Sat Nov 25 00:46:05 2006

Asterisk developer's documentation


fskmodem.c File Reference

FSK Modulator/Demodulator. More...

#include <stdio.h>
#include "asterisk.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.

Definition in file fskmodem.c.


Define Documentation

#define BWLIST   {75,800}
 

Definition at line 36 of file fskmodem.c.

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

Definition at line 38 of file fskmodem.c.

#define GET_SAMPLE   get_sample(&buffer, len)
 

Definition at line 54 of file fskmodem.c.

Referenced by demodulador().

#define NBW   2
 

Definition at line 35 of file fskmodem.c.

#define NF   6
 

Definition at line 37 of file fskmodem.c.

#define STATE_GET_BYTE   3
 

Definition at line 43 of file fskmodem.c.

#define STATE_SEARCH_STARTBIT   0
 

Definition at line 40 of file fskmodem.c.

#define STATE_SEARCH_STARTBIT2   1
 

Definition at line 41 of file fskmodem.c.

#define STATE_SEARCH_STARTBIT3   2
 

Definition at line 42 of file fskmodem.c.


Function Documentation

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

Definition at line 151 of file fskmodem.c.

References GET_SAMPLE, and fsk_data::spb.

00153 {
00154    /* Esta funcion implementa un DPLL para sincronizarse con los bits */
00155    float x,spb,spb2,ds;
00156    int f;
00157 
00158    spb=fskd->spb; 
00159    if (fskd->spb == 7) spb = 8000.0 / 1200.0;
00160    ds=spb/32.;
00161    spb2=spb/2.;
00162 
00163    for (f=0;;){
00164       if (demodulador(fskd,&x, GET_SAMPLE)) return(-1);
00165       if ((x*fskd->x0)<0) {   /* Transicion */
00166          if (!f) {
00167             if (fskd->cont<(spb2)) fskd->cont+=ds; else fskd->cont-=ds;
00168             f=1;
00169          }

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

Filtro pasa-bajos para datos demodulados

Definition at line 131 of file fskmodem.c.

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

00133 {
00134    float xS,xM;
00135 
00136    fskd->cola_in[fskd->pcola]=x;
00137    
00138    xS=filtroS(fskd,x);
00139    xM=filtroM(fskd,x);
00140 
00141    fskd->cola_filtro[fskd->pcola]=xM-xS;
00142 
00143    x=filtroL(fskd,xM*xM - xS*xS);
00144    
00145    fskd->cola_demod[fskd->pcola++]=x;
00146    fskd->pcola &= (NCOLA-1);
00147 
00148    *retval = x;
00149    return(0);

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

Filtro pasa-banda para frecuencia de MARCA

Definition at line 97 of file fskmodem.c.

Referenced by filtroL().

00113 {

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

Filtro pasa-banda para frecuencia de ESPACIO

Definition at line 114 of file fskmodem.c.

Referenced by filtroL().

00133 {

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

Definition at line 201 of file fskmodem.c.

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 }

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

Definition at line 171 of file fskmodem.c.

00173                           {
00174          fskd->cont-=spb;
00175          break;
00176       }
00177    }
00178    f=(x>0)?0x80:0;
00179    return(f);
00180 }
00181 
00182 int fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte)
00183 {
00184    int a;
00185    int i,j,n1,r;
00186    int samples=0;
00187    int olen;
00188    switch(fskd->state) {
00189       /* Pick up where we left off */
00190    case STATE_SEARCH_STARTBIT2:
00191       goto search_startbit2;
00192    case STATE_SEARCH_STARTBIT3:
00193       goto search_startbit3;
00194    case STATE_GET_BYTE:
00195       goto getbyte;
00196    }
00197    /* Esperamos bit de start  */
00198    do {
00199 /* this was jesus's nice, reasonable, working (at least with RTTY) code

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

Definition at line 45 of file fskmodem.c.

00046 {
00047    float retval;
00048    retval = (float) **buffer / 256;
00049    (*buffer)++;
00050    (*len)--;
00051    return retval;
00052 }


Variable Documentation

double coef_in[NF][NBW][8] [static]
 

Definition at line 62 of file fskmodem.c.

double coef_out[NBW][8] [static]
 

Definition at line 86 of file fskmodem.c.


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