demod_stqc.c

/*
 *      demod_stqc.c - a simple demodulator for the STQC protocol
 *
 * 	Copyright (C) 2013
 * 	    Jacek Lipkowski <sq5bpf@lipkowski.org>
 *
 *
 * To find examples of this call, search for "dsp-50" on youtube. 
 * Beware that those videos are usually filmed in closed rooms and 
 * have a lot of echo, and this decoder doesn't deal well with 
 * echoes. In case of any problems use software like audacity to get 
 * the tone frequencies, and plug them into parse_stqc() --sq5bpf
 *
 *
 * 	Based upon demod_zvei.c and selcall.c
 *      Copyright (C) 1996
 *          Thomas Sailer (sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu)
 *
 *      Copyright (C) 2013
 *          Elias Oenal    (EliasOenal@gmail.com)
 *
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *
 *      You should have received a copy of the GNU General Public License
 *      along with this program; if not, write to the Free Software
 *      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* ---------------------------------------------------------------------- */

#include "multimon.h"
#include "filter.h"
#include <math.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

/* ---------------------------------------------------------------------- */


#define SAMPLE_RATE 22050
#define PHINC(x) ((x)*0x10000/SAMPLE_RATE)


static const unsigned int stqc_freq[5] = {
	    PHINC(980), PHINC(1197), PHINC(1446), PHINC(1795),PHINC(2105) };



#define SAMPLE_RATE 22050
#define BLOCKLEN (SAMPLE_RATE/100)  /* 10ms blocks */
#define BLOCKNUM 4    /* must match numbers in multimon.h */
#define TIMEOUT_LIMIT 15 /* 150ms */

char callbuffer[128]; /* this should really go into struct demod_state somwhere :) --sq5bpf */

void selcall2_init(struct demod_state *s)
{
	memset(&s->l1.selcall, 0, sizeof(s->l1.selcall));
	callbuffer[0]=0;
}

void selcall2_deinit(struct demod_state *s)
{
    if(s->l1.selcall.timeout != 0)
        verbprintf(0, "\n");
}

int find_max_idx2(const float *f)
{
    float en = 0;
    int idx = -1, i;
    for (i = 0; i < 5; i++) {
        if ((f[i]) > en) {
            en = f[i];
            idx = i;
        }
    }
    if (idx < 0)
        return -1;
    en *= 0.1;
    for (i = 0; i < 5; i++)
        if (idx != i && f[i] > en)
            return -1;
    return idx;
}


static inline int process_block(struct demod_state *s)
{
    float tote;
    float totte[32];
    int i, j;

    tote = 0;
    for (i = 0; i < BLOCKNUM; i++)
        tote += s->l1.selcall.energy[i];
    for (i = 0; i < 32; i++) {
        totte[i] = 0;
        for (j = 0; j < BLOCKNUM; j++)
            totte[i] += s->l1.selcall.tenergy[j][i];
    }
    for (i = 0; i < 5; i++)
        totte[i] = fsqr(totte[i]) + fsqr(totte[i+5]);
    memmove(s->l1.selcall.energy+1, s->l1.selcall.energy,
            sizeof(s->l1.selcall.energy) - sizeof(s->l1.selcall.energy[0]));
    s->l1.selcall.energy[0] = 0;
    memmove(s->l1.selcall.tenergy+1, s->l1.selcall.tenergy,
            sizeof(s->l1.selcall.tenergy) - sizeof(s->l1.selcall.tenergy[0]));
    memset(s->l1.selcall.tenergy, 0, sizeof(s->l1.selcall.tenergy[0]));
    tote *= (BLOCKNUM*BLOCKLEN*0.5);  /* adjust for block lengths */
    verbprintf(10, "selcall: Energies: %8.5f  %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f"
               " %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f\n",
               tote, totte[0], totte[1], totte[2], totte[3], totte[4], totte[5], totte[6], totte[7],
               totte[8], totte[9], totte[10], totte[11], totte[12], totte[13], totte[14], totte[15]);
    if ((i = find_max_idx2(totte)) < 0)
        return -1;
    if ((tote * 0.4) > totte[i])
    { 
	    //printf("T");  
	    return -1;
    }
    return i;
}


