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freeswitch/libs/spandsp/src/v29rx.c

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#define IAXMODEM_STUFF
/*
* SpanDSP - a series of DSP components for telephony
*
* v29rx.c - ITU V.29 modem receive part
*
* Written by Steve Underwood <steveu@coppice.org>
*
* Copyright (C) 2003, 2004, 2005, 2006, 2007 Steve Underwood
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 2.1,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: v29rx.c,v 1.167 2009/07/08 15:11:09 steveu Exp $
*/
/*! \file */
#if defined(HAVE_CONFIG_H)
#include "config.h"
#endif
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <stdio.h>
#if defined(HAVE_TGMATH_H)
#include <tgmath.h>
#endif
#if defined(HAVE_MATH_H)
#include <math.h>
#endif
#include "floating_fudge.h"
#include "spandsp/telephony.h"
#include "spandsp/logging.h"
#include "spandsp/complex.h"
#include "spandsp/vector_float.h"
#include "spandsp/complex_vector_float.h"
#include "spandsp/vector_int.h"
#include "spandsp/complex_vector_int.h"
#include "spandsp/async.h"
#include "spandsp/power_meter.h"
#include "spandsp/arctan2.h"
#include "spandsp/dds.h"
#include "spandsp/complex_filters.h"
#include "spandsp/v29rx.h"
#include "spandsp/private/logging.h"
#include "spandsp/private/v29rx.h"
#include "v29tx_constellation_maps.h"
#if defined(SPANDSP_USE_FIXED_POINT)
#include "v29rx_fixed_rrc.h"
#else
#include "v29rx_floating_rrc.h"
#endif
/*! The nominal frequency of the carrier, in Hertz */
#define CARRIER_NOMINAL_FREQ 1700.0f
/*! The nominal baud or symbol rate */
#define BAUD_RATE 2400
/*! The adaption rate coefficient for the equalizer */
#define EQUALIZER_DELTA 0.21f
#if defined(SPANDSP_USE_FIXED_POINT)
#define FP_FACTOR 4096
#define FP_SHIFT_FACTOR 12
#endif
/* Segments of the training sequence */
/*! The length of training segment 2, in symbols */
#define V29_TRAINING_SEG_2_LEN 128
/*! The length of training segment 3, in symbols */
#define V29_TRAINING_SEG_3_LEN 384
/*! The length of training segment 4, in symbols */
#define V29_TRAINING_SEG_4_LEN 48
/*! The length of the equalizer buffer */
#define V29_EQUALIZER_LEN (V29_EQUALIZER_PRE_LEN + 1 + V29_EQUALIZER_POST_LEN)
enum
{
TRAINING_STAGE_NORMAL_OPERATION = 0,
TRAINING_STAGE_SYMBOL_ACQUISITION,
TRAINING_STAGE_LOG_PHASE,
TRAINING_STAGE_WAIT_FOR_CDCD,
TRAINING_STAGE_TRAIN_ON_CDCD,
TRAINING_STAGE_TRAIN_ON_CDCD_AND_TEST,
TRAINING_STAGE_TEST_ONES,
TRAINING_STAGE_PARKED
};
static const uint8_t space_map_9600[20][20] =
{
{13, 13, 13, 13, 13, 13, 12, 12, 12, 12, 12, 12, 12, 12, 11, 11, 11, 11, 11, 11},
{13, 13, 13, 13, 13, 13, 13, 12, 12, 12, 12, 12, 12, 11, 11, 11, 11, 11, 11, 11},
{13, 13, 13, 13, 13, 13, 13, 4, 4, 4, 4, 4, 4, 11, 11, 11, 11, 11, 11, 11},
{13, 13, 13, 13, 13, 13, 13, 4, 4, 4, 4, 4, 4, 11, 11, 11, 11, 11, 11, 11},
{13, 13, 13, 13, 13, 13, 13, 4, 4, 4, 4, 4, 4, 11, 11, 11, 11, 11, 11, 11},
{13, 13, 13, 13, 13, 13, 13, 5, 4, 4, 4, 4, 3, 11, 11, 11, 11, 11, 11, 11},
{14, 13, 13, 13, 13, 13, 5, 5, 5, 5, 3, 3, 3, 3, 11, 11, 11, 11, 11, 10},
{14, 14, 6, 6, 6, 5, 5, 5, 5, 5, 3, 3, 3, 3, 3, 2, 2, 2, 10, 10},
{14, 14, 6, 6, 6, 6, 5, 5, 5, 5, 3, 3, 3, 3, 2, 2, 2, 2, 10, 10},
{14, 14, 6, 6, 6, 6, 5, 5, 5, 5, 3, 3, 3, 3, 2, 2, 2, 2, 10, 10},
{14, 14, 6, 6, 6, 6, 7, 7, 7, 7, 1, 1, 1, 1, 2, 2, 2, 2, 10, 10},
{14, 14, 6, 6, 6, 6, 7, 7, 7, 7, 1, 1, 1, 1, 2, 2, 2, 2, 10, 10},
{14, 14, 6, 6, 6, 7, 7, 7, 7, 7, 1, 1, 1, 1, 1, 2, 2, 2, 10, 10},
{14, 15, 15, 15, 15, 15, 7, 7, 7, 7, 1, 1, 1, 1, 9, 9, 9, 9, 9, 10},
{15, 15, 15, 15, 15, 15, 15, 7, 0, 0, 0, 0, 1, 9, 9, 9, 9, 9, 9, 9},
{15, 15, 15, 15, 15, 15, 15, 0, 0, 0, 0, 0, 0, 9, 9, 9, 9, 9, 9, 9},
{15, 15, 15, 15, 15, 15, 15, 0, 0, 0, 0, 0, 0, 9, 9, 9, 9, 9, 9, 9},
{15, 15, 15, 15, 15, 15, 15, 0, 0, 0, 0, 0, 0, 9, 9, 9, 9, 9, 9, 9},
{15, 15, 15, 15, 15, 15, 15, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9},
{15, 15, 15, 15, 15, 15, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9}
};
/* Coefficients for the band edge symbol timing synchroniser (alpha = 0.99) */
/* low_edge = 2.0f*M_PI*(CARRIER_NOMINAL_FREQ - BAUD_RATE/2.0f)/SAMPLE_RATE; */
/* high_edge = 2.0f*M_PI*(CARRIER_NOMINAL_FREQ + BAUD_RATE/2.0f)/SAMPLE_RATE; */
#if defined(SPANDSP_USE_FIXED_POINT)
#define SYNC_LOW_BAND_EDGE_COEFF_0 ((int)(FP_FACTOR* 1.829281f)) /* 2*alpha*cos(low_edge) */
#define SYNC_LOW_BAND_EDGE_COEFF_1 ((int)(FP_FACTOR*-0.980100f)) /* -alpha^2 */
#define SYNC_HIGH_BAND_EDGE_COEFF_0 ((int)(FP_FACTOR*-1.285907f)) /* 2*alpha*cos(high_edge) */
#define SYNC_HIGH_BAND_EDGE_COEFF_1 ((int)(FP_FACTOR*-0.980100f)) /* -alpha^2 */
#define SYNC_CROSS_CORR_COEFF_A ((int)(FP_FACTOR*-0.932131f)) /* -alpha^2*sin(freq_diff) */
#define SYNC_CROSS_CORR_COEFF_B ((int)(FP_FACTOR* 0.752802f)) /* alpha*sin(high_edge) */
#define SYNC_CROSS_CORR_COEFF_C ((int)(FP_FACTOR*-0.378857f)) /* -alpha*sin(low_edge) */
#else
#define SYNC_LOW_BAND_EDGE_COEFF_0 1.829281f /* 2*alpha*cos(low_edge) */
#define SYNC_LOW_BAND_EDGE_COEFF_1 -0.980100f /* -alpha^2 */
#define SYNC_HIGH_BAND_EDGE_COEFF_0 -1.285907f /* 2*alpha*cos(high_edge) */
