Sat Aug 6 00:39:56 2011

Asterisk developer's documentation


fskmodem.h File Reference

FSK Modem Support. More...

Go to the source code of this file.

Data Structures

struct  fsk_data

Defines

#define NCOLA   0x4000
#define PARITY_EVEN   1
#define PARITY_NONE   0
#define PARITY_ODD   2

Functions

int fsk_serie (fsk_data *fskd, short *buffer, int *len, int *outbyte)


Detailed Description

FSK Modem Support.

Note:
Includes code and algorithms from the Zapata library.
Todo:
Translate Emiliano Zapata's spanish comments to english, please.

Definition in file fskmodem.h.


Define Documentation

#define NCOLA   0x4000

Definition at line 33 of file fskmodem.h.

Referenced by filtroL().

#define PARITY_EVEN   1

Definition at line 29 of file fskmodem.h.

#define PARITY_NONE   0

Definition at line 28 of file fskmodem.h.

#define PARITY_ODD   2

Definition at line 30 of file fskmodem.h.


Function Documentation

int fsk_serie ( fsk_data fskd,
short *  buffer,
int *  len,
int *  outbyte 
)

Definition at line 204 of file fskmodem.c.

References demodulador(), GET_SAMPLE, STATE_SEARCH_STARTBIT2, and STATE_SEARCH_STARTBIT3.

Referenced by callerid_feed(), callerid_feed_jp(), and tdd_feed().

00204       {
00205 /* this was jesus's nice, reasonable, working (at least with RTTY) code
00206 to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
00207 just start sending a start bit with nothing preceding it at the beginning
00208 of a transmission (what a LOSING design), we cant do it this elegantly */
00209 /*
00210       if (demodulador(zap,&x1)) return(-1);
00211       for(;;) {
00212          if (demodulador(zap,&x2)) return(-1);
00213          if (x1>0 && x2<0) break;
00214          x1=x2;
00215       }
00216 */
00217 /* this is now the imprecise, losing, but functional code to detect the
00218 beginning of a start bit in the TDD sceanario. It just looks for sufficient
00219 level to maybe, perhaps, guess, maybe that its maybe the beginning of
00220 a start bit, perhaps. This whole thing stinks! */
00221       beginlenx=beginlen; /* just to avoid unused war warnings */
00222       if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
00223       samples++;
00224       for(;;)
00225          {
00226 search_startbit2:       
00227          if (*len <= 0) {
00228             fskd->state = STATE_SEARCH_STARTBIT2;
00229             return 0;
00230          }
00231          samples++;
00232          if (demodulador(fskd,&fskd->x2,GET_SAMPLE)) return(-1);
00233 #if 0
00234          printf("x2 = %5.5f ", fskd->x2);
00235 #endif         
00236          if (fskd->x2 < -0.5) break; 
00237          }
00238 search_startbit3:       
00239       /* Esperamos 0.5 bits antes de usar DPLL */
00240       i=fskd->spb/2;
00241       if (*len < i) {
00242          fskd->state = STATE_SEARCH_STARTBIT3;
00243          return 0;
00244       }
00245       for(;i>0;i--) { if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1); 
00246 #if 0
00247          printf("x1 = %5.5f ", fskd->x1);
00248 #endif         
00249    samples++; }
00250 
00251       /* x1 debe ser negativo (confirmación del bit de start) */
00252 
00253    } while (fskd->x1>0);
00254    fskd->state = STATE_GET_BYTE;
00255 
00256 getbyte:
00257 
00258    /* Need at least 80 samples (for 1200) or
00259       1320 (for 45.5) to be sure we'll have a byte */
00260    if (fskd->nbit < 8) {
00261       if (*len < 1320)
00262          return 0;
00263    } else {
00264       if (*len < 80)
00265          return 0;
00266    }
00267    /* Leemos ahora los bits de datos */
00268    j=fskd->nbit;
00269    for (a=n1=0;j;j--) {
00270       olen = *len;
00271       i=get_bit_raw(fskd, buffer, len);
00272       buffer += (olen - *len);
00273       if (i == -1) return(-1);
00274       if (i) n1++;
00275       a>>=1; a|=i;
00276    }
00277    j=8-fskd->nbit;
00278    a>>=j;
00279 
00280    /* Leemos bit de paridad (si existe) y la comprobamos */
00281    if (fskd->paridad) {
00282       olen = *len;
00283       i=get_bit_raw(fskd, buffer, len); 
00284       buffer += (olen - *len);
00285       if (i == -1) return(-1);
00286       if (i) n1++;
00287       if (fskd->paridad==1) { /* paridad=1 (par) */
00288          if (n1&1) a|=0x100;     /* error */
00289       } else {       /* paridad=2 (impar) */
00290          if (!(n1&1)) a|=0x100;  /* error */
00291       }
00292    }
00293    
00294    /* Leemos bits de STOP. Todos deben ser 1 */
00295    
00296    for (j=fskd->nstop;j;j--) {
00297       r = get_bit_raw(fskd, buffer, len);
00298       if (r == -1) return(-1);
00299       if (!r) a|=0x200;
00300    }
00301 
00302    /* Por fin retornamos  */
00303    /* Bit 8 : Error de paridad */
00304    /* Bit 9 : Error de Framming */
00305 
00306    *outbyte = a;
00307    fskd->state = STATE_SEARCH_STARTBIT;
00308    return 1;
00309 }
00310 }


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