main/fskmodem.c

   1 /*
   2  * Asterisk -- An open source telephony toolkit.
   3  *
   4  * Copyright (C) 1999 - 2005, Digium, Inc.
   5  *
   6  * Mark Spencer <markster@digium.com>
   7  *
   8  * Includes code and algorithms from the Zapata library.
   9  *
  10  * See http://www.asterisk.org for more information about
  11  * the Asterisk project. Please do not directly contact
  12  * any of the maintainers of this project for assistance;
  13  * the project provides a web site, mailing lists and IRC
  14  * channels for your use.
  15  *
  16  * This program is free software, distributed under the terms of
  17  * the GNU General Public License Version 2. See the LICENSE file
  18  * at the top of the source tree.
  19  */
  20
  21 /*! \file
  22  *
  23  * \brief FSK Modulator/Demodulator
  24  *
  25  * \author Mark Spencer <markster@digium.com>
  26  *
  27  * \arg Includes code and algorithms from the Zapata library.
  28  */
  29
  30 #include "asterisk.h"
  31
  32 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
  33
  34 #include <stdio.h>
  35
  36 #include "asterisk/fskmodem.h"
  37
  38 #define NBW     2
  39 #define BWLIST  {75,800}
  40 #define NF      6
  41 #define FLIST {1400,1800,1200,2200,1300,2100}
  42
  43 #define STATE_SEARCH_STARTBIT   0
  44 #define STATE_SEARCH_STARTBIT2  1
  45 #define STATE_SEARCH_STARTBIT3  2
  46 #define STATE_GET_BYTE                  3
  47
  48 static inline float get_sample(short **buffer, int *len)
  49 {
  50         float retval;
  51         retval = (float) **buffer / 256;
  52         (*buffer)++;
  53         (*len)--;
  54         return retval;
  55 }
  56
  57 #define GET_SAMPLE get_sample(&buffer, len)
  58
  59 /* Coeficientes para filtros de entrada                                 */
  60 /* Tabla de coeficientes, generada a partir del programa "mkfilter"     */
  61 /* Formato: coef[IDX_FREC][IDX_BW][IDX_COEF]                            */
  62 /* IDX_COEF=0   =>      1/GAIN                                          */
  63 /* IDX_COEF=1-6 =>      Coeficientes y[n]                               */
  64
  65 static double coef_in[NF][NBW][8]={
  66 #include "coef_in.h"
  67 };
  68
  69 /* Coeficientes para filtro de salida                                   */
  70 /* Tabla de coeficientes, generada a partir del programa "mkfilter"     */
  71 /* Formato: coef[IDX_BW][IDX_COEF]                                      */
  72 /* IDX_COEF=0   =>      1/GAIN                                          */
  73 /* IDX_COEF=1-6 =>      Coeficientes y[n]                               */
  74
  75 static double coef_out[NBW][8]={
  76 #include "coef_out.h"
  77 };
  78
  79
  80 /*! Filtro pasa-banda para frecuencia de MARCA */
  81 static inline float filtroM(fsk_data *fskd,float in)
  82 {
  83         int i,j;
  84         double s;
  85         double *pc;
  86
  87         pc=&coef_in[fskd->f_mark_idx][fskd->bw][0];
  88         fskd->fmxv[(fskd->fmp+6)&7]=in*(*pc++);
  89
  90         s=(fskd->fmxv[(fskd->fmp+6)&7] - fskd->fmxv[fskd->fmp]) + 3 * (fskd->fmxv[(fskd->fmp+2)&7] - fskd->fmxv[(fskd->fmp+4)&7]);
  91         for (i=0,j=fskd->fmp;i<6;i++,j++) s+=fskd->fmyv[j&7]*(*pc++);
  92         fskd->fmyv[j&7]=s;
  93         fskd->fmp++; fskd->fmp&=7;
  94         return s;
  95 }
  96
  97 /*! Filtro pasa-banda para frecuencia de ESPACIO */
  98 static inline float filtroS(fsk_data *fskd,float in)
  99 {
 100         int i,j;
 101         double s;
 102         double *pc;
 103
 104         pc=&coef_in[fskd->f_space_idx][fskd->bw][0];
 105         fskd->fsxv[(fskd->fsp+6)&7]=in*(*pc++);
 106