#define SYNC_HIGH_BAND_EDGE_COEFF_1 -0.980100f /* -alpha^2 */
#define SYNC_CROSS_CORR_COEFF_A -0.932131f /* -alpha^2*sin(freq_diff) */
#define SYNC_CROSS_CORR_COEFF_B 0.752802f /* alpha*sin(high_edge) */
#define SYNC_CROSS_CORR_COEFF_C -0.378857f /* -alpha*sin(low_edge) */
#endif
SPAN_DECLARE(float) v29_rx_carrier_frequency(v29_rx_state_t *s)
{
return dds_frequencyf(s->carrier_phase_rate);
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(float) v29_rx_symbol_timing_correction(v29_rx_state_t *s)
{
return (float) s->total_baud_timing_correction/((float) RX_PULSESHAPER_COEFF_SETS*10.0f/3.0f);
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(float) v29_rx_signal_power(v29_rx_state_t *s)
{
return power_meter_current_dbm0(&s->power) + 3.98f;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v29_rx_signal_cutoff(v29_rx_state_t *s, float cutoff)
{
/* The 0.4 factor allows for the gain of the DC blocker */
s->carrier_on_power = (int32_t) (power_meter_level_dbm0(cutoff + 2.5f)*0.4f);
s->carrier_off_power = (int32_t) (power_meter_level_dbm0(cutoff - 2.5f)*0.4f);
}
/*- End of function --------------------------------------------------------*/
static void report_status_change(v29_rx_state_t *s, int status)
{
if (s->status_handler)
s->status_handler(s->status_user_data, status);
else if (s->put_bit)
s->put_bit(s->put_bit_user_data, status);
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
SPAN_DECLARE(int) v29_rx_equalizer_state(v29_rx_state_t *s, complexi16_t **coeffs)
#else
SPAN_DECLARE(int) v29_rx_equalizer_state(v29_rx_state_t *s, complexf_t **coeffs)
#endif
{
*coeffs = s->eq_coeff;
return V29_EQUALIZER_LEN;
}
/*- End of function --------------------------------------------------------*/
static void equalizer_save(v29_rx_state_t *s)
{
#if defined(SPANDSP_USE_FIXED_POINT)
cvec_copyi16(s->eq_coeff_save, s->eq_coeff, V29_EQUALIZER_LEN);
#else
cvec_copyf(s->eq_coeff_save, s->eq_coeff, V29_EQUALIZER_LEN);
#endif
}
/*- End of function --------------------------------------------------------*/
static void equalizer_restore(v29_rx_state_t *s)
{
#if defined(SPANDSP_USE_FIXED_POINT)
cvec_copyi16(s->eq_coeff, s->eq_coeff_save, V29_EQUALIZER_LEN);
cvec_zeroi16(s->eq_buf, V29_EQUALIZER_LEN);
s->eq_delta = 32768.0f*EQUALIZER_DELTA/V29_EQUALIZER_LEN;
#else
cvec_copyf(s->eq_coeff, s->eq_coeff_save, V29_EQUALIZER_LEN);
cvec_zerof(s->eq_buf, V29_EQUALIZER_LEN);
s->eq_delta = EQUALIZER_DELTA/V29_EQUALIZER_LEN;
#endif
s->eq_put_step = RX_PULSESHAPER_COEFF_SETS*10/(3*2) - 1;
s->eq_step = 0;
}
/*- End of function --------------------------------------------------------*/
static void equalizer_reset(v29_rx_state_t *s)
{
/* Start with an equalizer based on everything being perfect */
#if defined(SPANDSP_USE_FIXED_POINT)
cvec_zeroi16(s->eq_coeff, V29_EQUALIZER_LEN);
s->eq_coeff[V29_EQUALIZER_POST_LEN] = complex_seti16(3*FP_FACTOR, 0*FP_FACTOR);
cvec_zeroi16(s->eq_buf, V29_EQUALIZER_LEN);
s->eq_delta = 32768.0f*EQUALIZER_DELTA/V29_EQUALIZER_LEN;
#else
cvec_zerof(s->eq_coeff, V29_EQUALIZER_LEN);
s->eq_coeff[V29_EQUALIZER_POST_LEN] = complex_setf(3.0f, 0.0f);
cvec_zerof(s->eq_buf, V29_EQUALIZER_LEN);
s->eq_delta = EQUALIZER_DELTA/V29_EQUALIZER_LEN;
#endif
s->eq_put_step = RX_PULSESHAPER_COEFF_SETS*10/(3*2) - 1;
s->eq_step = 0;
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static __inline__ complexi16_t complex_mul_q4_12(const complexi16_t *x, const complexi16_t *y)
{
complexi16_t z;
z.re = ((int32_t) x->re*(int32_t) y->re - (int32_t) x->im*(int32_t) y->im) >> FP_SHIFT_FACTOR;
z.im = ((int32_t) x->re*(int32_t) y->im + (int32_t) x->im*(int32_t) y->re) >> FP_SHIFT_FACTOR;
return z;
}
/*- End of function --------------------------------------------------------*/
#endif
#if defined(SPANDSP_USE_FIXED_POINT)
static __inline__ complexi16_t equalizer_get(v29_rx_state_t *s)
#else
static __inline__ complexf_t equalizer_get(v29_rx_state_t *s)
#endif
{
#if defined(SPANDSP_USE_FIXED_POINT)
complexi32_t zz;
complexi16_t z;
/* Get the next equalized value. */
zz = cvec_circular_dot_prodi16(s->eq_buf, s->eq_coeff, V29_EQUALIZER_LEN, s->eq_step);
z.re = zz.re >> FP_SHIFT_FACTOR;
z.im = zz.im >> FP_SHIFT_FACTOR;
return z;
#else
/* Get the next equalized value. */
return cvec_circular_dot_prodf(s->eq_buf, s->eq_coeff, V29_EQUALIZER_LEN, s->eq_step);
#endif
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static void tune_equalizer(v29_rx_state_t *s, const complexi16_t *z, const complexi16_t *target)
{
complexi16_t err;
/* Find the x and y mismatch from the exact constellation position. */
err.re = target->re*FP_FACTOR - z->re;
err.im = target->im*FP_FACTOR - z->im;
err.re = ((int32_t) err.re*(int32_t) s->eq_delta) >> 15;
err.im = ((int32_t) err.im*(int32_t) s->eq_delta) >> 15;
cvec_circular_lmsi16(s->eq_buf, s->eq_coeff, V29_EQUALIZER_LEN, s->eq_step, &err);
}
#else
static void tune_equalizer(v29_rx_state_t *s, const complexf_t *z, const complexf_t *target)
{
complexf_t err;
/* Find the x and y mismatch from the exact constellation position. */
err = complex_subf(target, z);
err.re *= s->eq_delta;
