RE: [CA][waveform] how to NELM?

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

I don't have much experience with writing CA clients in C, I mostly use IDL, Java, Python, etc.  Perhaps someone else can help.

Mark

________________________________
From: Pavel Masloff [pavel.masloff@gmail.com]
Sent: Friday, May 11, 2012 9:07 AM
To: Mark Rivers
Cc: EPICS Tech Talk
Subject: Re: [CA][waveform] how to NELM?

Thanks, Mark! It works if I am reading just one PV. But when I am reading 2 PVs - (waveform and NELM), my NELM value is enormously big!!!
How can I read several PVs?

This is my code:

#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "cadef.h"

int main(int argc,char **argv)
{
    int data;         /* NELM */
    chid mychid;

    chid chan;        /* WAVEFORM - file*/
    int status;
    unsigned elementCount, nBytes, i;
    struct dbr_time_char * pTD;
    const dbr_char_t * pValue;

    SEVCHK(ca_context_create(ca_disable_preemptive_callback),"ca_context_create");
    SEVCHK(ca_create_channel("file.NORD",NULL,NULL,10,&mychid),"ca_create_channel failure");
    SEVCHK(ca_pend_io(1.0),"ca_pend_io failure");
    SEVCHK(ca_get(DBR_INT,mychid,(void *)&data),"ca_get failure");
    SEVCHK(ca_pend_io(1.0),"ca_pend_io failure");
    printf("file.NORD: %d\n",data);

    ca_clear_channel ( mychid );
    ca_task_exit ();


    SEVCHK(ca_context_create(ca_disable_preemptive_callback),"ca_context_create");
    status = ca_create_channel ( argv[1], 0, 0, 0, & chan );
    ca_search(argv[1], &chan);
    SEVCHK ( status, "ca_create_channel()" );
    status = ca_pend_io ( 1.0 );
    if ( status != ECA_NORMAL ) {
        fprintf ( stderr, "\"%s\" not found.\n", argv[1] );
        return -1;
    }

    elementCount = ca_element_count ( chan );
    nBytes = dbr_size_n ( DBR_TIME_CHAR, elementCount );
    pTD = ( struct dbr_time_char * ) malloc ( nBytes );
    if ( ! pTD ) {
        fprintf ( stderr, "insufficient memory to complete request\n" );
        return -1;
    }

    status = ca_array_get (DBR_TIME_CHAR, elementCount, chan, pTD );
    SEVCHK ( status, "ca_array_get()" );
    status = ca_pend_io ( 1.0 );
    if ( status != ECA_NORMAL ) {
        fprintf ( stderr, "\"%s\" didnt return a value.\n", argv[1] );
        return -1;
    }

    pValue = & pTD->value;
    for ( i = 0; i < 10; i++ )    printf("%d ", pValue[i]);
    printf("\nTotal size: %d\n", elementCount);
    printf("Timestamp: %d\n", pTD->stamp.nsec);
    ca_clear_channel ( chan );
    free ( pTD );

    return(0);
}






On Fri, May 11, 2012 at 3:42 PM, Mark Rivers <rivers@cars.uchicago.edu<mailto:rivers@cars.uchicago.edu>> wrote:
You can just do a ca_get of record.NELM.
________________________________
From: tech-talk-bounces@aps.anl.gov<mailto:tech-talk-bounces@aps.anl.gov> [tech-talk-bounces@aps.anl.gov<mailto:tech-talk-bounces@aps.anl.gov>] on behalf of Pavel Masloff [pavel.masloff@gmail.com<mailto:pavel.masloff@gmail.com>]
Sent: Friday, May 11, 2012 6:39 AM
To: EPICS Tech Talk
Subject: [CA][waveform] how to NELM?

I am writing a simple CA client in C.
The client reads the waveform record. And I need to know how many elements there are in it (NELM field).
There is a function entitled ca_element_count() which happens to read the NORD field.

Does anybody know how can I get the NELM field ?



--
Best regards,


Pavel Maslov, MS
Controls Engineer at Pulsed power Lab
Efremov Institute for Electro-Physical Apparatus
St. Petersburg, Russia

Mobile: +7 (951) 672 22 19
Landline: +7 (812) 461 01 01



--
Best regards,


Pavel Maslov, MS
Controls Engineer at Pulsed power Lab
Efremov Institute for Electro-Physical Apparatus
St. Petersburg, Russia

Mobile: +7 (951) 672 22 19
Landline: +7 (812) 461 01 01