 107         s=(fskd->fsxv[(fskd->fsp+6)&7] - fskd->fsxv[fskd->fsp]) + 3 * (fskd->fsxv[(fskd->fsp+2)&7] - fskd->fsxv[(fskd->fsp+4)&7]);
 108         for (i=0,j=fskd->fsp;i<6;i++,j++) s+=fskd->fsyv[j&7]*(*pc++);
 109         fskd->fsyv[j&7]=s;
 110         fskd->fsp++; fskd->fsp&=7;
 111         return s;
 112 }
 113
 114 /*! Filtro pasa-bajos para datos demodulados */
 115 static inline float filtroL(fsk_data *fskd,float in)
 116 {
 117         int i,j;
 118         double s;
 119         double *pc;
 120
 121         pc=&coef_out[fskd->bw][0];
 122         fskd->flxv[(fskd->flp + 6) & 7]=in * (*pc++);
 123
 124         s=     (fskd->flxv[fskd->flp]       + fskd->flxv[(fskd->flp+6)&7]) +
 125           6  * (fskd->flxv[(fskd->flp+1)&7] + fskd->flxv[(fskd->flp+5)&7]) +
 126           15 * (fskd->flxv[(fskd->flp+2)&7] + fskd->flxv[(fskd->flp+4)&7]) +
 127           20 *  fskd->flxv[(fskd->flp+3)&7];
 128
 129         for (i=0,j=fskd->flp;i<6;i++,j++) s+=fskd->flyv[j&7]*(*pc++);
 130         fskd->flyv[j&7]=s;
 131         fskd->flp++; fskd->flp&=7;
 132         return s;
 133 }
 134
 135 static inline int demodulador(fsk_data *fskd, float *retval, float x)
 136 {
 137         float xS,xM;
 138
 139         fskd->cola_in[fskd->pcola]=x;
 140
 141         xS=filtroS(fskd,x);
 142         xM=filtroM(fskd,x);
 143
 144         fskd->cola_filtro[fskd->pcola]=xM-xS;
 145
 146         x=filtroL(fskd,xM*xM - xS*xS);
 147
 148         fskd->cola_demod[fskd->pcola++]=x;
 149         fskd->pcola &= (NCOLA-1);
 150
 151         *retval = x;
 152         return(0);
 153 }
 154
 155 static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
 156 {
 157         /* Esta funcion implementa un DPLL para sincronizarse con los bits */
 158         float x,spb,spb2,ds;
 159         int f;
 160
 161         spb=fskd->spb;
 162         if (fskd->spb == 7) spb = 8000.0 / 1200.0;
 163         ds=spb/32.;
 164         spb2=spb/2.;
 165
 166         for (f=0;;){
 167                 if (demodulador(fskd,&x, GET_SAMPLE)) return(-1);
 168                 if ((x*fskd->x0)<0) {   /* Transicion */
 169                         if (!f) {
 170                                 if (fskd->cont<(spb2)) fskd->cont+=ds; else fskd->cont-=ds;
 171                                 f=1;
 172                         }
 173                 }
 174                 fskd->x0=x;
 175                 fskd->cont+=1.;
 176                 if (fskd->cont>spb) {
 177                         fskd->cont-=spb;
 178                         break;
 179                 }
 180         }
 181         f=(x>0)?0x80:0;
 182         return(f);
 183 }
 184
 185 int fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte)
 186 {
 187         int a;
 188         int i,j,n1,r;
 189         int samples=0;
 190         int olen;
 191         switch(fskd->state) {
 192                 /* Pick up where we left off */
 193         case STATE_SEARCH_STARTBIT2:
 194                 goto search_startbit2;
 195         case STATE_SEARCH_STARTBIT3:
 196                 goto search_startbit3;
 197         case STATE_GET_BYTE:
 198                 goto getbyte;
 199         }
 200         /* Esperamos bit de start       */
 201         do {
 202 /* this was jesus's nice, reasonable, working (at least with RTTY) code
 203 to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
 204 just start sending a start bit with nothing preceding it at the beginning
 205 of a transmission (what a LOSING design), we cant do it this elegantly */
 206 /*
 207                 if (demodulador(zap,&x1)) return(-1);
 208                 for(;;) {
 209                         if (demodulador(zap,&x2)) return(-1);
 210                         if (x1>0 && x2<0) break;