err.im *= s->eq_delta;
cvec_circular_lmsf(s->eq_buf, s->eq_coeff, V29_EQUALIZER_LEN, s->eq_step, &err);
}
#endif
/*- End of function --------------------------------------------------------*/
static int scrambled_training_bit(v29_rx_state_t *s)
{
int bit;
/* Segment 3 of the training sequence - the scrambled CDCD part. */
/* Apply the 1 + x^-6 + x^-7 scrambler */
bit = s->training_scramble_reg & 1;
s->training_scramble_reg >>= 1;
if (bit ^ (s->training_scramble_reg & 1))
s->training_scramble_reg |= 0x40;
return bit;
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static __inline__ int find_quadrant(const complexi16_t *z)
#else
static __inline__ int find_quadrant(const complexf_t *z)
#endif
{
int b1;
int b2;
/* Split the space along the two diagonals. */
b1 = (z->im > z->re);
b2 = (z->im < -z->re);
return (b2 << 1) | (b1 ^ b2);
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static __inline__ void track_carrier(v29_rx_state_t *s, const complexi16_t *z, const complexi16_t *target)
#else
static __inline__ void track_carrier(v29_rx_state_t *s, const complexf_t *z, const complexf_t *target)
#endif
{
#if defined(SPANDSP_USE_FIXED_POINT)
int32_t error;
#else
float error;
#endif
/* The initial coarse carrier frequency and phase estimation should have
got us in the right ballpark. Now we need to fine tune fairly quickly,
to get the receovered carrier more precisely on target. Then we need to
fine tune in a more damped way to keep us on target. The goal is to have
things running really well by the time the training is complete.
We assume the frequency of the oscillators at the two ends drift only
very slowly. The PSTN has rather limited doppler problems. :-) Any
remaining FDM in the network should also drift slowly. */
/* For small errors the imaginary part of the difference between the actual and the target
positions is proportional to the phase error, for any particular target. However, the
different amplitudes of the various target positions scale things. This isn't all bad,
as the angular error for the larger amplitude constellation points is probably
a more reliable indicator, and we are weighting it as such. */
error = z->im*target->re - z->re*target->im;
/* Use a proportional-integral approach to tracking the carrier. The PI
parameters are coarser at first, until we get precisely on target. Then,
the filter will be damped more to keep us on target. */
#if defined(SPANDSP_USE_FIXED_POINT)
s->carrier_phase_rate += ((s->carrier_track_i*error) >> FP_SHIFT_FACTOR);
s->carrier_phase += ((s->carrier_track_p*error) >> FP_SHIFT_FACTOR);
#else
s->carrier_phase_rate += (int32_t) (s->carrier_track_i*error);
s->carrier_phase += (int32_t) (s->carrier_track_p*error);
//span_log(&s->logging, SPAN_LOG_FLOW, "Im = %15.5f f = %15.5f\n", error, dds_frequencyf(s->carrier_phase_rate));
#endif
}
/*- End of function --------------------------------------------------------*/
static __inline__ void put_bit(v29_rx_state_t *s, int bit)
{
int out_bit;
bit &= 1;
/* Descramble the bit */
out_bit = (bit ^ (s->scramble_reg >> 17) ^ (s->scramble_reg >> 22)) & 1;
s->scramble_reg = (s->scramble_reg << 1) | bit;
/* We need to strip the last part of the training - the test period of all 1s -
before we let data go to the application. */
if (s->training_stage == TRAINING_STAGE_NORMAL_OPERATION)
{
s->put_bit(s->put_bit_user_data, out_bit);
}
else
{
/* The bits during the final stage of training should be all ones. However,
buggy modems mean you cannot rely on this. Therefore we don't bother
testing for ones, but just rely on a constellation mismatch measurement. */
}
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static void decode_baud(v29_rx_state_t *s, complexi16_t *z)
#else
static void decode_baud(v29_rx_state_t *s, complexf_t *z)
#endif
{
static const uint8_t phase_steps_9600[8] =
{
4, 0, 2, 6, 7, 3, 1, 5
};
static const uint8_t phase_steps_4800[4] =
{
0, 2, 3, 1
};
int nearest;
int raw_bits;
int i;
int re;
int im;
if (s->bit_rate == 4800)
{
/* 4800 is a special case. */
nearest = find_quadrant(z) << 1;
raw_bits = phase_steps_4800[((nearest - s->constellation_state) >> 1) & 3];
put_bit(s, raw_bits);
put_bit(s, raw_bits >> 1);
}
else
{
/* 9600 and 7200 are quite similar. */
#if defined(SPANDSP_USE_FIXED_POINT)
re = (z->re + 5*FP_FACTOR) >> (FP_SHIFT_FACTOR - 1);
im = (z->im + 5*FP_FACTOR) >> (FP_SHIFT_FACTOR - 1);
#else
re = (int) ((z->re + 5.0f)*2.0f);
im = (int) ((z->im + 5.0f)*2.0f);
#endif
if (re > 19)
re = 19;
else if (re < 0)
re = 0;
if (im > 19)
im = 19;
else if (im < 0)
im = 0;
nearest = space_map_9600[re][im];
if (s->bit_rate == 9600)
{
/* Send out the top (amplitude) bit. */
put_bit(s, nearest >> 3);
}
else
{
/* We can reuse the space map for 9600, but drop the top bit. */
nearest &= 7;
}
raw_bits = phase_steps_9600[(nearest - s->constellation_state) & 7];
for (i = 0; i < 3; i++)
{
put_bit(s, raw_bits);
raw_bits >>= 1;
}
}
track_carrier(s, z, &v29_9600_constellation[nearest]);
if (--s->eq_skip <= 0)
{
/* Once we are in the data the equalization should not need updating.
