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///////////////////////////////////////////////////////////////////////////////////

//                        A small demo of sonar.

// Program allow distance measuring.

// Uses cross-correlation algorithm to find echos

//

// Author: kaklik  (kaklik@mlab.cz)

//

///////////////////////////////////////////////////////////////////////////////////

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sched.h>

#include <errno.h>

#include <getopt.h>

#include <alsa/asoundlib.h>

#include <sys/time.h>

#include <math.h>

#define SOUND_SPEED	340.0	// sound speed in air in metrs per second

#define MAX_RANGE	10.0	// maximal working radius in meters

static char *device = "plughw:0,0";			/* playback device */

static snd_pcm_format_t format = SND_PCM_FORMAT_S16;	/* sample format */

static unsigned int rate = 96000;			/* stream rate */

static unsigned int buffer_time = 2 * (MAX_RANGE / SOUND_SPEED * 1e6);		/* ring buffer length in us */

static unsigned int period_time = MAX_RANGE / SOUND_SPEED * 1e6;		/* period time in us */

static int resample = 1;				/* enable alsa-lib resampling */

unsigned int chirp_size;

static snd_pcm_sframes_t buffer_size;	// size of buffer at sound card

static snd_pcm_sframes_t period_size;	//samples per frame

static snd_output_t *output = NULL;

static int set_hwparams(snd_pcm_t *handle, snd_pcm_hw_params_t *params, unsigned int channels)

{

    unsigned int rrate;

    snd_pcm_uframes_t size;

    int err, dir;

    /* choose all parameters */

    err = snd_pcm_hw_params_any(handle, params);

    if (err < 0)

    {

        printf("Broken configuration for playback: no configurations available: %s\n", snd_strerror(err));

        return err;

    }

    /* set hardware resampling */

    err = snd_pcm_hw_params_set_rate_resample(handle, params, resample);

    if (err < 0)

    {

        printf("Resampling setup failed for playback: %s\n", snd_strerror(err));

        return err;

    }

    /* set the interleaved read/write format */

    err = snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);

    if (err < 0)

    {

        printf("Access type not available for playback: %s\n", snd_strerror(err));

        return err;

    }

    /* set the sample format */

    err = snd_pcm_hw_params_set_format(handle, params, format);

    if (err < 0)

    {

        printf("Sample format not available for playback: %s\n", snd_strerror(err));

        return err;

    }

    /* set the count of channels */

    err = snd_pcm_hw_params_set_channels(handle, params, channels);

    if (err < 0)

    {

        printf("Channels count (%i) not available for playbacks: %s\n", channels, snd_strerror(err));

        return err;

    }

    /* set the stream rate */

    rrate = rate;

    err = snd_pcm_hw_params_set_rate_near(handle, params, &rrate, 0);

    if (err < 0)

    {

        printf("Rate %iHz not available for playback: %s\n", rate, snd_strerror(err));

        return err;

    }

    if (rrate != rate)

    {

        printf("Rate doesn't match (requested %iHz, get %iHz)\n", rate, err);

        return -EINVAL;

    }

    else printf("Rate set to %i Hz\n", rate, err);

    /* set the buffer time */

    err = snd_pcm_hw_params_set_buffer_time_near(handle, params, &buffer_time, &dir);

    if (err < 0)

    {

        printf("Unable to set buffer time %i for playback: %s\n", buffer_time, snd_strerror(err));

        return err;

    }

    err = snd_pcm_hw_params_get_buffer_size(params, &size);

    if (err < 0)

    {

        printf("Unable to get buffer size for playback: %s\n", snd_strerror(err));

        return err;

    }

    buffer_size = size;

    printf("Bufffer size set to:  %d  Requested buffer time: %ld \n", (int) buffer_size, (long) buffer_time);

    /// set the period time

    err = snd_pcm_hw_params_set_period_time_near(handle, params, &period_time, &dir);

    if (err < 0)

    {

        printf("Unable to set period time %i for playback: %s\n", period_time, snd_strerror(err));

        return err;

    }

    err = snd_pcm_hw_params_get_period_size(params, &size, &dir);

    if (err < 0)

    {

        printf("Unable to get period size for playback: %s\n", snd_strerror(err));

        return err;

    }

    period_size = size;

    printf("Period size set to:  %d Requested period time: %ld \n", (int) period_size, (long) period_time);

    /* write the parameters to device */

    err = snd_pcm_hw_params(handle, params);

    if (err < 0)

    {

        printf("Unable to set hw params for playback: %s\n", snd_strerror(err));

        return err;

    }

    return 0;

}

static int set_swparams(snd_pcm_t *handle, snd_pcm_sw_params_t *swparams)

{

    int err;

    /* get the current swparams */

    err = snd_pcm_sw_params_current(handle, swparams);

    if (err < 0)

    {

        printf("Unable to determine current swparams for playback: %s\n", snd_strerror(err));

        return err;

    }

    // start the transfer when the buffer is almost full: never fou our case 

    err = snd_pcm_sw_params_set_start_threshold(handle, swparams, 2 * buffer_size);

    if (err < 0)

    {

        printf("Unable to set start threshold mode for playback: %s\n", snd_strerror(err));

        return err;

    }

    err = snd_pcm_sw_params_set_period_event(handle, swparams, 1);

    if (err < 0)

    {

        printf("Unable to set period event: %s\n", snd_strerror(err));

        return err;

    }

    /* write the parameters to the playback device */

    err = snd_pcm_sw_params(handle, swparams);

    if (err < 0)

    {

        printf("Unable to set sw params for playback: %s\n", snd_strerror(err));

        return err;

    }

    return 0;

}

////// SIGNAL GENERATION STUFF

unsigned int linear_windowed_chirp(short *pole)