 211                         x1=x2;
 212                 }
 213 */
 214 /* this is now the imprecise, losing, but functional code to detect the
 215 beginning of a start bit in the TDD sceanario. It just looks for sufficient
 216 level to maybe, perhaps, guess, maybe that its maybe the beginning of
 217 a start bit, perhaps. This whole thing stinks! */
 218                 if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
 219                 samples++;
 220                 for(;;)
 221                    {
 222 search_startbit2:
 223                         if (!*len) {
 224                                 fskd->state = STATE_SEARCH_STARTBIT2;
 225                                 return 0;
 226                         }
 227                         samples++;
 228                         if (demodulador(fskd,&fskd->x2,GET_SAMPLE)) return(-1);
 229 #if 0
 230                         printf("x2 = %5.5f ", fskd->x2);
 231 #endif
 232                         if (fskd->x2 < -0.5) break;
 233                    }
 234 search_startbit3:
 235                 /* Esperamos 0.5 bits antes de usar DPLL */
 236                 i=fskd->spb/2;
 237                 if (*len < i) {
 238                         fskd->state = STATE_SEARCH_STARTBIT3;
 239                         return 0;
 240                 }
 241                 for(;i;i--) { if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
 242 #if 0
 243                         printf("x1 = %5.5f ", fskd->x1);
 244 #endif
 245         samples++; }
 246
 247                 /* x1 debe ser negativo (confirmación del bit de start) */
 248
 249         } while (fskd->x1>0);
 250         fskd->state = STATE_GET_BYTE;
 251
 252 getbyte:
 253
 254         /* Need at least 80 samples (for 1200) or
 255                 1320 (for 45.5) to be sure we'll have a byte */
 256         if (fskd->nbit < 8) {
 257                 if (*len < 1320)
 258                         return 0;
 259         } else {
 260                 if (*len < 80)
 261                         return 0;
 262         }
 263         /* Leemos ahora los bits de datos */
 264         j=fskd->nbit;
 265         for (a=n1=0;j;j--) {
 266                 olen = *len;
 267                 i=get_bit_raw(fskd, buffer, len);
 268                 buffer += (olen - *len);
 269                 if (i == -1) return(-1);
 270                 if (i) n1++;
 271                 a>>=1; a|=i;
 272         }
 273         j=8-fskd->nbit;
 274         a>>=j;
 275
 276         /* Leemos bit de paridad (si existe) y la comprobamos */
 277         if (fskd->paridad) {
 278                 olen = *len;
 279                 i=get_bit_raw(fskd, buffer, len);
 280                 buffer += (olen - *len);
 281                 if (i == -1) return(-1);
 282                 if (i) n1++;
 283                 if (fskd->paridad==1) { /* paridad=1 (par) */
 284                         if (n1&1) a|=0x100;             /* error */
 285                 } else {                        /* paridad=2 (impar) */
 286                         if (!(n1&1)) a|=0x100;  /* error */
 287                 }
 288         }
 289
 290         /* Leemos bits de STOP. Todos deben ser 1 */
 291
 292         for (j=fskd->nstop;j;j--) {
 293                 r = get_bit_raw(fskd, buffer, len);
 294                 if (r == -1) return(-1);
 295                 if (!r) a|=0x200;
 296         }
 297
 298         /* Por fin retornamos  */
 299         /* Bit 8 : Error de paridad */
 300         /* Bit 9 : Error de Framming */
 301
 302         *outbyte = a;
 303         fskd->state = STATE_SEARCH_STARTBIT;
 304         return 1;
 305 }