However, the line characteristics may slowly drift. We, therefore,
tune up on the occassional sample, keeping the compute down. */
s->eq_skip = 10;
tune_equalizer(s, z, &v29_9600_constellation[nearest]);
}
s->constellation_state = nearest;
}
/*- End of function --------------------------------------------------------*/
static __inline__ void symbol_sync(v29_rx_state_t *s)
{
int i;
#if defined(SPANDSP_USE_FIXED_POINT)
int32_t v;
int32_t p;
#else
float v;
float p;
#endif
/* This routine adapts the position of the half baud samples entering the equalizer. */
#if defined(SPANDSP_USE_FIXED_POINT)
/* TODO: The scalings used here need more thorough evaluation, to see if overflows are possible. */
/* Cross correlate */
v = (((s->symbol_sync_low[1] >> 5)*(s->symbol_sync_high[1] >> 4)) >> 15)*SYNC_CROSS_CORR_COEFF_A
+ (((s->symbol_sync_low[0] >> 5)*(s->symbol_sync_high[1] >> 4)) >> 15)*SYNC_CROSS_CORR_COEFF_B
+ (((s->symbol_sync_low[1] >> 5)*(s->symbol_sync_high[0] >> 4)) >> 15)*SYNC_CROSS_CORR_COEFF_C;
/* Filter away any DC component */
p = v - s->symbol_sync_dc_filter[1];
s->symbol_sync_dc_filter[1] = s->symbol_sync_dc_filter[0];
s->symbol_sync_dc_filter[0] = v;
/* A little integration will now filter away much of the noise */
s->baud_phase -= p;
if (abs(s->baud_phase) > 30*FP_FACTOR)
{
if (s->baud_phase > 0)
i = (s->baud_phase > 1000*FP_FACTOR) ? 5 : 1;
else
i = (s->baud_phase < -1000*FP_FACTOR) ? -5 : -1;
//printf("v = %10.5f %5d - %f %f %d %d\n", v, i, p, s->baud_phase, s->total_baud_timing_correction);
s->eq_put_step += i;
s->total_baud_timing_correction += i;
}
#else
/* Cross correlate */
v = s->symbol_sync_low[1]*s->symbol_sync_high[1]*SYNC_CROSS_CORR_COEFF_A
+ s->symbol_sync_low[0]*s->symbol_sync_high[1]*SYNC_CROSS_CORR_COEFF_B
+ s->symbol_sync_low[1]*s->symbol_sync_high[0]*SYNC_CROSS_CORR_COEFF_C;
/* Filter away any DC component */
p = v - s->symbol_sync_dc_filter[1];
s->symbol_sync_dc_filter[1] = s->symbol_sync_dc_filter[0];
s->symbol_sync_dc_filter[0] = v;
/* A little integration will now filter away much of the noise */
s->baud_phase -= p;
#if 0
if (fabsf(s->baud_phase) > 100.0f)
#else
if (fabsf(s->baud_phase) > 30.0f)
#endif
{
if (s->baud_phase > 0.0f)
i = (s->baud_phase > 1000.0f) ? 5 : 1;
else
i = (s->baud_phase < -1000.0f) ? -5 : -1;
//printf("v = %10.5f %5d - %f %f %d %d\n", v, i, p, s->baud_phase, s->total_baud_timing_correction);
s->eq_put_step += i;
s->total_baud_timing_correction += i;
}
#endif
}
/*- End of function --------------------------------------------------------*/
#if defined(SPANDSP_USE_FIXED_POINT)
static void process_half_baud(v29_rx_state_t *s, complexi16_t *sample)
#else
static void process_half_baud(v29_rx_state_t *s, complexf_t *sample)
#endif
{
static const int cdcd_pos[6] =
{
0, 11,
0, 3,
0, 2
};
complexf_t zz;
#if defined(SPANDSP_USE_FIXED_POINT)
complexf_t z1;
complexi16_t z;
const complexi16_t *target;
static const complexi16_t zero = {0, 0};
#else
complexf_t z;
const complexf_t *target;
static const complexf_t zero = {0.0f, 0.0f};
#endif
float p;
int bit;
int i;
int j;
int32_t angle;
int32_t ang;
/* This routine processes every half a baud, as we put things into the equalizer at the T/2 rate. */
/* Add a sample to the equalizer's circular buffer, but don't calculate anything
at this time. */
s->eq_buf[s->eq_step] = *sample;
if (++s->eq_step >= V29_EQUALIZER_LEN)
s->eq_step = 0;
/* On alternate insertions we have a whole baud, and must process it. */
if ((s->baud_half ^= 1))
return;
/* Symbol timing synchronisation */
symbol_sync(s);
z = equalizer_get(s);
switch (s->training_stage)
{
case TRAINING_STAGE_NORMAL_OPERATION:
/* Normal operation. */
decode_baud(s, &z);
target = &v29_9600_constellation[s->constellation_state];
break;
case TRAINING_STAGE_SYMBOL_ACQUISITION:
/* Allow time for symbol synchronisation to settle the symbol timing. */
target = &zero;
if (++s->training_count >= 60)
{
/* Record the current phase angle */
s->training_stage = TRAINING_STAGE_LOG_PHASE;
s->angles[0] =
s->start_angles[0] = arctan2(z.im, z.re);
#if defined(SPANDSP_USE_FIXED_POINT)
if (s->agc_scaling_save == 0)
