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

//                        This small demo of sonar.

// Program allow distance measuring.

//

//

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

#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>

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

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

static unsigned int rate = 98000;			/* stream rate */

static unsigned int channels = 1;			/* count of channels */

static unsigned int buffer_time = 500000;		/* ring buffer length in us */

static unsigned int period_time = 100000;		/* period time in us */

static int verbose = 0;					/* verbose flag */

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

static int period_event = 0;				/* produce poll event after each period */

#define SOUND_SPEED	340

#define SIGNAL_SAMPLES 100000

unsigned int chirp_size;

int period=0;

int cperiod=0;

int chirp[100000];

short signal[1000000];		// record 6s of input samples

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,

			snd_pcm_access_t access)

{

	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, access);

	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;

	/* 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;

	/* 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: */

	/* (buffer_size / avail_min) * avail_min */

	err = snd_pcm_sw_params_set_start_threshold(handle, swparams, (buffer_size / period_size) * period_size);

	if (err < 0) {

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

		return err;

	}

	/* allow the transfer when at least period_size samples can be processed */

	/* or disable this mechanism when period event is enabled (aka interrupt like style processing) */

	err = snd_pcm_sw_params_set_avail_min(handle, swparams, period_event ? buffer_size : period_size);

	if (err < 0) {

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

		return err;

	}

	/* enable period events when requested */

	if (period_event) {

		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;

}

struct async_private_data {

	signed short *samples;

	snd_pcm_channel_area_t *areas;

	unsigned int period;

};

/*int linear_chirp(int *pole, int delka_pole){  // vygeneruje linearni chirp a vzorky ulozi do pole

static const float f0 = 0.0001;

static const float k = 0.00001;

int t;

//  if((spozdeni+delka) < delka_pole)

    for(t=0;t < delka_pole;t++) pole[t] = round ( 10000*sin(2*M_PI*(t+faze)*(f0+(k/2)*(t+faze))) );

    faze +=t;

//  else return 0;

}*/

// vygeneruje linearni chirp a vzorky ulozi do pole

unsigned int linear_windowed_chirp(unsigned int *pole, unsigned int delka_pole)

{  

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

static const float f0 = 3000;

static const float fmax = 5000;

static const float Tw = 0.002;

static float k;

unsigned int n=0;

double t;

unsigned int perioda;

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

  perioda = rate*Tw; 

  for(n=0;n<=perioda;n++){

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

     pole[n] = (short) round ( (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 perioda;

}

// generate sine samples and store

int sine(unsigned int *pole, unsigned int delka_pole)

{

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

unsigned int n;

double t;

  for(n=0;n < delka_pole;n++){

    t = 440.0 * (double) n/ (double)rate;

    pole[n] = (short) round(maxval*sin(2*M_PI*t));

  }

}

static void async_playback_callback(snd_async_handler_t *ahandler)

{

	snd_pcm_t *handle = snd_async_handler_get_pcm(ahandler);

/*	struct async_private_data *data = snd_async_handler_get_callback_private(ahandler);

	signed short *samples = data->samples;

	snd_pcm_channel_area_t *areas = data->areas;*/

	snd_pcm_sframes_t avail;

	int err;

	avail = snd_pcm_avail_update(handle);

	while ((avail >= period_size) && ((period*period_size) < chirp_size) ) {

		err = snd_pcm_writei(handle, (chirp+period*period_size), period_size);

		if (err < 0) {

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

			exit(EXIT_FAILURE);

		}

		if (err != period_size) {

			printf("Write error: written %i expected %li\n", err, period_size);

			exit(EXIT_FAILURE);

		}

		avail = snd_pcm_avail_update(handle);

		period++;

	}

}

static void async_capture_callback(snd_async_handler_t *ahandler)

{

	snd_pcm_t *handle = snd_async_handler_get_pcm(ahandler);

