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isdnfax/modules/V.29-demod.c

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/*
******************************************************************************
Fax program for ISDN.
This is the V.29 demodulator. The module handles the training phase as well
as the final data transmission.
Copyright (C) 1999 Oliver Eichler [oliver.eichler@regensburg.netsurf.de
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
******************************************************************************
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ifax/ifax.h>
#include "../include/ifax/modules/V.29_demod.h"
#define PHASEINC1700HZ 15474
#define INTERVAL_CNT 2
#define X1 0x1555
#define X2 0x2AAA
#define X3 0x4000
#define X4 0x5555
#define X5 0x6AAA
#define X6 0x7FFF
#define Y1 0x1555
#define Y2 0x2AAA
#define Y3 0x4000
#define Y4 0x5555
#define Y5 0x6AAA
#define Y6 0x7FFF
#define DEG0 0x0000
#define DEG45 0x2000
#define DEG90 0x4000
#define DEG135 0x6000
#define DEG180 0x8000
#define DEG225 0xA000
#define DEG270 0xC000
#define DEG315 0xE000
#define A9600 8
#define B9600 15
#define NOSYMB 3
#define NOSAMP 3
#define L_MIN 0x0006
#define L_2 0x0013
#define NIL 0x0
#define ESTIMATEGAIN 0x1
#define LISTEN 0x2
#define PHASEHUNT 0x3
#define TAU50
#undef TAU30
#ifdef TAU50
#define AGCESTDLY 50
#define TAU 0x0288
#endif
#ifdef TAU30
#define AGCESTDLY 30
#define TAU 0x0432
#endif
#define B 0x7FFF
#define LEVEL 0x16D6
#define LEVEL63 0x0E63
#define SQRT_LEVEL63 0x2AE9
typedef struct
{
signed short Re;
signed short Im;
unsigned short angl;
}
V29_symbol;
V29_symbol V29_symb_tbl[] =
{
{0x4000, 0x0000, DEG0}, /* P=000 Q=0 (0) */
{0x6AAA, 0x0000, DEG0}, /* P=000 Q=1 (0) */
{0x1555, 0x1555, DEG45}, /* P=001 Q=0 (45) */
{0x4000, 0x4000, DEG45}, /* P=001 Q=1 (45) */
{0x0000, 0x4000, DEG90}, /* P=010 Q=0 (90) */
{0x0000, 0x6AAA, DEG90}, /* P=010 Q=1 (90) */
{0xEAAB, 0x1555, DEG135}, /* P=011 Q=0 (135) */
{0xC000, 0x4000, DEG135}, /* P=011 Q=1 (135) */
{0xC000, 0x0000, DEG180}, /* P=100 Q=0 (180) */
{0x9556, 0x0000, DEG180}, /* P=100 Q=1 (180) */
{0xEAAB, 0xEAAB, DEG225}, /* P=101 Q=0 (225) */
{0xC000, 0xC000, DEG225}, /* P=101 Q=1 (225) */
{0x0000, 0xC000, DEG270}, /* P=110 Q=0 (270) */
{0x0000, 0x9556, DEG270}, /* P=110 Q=1 (270) */
{0x1555, 0xEAAB, DEG315}, /* P=111 Q=0 (315) */
{0x4000, 0xC000, DEG315}, /* P=111 Q=1 (315) */
};
typedef struct
{
unsigned short agc_gain;
unsigned short w;
int phi;
short a;
short power;
int state;
short dem_lpf_buf[NOSYMB * NOSAMP];
short dem_re[NOSYMB * NOSAMP];
short dem_im[NOSYMB * NOSAMP];
unsigned short dem_angl[2 * NOSYMB * NOSAMP];
int dem_angl_dif[NOSYMB * NOSAMP];
int dem_angl_dist[NOSYMB * NOSAMP];
int dem_index;
int smpl_cnt;
V29_symbol current_symbol;
}
V29demod_private;
short dem_lpf_coef[] = {0x203E, 0x3F82, 0x203E};
int FirstQuadTbl[] = {0,1,2,3,4,5,2,3};
int ReMinusTbl[] = {8,9,6,7,4,5};