s->agc_scaling_save = s->agc_scaling;
#else
if (s->agc_scaling_save == 0.0f)
s->agc_scaling_save = s->agc_scaling;
#endif
}
break;
case TRAINING_STAGE_LOG_PHASE:
/* Record the current alternate phase angle */
target = &zero;
s->angles[1] =
s->start_angles[1] = arctan2(z.im, z.re);
s->training_count = 1;
s->training_stage = TRAINING_STAGE_WAIT_FOR_CDCD;
break;
case TRAINING_STAGE_WAIT_FOR_CDCD:
target = &zero;
angle = arctan2(z.im, z.re);
/* Look for the initial ABAB sequence to display a phase reversal, which will
signal the start of the scrambled CDCD segment */
ang = angle - s->angles[(s->training_count - 1) & 0xF];
s->angles[(s->training_count + 1) & 0xF] = angle;
if ((ang > 0x20000000 || ang < -0x20000000) && s->training_count >= 13)
{
/* We seem to have a phase reversal */
/* Slam the carrier frequency into line, based on the total phase drift over the last
section. Use the shift from the odd bits and the shift from the even bits to get
better jitter suppression. We need to scale here, or at the maximum specified
frequency deviation we could overflow, and get a silly answer. */
/* Step back a few symbols so we don't get ISI distorting things. */
i = (s->training_count - 8) & ~1;
/* Avoid the possibility of a divide by zero */
if (i)
{
j = i & 0xF;
ang = (s->angles[j] - s->start_angles[0])/i
+ (s->angles[j | 0x1] - s->start_angles[1])/i;
s->carrier_phase_rate += 3*(ang/20);
}
span_log(&s->logging, SPAN_LOG_FLOW, "Coarse carrier frequency %7.2f\n", dds_frequencyf(s->carrier_phase_rate));
/* Check if the carrier frequency is plausible */
if (s->carrier_phase_rate < dds_phase_ratef(CARRIER_NOMINAL_FREQ - 20.0f)
||
s->carrier_phase_rate > dds_phase_ratef(CARRIER_NOMINAL_FREQ + 20.0f))
{
span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (sequence failed)\n");
/* Park this modem */
#if defined(SPANDSP_USE_FIXED_POINT)
s->agc_scaling_save = 0;
#else
s->agc_scaling_save = 0.0f;
#endif
s->training_stage = TRAINING_STAGE_PARKED;
report_status_change(s, SIG_STATUS_TRAINING_FAILED);
break;
}
/* Make a step shift in the phase, to pull it into line. We need to rotate the equalizer
buffer, as well as the carrier phase, for this to play out nicely. */
p = angle*2.0f*3.14159f/(65536.0f*65536.0f);
#if defined(SPANDSP_USE_FIXED_POINT)
zz = complex_setf(cosf(p), -sinf(p));
for (i = 0; i < V29_EQUALIZER_LEN; i++)
{
z1 = complex_setf(s->eq_buf[i].re, s->eq_buf[i].im);
z1 = complex_mulf(&z1, &zz);
s->eq_buf[i].re = z1.re;
s->eq_buf[i].im = z1.im;
}
#else
zz = complex_setf(cosf(p), -sinf(p));
for (i = 0; i < V29_EQUALIZER_LEN; i++)
s->eq_buf[i] = complex_mulf(&s->eq_buf[i], &zz);
#endif
s->carrier_phase += angle;
/* We have just seen the first bit of the scrambled sequence, so skip it. */
bit = scrambled_training_bit(s);
s->constellation_state = cdcd_pos[s->training_cd + bit];
target = &v29_9600_constellation[s->constellation_state];
s->training_count = 1;
s->training_stage = TRAINING_STAGE_TRAIN_ON_CDCD;
report_status_change(s, SIG_STATUS_TRAINING_IN_PROGRESS);
break;
}
if (++s->training_count > V29_TRAINING_SEG_2_LEN)
{
/* This is bogus. There are not this many bauds in this section
of a real training sequence. */
span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (sequence failed)\n");
/* Park this modem */
#if defined(SPANDSP_USE_FIXED_POINT)
s->agc_scaling_save = 0;
#else
s->agc_scaling_save = 0.0f;
#endif
s->training_stage = TRAINING_STAGE_PARKED;
report_status_change(s, SIG_STATUS_TRAINING_FAILED);
}
break;
case TRAINING_STAGE_TRAIN_ON_CDCD:
/* Train on the scrambled CDCD section. */
bit = scrambled_training_bit(s);
//span_log(&s->logging, SPAN_LOG_FLOW, "%5d %15.5f, %15.5f %15.5f, %15.5f\n", s->training_count, z.re, z.im, v29_9600_constellation[cdcd_pos[s->training_cd + bit]].re, v29_9600_constellation[cdcd_pos[s->training_cd + bit]].im);
s->constellation_state = cdcd_pos[s->training_cd + bit];
target = &v29_9600_constellation[s->constellation_state];
track_carrier(s, &z, target);
tune_equalizer(s, &z, target);
if (++s->training_count >= V29_TRAINING_SEG_3_LEN - 48)
{
