Sat Sep 16 05:48:02 2006

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 201 of file fskmodem.c.

References demodulador(), GET_SAMPLE, and STATE_SEARCH_STARTBIT2.

Referenced by callerid_feed(), and tdd_feed().

00205               {
00206          if (demodulador(zap,&x2)) return(-1);
00207          if (x1>0 && x2<0) break;
00208          x1=x2;
00209       }
00210 */
00211 /* this is now the imprecise, losing, but functional code to detect the
00212 beginning of a start bit in the TDD sceanario. It just looks for sufficient
00213 level to maybe, perhaps, guess, maybe that its maybe the beginning of
00214 a start bit, perhaps. This whole thing stinks! */
00215       if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1);
00216       samples++;
00217       for(;;)
00218          {
00219 search_startbit2:       
00220          if (!*len) {
00221             fskd->state = STATE_SEARCH_STARTBIT2;
00222             return 0;
00223          }
00224          samples++;
00225          if (demodulador(fskd,&fskd->x2,GET_SAMPLE)) return(-1);
00226 #if 0
00227          printf("x2 = %5.5f ", fskd->x2);
00228 #endif         
00229          if (fskd->x2 < -0.5) break; 
00230          }
00231 search_startbit3:       
00232       /* Esperamos 0.5 bits antes de usar DPLL */
00233       i=fskd->spb/2;
00234       if (*len < i) {
00235          fskd->state = STATE_SEARCH_STARTBIT3;
00236          return 0;
00237       }
00238       for(;i;i--) { if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1); 
00239 #if 0
00240          printf("x1 = %5.5f ", fskd->x1);
00241 #endif         
00242    samples++; }
00243 
00244       /* x1 debe ser negativo (confirmación del bit de start) */
00245 
00246    } while (fskd->x1>0);
00247    fskd->state = STATE_GET_BYTE;
00248 
00249 getbyte:
00250 
00251    /* Need at least 80 samples (for 1200) or
00252       1320 (for 45.5) to be sure we'll have a byte */
00253    if (fskd->nbit < 8) {
00254       if (*len < 1320)
00255          return 0;
00256    } else {
00257       if (*len < 80)
00258          return 0;
00259    }
00260    /* Leemos ahora los bits de datos */
00261    j=fskd->nbit;
00262    for (a=n1=0;j;j--) {
00263       olen = *len;
00264       i=get_bit_raw(fskd, buffer, len);
00265       buffer += (olen - *len);
00266       if (i == -1) return(-1);
00267       if (i) n1++;
00268       a>>=1; a|=i;
00269    }
00270    j=8-fskd->nbit;
00271    a>>=j;
00272 
00273    /* Leemos bit de paridad (si existe) y la comprobamos */
00274    if (fskd->paridad) {
00275       olen = *len;
00276       i=get_bit_raw(fskd, buffer, len); 
00277       buffer += (olen - *len);
00278       if (i == -1) return(-1);
00279       if (i) n1++;
00280       if (fskd->paridad==1) { /* paridad=1 (par) */
00281          if (n1&1) a|=0x100;     /* error */
00282       } else {       /* paridad=2 (impar) */
00283          if (!(n1&1)) a|=0x100;  /* error */
00284       }
00285    }
00286    
00287    /* Leemos bits de STOP. Todos deben ser 1 */
00288    
00289    for (j=fskd->nstop;j;j--) {
00290       r = get_bit_raw(fskd, buffer, len);
00291       if (r == -1) return(-1);
00292       if (!r) a|=0x200;
00293    }
00294 
00295    /* Por fin retornamos  */
00296    /* Bit 8 : Error de paridad */
00297    /* Bit 9 : Error de Framming */
00298 
00299    *outbyte = a;
00300    fskd->state = STATE_SEARCH_STARTBIT;
00301    return 1;
00302 }
00303 }


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