int ImMinusTbl[] = {0,1,14,15,12,13,10,11,8,9};
short DCD (short s, V29demod_private * priv);
short Demod (short s, V29demod_private * priv);
short FindSeq2(V29demod_private * priv);
short PhaseHuntSeq2(V29demod_private * priv);
short agc_dummy(short s, V29demod_private * priv);
short SymbolMapping(V29demod_private * priv);
void agc_estimate(V29demod_private *priv);
void
V29demod_destroy (ifax_modp self)
{
/* V29demod_private *priv=(V29demod_private *)self->private; */
free (self->private);
return;
}
int
V29demod_command (ifax_modp self, int cmd, va_list cmds)
{
return 0; /* Not yet used. */
}
int
V29demod_handle (ifax_modp self, void *data, size_t length)
{
V29demod_private *priv = (V29demod_private *) self->private;
int n;
short *ps_s = data;
static short max = 0;
for (n = 0; n < length; n++)
{
if(max<*ps_s){
max = *ps_s;
printf("max %i\n",max);
}
*ps_s = (*ps_s*0x1300)>>15;
switch (priv->state)
{
case NIL: /* idle and measure power */
DCD (*ps_s, priv);
ps_s++;
break;
case ESTIMATEGAIN: /* estimate initial input gain */
DCD (*ps_s, priv);
agc_estimate(priv);
ps_s++;
break;
case LISTEN: /* try to detect Segment 2 */
*ps_s = agc_dummy(*ps_s, priv);
DCD (*ps_s, priv);
Demod (*ps_s, priv);
FindSeq2(priv);
ps_s++;
break;
case PHASEHUNT: /* synchronize the carrier phase */
*ps_s = agc_dummy(*ps_s, priv);
DCD (*ps_s, priv);
Demod (*ps_s, priv);
if(priv->smpl_cnt == 0){
PhaseHuntSeq2(priv);
SymbolMapping(priv);
priv->smpl_cnt = 3;
}
priv->smpl_cnt--;
ps_s++;
break;
}
}
return 0;
}
static void
V29demod_demand (ifax_modp self, size_t demand)
{
V29demod_private *priv = (V29demod_private *) self->private;
return;
}
int
V29demod_construct (ifax_modp self, va_list args)
{
V29demod_private *priv;
if (NULL == (priv = self->private = malloc (sizeof (V29demod_private))))
return 1;
self->destroy = V29demod_destroy;
self->handle_input = V29demod_handle;
self->command = V29demod_command;
self->handle_demand = V29demod_demand;
priv->w = 0; /* the carrier's omega */
priv->phi = 0; /* phi to achive carrier sync. */
priv->a = TAU;
priv->state = NIL; /* state variable for the demodulators statemachine*/
priv->dem_index = 0; /* index of the actual demodulated sample within
the demodulator buffers */
priv->smpl_cnt = -1; /* offset for symbol sync.
-1 stands for 'no symb. found' */
priv->agc_gain = 0x0D55; /* equals 0.8333 in (4:12) format */
return 0;
}
short agc_dummy(short s, V29demod_private * priv)
{
return (s*priv->agc_gain)>>12;
}
void agc_estimate(V29demod_private *priv)
{
static int cnt;
long num;
short g;
cnt++;
if(cnt == AGCESTDLY){
num = intsqrt(LEVEL63);
num <<= 12;
g = num/intsqrt(priv->power);
priv->agc_gain = g;
printf("I would guess gain is %04X\n", g);
priv->state = LISTEN;
}
}
short Demod (short s, V29demod_private * priv)
{
static int cnt = 0;
int sum_Re = 0;
int sum_Im = 0;
unsigned short w;
/*modulo increment of sample index */
priv->dem_index = (priv->dem_index < NOSYMB * NOSAMP - 1) ?
