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/*
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* Asterisk -- A telephony toolkit for Linux.
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*
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* FSK Modulator/Demodulator
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*
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* Copyright (C) 1999, Mark Spencer
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*
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* Mark Spencer <markster@linux-support.net>
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License.
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*
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* Includes code and algorithms from the Zapata library.
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*
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*/
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#include <asterisk/fskmodem.h>
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#include <stdio.h>
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#define NBW 2
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#define BWLIST {75,800}
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#define NF 4
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#define FLIST {1400,1800,1200,2200}
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#define STATE_SEARCH_STARTBIT 0
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#define STATE_SEARCH_STARTBIT2 1
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#define STATE_SEARCH_STARTBIT3 2
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#define STATE_GET_BYTE 3
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static inline float get_sample(short **buffer, int *len)
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{
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float retval;
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retval = (float) **buffer / 256;
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(*buffer)++;
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(*len)--;
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return retval;
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}
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#define GET_SAMPLE get_sample(&buffer, len)
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/* Coeficientes para filtros de entrada */
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/* Tabla de coeficientes, generada a partir del programa "mkfilter" */
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/* Formato: coef[IDX_FREC][IDX_BW][IDX_COEF] */
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/* IDX_COEF=0 => 1/GAIN */
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/* IDX_COEF=1-6 => Coeficientes y[n] */
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static double coef_in[NF][NBW][8]={
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#include "coef_in.h"
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};
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/* Coeficientes para filtro de salida */
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/* Tabla de coeficientes, generada a partir del programa "mkfilter" */
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/* Formato: coef[IDX_BW][IDX_COEF] */
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/* IDX_COEF=0 => 1/GAIN */
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/* IDX_COEF=1-6 => Coeficientes y[n] */
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static double coef_out[NBW][8]={
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#include "coef_out.h"
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};
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/* Filtro pasa-banda para frecuencia de MARCA */
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static inline float filtroM(fsk_data *fskd,float in)
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{
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int i,j;
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double s;
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double *pc;
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pc=&coef_in[fskd->f_mark_idx][fskd->bw][0];
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fskd->fmxv[(fskd->fmp+6)&7]=in*(*pc++);
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s=(fskd->fmxv[(fskd->fmp+6)&7] - fskd->fmxv[fskd->fmp]) + 3 * (fskd->fmxv[(fskd->fmp+2)&7] - fskd->fmxv[(fskd->fmp+4)&7]);
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for (i=0,j=fskd->fmp;i<6;i++,j++) s+=fskd->fmyv[j&7]*(*pc++);
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fskd->fmyv[j&7]=s;
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fskd->fmp++; fskd->fmp&=7;
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return s;
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}
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/* Filtro pasa-banda para frecuencia de ESPACIO */
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static inline float filtroS(fsk_data *fskd,float in)
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{
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int i,j;
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double s;
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double *pc;
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pc=&coef_in[fskd->f_space_idx][fskd->bw][0];
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fskd->fsxv[(fskd->fsp+6)&7]=in*(*pc++);
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s=(fskd->fsxv[(fskd->fsp+6)&7] - fskd->fsxv[fskd->fsp]) + 3 * (fskd->fsxv[(fskd->fsp+2)&7] - fskd->fsxv[(fskd->fsp+4)&7]);
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for (i=0,j=fskd->fsp;i<6;i++,j++) s+=fskd->fsyv[j&7]*(*pc++);
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fskd->fsyv[j&7]=s;
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fskd->fsp++; fskd->fsp&=7;
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return s;
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}
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/* Filtro pasa-bajos para datos demodulados */
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static inline float filtroL(fsk_data *fskd,float in)
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{
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int i,j;
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double s;
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double *pc;
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pc=&coef_out[fskd->bw][0];
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fskd->flxv[(fskd->flp + 6) & 7]=in * (*pc++);
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s= (fskd->flxv[fskd->flp] + fskd->flxv[(fskd->flp+6)&7]) +
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6 * (fskd->flxv[(fskd->flp+1)&7] + fskd->flxv[(fskd->flp+5)&7]) +
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15 * (fskd->flxv[(fskd->flp+2)&7] + fskd->flxv[(fskd->flp+4)&7]) +
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20 * fskd->flxv[(fskd->flp+3)&7];
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for (i=0,j=fskd->flp;i<6;i++,j++) s+=fskd->flyv[j&7]*(*pc++);
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fskd->flyv[j&7]=s;
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fskd->flp++; fskd->flp&=7;
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return s;
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}
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static inline int demodulador(fsk_data *fskd, float *retval, float x)
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{
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float xS,xM;
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fskd->cola_in[fskd->pcola]=x;
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xS=filtroS(fskd,x);
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xM=filtroM(fskd,x);
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fskd->cola_filtro[fskd->pcola]=xM-xS;
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x=filtroL(fskd,xM*xM - xS*xS);
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fskd->cola_demod[fskd->pcola++]=x;
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fskd->pcola &= (NCOLA-1);
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*retval = x;
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return(0);
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}
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static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
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{
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/* Esta funcion implementa un DPLL para sincronizarse con los bits */
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float x,spb,spb2,ds;
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int f;
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spb=fskd->spb;
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if (fskd->spb == 7) spb = 8000.0 / 1200.0;
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ds=spb/32.;
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spb2=spb/2.;
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for (f=0;;){