/* STQC decoder
 * usually there are 2 blocks in a transmission, a shorter one (4-7 tones) 
 * and a longer one (8 tones). the shorter is probably the device address 
 * and the longer is the command --sq5bpf
 */
void parse_stqc(char *buf)
{
	uint32_t val;
	int prev='0';
	char *c,*d;
	char parsed[128];
	int len=0;

	if (strlen(buf)<3) return; /* haven't seen shorter calls --sq5bpf */
	c=buf;
	d=parsed;
	while (*c) {
		if (*c=='4') {
			*d=prev;
		} else
		{
			*d=*c;
		}
		prev=*d;
		c++;
		d++;
		len++;
	}
	*d=0;
	val=strtoul((char *)&parsed,0,4);
	verbprintf (0,"STQC: %i tones  orig:[%s] parsed:[%s]  VALUES: dec: %i hex: 0x%X\n",len,buf,(char *)&parsed,val,val);

}

void selcall2_demod(struct demod_state *s, const float *buffer, int length,
		const unsigned int *selcall_freq, const char * const name)
{
	float s_in;
	int i;
	char c[2];
	for (; length > 0; length--, buffer++) {
		s_in = *buffer;
		s->l1.selcall.energy[0] += fsqr(s_in);
		for (i = 0; i < 5; i++) {
			s->l1.selcall.tenergy[0][i] += COS(s->l1.selcall.ph[i]) * s_in;
			s->l1.selcall.tenergy[0][i+5] += SIN(s->l1.selcall.ph[i]) * s_in;
			s->l1.selcall.ph[i] += selcall_freq[i];
		}
		if ((s->l1.selcall.blkcount--) <= 0) {
			s->l1.selcall.blkcount = BLOCKLEN;
			i = process_block(s);
			if ((i!=-1)&&(i == s->l1.selcall.lastch)) { 
			}
			if (i != s->l1.selcall.lastch && i >= 0)
			{
			/*	if(s->l1.selcall.timeout == 0)
				{ verbprintf(0, "%s: ", name);
				}
			*/
				c[0]='0'+i;
				c[1]=0;
				strncat(callbuffer,c,16);
				/* these calls are usually 7 or 8 tones, so put a limit here at 16 tones
				 * just in case there are longer ones */
				if (strlen(callbuffer)>16) 
				{
					verbprintf (0,"STQC: too many tones\n");
					parse_stqc((char *)&callbuffer);
					callbuffer[0]=0;
				}

				//		verbprintf(0, "%s", (char *)&c);
				s->l1.selcall.timeout = 1;
			}
			if(i == -1 && s->l1.selcall.timeout != 0)
				s->l1.selcall.timeout++;
			if(s->l1.selcall.timeout > TIMEOUT_LIMIT+1)
			{
		//		verbprintf(0, "\n");
				parse_stqc((char *)&callbuffer);
				s->l1.selcall.timeout = 0;
				s->l1.selcall.lastch = -1;
				callbuffer[0]=0;
			}

			if (i!=-1) s->l1.selcall.lastch = i;
		}
	}

}


/* ---------------------------------------------------------------------- */

static void stqc_init(struct demod_state *s)
{
	    selcall2_init(s);
}

static void stqc_deinit(struct demod_state *s)
{
	    selcall2_deinit(s);
	         parse_stqc((char *)&callbuffer);

}

static void stqc_demod(struct demod_state *s, buffer_t buffer, int length)
{
	    selcall2_demod(s, buffer.fbuffer, length, stqc_freq, demod_stqc.name);

}

const struct demod_param demod_stqc = {
	    "STQC", true, SAMPLE_RATE, 0, stqc_init, stqc_demod, stqc_deinit
};