(priv->dem_index + 1) : 0;
/* calulate phase corrected omega */
w = priv->w + priv->phi;
/* demodulate signal. The lowpass filter supresses frequencies
at 2*f_c */
switch (cnt)
{
case 0:
priv->dem_lpf_buf[0] = (s * intcos (w)) >> 15;
priv->dem_lpf_buf[1] = (s * intsin (w)) >> 15;
sum_Re += priv->dem_lpf_buf[0] * dem_lpf_coef[0];
sum_Im += priv->dem_lpf_buf[1] * dem_lpf_coef[0];
sum_Re += priv->dem_lpf_buf[2] * dem_lpf_coef[2];
sum_Im += priv->dem_lpf_buf[3] * dem_lpf_coef[2];
sum_Re += priv->dem_lpf_buf[4] * dem_lpf_coef[1];
sum_Im += priv->dem_lpf_buf[5] * dem_lpf_coef[1];
cnt++;
break;
case 1:
priv->dem_lpf_buf[2] = (s * intcos (w)) >> 15;
priv->dem_lpf_buf[3] = (s * intsin (w)) >> 15;
sum_Re += priv->dem_lpf_buf[0] * dem_lpf_coef[1];
sum_Im += priv->dem_lpf_buf[1] * dem_lpf_coef[1];
sum_Re += priv->dem_lpf_buf[2] * dem_lpf_coef[0];
sum_Im += priv->dem_lpf_buf[3] * dem_lpf_coef[0];
sum_Re += priv->dem_lpf_buf[4] * dem_lpf_coef[2];
sum_Im += priv->dem_lpf_buf[5] * dem_lpf_coef[2];
cnt++;
break;
case 2:
priv->dem_lpf_buf[4] = (s * intcos (w)) >> 15;
priv->dem_lpf_buf[5] = (s * intsin (w)) >> 15;
sum_Re += priv->dem_lpf_buf[0] * dem_lpf_coef[2];
sum_Im += priv->dem_lpf_buf[1] * dem_lpf_coef[2];
sum_Re += priv->dem_lpf_buf[2] * dem_lpf_coef[1];
sum_Im += priv->dem_lpf_buf[3] * dem_lpf_coef[1];
sum_Re += priv->dem_lpf_buf[4] * dem_lpf_coef[0];
sum_Im += priv->dem_lpf_buf[5] * dem_lpf_coef[0];
cnt = 0;
break;
}
sum_Re = sum_Re >> 14;
sum_Im = sum_Im >> 14;
priv->dem_re[priv->dem_index] = sum_Re;
priv->dem_im[priv->dem_index] = sum_Im;
/* calculate the absolute angle of the signal */
priv->dem_angl[priv->dem_index] = intatan (sum_Im, sum_Re);
priv->dem_angl[priv->dem_index + NOSYMB * NOSAMP] =
priv->dem_angl[priv->dem_index];
priv->w += PHASEINC1700HZ;
return 0;
}
short SymbolMapping(V29demod_private * priv)
{
short re = priv->dem_re[priv->dem_index];
short im = priv->dem_im[priv->dem_index];
short abs_re;
short abs_im;
short tmp;
int d1, d2, point;
int offset = 0;
abs_re = re < 0 ? -re : re;
abs_im = im < 0 ? -im : im;
if(abs_re < abs_im){
tmp = abs_re;
abs_re = abs_im;
abs_im = tmp;
offset = 4;
}
if(abs_re < X4){
if((abs_re+abs_im) < X2+Y2){
d1 = (abs_re - X3)*(abs_re - X3) + abs_im*abs_im;
d2 = (abs_re - X1)*(abs_re - X1) + (abs_im-Y1)*(abs_im-Y1);
point = d1 > d2 ? 2 : 0;
}
else{
d1 = (abs_re - X3)*(abs_re - X3) + abs_im*abs_im;
d2 = (abs_re - X3)*(abs_re - X3) + (abs_im-Y3)*(abs_im-Y3);
point = d1 > d2 ? 3 : 0;
}
}
else{
d1 = (abs_re - X5)*(abs_re - X5) + abs_im*abs_im;
d2 = (abs_re - X3)*(abs_re - X3) + (abs_im-Y3)*(abs_im-Y3);
point = d1 > d2 ? 3 : 1;
}
point = FirstQuadTbl[offset+point];
if(re < 0) point = ReMinusTbl[point];
if(im < 0) point = ImMinusTbl[point];
printf("%i\n",point);
return 0;
}
short
FindSeq2(V29demod_private * priv)
{
int i;
int res = 0;
/* calculate the relative angle between two symbols */
priv->dem_angl_dif[priv->dem_index] =
priv->dem_angl[priv->dem_index + NOSYMB * NOSAMP] -
priv->dem_angl[priv->dem_index + NOSYMB * NOSAMP - 3];
/* calculate the absolute distance to the expected 135<33> phase difference */