{

    unsigned int maxval = (1 << (snd_pcm_format_width(format) - 1)) - 1;

    static const float f0 = 5000;		//starting frequency

    static const float fmax = 13000;		//ending frequency

    static const float Tw = 0.0015;

    static float k;

    unsigned int n=0;

    double t;

    unsigned int chirp_samples;		// number of samples per period

    k=2*(fmax-f0)/Tw;

    chirp_samples = ceil(rate*Tw);

    for (n=0;n<=chirp_samples;n++)

    {

        t = (double) n / (double)rate;

        pole[n] = (short) floor( (0.35875 - 0.48829*cos(2*M_PI*t*1/Tw) + 0.14128*cos(2*M_PI*2*t*1/Tw) - 0.01168*cos(2*M_PI*3*t*1/Tw))*maxval*sin(2*M_PI*(t)*(f0+(k/2)*(t))) );

    }

    return (chirp_samples);

}

int main(int argc, char *argv[])

{

    snd_pcm_t *playback_handle, *capture_handle;

    int err;

    snd_pcm_hw_params_t *hwparams;

    snd_pcm_sw_params_t *swparams;

    long int *correlationl, *correlationr;

    int *L_signal, *R_signal;

    short *chirp, *signal;

    unsigned int i,j,m,n;

    unsigned int delay[10];	//store delay of signifed correlation

    long int l,r;  // store correlation at strict time

    FILE *out;

    snd_pcm_hw_params_alloca(&hwparams);

    snd_pcm_sw_params_alloca(&swparams);

    printf("Simple PC sonar ver. 000000001 starting work.. \n");

//open and set playback device

    if ((err = snd_pcm_open(&playback_handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0)

    {

        printf("Playback open error: %s\n", snd_strerror(err));

        return 0;

    }

    if ((err = set_hwparams(playback_handle, hwparams, 1)) < 0)

    {

        printf("Setting of hwparams failed: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

    if ((err = set_swparams(playback_handle, swparams)) < 0)

    {

        printf("Setting of swparams failed: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

//open and set capture device

    if ((err = snd_pcm_open(&capture_handle, device, SND_PCM_STREAM_CAPTURE, 0)) < 0)

    {

        printf("Playback open error: %s\n", snd_strerror(err));

        return 0;

    }

    if ((err = set_hwparams(capture_handle, hwparams, 2)) < 0)

    {

        printf("Setting of hwparams failed: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

    if ((err = set_swparams(capture_handle, swparams)) < 0)

    {

        printf("Setting of swparams failed: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

/*    err = snd_pcm_link( capture_handle, playback_handle); //link capture and playback together

    if (err < 0)

    {

        printf("Device linking error: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }*/

    correlationl = malloc(period_size * sizeof(long int)); //array to store correlation curve

    correlationr = malloc(period_size * sizeof(long int)); //array to store correlation curve

    L_signal = malloc(period_size * sizeof(int));

    R_signal = malloc(period_size * sizeof(int));

    chirp = calloc(2*period_size, sizeof(short));

    signal = malloc(2*period_size * sizeof(short));

// generate ping pattern

    chirp_size = linear_windowed_chirp(chirp);

    err = snd_pcm_writei(playback_handle, chirp, period_size);

    if (err < 0)

    {

        printf("Initial write error: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

//start sream

    err = snd_pcm_start(playback_handle);

    if (err < 0)

    {

        printf("Start error: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

    err = snd_pcm_start(capture_handle);

    if (err < 0)

    {

        printf("Start error: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

    else printf("Waiting for transmitt all samples\n");

//--------------

    while ( snd_pcm_avail_update(capture_handle) < period_size)

    {

        usleep(1000);

        printf(".");

    }

    err = snd_pcm_drop(playback_handle);

    err = snd_pcm_drain(capture_handle);

    if (err < 0)

    {

        printf("Stop error: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

    err = snd_pcm_readi(capture_handle, signal, period_size);

    if (err < 0)

    {

        printf("Read error: %s\n", snd_strerror(err));

        exit(EXIT_FAILURE);

    }

    j=0;

    for (i=0;i < period_size;i++)		// separe inretleaved samples to two arrays

    {

        L_signal[i]=signal[j];

        R_signal[i]=signal[j+1];

        j+=2;

    }

    printf("\nData transmitted \ncorrelating\n");

    for (n=0; n < (period_size - chirp_size - 1); n++)

    {

        l=0;

        r=0;

        for (m=0;m < chirp_size;m++)

        {

            l += chirp[m]*L_signal[m+n];	// correlate with left channel

            r += chirp[m]*R_signal[m+n];	// correlate with right channel

        }

        correlationl[n]=l;

        correlationr[n]=r;

    }

    printf("Searching echos\n");

    r=0;

    l=0;

    for (n=0; n < period_size;n++) 			//najde nejvetsi korelace

    {

        if (l < correlationl[n])

        {

            delay[1] = n;

            l = correlationl[n];

        }

        if (r < correlationr[n])

        {

            delay[2] = n;

            r = correlationr[n];

        }

    }

    printf("Writing output file\n");

    out=fopen("/tmp/sonar.txt","w");

    j=0;

    for (i=0; i <= (period_size -1); i++)

    {

        fprintf(out,"%6d %6d %6d %6d %9ld %9ld\n",i,chirp[i],L_signal[i],R_signal[i],correlationl[i], correlationr[i]);

        j+=2;

    }

    fclose(out);

    printf("Echo zacina na: %d vzorku.\n", delay[1]);

    printf("Casove na: %f s\n", ((float)delay[1]/rate));

    printf("vzdalenost: %f m\n", (SOUND_SPEED*(float)delay[1]/rate));

    snd_pcm_close(playback_handle);

    snd_pcm_close(capture_handle);

    return 0;

}