/*	struct async_private_data *data = snd_async_handler_get_callback_private(ahandler);

	signed short *samples = data->samples;

	snd_pcm_channel_area_t *areas = data->areas;*/

	snd_pcm_sframes_t avail;

	int err;

	avail = snd_pcm_avail_update(handle);

	while ((avail >= period_size) /*&& ((period*period_size) < (CHIRP_SIZE-100))*/ ) {  // segmentation fault checking disabled

		err = snd_pcm_readi(handle, (signal+cperiod*period_size), period_size);

		if (err < 0) {

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

			exit(EXIT_FAILURE);

		}

		if (err != period_size) {

			printf("Read error: red %i expected %li\n", err, period_size);

			exit(EXIT_FAILURE);

		}

		avail = snd_pcm_avail_update(handle);

		cperiod++;

	}

}

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;

	signed short *frame;  // pointer to array of samples

	unsigned int chn;

	snd_pcm_channel_area_t *areas;

	struct async_private_data data;

	snd_async_handler_t *chandler, *phandler;

	int count;

	unsigned int i,j,m,n;

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

  	double r;

	double correlation[1000000]; //array to store correlation curve

	FILE *out;

	snd_pcm_hw_params_alloca(&hwparams);

	snd_pcm_sw_params_alloca(&swparams);

//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, SND_PCM_ACCESS_RW_INTERLEAVED)) < 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, SND_PCM_ACCESS_RW_INTERLEAVED)) < 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);

	}

        chirp_size=linear_windowed_chirp(chirp,1000000);

/// register playback callback 

	err = snd_async_add_pcm_handler(&phandler, playback_handle, async_playback_callback, &data); // fill by dummy &data

	if (err < 0) {

		printf("Unable to register async handler\n");

		exit(EXIT_FAILURE);

	}

	for (period = 0; period < 2; period++) {

		err = snd_pcm_writei(playback_handle, (chirp+period*period_size), period_size);

		if (err < 0) {

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

			exit(EXIT_FAILURE);

		}

		if (err != period_size) {

			printf("Initial write error: written %i expected %li\n", err, period_size);

			exit(EXIT_FAILURE);

		}

	}

// register capture callback 

	err = snd_async_add_pcm_handler(&chandler, capture_handle, async_capture_callback, &data); // fill by dummy &data

	if (err < 0) {

		printf("Unable to register async handler\n");

		exit(EXIT_FAILURE);

	}

//start capture

	if ((err = snd_pcm_prepare (capture_handle)) < 0) {

		fprintf (stderr, "cannot prepare audio interface for use (%s)\n",

			 snd_strerror (err));

		exit (1);

	}

	err = snd_pcm_start(capture_handle);

	if (err < 0) {

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

			exit(EXIT_FAILURE);

	}

//start playback

	if (snd_pcm_state(playback_handle) == SND_PCM_STATE_PREPARED) {

		err = snd_pcm_start(playback_handle);

		if (err < 0) {

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

			exit(EXIT_FAILURE);

		}

	}

//wait until all samples aren't transmitted

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

	while(cperiod<10) {

		sleep(1);

		printf(".");

	}	

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

	for(n=0; n < (SIGNAL_SAMPLES - chirp_size);n++){			//spocita korelaci pro mozna spozdeni

	  r=0;

	  for(m=chirp_size;m > 0;m--) r += chirp[m]*signal[m+n];	// reverse echo patern

	  correlation[n]=abs(r);

	}

	printf("\nFinding echos...\n");

	r=0;

	for(n=0; n < (SIGNAL_SAMPLES - chirp_size);n++){			//najde nejvetsi korelace

	  if (r < correlation[n]){

	  delay[1] = n;

	  r = correlation[n];

	  }

	}

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

	for(i=0;i<=100000;i++) fprintf(out,"%6d	%6d %6d %6.2f\n",i,chirp[i],signal[i],correlation[i]); 

	fclose(out);

	printf("\nEcho 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;

}