Re: How to output a calculated waveform using aSub record in EPICS

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

I think you can do this with an aCalcout record with no C code.

Mark

---

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Varuna Crishan Meddage via Tech-talk <tech-talk at aps.anl.gov>
Sent: Thursday, April 2, 2026 2:53 PM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: How to output a calculated waveform using aSub record in EPICS

 

Hi,

I want to perform some operation using elements in 3 EPICS records, where one record is a waveform and other two are subArrays. (As indicated below)

========================= Waveform record ================================

record(waveform, "$(acc):$(sys)_$(group):acq2106_current")

{

  field(INP, {pva:{pv:"acq2106_347:1:AI:WF:17", "proc": "CP"}})

  field(FTVL, "DOUBLE")

  field(NELM, "4096")

  field(SCAN, "1 second")

  }

======================== subArrary record 1 ==============================

record(subArray, "$(acc):$(sys)_$(group):acq2106_calibvalue_eslo") {

    field(DESC, "Extracted subset of WAVE")

    field(INP, {pva:{pv:"acq2106_347:1:AI:CAL:ESLO", "proc":"CP"}})

    field(FTVL, "DOUBLE")     

    field(MALM, "10")        

    field(NELM, "1")         

    field(INDX, "17")

    field(SCAN, "1 second")

}

==================== subArray record 2 ================================

record(subArray, "$(acc):$(sys)_$(group):acq2106_calibvalue_eoff") {

    field(DESC, "Extracted subset of WAVE")

    field(INP, {pva:{pv:"acq2106_347:1:AI:CAL:EOFF", "proc":"CP"}})

    field(FTVL, "DOUBLE")     

    field(MALM, "10") # If set this to 1, does not return the expected outcome       

    field(NELM, "1")         

    field(INDX, "17")

    field(SCAN, "1 second")

}

===================================================================

Here I am trying to loop over every element of the wave form and multiply each element by the single element of the subarray 1 and add the only element in the subarray 2 to the result (subarray 1 and subarray 2 have only one element)

So to achieve this goal, I created  aSub record (pasted below) and inside that I called the function named calibWave.c (pasted below).

========================== calibWave.c ==============================

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

#include <ctype.h>

#include <unistd.h>

#include <stdio.h>

#include <math.h>

#include <ncurses.h>

#include "dbDefs.h"

#include "registryFunction.h"

#include "epicsExport.h"

#include "epicsExit.h"

#include "epicsThread.h"

#include "iocsh.h"

#include "aSubRecord.h"

static double calibWave(aSubRecord *prec)

{

 double *in  = (double*)prec->a;

 double *out = (double*)prec->vala;

 double eslo = *(double*)prec->b;

 double eoff = *(double*)prec->c;

 int n = prec->nea;

 for(int i = 0; i < n; i++) {

     out[i] = in[i] * eslo + eoff;

 }

 return 0;

}

EpicsRegisterFunction(calibWave);

====================================================================

==================== aSub record for the calculated waveform ===============

record(aSub, "$(acc):$(sys)_$(group):acq2106_calib_current") {

    field(INPA, "$(acc):$(sys)_$(group):acq2106_current CPP")

    field(INPB, "$(acc):$(sys)_$(group):acq2106_calibvalue_eslo CPP")

    field(INPC, "$(acc):$(sys)_$(group):acq2106_calibvalue_eoff CPP")

    field(FTA, "DOUBLE")

    field(FTB, "DOUBLE")

    field(FTC, "DOUBLE")

    field(NOA, "4096")

    field(NOB, "1")

    field(NOC, "1")

    field(FTVA, "DOUBLE")

    field(NOVA, "4096")

    field(SNAM, "calibWave")  

    field(SCAN, "1 second")

    field(PREC, 5)

}

===================================================================

But this aSub only returns a single number instead of a waveform (as indicated below)

