Sat Aug 6 00:39:56 2011

Asterisk developer's documentation


fskmodem.c File Reference

FSK Modulator/Demodulator. More...

#include "asterisk.h"
#include <stdio.h>
#include "asterisk/fskmodem.h"
#include "coef_in.h"
#include "coef_out.h"

Go to the source code of this file.

Defines

#define BWLIST   {75,800}
#define FLIST   {1400,1800,1200,2200,1300,2100}
#define GET_SAMPLE   get_sample(&buffer, len)
#define NBW   2
#define NF   6
#define STATE_GET_BYTE   3
#define STATE_SEARCH_STARTBIT   0
#define STATE_SEARCH_STARTBIT2   1
#define STATE_SEARCH_STARTBIT3   2

Functions

static int demodulador (fsk_data *fskd, float *retval, float x)
static float filtroL (fsk_data *fskd, float in)
static float filtroM (fsk_data *fskd, float in)
static float filtroS (fsk_data *fskd, float in)
int fsk_serie (fsk_data *fskd, short *buffer, int *len, int *outbyte)
static int get_bit_raw (fsk_data *fskd, short *buffer, int *len)
static float get_sample (short **buffer, int *len)

Variables

static double coef_in [NF][NBW][8]
static double coef_out [NBW][8]


Detailed Description

FSK Modulator/Demodulator.

Author:
Mark Spencer <markster@digium.com>

Definition in file fskmodem.c.


Define Documentation

#define BWLIST   {75,800}

Definition at line 39 of file fskmodem.c.

#define FLIST   {1400,1800,1200,2200,1300,2100}

Definition at line 41 of file fskmodem.c.

#define GET_SAMPLE   get_sample(&buffer, len)

Definition at line 57 of file fskmodem.c.

Referenced by demodulador(), and fsk_serie().

#define NBW   2

Definition at line 38 of file fskmodem.c.

#define NF   6

Definition at line 40 of file fskmodem.c.

#define STATE_GET_BYTE   3

Definition at line 46 of file fskmodem.c.

#define STATE_SEARCH_STARTBIT   0

Definition at line 43 of file fskmodem.c.

#define STATE_SEARCH_STARTBIT2   1

Definition at line 44 of file fskmodem.c.

Referenced by fsk_serie().

#define STATE_SEARCH_STARTBIT3   2

Definition at line 45 of file fskmodem.c.

Referenced by fsk_serie().


Function Documentation

static int demodulador ( fsk_data fskd,
float *  retval,
float  x 
) [inline, static]

Definition at line 154 of file fskmodem.c.

References f, GET_SAMPLE, and fsk_data::spb.

Referenced by fsk_serie().

00156 {
00157    /* Esta funcion implementa un DPLL para sincronizarse con los bits */
00158    float x,spb,spb2,ds;
00159    int f;
00160 
00161    spb=fskd->spb; 
00162    if (fskd->spb == 7) spb = 8000.0 / 1200.0;
00163    ds=spb/32.;
00164    spb2=spb/2.;
00165 
00166    for (f=0;;){
00167       if (demodulador(fskd,&x, GET_SAMPLE)) return(-1);
00168       if ((x*fskd->x0)<0) {   /* Transicion */
00169          if (!f) {
00170             if (fskd->cont<(spb2)) fskd->cont+=ds; else fskd->cont-=ds;
00171             f=1;
00172          }

static float filtroL ( fsk_data fskd,
float  in 
) [inline, static]

Filtro pasa-bajos para datos demodulados

Definition at line 134 of file fskmodem.c.

References fsk_data::cola_demod, fsk_data::cola_filtro, fsk_data::cola_in, filtroM(), filtroS(), NCOLA, and fsk_data::pcola.

00136 {
00137    float xS,xM;
00138 
00139    fskd->cola_in[fskd->pcola]=x;
00140    
00141    xS=filtroS(fskd,x);
00142    xM=filtroM(fskd,x);
00143 
00144    fskd->cola_filtro[fskd->pcola]=xM-xS;
00145 
00146    x=filtroL(fskd,xM*xM - xS*xS);
00147    
00148    fskd->cola_demod[fskd->pcola++]=x;
00149    fskd->pcola &= (NCOLA-1);
00150 
00151    *retval = x;
00152    return(0);

static float filtroM ( fsk_data fskd,
float  in 
) [inline, static]

Filtro pasa-banda para frecuencia de MARCA

Definition at line 100 of file fskmodem.c.

Referenced by filtroL().

00116 {

static float filtroS ( fsk_data fskd,
float  in 
) [inline, static]

Filtro pasa-banda para frecuencia de ESPACIO

Definition at line 117 of file fskmodem.c.

Referenced by filtroL().

00136 {

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 }

static int get_bit_raw ( fsk_data fskd,
short *  buffer,
int *  len 
) [static]

Definition at line 174 of file fskmodem.c.

00176                           {
00177          fskd->cont-=spb;
00178          break;
00179       }
00180    }
00181    f=(x>0)?0x80:0;
00182    return(f);
00183 }
00184 
00185 int fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte)
00186 {
00187    int a;
00188    int i,j,n1,r;
00189    int samples=0;
00190    int olen;
00191    int beginlen=*len;
00192    int beginlenx;
00193    
00194    switch(fskd->state) {
00195       /* Pick up where we left off */
00196    case STATE_SEARCH_STARTBIT2:
00197       goto search_startbit2;
00198    case STATE_SEARCH_STARTBIT3:
00199       goto search_startbit3;
00200    case STATE_GET_BYTE:
00201       goto getbyte;
00202    }

static float get_sample ( short **  buffer,
int *  len 
) [inline, static]

Definition at line 48 of file fskmodem.c.

00049 {
00050    float retval;
00051    retval = (float) **buffer / 256;
00052    (*buffer)++;
00053    (*len)--;
00054    return retval;
00055 }


Variable Documentation

double coef_in[NF][NBW][8] [static]

Definition at line 65 of file fskmodem.c.

double coef_out[NBW][8] [static]

Definition at line 89 of file fskmodem.c.


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