s->training_stage = TRAINING_STAGE_TRAIN_ON_CDCD_AND_TEST;
s->training_error = 0.0f;
#if defined(SPANDSP_USE_FIXED_POINT)
s->carrier_track_i = 200;
s->carrier_track_p = 1000000;
#else
s->carrier_track_i = 200.0f;
s->carrier_track_p = 1000000.0f;
#endif
}
break;
case TRAINING_STAGE_TRAIN_ON_CDCD_AND_TEST:
/* Continue training on the scrambled CDCD section, but measure the quality of training too. */
bit = scrambled_training_bit(s);
//span_log(&s->logging, SPAN_LOG_FLOW, "%5d %15.5f, %15.5f %15.5f, %15.5f\n", s->training_count, z.re, z.im, v29_9600_constellation[cdcd_pos[s->training_cd + bit]].re, v29_9600_constellation[cdcd_pos[s->training_cd + bit]].im);
s->constellation_state = cdcd_pos[s->training_cd + bit];
target = &v29_9600_constellation[s->constellation_state];
track_carrier(s, &z, target);
tune_equalizer(s, &z, target);
/* Measure the training error */
#if defined(SPANDSP_USE_FIXED_POINT)
z1.re = z.re/(float) FP_FACTOR;
z1.im = z.im/(float) FP_FACTOR;
zz.re = target->re;
zz.im = target->im;
zz = complex_subf(&z1, &zz);
s->training_error += powerf(&zz);
#else
zz = complex_subf(&z, target);
s->training_error += powerf(&zz);
#endif
if (++s->training_count >= V29_TRAINING_SEG_3_LEN)
{
span_log(&s->logging, SPAN_LOG_FLOW, "Constellation mismatch %f\n", s->training_error);
if (s->training_error < 48.0f*2.0f)
{
s->training_count = 0;
s->training_error = 0.0f;
s->constellation_state = 0;
s->training_stage = TRAINING_STAGE_TEST_ONES;
}
else
{
span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (convergence failed)\n");
/* Park this modem */
#if defined(SPANDSP_USE_FIXED_POINT)
s->agc_scaling_save = 0;
#else
s->agc_scaling_save = 0.0f;
#endif
s->training_stage = TRAINING_STAGE_PARKED;
report_status_change(s, SIG_STATUS_TRAINING_FAILED);
}
}
break;
case TRAINING_STAGE_TEST_ONES:
/* We are in the test phase, where we check that we can receive reliably.
We should get a run of 1's, 48 symbols (192 bits at 9600bps) long. */
//span_log(&s->logging, SPAN_LOG_FLOW, "%5d %15.5f, %15.5f\n", s->training_count, z.re, z.im);
decode_baud(s, &z);
target = &v29_9600_constellation[s->constellation_state];
/* Measure the training error */
#if defined(SPANDSP_USE_FIXED_POINT)
z1.re = z.re/(float) FP_FACTOR;
z1.im = z.im/(float) FP_FACTOR;
zz.re = target->re;
zz.im = target->im;
zz = complex_subf(&z1, &zz);
s->training_error += powerf(&zz);
#else
zz = complex_subf(&z, target);
s->training_error += powerf(&zz);
#endif
if (++s->training_count >= V29_TRAINING_SEG_4_LEN)
{
if (s->training_error < 48.0f)
{
/* We are up and running */
span_log(&s->logging, SPAN_LOG_FLOW, "Training succeeded at %dbps (constellation mismatch %f)\n", s->bit_rate, s->training_error);
report_status_change(s, SIG_STATUS_TRAINING_SUCCEEDED);
/* Apply some lag to the carrier off condition, to ensure the last few bits get pushed through
the processing. */
s->signal_present = 60;
s->training_stage = TRAINING_STAGE_NORMAL_OPERATION;
equalizer_save(s);
s->carrier_phase_rate_save = s->carrier_phase_rate;
s->agc_scaling_save = s->agc_scaling;
}
else
{
/* Training has failed */
span_log(&s->logging, SPAN_LOG_FLOW, "Training failed (constellation mismatch %f)\n", s->training_error);
/* Park this modem */
#if defined(SPANDSP_USE_FIXED_POINT)
s->agc_scaling_save = 0;
#else
s->agc_scaling_save = 0.0f;
#endif
s->training_stage = TRAINING_STAGE_PARKED;
report_status_change(s, SIG_STATUS_TRAINING_FAILED);
}
}
break;
case TRAINING_STAGE_PARKED:
default:
/* We failed to train! */
/* Park here until the carrier drops. */
target = &zero;
break;
}
if (s->qam_report)
{
#if defined(SPANDSP_USE_FIXED_POINT)
z1.re = z.re/(float) FP_FACTOR;
z1.im = z.im/(float) FP_FACTOR;
zz.re = target->re;
zz.im = target->im;
s->qam_report(s->qam_user_data, &z1, &zz, s->constellation_state);
#else
s->qam_report(s->qam_user_data, &z, target, s->constellation_state);
#endif
}
}
/*- End of function --------------------------------------------------------*/
static __inline__ int signal_detect(v29_rx_state_t *s, int16_t amp)
{
int16_t diff;
int16_t x;
int32_t power;
/* There should be no DC in the signal, but sometimes there is.
