comedilib/demo/ao_waveform.c

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/*
 * Asynchronous Analog Output Example
 * Part of Comedilib
 *
 * Copyright (c) 1999,2000 David A. Schleef <ds@schleef.org>
 *
 * This file may be freely modified, distributed, and combined with
 * other software, as long as proper attribution is given in the
 * source code.
 */

/*
 * Requirements: Analog output device capable of
 *    asynchronous commands.
 *
 * This demo uses an analog output subdevice with an
 * asynchronous command to generate a waveform.  The
 * demo hijacks for -n option to select a waveform from
 * a predefined list.  The default waveform is a sine
 * wave (surprise!).  Other waveforms include sawtooth,
 * square, triangle and cycloid.
 *
 * The function generation algorithm is the same as
 * what is typically used in digital function generators.
 * A 32-bit accumulator is incremented by a phase factor,
 * which is the amount (in radians) that the generator
 * advances each time step.  The accumulator is then
 * shifted right by 20 bits, to get a 12 bit offset into
 * a lookup table.  The value in the lookup table at
 * that offset is then put into a buffer for output to
 * the DAC.
 *
 * [ Actually, the accumulator is only 26 bits, for some
 * reason.  I'll fix this sometime. ]
 *
 */

#include <stdio.h>
#include <comedilib.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <getopt.h>
#include <ctype.h>
#include <math.h>
#include <string.h>
#include "examples.h"


/* frequency of the sine wave to output */
double waveform_frequency       = 10.0;

/* peak-to-peak amplitude, in DAC units (i.e., 0-4095) */
double amplitude                = 4000;

/* offset, in DAC units */
double offset                   = 2048;

/* This is the size of chunks we deal with when creating and
   outputting data.  This *could* be 1, but that would be
   inefficient */
#define BUF_LEN 0x8000

int external_trigger_number = 0;

sampl_t data[BUF_LEN];

void dds_output(sampl_t *buf,int n);
void dds_init(double waveform_frequency, double update_frequency, int fn);

void dds_init_sine(void);
void dds_init_pseudocycloid(void);
void dds_init_cycloid(void);
void dds_init_ramp_up(void);
void dds_init_ramp_down(void);
void dds_init_triangle(void);
void dds_init_square(void);
void dds_init_blancmange(void);

static void (* const dds_init_function[])(void) = {
        dds_init_sine,
        dds_init_ramp_up,
        dds_init_ramp_down,
        dds_init_triangle,
        dds_init_square,
        dds_init_cycloid,
        dds_init_blancmange,
};

#define NUMFUNCS        (sizeof(dds_init_function)/sizeof(dds_init_function[0]))

int main(int argc, char *argv[])
{
        comedi_cmd cmd;
        int err;
        int n,m;
        int total=0;
        comedi_t *dev;
        unsigned int chanlist[16];
        unsigned int maxdata;
        comedi_range *rng;
        int ret;
        struct parsed_options options;
        int fn;

        init_parsed_options(&options);
        options.subdevice = -1;
        options.n_chan = 0;     /* default waveform */
        parse_options(&options, argc, argv);

        /* Use n_chan to select waveform (cheat!) */
        fn = options.n_chan;
        if(fn < 0 || fn >= NUMFUNCS){
                fn = 0;
        }

        /* Force n_chan to be 1 */
        options.n_chan = 1;

        if(options.value){
                waveform_frequency = options.value;
        }

        dev = comedi_open(options.filename);
        if(dev == NULL){
                fprintf(stderr, "error opening %s\n", options.filename);
                return -1;
        }
        if(options.subdevice < 0)
                options.subdevice = comedi_find_subdevice_by_type(dev, COMEDI_SUBD_AO, 0);

        maxdata = comedi_get_maxdata(dev, options.subdevice, options.channel);
        rng = comedi_get_range(dev, options.subdevice, options.channel, options.range);

        offset = (double)comedi_from_phys(0.0, rng, maxdata);
        amplitude = (double)comedi_from_phys(1.0, rng, maxdata) - offset;

        memset(&cmd,0,sizeof(cmd));
        cmd.subdev = options.subdevice;
        cmd.flags = CMDF_WRITE;
        cmd.start_src = TRIG_INT;
        cmd.start_arg = 0;
        cmd.scan_begin_src = TRIG_TIMER;
        cmd.scan_begin_arg = 1e9 / options.freq;
        cmd.convert_src = TRIG_NOW;
        cmd.convert_arg = 0;
        cmd.scan_end_src = TRIG_COUNT;
        cmd.scan_end_arg = options.n_chan;
        cmd.stop_src = TRIG_NONE;
        cmd.stop_arg = 0;

        cmd.chanlist = chanlist;
        cmd.chanlist_len = options.n_chan;

        chanlist[0] = CR_PACK(options.channel, options.range, options.aref);
        //chanlist[1] = CR_PACK(options.channel + 1, options.range, options.aref);

        dds_init(waveform_frequency, options.freq, fn);

        dump_cmd(stdout,&cmd);

        err = comedi_command_test(dev, &cmd);
        if (err < 0) {
                comedi_perror("comedi_command_test");
                exit(1);
        }

        err = comedi_command_test(dev, &cmd);
        if (err < 0) {
                comedi_perror("comedi_command_test");
                exit(1);
        }