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if (demodulador(fskd,&x, GET_SAMPLE)) return(-1);
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if ((x*fskd->x0)<0) { /* Transicion */
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if (!f) {
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if (fskd->cont<(spb2)) fskd->cont+=ds; else fskd->cont-=ds;
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f=1;
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}
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}
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fskd->x0=x;
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fskd->cont+=1.;
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if (fskd->cont>spb) {
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fskd->cont-=spb;
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break;
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}
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}
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f=(x>0)?0x80:0;
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return(f);
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}
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int fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte)
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{
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int a;
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int i,j,n1,r;
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int samples=0;
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int olen;
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switch(fskd->state) {
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/* Pick up where we left off */
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case STATE_SEARCH_STARTBIT2:
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goto search_startbit2;
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case STATE_SEARCH_STARTBIT3:
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goto search_startbit3;
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case STATE_GET_BYTE:
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goto getbyte;
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}
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/* Esperamos bit de start */
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do {
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/* this was jesus's nice, reasonable, working (at least with RTTY) code
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to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
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just start sending a start bit with nothing preceding it at the beginning
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of a transmission (what a LOSING design), we cant do it this elegantly */
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/*
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if (demodulador(zap,&x1)) return(-1);
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for(;;) {
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if (demodulador(zap,&x2)) return(-1);
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if (x1>0 && x2<0) break;
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x1=x2;
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}
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*/
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/* this is now the imprecise, losing, but functional code to detect the
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beginning of a start bit in the TDD sceanario. It just looks for sufficient
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level to maybe, perhaps, guess, maybe that its maybe the beginning of
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a start bit, perhaps. This whole thing stinks! */
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if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
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samples++;
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for(;;)
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{
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search_startbit2:
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if (!*len) {
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fskd->state = STATE_SEARCH_STARTBIT2;
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return 0;
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}
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samples++;
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if (demodulador(fskd,&fskd->x2,GET_SAMPLE)) return(-1);
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#if 0
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printf("x2 = %5.5f ", fskd->x2);
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#endif
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if (fskd->x2 < -0.5) break;
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}
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search_startbit3:
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/* Esperamos 0.5 bits antes de usar DPLL */
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i=fskd->spb/2;
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if (*len < i) {
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fskd->state = STATE_SEARCH_STARTBIT3;
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return 0;
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}
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for(;i;i--) { if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
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#if 0
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printf("x1 = %5.5f ", fskd->x1);
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#endif
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samples++; }
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/* x1 debe ser negativo (confirmaci<63>n del bit de start) */
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} while (fskd->x1>0);
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fskd->state = STATE_GET_BYTE;
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getbyte:
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/* Need at least 80 samples to be sure we'll have a byte */
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if (*len < 80)
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return 0;
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/* Leemos ahora los bits de datos */
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j=fskd->nbit;
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for (a=n1=0;j;j--) {
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olen = *len;
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i=get_bit_raw(fskd, buffer, len);
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buffer += (olen - *len);
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if (i == -1) return(-1);
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if (i) n1++;
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a>>=1; a|=i;
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}
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j=8-fskd->nbit;
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a>>=j;
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/* Leemos bit de paridad (si existe) y la comprobamos */
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if (fskd->paridad) {
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olen = *len;
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i=get_bit_raw(fskd, buffer, len);
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buffer += (olen - *len);
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if (i == -1) return(-1);
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if (i) n1++;
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if (fskd->paridad==1) { /* paridad=1 (par) */
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if (n1&1) a|=0x100; /* error */
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} else { /* paridad=2 (impar) */
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if (!(n1&1)) a|=0x100; /* error */
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}
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}
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/* Leemos bits de STOP. Todos deben ser 1 */
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for (j=fskd->nstop;j;j--) {
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r = get_bit_raw(fskd, buffer, len);
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if (r == -1) return(-1);
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if (!r) a|=0x200;
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}
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/* Por fin retornamos */
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/* Bit 8 : Error de paridad */
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/* Bit 9 : Error de Framming */
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*outbyte = a;
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fskd->state = STATE_SEARCH_STARTBIT;
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return 1;
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}
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