We need to measure the power with the DC blocked, but not using
a slow to respond DC blocker. Use the most elementary HPF. */
x = amp >> 1;
/* There could be overflow here, but it isn't a problem in practice */
diff = x - s->last_sample;
s->last_sample = x;
power = power_meter_update(&(s->power), diff);
#if defined(IAXMODEM_STUFF)
/* Quick power drop fudge */
diff = abs(diff);
if (10*diff < s->high_sample)
{
if (++s->low_samples > 120)
{
power_meter_init(&(s->power), 4);
s->high_sample = 0;
s->low_samples = 0;
}
}
else
{
s->low_samples = 0;
if (diff > s->high_sample)
s->high_sample = diff;
}
#endif
if (s->signal_present > 0)
{
/* Look for power below turn-off threshold to turn the carrier off */
#if defined(IAXMODEM_STUFF)
if (s->carrier_drop_pending || power < s->carrier_off_power)
#else
if (power < s->carrier_off_power)
#endif
{
if (--s->signal_present <= 0)
{
/* Count down a short delay, to ensure we push the last
few bits through the filters before stopping. */
v29_rx_restart(s, s->bit_rate, FALSE);
report_status_change(s, SIG_STATUS_CARRIER_DOWN);
return 0;
}
#if defined(IAXMODEM_STUFF)
/* Carrier has dropped, but the put_bit is
pending the signal_present delay. */
s->carrier_drop_pending = TRUE;
#endif
}
}
else
{
/* Look for power exceeding turn-on threshold to turn the carrier on */
if (power < s->carrier_on_power)
return 0;
s->signal_present = 1;
#if defined(IAXMODEM_STUFF)
s->carrier_drop_pending = FALSE;
#endif
report_status_change(s, SIG_STATUS_CARRIER_UP);
}
return power;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE_NONSTD(int) v29_rx(v29_rx_state_t *s, const int16_t amp[], int len)
{
int i;
int step;
#if defined(SPANDSP_USE_FIXED_POINT)
complexi16_t z;
complexi16_t zz;
complexi16_t sample;
int32_t v;
#else
complexf_t z;
complexf_t zz;
complexf_t sample;
float v;
#endif
int32_t power;
for (i = 0; i < len; i++)
{
s->rrc_filter[s->rrc_filter_step] = amp[i];
if (++s->rrc_filter_step >= V29_RX_FILTER_STEPS)
s->rrc_filter_step = 0;
if ((power = signal_detect(s, amp[i])) == 0)
continue;
if (s->training_stage == TRAINING_STAGE_PARKED)
continue;
/* Only spend effort processing this data if the modem is not
parked, after training failure. */
s->eq_put_step -= RX_PULSESHAPER_COEFF_SETS;
step = -s->eq_put_step;
if (step > RX_PULSESHAPER_COEFF_SETS - 1)
step = RX_PULSESHAPER_COEFF_SETS - 1;
if (step < 0)
step += RX_PULSESHAPER_COEFF_SETS;
#if defined(SPANDSP_USE_FIXED_POINT)
v = vec_circular_dot_prodi16(s->rrc_filter, rx_pulseshaper_re[step], V29_RX_FILTER_STEPS, s->rrc_filter_step);
sample.re = (v*s->agc_scaling) >> 15;
#else
v = vec_circular_dot_prodf(s->rrc_filter, rx_pulseshaper_re[step], V29_RX_FILTER_STEPS, s->rrc_filter_step);
sample.re = v*s->agc_scaling;
#endif
/* Symbol timing synchronisation band edge filters */
#if defined(SPANDSP_USE_FIXED_POINT)
/* Low Nyquist band edge filter */
v = ((s->symbol_sync_low[0]*SYNC_LOW_BAND_EDGE_COEFF_0) >> FP_SHIFT_FACTOR) + ((s->symbol_sync_low[1]*SYNC_LOW_BAND_EDGE_COEFF_1) >> FP_SHIFT_FACTOR) + sample.re;
s->symbol_sync_low[1] = s->symbol_sync_low[0];
s->symbol_sync_low[0] = v;
/* High Nyquist band edge filter */
v = ((s->symbol_sync_high[0]*SYNC_HIGH_BAND_EDGE_COEFF_0) >> FP_SHIFT_FACTOR) + ((s->symbol_sync_high[1]*SYNC_HIGH_BAND_EDGE_COEFF_1) >> FP_SHIFT_FACTOR) + sample.re;
s->symbol_sync_high[1] = s->symbol_sync_high[0];
s->symbol_sync_high[0] = v;
#else
/* Low Nyquist band edge filter */
v = s->symbol_sync_low[0]*SYNC_LOW_BAND_EDGE_COEFF_0 + s->symbol_sync_low[1]*SYNC_LOW_BAND_EDGE_COEFF_1 + sample.re;
s->symbol_sync_low[1] = s->symbol_sync_low[0];
s->symbol_sync_low[0] = v;
/* High Nyquist band edge filter */
v = s->symbol_sync_high[0]*SYNC_HIGH_BAND_EDGE_COEFF_0 + s->symbol_sync_high[1]*SYNC_HIGH_BAND_EDGE_COEFF_1 + sample.re;
s->symbol_sync_high[1] = s->symbol_sync_high[0];
s->symbol_sync_high[0] = v;
#endif
/* Put things into the equalization buffer at T/2 rate. The symbol synchronisation
will fiddle the step to align this with the symbols. */
if (s->eq_put_step <= 0)
{
/* Only AGC until we have locked down the setting. */
#if defined(SPANDSP_USE_FIXED_POINT)
if (s->agc_scaling_save == 0)
s->agc_scaling = (float) FP_FACTOR*32768.0f*(1.0f/RX_PULSESHAPER_GAIN)*5.0f*0.25f/sqrtf(power);
#else
if (s->agc_scaling_save == 0.0f)
s->agc_scaling = (1.0f/RX_PULSESHAPER_GAIN)*5.0f*0.25f/sqrtf(power);
#endif
/* Pulse shape while still at the carrier frequency, using a quadrature
pair of filters. This results in a properly bandpass filtered complex
signal, which can be brought directly to baseband by complex mixing.
