
    field (FTVC, "DOUBLE")
    field (NOVC, "1")
    field (OUTD, "${PREFIX}SumVolt-I PP")
    field (FTVD, "DOUBLE")
    field (NOVD, "1")
    field (OUTE, "${PREFIX}StdVolt-I_ PP")
    field (FTVE, "DOUBLE")
    field (NOVE, "1")

}



record(ai,"${PREFIX}AveVolt-I")
{
   field(DESC,"averaged voltage")
   field(INP,"${PREFIX}VoltWf-aSub_.VALA")
   field(PREC,"6")
   field(EGU,"V")
}
...


Here's the simplified source code:

...

static double *pwfData;
static long ics710InitWfAsub(aSubRecord *precord,processMethod process)
{
    if (Initialized) return (0);
    if (NULL == (pwfData = (double *)malloc(precord->noa *
sizeof(double))))   return -1;
    else Initialized = TRUE;
    return(0);
}

static long ics710ProcessWfAsub(aSubRecord *precord)
{
//get array data from input link
    memcpy(pwfData, (double *)precord->a, precord->noa *
sizeof(double));
//data processing on pwfData: std, max, min, fft,...
    ...

    /* put the calculated results into ai records*/
    *(double *)precord->vala = ave;
     ...



 return(0);

}

You might think about using EPICS waveProc [3] for processing array.

Good luck!

Yong

[1]

http://www.aps.anl.gov/epics/wiki/index.php/RRM_3-14_Array_Subroutine

[2]

http://epics.hg.sourceforge.net/hgweb/epics/ics710/file/1f6166468c9c/ics

710App/Db/ics710Channel.db



http://epics.hg.sourceforge.net/hgweb/epics/ics710/file/1f6166468c9c/ics

710App/src/ics710ProcessWfAsub.cpp

[3] http://www.aps.anl.gov/epics/modules/soft/waveProc/index.html




-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Bruce Hill
Sent: Thursday, September 15, 2011 1:05 AM
To: Techtalk
Subject: aSubRecord VAL field

I have an application where I'm using aSub to calculate RMS for an
array.
It worked fine when I just wanted to generate the RMS value and return
it

via VAL. However, when I extended the routine to also calculate MIN

and MAX

and return them via OUT links, I found that if my SNAM routine returns a

non-zero value, it's treated as a status error and aSubRecord.c

suppresses the

updates of the output links.

I'm getting around it by returning zero from my SNAM routine and
returning
all my results via OUT link waveforms, but it seems we should either
update
the wiki documentation to note this behaviour or modify aSubRecord.c to
not
treat the SNAM return value as an error code.

i.e.

--- rec/aSubRecord.c    (revision 7338)
+++ rec/aSubRecord.c    (working copy)
@@ -269,8 +269,7 @@
     }



 if (!status) {

-        status = do_sub(prec);
-        prec->val = status;
+        prec->val = do_sub(prec);
     }

I'm running base version 3.14.12.
Comments welcome.

Thanks,
- Bruce





--
Bruce Hill
Member Technical Staff
SLAC National Accelerator Lab
2575 Sand Hill Road M/S 10
Menlo Park, CA  94025



Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System