RE: calling the output of one record into another record

[Mark Rivers <rivers@cars.uchicago.edu>]

Hi Ana,

 

If you are new to EPICS then I suggest that you not use the devGPIB support that you appear to be using, but rather use the StreamDevice support.  devGPIB is obsolete and is not being developed any more.  We still support it for existing applications, but it really should not be used for new applications.

 

Mark

 

 

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Ana Malagon
Sent: Wednesday, January 14, 2015 1:32 PM
To: tech-talk@aps.anl.gov
Subject: calling the output of one record into another record

 

Hi,

 

Sorry, this is a newbie Epics question: I'm working on making an IOC for a fieldfox network analyzer (model KT-N9918A) and need to cut off the number of values returned in a 'read measurement' command based on the number of points in the measurement, but I'm not sure how to go about doing this.

 

I have one record to store the number of points in the measurement, and another record that reads in the measurement values - how would I go about incorporating the number of points in the 'read measurement' record?

 

 

Here is how I've defined the read measurement command:

 /* Param 18 -- Read S21 Format: (Re,Im) dB */

    {&DSET_WF, GPIBREAD, IB_Q_HIGH, ":CALC1:PAR1:DEF S21;:CALC1:PAR1:SEL;:CALC1\

:SEL:DATA:SDAT?", NULL, 0, 1E6, readWF, 0, 0, NULL, NULL, NULL}

and here is the query of the points:

    /* Param 21 - Get Points in Sweep */

    {&DSET_AI, GPIBREAD, IB_Q_HIGH, ":SENS1:SWE:POIN?", NULL, 0, 100, readData, 0, 0, N\

ULL, NULL, NULL},

where the conversion function readWF is defined as:

static int readWF(struct gpibDpvt *pdpvt,int P1, int P2, char**P3) {

  struct waveformRecord *pwf=(struct waveformRecord *)pdpvt->precord;

  asynUser *pasynUser = pdpvt->pasynUser;

  double* value = (double *)pwf->bptr;

  const char* cpymsg = pdpvt->msg;

  double data;

  int n;

  pwf->nord=0;

  while ((pwf->nord < pwf->nelm) && sscanf(cpymsg,"%lE,%n",&data,&n)==1) {

    if (P1==1) data/=1E6;

    if (P1==2 && (pwf->nord==0 || pwf->nord==1)) data/=1E6;

    memcpy(value+pwf->nord,&data,sizeof(double));

    pwf->nord++;

    cpymsg+=n;

       asynPrint(pasynUser,ASYN_TRACE_FLOW,"(NORD,VAL) : (%i,%E)\n",pwf->nord,data);   \

  }

  if (pwf->nord == 0) return -1;

  pwf->udf = 0;

  return 0;

}

the readData conversion function is:

 

static int readData(struct gpibDpvt *pdpvt,int P1, int P2, char**P3) {

  struct aiRecord *pai=(struct aiRecord *)pdpvt->precord;

printf("got: %s\n",pdpvt->msg);

  double meas =(double)atof(pdpvt->msg);

  pai->val = meas;

  pai->udf = 0;

  return 0;

}

and the database definition entry for the read measurement comand is below, where NELM was defined to be 2x the maximum number of points one can request in a measurement:

record(waveform, "$(P):S21")

{

    field(DESC, "S21 (Re,Im)")

    field(EGU,"dB")

    field(SCAN, "Passive")

    field(NELM, "20002")

    field(DTYP, "fieldfox")

    field(FTVL, "DOUBLE")

    field(INP,  "#L$(L) A$(A) @18")

    field(FLNK, "$(P):FREQ")

    field(DISV, "0")

    field(SDIS, "$(P):OPC.VAL PP")

}

 

The reason I need to cut off the values is because the current syntax in the read measurement command not only returns the measurement data but also the x-axis values, which I don't want.

 

Sorry again for the very basic question, and thanks!

 

Ana Malagon