=================== pvxget for asub record ==========================

PIP2:CTRL_MPS:acq2106_calib_current

    value int32_t = 4090

    alarm.severity int32_t = 0

    alarm.status int32_t = 0

    alarm.message string = ""

    timeStamp.secondsPastEpoch int64_t = 1775158362

    timeStamp.nanoseconds int32_t = 7852163

    timeStamp.userTag int32_t = 0

    display.limitLow int32_t = 0

    display.limitHigh int32_t = 0

    display.description string = ""

    display.units string = ""

    display.form.index int32_t = 0

    display.form.choices string[] = {7}["Default", "String", "Binary", "Decimal", "Hex", "Exponential", "Engineering"]

    control.limitLow int32_t = -2147483648

    control.limitHigh int32_t = 2147483647

    valueAlarm.lowAlarmLimit int32_t = 0

    valueAlarm.lowWarningLimit int32_t = 0

    valueAlarm.highWarningLimit int32_t = 0

    valueAlarm.highAlarmLimit int32_t = 0

====================================================================

I am not sure, where the problem happens (either calibWave.C function or aSub record ) or not sure whether aSub record is the best solution to achieve this goal.

Any help to debug this is highly appreciated.

============================================== Additional information ==============================================================

I am not 100% the way I created the custom calibWave. Function. Following are the steps, I followed.

1.  First I created a .dbd file named waveCalib.dbd inside "src" directory and added the function name

************************************** content of waveCalib.dbd ********************************************

Function(calibWave)

***********************************************************************************************************

2.  Modified Make file at "src" directory by adding the commented lines

******************************************** Makefile content at src directory *******************************

TOP=../..

include $(TOP)/configure/CONFIG

#----------------------------------------

#  ADD MACRO DEFINITIONS AFTER THIS LINE

#=============================

#=============================

# Build the IOC application

PROD_IOC = XRM

# XRM.dbd will be created and installed

DBD += XRM.dbd

# XRM.dbd will be made up from these files:

XRM_DBD += base.dbd

# modified menuScan.dbd to include FNAL scan rates

XRM_DBD += menuScan.dbd

# waveCalib.dbd including the calibWave.c function

XRM_DBD += waveCalib.dbd  // ***********************************Addition

# Include dbd files from all support applications:

XRM_DBD += pvxsIoc.dbd

XRM_DBD += iocAdmin.dbd

XRM_DBD += aliveRecord.dbd

XRM_DBD += sseqRecord.dbd

XRM_DBD += sscanSupport.dbd

XRM_DBD += acnetPV.dbd

XRM_DBD += tcast.dbd

XRM_DBD += reccaster.dbd

XRM_DBD += asSupport.dbd

XRM_DBD += caPutJsonLog.dbd

XRM_DBD += sCalcoutRecord.dbd

XRM_DBD += calcSupport.dbd

XRM_DBD += aCalcoutRecord.dbd

# Add all the support libraries needed by this IOC

XRM_LIBS += devIocStats

XRM_LIBS += alive

XRM_LIBS += acnetPV

XRM_LIBS += calc

XRM_LIBS += pv seq

XRM_LIBS += sscan

XRM_LIBS += tcast

XRM_LIBS += reccaster

XRM_LIBS += autosave

XRM_LIBS += caPutLog

XRM_LIBS += pvxsIoc pvxs

# XRM_registerRecordDeviceDriver.cpp derives from XRM.dbd

XRM_SRCS += XRM_registerRecordDeviceDriver.cpp

XRM_SRCS += CopyArray.c

XRM_SRCS += calibWave.c // *************************** Addition

# Build the main IOC entry point on workstation OSs.

XRM_SRCS_DEFAULT += XRMMain.cpp

XRM_SRCS_vxWorks += -nil-

# Add header files:

#USR_INCLUDES += -I/usr/include

#

# Finally link to the EPICS Base libraries

XRM_LIBS += $(EPICS_BASE_IOC_LIBS)

#===========================

include $(TOP)/configure/RULES

#----------------------------------------

#  ADD RULES AFTER THIS LINE

USR_CXXFLAGS_DEFAULT += -fno-operator-names -pedantic

USR_CXXFLAGS += -W -Wall

**************************************************************************************************************

After compilng the project successfully, I checked the XRM.dbd file at .dbd directory and I can that it contains the line

Function(calibWave)

================================================== End of Additional Information ====================

Thanks

Varuna Meddage