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Move FFSK modem from NMT to common code, so it can be used by other networks

This commit is contained in:
Andreas Eversberg 2017-07-24 16:18:10 +02:00
parent 92ce6d4a42
commit 6c64025717
11 changed files with 371 additions and 239 deletions
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1
src/common/Makefile.am
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@ -24,6 +24,7 @@ libcommon_a_SOURCES = \
compandor.c \
fft.c \
fm_modulation.c \
ffsk.c \
sender.c \
display_wave.c \
display_status.c \

256
src/common/ffsk.c Normal file
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@ -0,0 +1,256 @@
/* FFSK audio processing (NMT / Radiocom 2000)
*
* (C) 2017 by Andreas Eversberg <jolly@eversberg.eu>
* All Rights Reserved
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#define CHAN ffsk->channel
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <math.h>
#include "../common/sample.h"
#include "../common/debug.h"
#include "ffsk.h"
#define PI M_PI
#define BIT_RATE 1200 /* baud rate */
#define FILTER_STEPS 0.1 /* step every 1/12000 sec */
/* two signaling tones */
static double ffsk_freq[2] = {
1800.0,
1200.0,
};
static sample_t dsp_tone_bit[2][2][65536]; /* polarity, bit, phase */
/* global init for FFSK */
void ffsk_global_init(double peak_fsk)
{
int i;
double s;
PDEBUG(DDSP, DEBUG_DEBUG, "Generating sine table for FFSK tones.\n");
for (i = 0; i < 65536; i++) {
s = sin((double)i / 65536.0 * 2.0 * PI);
/* bit(1) 1 cycle */
dsp_tone_bit[0][1][i] = s * peak_fsk;
dsp_tone_bit[1][1][i] = -s * peak_fsk;
/* bit(0) 1.5 cycles */
s = sin((double)i / 65536.0 * 3.0 * PI);
dsp_tone_bit[0][0][i] = s * peak_fsk;
dsp_tone_bit[1][0][i] = -s * peak_fsk;
}
}
/* Init FFSK */
int ffsk_init(ffsk_t *ffsk, void *inst, void (*receive_bit)(void *inst, int bit, double quality, double level), int channel, int samplerate)
{
sample_t *spl;
int i;
/* a symbol rate of 1200 Hz, times check interval of FILTER_STEPS */
if (samplerate < (double)BIT_RATE / (double)FILTER_STEPS) {
PDEBUG(DDSP, DEBUG_ERROR, "Sample rate must be at least 12000 Hz to process FSK+supervisory signal.\n");
return -EINVAL;
}
memset(ffsk, 0, sizeof(*ffsk));
ffsk->inst = inst;
ffsk->receive_bit = receive_bit;
ffsk->channel = channel;
ffsk->samplerate = samplerate;
ffsk->samples_per_bit = (double)ffsk->samplerate / (double)BIT_RATE;
ffsk->bits_per_sample = 1.0 / ffsk->samples_per_bit;
PDEBUG(DDSP, DEBUG_DEBUG, "Use %.4f samples for full bit duration @ %d.\n", ffsk->samples_per_bit, ffsk->samplerate);
/* allocate ring buffers, one bit duration */
ffsk->filter_size = floor(ffsk->samples_per_bit); /* buffer holds one bit (rounded down) */
spl = calloc(1, ffsk->filter_size * sizeof(*spl));
if (!spl) {
PDEBUG(DDSP, DEBUG_ERROR, "No memory!\n");
ffsk_cleanup(ffsk);
return -ENOMEM;
}
ffsk->filter_spl = spl;
ffsk->filter_bit = -1;
/* count symbols */
for (i = 0; i < 2; i++)
audio_goertzel_init(&ffsk->goertzel[i], ffsk_freq[i], ffsk->samplerate);
ffsk->phaseshift65536 = 65536.0 / ffsk->samples_per_bit;
PDEBUG(DDSP, DEBUG_DEBUG, "fsk_phaseshift = %.4f\n", ffsk->phaseshift65536);
return 0;
}
/* Cleanup transceiver instance. */
void ffsk_cleanup(ffsk_t *ffsk)
{
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Cleanup DSP for Transceiver.\n");
if (ffsk->filter_spl) {
free(ffsk->filter_spl);
ffsk->filter_spl = NULL;
}
}
//#define DEBUG_MODULATOR
//#define DEBUG_FILTER
//#define DEBUG_QUALITY
/* Filter one chunk of audio an detect tone, quality and loss of signal.
* The chunk is a window of 1/1200s. This window slides over audio stream
* and is processed every 1/12000s. (one step) */
static inline void ffsk_decode_step(ffsk_t *ffsk, int pos)
{
double level, result[2], softbit, quality;
int max;
sample_t *spl;
int bit;
max = ffsk->filter_size;
spl = ffsk->filter_spl;
level = audio_level(spl, max);
/* limit level to prevent division by zero */
if (level < 0.001)
level = 0.001;
audio_goertzel(ffsk->goertzel, spl, max, pos, result, 2);
/* calculate soft bit from both frequencies */
softbit = (result[1] / level - result[0] / level + 1.0) / 2.0;
//printf("%.3f: %.3f\n", level, softbit);
/* scale it, since both filters overlap by some percent */
#define MIN_QUALITY 0.33
softbit = (softbit - MIN_QUALITY) / (1.0 - MIN_QUALITY - MIN_QUALITY);
#ifdef DEBUG_FILTER
// printf("|%s", debug_amplitude(result[0]/level));
// printf("|%s| low=%.3f high=%.3f level=%d\n", debug_amplitude(result[1]/level), result[0]/level, result[1]/level, (int)level);
printf("|%s| softbit=%.3f\n", debug_amplitude(softbit), softbit);
#endif
if (softbit > 1)
softbit = 1;
if (softbit < 0)
softbit = 0;
if (softbit > 0.5)
bit = 1;
else
bit = 0;
if (ffsk->filter_bit != bit) {
/* If we have a bit change, move sample counter towards one half bit duration.
* We may have noise, so the bit change may be wrong or not at the correct place.
* This can cause bit slips.
* Therefore we change the sample counter only slightly, so bit slips may not
* happen so quickly.
* */
#ifdef DEBUG_FILTER
puts("bit change");
#endif
ffsk->filter_bit = bit;
if (ffsk->filter_sample < 5)
ffsk->filter_sample++;
if (ffsk->filter_sample > 5)
ffsk->filter_sample--;
} else if (--ffsk->filter_sample == 0) {
/* if sample counter bit reaches 0, we reset sample counter to one bit duration */
#ifdef DEBUG_FILTER
puts("sample");
#endif
// quality = result[bit] / level;
if (softbit > 0.5)
quality = softbit * 2.0 - 1.0;
else
quality = 1.0 - softbit * 2.0;
#ifdef DEBUG_QUALITY
printf("|%s| quality=%.2f ", debug_amplitude(softbit), quality);
printf("|%s|\n", debug_amplitude(quality));
#endif
/* adjust level, so a peak level becomes 100% */
ffsk->receive_bit(ffsk->inst, bit, quality, level / 0.63662);
ffsk->filter_sample = 10;
}
}
void ffsk_receive(ffsk_t *ffsk, sample_t *sample, int length)
{
sample_t *spl;
int max, pos;
double step, bps;
int i;
/* write received samples to decode buffer */
max = ffsk->filter_size;
pos = ffsk->filter_pos;
step = ffsk->filter_step;
bps = ffsk->bits_per_sample;
spl = ffsk->filter_spl;
for (i = 0; i < length; i++) {
#ifdef DEBUG_MODULATOR
printf("|%s|\n", debug_amplitude((double)samples[i] / 2333.0 /*fsk peak*/ / 2.0));
#endif
/* write into ring buffer */
spl[pos++] = sample[i];
if (pos == max)
pos = 0;
/* if 1/10th of a bit duration is reached, decode buffer */
step += bps;
if (step >= FILTER_STEPS) {
step -= FILTER_STEPS;
ffsk_decode_step(ffsk, pos);
}
}
ffsk->filter_step = step;
ffsk->filter_pos = pos;
}
/* render frame */
int ffsk_render_frame(ffsk_t *ffsk, const char *frame, int length, sample_t *sample)
{
int bit, polarity;
double phaseshift, phase;
int count = 0, i;
polarity = ffsk->polarity;
phaseshift = ffsk->phaseshift65536;
phase = ffsk->phase65536;
for (i = 0; i < length; i++) {
bit = (frame[i] == '1');
do {
*sample++ = dsp_tone_bit[polarity][bit][(uint16_t)phase];
count++;
phase += phaseshift;
} while (phase < 65536.0);
phase -= 65536.0;
/* flip polarity when we have 1.5 sine waves */
if (bit == 0)
polarity = 1 - polarity;
}
ffsk->phase65536 = phase;
ffsk->polarity = polarity;
/* return number of samples created for frame */
return count;
}