No further filtering, to remove mixer harmonics, is needed. */
step = -s->eq_put_step;
if (step > RX_PULSESHAPER_COEFF_SETS - 1)
step = RX_PULSESHAPER_COEFF_SETS - 1;
s->eq_put_step += RX_PULSESHAPER_COEFF_SETS*10/(3*2);
#if defined(SPANDSP_USE_FIXED_POINT)
v = vec_circular_dot_prodi16(s->rrc_filter, rx_pulseshaper_im[step], V29_RX_FILTER_STEPS, s->rrc_filter_step);
sample.im = (v*s->agc_scaling) >> 15;
z = dds_lookup_complexi16(s->carrier_phase);
zz.re = ((int32_t) sample.re*(int32_t) z.re - (int32_t) sample.im*(int32_t) z.im) >> 15;
zz.im = ((int32_t) -sample.re*(int32_t) z.im - (int32_t) sample.im*(int32_t) z.re) >> 15;
#else
v = vec_circular_dot_prodf(s->rrc_filter, rx_pulseshaper_im[step], V29_RX_FILTER_STEPS, s->rrc_filter_step);
sample.im = v*s->agc_scaling;
z = dds_lookup_complexf(s->carrier_phase);
zz.re = sample.re*z.re - sample.im*z.im;
zz.im = -sample.re*z.im - sample.im*z.re;
#endif
process_half_baud(s, &zz);
}
#if defined(SPANDSP_USE_FIXED_POINT)
dds_advance(&s->carrier_phase, s->carrier_phase_rate);
#else
dds_advancef(&s->carrier_phase, s->carrier_phase_rate);
#endif
}
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v29_rx_fillin(v29_rx_state_t *s, int len)
{
int i;
/* We want to sustain the current state (i.e carrier on<->carrier off), and
try to sustain the carrier phase. We should probably push the filters, as well */
span_log(&s->logging, SPAN_LOG_FLOW, "Fill-in %d samples\n", len);
if (s->signal_present <= 0)
return 0;
if (s->training_stage == TRAINING_STAGE_PARKED)
return 0;
for (i = 0; i < len; i++)
{
#if defined(SPANDSP_USE_FIXED_POINT)
dds_advance(&s->carrier_phase, s->carrier_phase_rate);
#else
dds_advancef(&s->carrier_phase, s->carrier_phase_rate);
#endif
/* Advance the symbol phase the appropriate amount */
s->eq_put_step -= RX_PULSESHAPER_COEFF_SETS;
if (s->eq_put_step <= 0)
s->eq_put_step += RX_PULSESHAPER_COEFF_SETS*10/(3*2);
/* TODO: Should we rotate any buffers */
}
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v29_rx_set_put_bit(v29_rx_state_t *s, put_bit_func_t put_bit, void *user_data)
{
s->put_bit = put_bit;
s->put_bit_user_data = user_data;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v29_rx_set_modem_status_handler(v29_rx_state_t *s, modem_tx_status_func_t handler, void *user_data)
{
s->status_handler = handler;
s->status_user_data = user_data;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(logging_state_t *) v29_rx_get_logging_state(v29_rx_state_t *s)
{
return &s->logging;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v29_rx_restart(v29_rx_state_t *s, int bit_rate, int old_train)
{
switch (bit_rate)
{
case 9600:
s->training_cd = 0;
break;
case 7200:
s->training_cd = 2;
break;
case 4800:
s->training_cd = 4;
break;
default:
return -1;
}
s->bit_rate = bit_rate;
#if defined(SPANDSP_USE_FIXED_POINT)
vec_zeroi16(s->rrc_filter, sizeof(s->rrc_filter)/sizeof(s->rrc_filter[0]));
#else
vec_zerof(s->rrc_filter, sizeof(s->rrc_filter)/sizeof(s->rrc_filter[0]));
#endif
s->rrc_filter_step = 0;
s->scramble_reg = 0;
s->training_scramble_reg = 0x2A;
s->training_stage = TRAINING_STAGE_SYMBOL_ACQUISITION;
s->training_count = 0;
s->signal_present = 0;
#if defined(IAXMODEM_STUFF)
s->high_sample = 0;
s->low_samples = 0;
s->carrier_drop_pending = FALSE;
#endif
s->old_train = old_train;
s->carrier_phase = 0;
power_meter_init(&(s->power), 4);
s->constellation_state = 0;
if (s->old_train)
{
s->carrier_phase_rate = s->carrier_phase_rate_save;
s->agc_scaling = s->agc_scaling_save;
equalizer_restore(s);
}
else
{
s->carrier_phase_rate = dds_phase_ratef(CARRIER_NOMINAL_FREQ);
#if defined(SPANDSP_USE_FIXED_POINT)
s->agc_scaling_save = 0;
s->agc_scaling = (float) FP_FACTOR*32768.0f*0.0017f/RX_PULSESHAPER_GAIN;
#else
s->agc_scaling_save = 0.0f;
s->agc_scaling = 0.0017f/RX_PULSESHAPER_GAIN;
#endif
equalizer_reset(s);
}
#if defined(SPANDSP_USE_FIXED_POINT)
s->carrier_track_i = 8000;
s->carrier_track_p = 8000000;
#else
s->carrier_track_i = 8000.0f;
s->carrier_track_p = 8000000.0f;
#endif
s->last_sample = 0;
s->eq_skip = 0;
/* Initialise the working data for symbol timing synchronisation */
#if defined(SPANDSP_USE_FIXED_POINT)
s->symbol_sync_low[0] = 0;
s->symbol_sync_low[1] = 0;
s->symbol_sync_high[0] = 0;
s->symbol_sync_high[1] = 0;
s->symbol_sync_dc_filter[0] = 0;
s->symbol_sync_dc_filter[1] = 0;
s->baud_phase = 0;
#else
s->symbol_sync_low[0] = 0.0f;
s->symbol_sync_low[1] = 0.0f;
s->symbol_sync_high[0] = 0.0f;
s->symbol_sync_high[1] = 0.0f;
s->symbol_sync_dc_filter[0] = 0.0f;
s->symbol_sync_dc_filter[1] = 0.0f;
s->baud_phase = 0.0f;
#endif
s->baud_half = 0;
s->total_baud_timing_correction = 0;
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(v29_rx_state_t *) v29_rx_init(v29_rx_state_t *s, int bit_rate, put_bit_func_t put_bit, void *user_data)
{
switch (bit_rate)
{
case 9600:
case 7200:
case 4800:
break;
default:
return NULL;
}
if (s == NULL)
{
if ((s = (v29_rx_state_t *) malloc(sizeof(*s))) == NULL)
return NULL;
}
memset(s, 0, sizeof(*s));
span_log_init(&s->logging, SPAN_LOG_NONE, NULL);
span_log_set_protocol(&s->logging, "V.29 RX");
s->put_bit = put_bit;
s->put_bit_user_data = user_data;
/* The V.29 spec says the thresholds should be -31dBm and -26dBm, but that makes little
sense. V.17 uses -48dBm and -43dBm, and there seems no good reason to cut off at a
higher level (though at 9600bps and 7200bps, TCM should put V.17 sensitivity several
dB ahead of V.29). */
/* The thresholds should be on at -26dBm0 and off at -31dBm0 */
v29_rx_signal_cutoff(s, -28.5f);
v29_rx_restart(s, bit_rate, FALSE);
return s;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v29_rx_release(v29_rx_state_t *s)
{
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(int) v29_rx_free(v29_rx_state_t *s)
{
free(s);
return 0;
}
/*- End of function --------------------------------------------------------*/
SPAN_DECLARE(void) v29_rx_set_qam_report_handler(v29_rx_state_t *s, qam_report_handler_t handler, void *user_data)
{
s->qam_report = handler;
s->qam_user_data = user_data;
}
/*- End of function --------------------------------------------------------*/
/*- End of file ------------------------------------------------------------*/
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