comedilib/demo/tut2.c

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/*
 * Tutorial example #2
 * Part of Comedilib
 *
 * Copyright (c) 1999,2000 David A. Schleef <ds@schleef.org>
 * Copyright (c) 2008 Frank Mori Hess <fmhess@users.sourceforge.net>
 *
 * This file may be freely modified, distributed, and combined with
 * other software, as long as proper attribution is given in the
 * source code.
 */

#include <stdio.h>              /* for printf() */
#include <stdlib.h>
#include <comedilib.h>

int subdev = 0;                 /* change this to your input subdevice */
int chan = 0;                   /* change this to your channel */
int range = 0;                  /* more on this later */
int aref = AREF_GROUND;         /* more on this later */
const char filename[] = "/dev/comedi0";

/* figure out if we are talking to a hardware-calibrated or software-calibrated board,
        then obtain a comedi_polynomial_t which can be used with comedi_to_physical */
int get_converter(comedi_t *device, unsigned subdevice, unsigned channel,
        unsigned range, comedi_polynomial_t *converter)
{
        int retval;
        int flags;

        flags = comedi_get_subdevice_flags(device, subdevice);
        if(flags < 0)
        {
                comedi_perror("comedi_get_subdevice_flags");
                return -1;
        }

        if(flags & SDF_SOFT_CALIBRATED) /* board uses software calibration */
        {
                char *calibration_file_path = comedi_get_default_calibration_path(device);

                /* parse a calibration file which was produced by the
                        comedi_soft_calibrate program */
                comedi_calibration_t* parsed_calibration =
                        comedi_parse_calibration_file(calibration_file_path);
                free(calibration_file_path);
                if(parsed_calibration == NULL)
                {
                        comedi_perror("comedi_parse_calibration_file");
                        return -1;
                }

                /* get the comedi_polynomial_t for the subdevice/channel/range
                        we are interested in */
                retval = comedi_get_softcal_converter(subdevice, channel, range,
                        COMEDI_TO_PHYSICAL, parsed_calibration, converter);
                comedi_cleanup_calibration(parsed_calibration);
                if(retval < 0)
                {
                        comedi_perror("comedi_get_softcal_converter");
                        return -1;
                }
        }else /* board uses hardware calibration */
        {
                retval = comedi_get_hardcal_converter(device, subdevice, channel, range,
                        COMEDI_TO_PHYSICAL, converter);
                if(retval < 0)
                {
                        comedi_perror("comedi_get_hardcal_converter");
                        return -1;
                }
        }

        return 0;
}

int main(int argc, char *argv[])
{
        comedi_t *it;
        lsampl_t data;
        double physical_value;
        int retval;
        comedi_polynomial_t converter;

        it = comedi_open(filename);
        if(it == NULL)
        {
                comedi_perror(filename);
                return -1;
        }

        retval = comedi_data_read(it, subdev, chan, range, aref, &data);
        if(retval < 0)
        {
                comedi_perror(filename);
                return -1;
        }

        retval = get_converter(it, subdev, chan, range, &converter);
        if(retval < 0)
        {
                return -1;
        }

        physical_value = comedi_to_physical(data, &converter);
        printf("%d %g\n", data, physical_value);

        return 0;
}