        if ((err = comedi_command(dev, &cmd)) < 0) {
                comedi_perror("comedi_command");
                exit(1);
        }

        dds_output(data,BUF_LEN);
        n = BUF_LEN * sizeof(sampl_t);
        m = write(comedi_fileno(dev), (void *)data, n);
        if(m < 0){
                perror("write");
                exit(1);
        }else if(m < n)
        {
                fprintf(stderr, "failed to preload output buffer with %i bytes, is it too small?\n"
                        "See the --write-buffer option of comedi_config\n", n);
                exit(1);
        }
        printf("m=%d\n",m);

        ret = comedi_internal_trigger(dev, options.subdevice, 0);
        if(ret < 0){
                perror("comedi_internal_trigger\n");
                exit(1);
        }

        while(1){
                dds_output(data,BUF_LEN);
                n=BUF_LEN*sizeof(sampl_t);
                while(n>0){
                        m=write(comedi_fileno(dev),(void *)data+(BUF_LEN*sizeof(sampl_t)-n),n);
                        if(m<0){
                                perror("write");
                                exit(0);
                        }
                        printf("m=%d\n",m);
                        n-=m;
                }
                total+=BUF_LEN;
                //printf("%d\n",total);
        }

        return 0;
}



#define WAVEFORM_SHIFT 16
#define WAVEFORM_LEN (1<<WAVEFORM_SHIFT)
#define WAVEFORM_MASK (WAVEFORM_LEN-1)


sampl_t waveform[WAVEFORM_LEN];

unsigned int acc;
unsigned int adder;

void dds_init(double waveform_frequency, double update_frequency, int fn)
{
        adder = waveform_frequency / update_frequency * (1 << 16) * (1 << WAVEFORM_SHIFT);

        (*dds_init_function[fn])();
}

void dds_output(sampl_t *buf,int n)
{
        int i;
        sampl_t *p=buf;

        for(i=0;i<n;i++){
                *p=waveform[(acc>>16)&WAVEFORM_MASK];
                p++;
                acc+=adder;
        }
}

/* Defined for x in [0,1] */
static inline double triangle(double x)
{
        return (x > 0.5) ? 1.0 - x : x;
}

void dds_init_sine(void)
{
        int i;
        double ofs = offset;
        double amp = 0.5 * amplitude;

        if(ofs < amp){
                /* Probably a unipolar range.  Bump up the offset. */
                ofs = amp;
        }
        for(i=0;i<WAVEFORM_LEN;i++){
                waveform[i]=rint(ofs+amp*cos(i*2*M_PI/WAVEFORM_LEN));
        }
}

/* Yes, I know this is not the proper equation for a
   cycloid.  Fix it. */
void dds_init_pseudocycloid(void)
{
        int i;
        double t;

        for(i=0;i<WAVEFORM_LEN/2;i++){
                t=2*((double)i)/WAVEFORM_LEN;
                waveform[i]=rint(offset+amplitude*sqrt(1-4*t*t));
        }
        for(i=WAVEFORM_LEN/2;i<WAVEFORM_LEN;i++){
                t=2*(1-((double)i)/WAVEFORM_LEN);
                waveform[i]=rint(offset+amplitude*sqrt(1-t*t));
        }
}

void dds_init_cycloid(void)
{
        enum { SUBSCALE = 2 };  /* Needs to be >= 2. */
        int h, i, ni;
        double t, x, y;

        i = -1;
        for (h = 0; h < WAVEFORM_LEN * SUBSCALE; h++){
                t = (h * (2 * M_PI)) / (WAVEFORM_LEN * SUBSCALE);
                x = t - sin(t);
                ni = (int)floor((x * WAVEFORM_LEN) / (2 * M_PI));
                if (ni > i) {
                        i = ni;
                        y = 1 - cos(t);
                        waveform[i] = rint(offset + (amplitude * y / 2));
                }
        }
}

void dds_init_ramp_up(void)
{
        int i;

        for(i=0;i<WAVEFORM_LEN;i++){
                waveform[i]=rint(offset+amplitude*((double)i)/WAVEFORM_LEN);
        }
}

void dds_init_ramp_down(void)
{
        int i;

        for(i=0;i<WAVEFORM_LEN;i++){
                waveform[i]=rint(offset+amplitude*((double)(WAVEFORM_LEN-1-i))/WAVEFORM_LEN);
        }
}

void dds_init_triangle(void)
{
        int i;

        for (i = 0; i < WAVEFORM_LEN; i++) {
                waveform[i] = rint(offset + amplitude * 2 * triangle((double)i / WAVEFORM_LEN));
        }
}

void dds_init_square(void)
{
        int i;

        for (i = 0; i < WAVEFORM_LEN / 2; i++) {
                waveform[i] = rint(offset);
        }
        for ( ; i < WAVEFORM_LEN; i++) {
                waveform[i] = rint(offset + amplitude);
        }
}

void dds_init_blancmange(void)
{
        int i, n;
        double b, x;

        for (i = 0; i < WAVEFORM_LEN; i++) {
                b = 0;
                for (n = 0; n < 16; n++) {
                        x = (double)i / WAVEFORM_LEN;
                        x *= (1 << n);
                        x -= floor(x);
                        b += triangle(x) / (1 << n);
                }
                waveform[i] = rint(offset + amplitude * 1.5 * b);
        }
}