NI DAQCard 6024E Counter Code

• From: Chuck Haines <chaines_at_gmail.com>
• Date: Mon, 26 Jul 2004 15:14:55 -0400

For the benefit of all who have asked (since I've gotten a few
emails), here is code that demonstrates the use of the counter's on a
National Instruments DAQCard 6024E.  This is only test code, so it's
not efficient, I'm simply showing you how to use it.

<begin code snippet>
#include<stdio.h>
#include<comedilib.h>
#include<unistd.h>

int main ( int argc, char *argv[] )
{
    comedi_t *card;
    lsampl_t op[2], data = 5, lastData;
    comedi_insn insn;
    unsigned int counter = 4, pfi = 7, counter_chan = 0, pfi_chan = 8;
    int n = 0, i = 0, nError = 0;

    /* open the device */
    card = comedi_open("/dev/comedi0");
    if ( NULL == card )
    {
        printf ( "Error opening comedi card: %s\n", comedi_strerror (
comedi_errno() ) );
        return -1;
    }
    /* lock the subdevice */
    nError = comedi_lock(card, counter);
    if( -1 == nError )
    {
        /* there was an error locking the device, we can continue but
might be unexpected results */
        printf("Error locking subdevice: %s\n",
comedi_strerror(comedi_errno()));
    }

    /* set up PFI8 for input */
    op[0] = COMEDI_INPUT;
    insn.insn = INSN_CONFIG;
    insn.n = 1;
    insn.data = op;
    insn.subdev = pfi;
    insn.chanspec = CR_PACK ( pfi_chan, 0, 0 );
    if ( ( comedi_do_insn ( card, &insn ) ) < 0 )
    {
        printf ( "Error performing insn: %s\n", comedi_strerror (
comedi_errno() ) );
    }

    for ( i = 0; i < 5; i++ )
    {
        switch ( i )
        {
            case 0:
                /* reset all counter settings */
                op[0] = GPCT_RESET;
                n = 1;
                break;
            case 1:
                /* set the source of the counts
                 * if this is counter 0, the external pin is PFI8/GPCT0_SOURCE
                 * if this is counter 1, the external pin is PFI3/GPCT1_SOURCE
                 */
                op[0] = GPCT_SET_SOURCE;
                op[1] = GPCT_EXT_PIN;   /* set to external pin as above */
                /* op[1] = GPCT_INT_CLOCK; */   /* set to the internal clock */
                n = 2;
                break;
            case 2:
                /* set the gate to latch the input to
                 * if this is counter 0, the external latch would be
PFI10/GPCT0_GATE
                 * if this is counter 1, the external latch would be
PFI4/GPCT1_GATE
                 */
                op[0] = GPCT_SET_GATE;
                op[1] = GPCT_NO_GATE;           /* no latch on the gate */
                /* op[1] = GPCT_EXT_PIN; */     /* latch to the
external pin as above */
                n = 2;
                break;
            case 3:
                /* set the direction the counter should count */
                op[0] = GPCT_SET_DIRECTION;
                op[1] = GPCT_UP;                /* increment counter */
                /* op[1] = GPCT_DOWN; */        /* decrement the counter */
                n = 2;
                break;
            case 4:
                /* set the type of counter */
                op[0] = GPCT_SET_OPERATION;
                op[1] = GPCT_SIMPLE_EVENT;      /* count the edges of
the pulse */
                n = 2;
                break;
        }
        insn.insn = INSN_CONFIG;
        insn.n = n;
        insn.data = op;
        insn.subdev = counter;
        insn.chanspec = CR_CHAN ( counter_chan );
        if ( ( comedi_do_insn ( card, &insn ) ) < 0 )
        {
            printf ( "Error performing insn: %s\n", comedi_strerror (
comedi_errno() ) );
        }
    }
    for ( i = 0; i < 31; i ++ )
    {
        /* stop the counter */
        insn.insn = INSN_CONFIG;
        insn.n = 1;
        op[0] = GPCT_DISARM;
        insn.data = op;
        insn.subdev = counter;
        insn.chanspec = CR_CHAN ( counter_chan );
        if ( ( comedi_do_insn ( card, &insn ) ) < 0 )
        {
            printf ( "Error performing insn: %s\n", comedi_strerror (
comedi_errno() ) );
        }
        /* reset the counter to zero */
        insn.insn = INSN_WRITE;
        insn.n = 1;
        op[0] = 0;
        insn.data = op; 
        insn.subdev = counter;
        insn.chanspec = CR_CHAN ( counter_chan );
        if ( ( comedi_do_insn ( card, &insn ) ) < 0 )
        {
            printf ( "Error performing insn: %s\n", comedi_strerror (
comedi_errno() ) );
        }
        /* start the counter */
        insn.insn = INSN_CONFIG;
        insn.n = 1;
        op[0] = GPCT_ARM;
        insn.data = op;
        insn.subdev = counter;
        insn.chanspec = CR_CHAN ( counter_chan );
        if ( ( comedi_do_insn ( card, &insn ) ) < 0 )
        {
            printf ( "Error performing insn: %s\n", comedi_strerror (
comedi_errno() ) );
        }
        sleep ( 2 );
        /* read the count from the counter */
        comedi_data_read ( card, counter, counter_chan, 0, 0, &data );
        printf ( "Counter value: %d\n", data );
        /* do a raw read */
        /*insn.insn = INSN_READ;
        insn.n = 1;
        insn.subdev = counter;
        insn.chanspec = CR_CHAN ( counter_chan );
        if ( ( comedi_do_insn ( card, &insn ) ) < 0 )
        {
            printf ( "Error performing insn: %s\n", comedi_strerror (
comedi_errno() ) );
        }
        printf ( "Raw Counter value: %d\n", insn.data[0] );*/
    }

    return 0;
}
<end code snippet>

Chuck
-- 
Chuck Haines
chaines_at_gmail.com
-------------------------------------------
Tau Kappa Epsilon Fraternity
WPI Class of 2005
-------------------------------------------
AIM: CyberGrex
YIM: CyberGrex_27
ICQ: 3707881
-------------------------------------------

Received on 2004-07-26Z18:14:55