if(priv->dem_angl_dif[priv->dem_index] > 0){
priv->dem_angl_dist[priv->dem_index] = priv->dem_angl_dif[priv->dem_index] - DEG135;
}
else{
priv->dem_angl_dist[priv->dem_index] = DEG135 + priv->dem_angl_dif[priv->dem_index];
}
abs(priv->dem_angl_dist[priv->dem_index]) ;
/* check for sequence 2 every NOSYMB*NOSAMP */
if(priv->dem_index == 0)
{
static int flag = INTERVAL_CNT;
/* find minima within angle distance buffer */
res |= (priv->dem_angl_dist[0] < priv->dem_angl_dist[NOSYMB*NOSAMP-1]) &&
(priv->dem_angl_dist[0] < priv->dem_angl_dist[1]) ? 0 : 1;
res <<= 1;
for(i=1; i< NOSYMB*NOSAMP-1; i++){
res |= (priv->dem_angl_dist[i] < priv->dem_angl_dist[i-1]) &&
(priv->dem_angl_dist[i] < priv->dem_angl_dist[i+1]) ? 0 : 1;
res <<= 1;
}
res |= (priv->dem_angl_dist[NOSYMB*NOSAMP-1] < priv->dem_angl_dist[NOSYMB*NOSAMP-2]) &&
(priv->dem_angl_dist[NOSYMB*NOSAMP-1] < priv->dem_angl_dist[0]) ? 0 : 1;
/* valid received symbols will produce the binary patterns:
110110110b
101101101b
011011011b
Depending on the point of maximum likelihood for sampling, given by
the positions of '0''s in the result line, the initial value for
the sample counter is set.
Depending on the absolute phases of the symbols the angle difference
can be either 135<33> or 225<32>. As the distance is only derived for 135<33>
the received signal is turned by 180<38> after INTERVAL_CNT (>0) decision
intervals.
*/
if (res == 0x1B6) priv->smpl_cnt = 1;
if (res == 0x16B) priv->smpl_cnt = 0;
if (res == 0x0DB) priv->smpl_cnt = 5;
if (priv->smpl_cnt < 0){
if(flag){
flag--;
}
else{
priv->phi += DEG180;
priv->phi &= 0x0000FFFF;
flag = INTERVAL_CNT;
}
}
else{ /* symbol sync. achieved */
/* depending on the current symbol the sign of the angle difference
will change.
[n] [n-1]
135<33> - 315<31> < 0
315<31> - 135 > 0
*/
if(priv->dem_angl_dif[priv->dem_index + priv->smpl_cnt] < 0)
priv->current_symbol = V29_symb_tbl[B9600];
else
priv->current_symbol = V29_symb_tbl[A9600];
priv->state = PHASEHUNT;
printf("Locked on symbol \n");
}
}
return res;
}
short
PhaseHuntSeq2(V29demod_private * priv)
{
short e;
static int cnt = 0;
/* adjust phi by the current phase difference */
priv->phi +=
priv->current_symbol.angl -
priv->dem_angl[priv->dem_index];
/*printf("0x%04X\n",priv->dem_re[priv->dem_index]);*/
/* toggle symbol */
if(priv->current_symbol.angl == DEG180){
if(cnt > 10){
e = priv->current_symbol.Re - priv->dem_re[priv->dem_index];
/*printf("%04X ",e);*/
e = (e * B) >> 18;
priv->agc_gain -= e;
printf("agc gain: %04X\n",priv->agc_gain);
}
cnt++;
priv->current_symbol = V29_symb_tbl[B9600];
}
else
priv->current_symbol = V29_symb_tbl[A9600];
return 0;
}
short
DCD (short s, V29demod_private * priv)
{
int s_s;
/* Power Measurement s_s = a*(s[n] ) + s_s[n-1]*(1-a) */
s_s = (s * s) >> 15;
s_s = s_s - priv->power;
s_s = (s_s * priv->a) >> 15;
s_s = s_s + priv->power;
priv->power = s_s;
printf("power: 0x%04X\n",s_s);
if (s_s < L_MIN){
priv->state = NIL;
return s_s;
}
if (s_s > L_2){
if(priv->state == NIL) priv->state = ESTIMATEGAIN;
return s_s;
}
return s_s;
}
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