27
src/common/ffsk.h Normal file
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@ -0,0 +1,27 @@
#include "../common/goertzel.h"
typedef struct ffsk {
void *inst;
void (*receive_bit)(void *inst, int bit, double quality, double level);
int channel; /* channel number */
int samplerate; /* current sample rate */
double samples_per_bit; /* number of samples for one bit (1200 Baud) */
double bits_per_sample; /* fraction of a bit per sample */
goertzel_t goertzel[2]; /* filter for fsk decoding */
int polarity; /* current polarity state of bit */
sample_t *filter_spl; /* array to hold ring buffer for bit decoding */
int filter_size; /* size of ring buffer */
int filter_pos; /* position to write next sample */
double filter_step; /* counts bit duration, to trigger decoding every 10th bit */
int filter_bit; /* last bit state, so we detect a bit change */
int filter_sample; /* count until it is time to sample bit */
double phaseshift65536; /* how much the phase of fsk synbol changes per sample */
double phase65536; /* current phase */
} ffsk_t;
void ffsk_global_init(double peak_fsk);
int ffsk_init(ffsk_t *ffsk, void *inst, void (*receive_bit)(void *inst, int bit, double quality, double level), int channel, int samplerate);
void ffsk_cleanup(ffsk_t *ffsk);
void ffsk_receive(ffsk_t *ffsk, sample_t *sample, int lenght);
int ffsk_render_frame(ffsk_t *ffsk, const char *frame, int length, sample_t *sample);

9
src/nmt/dms.c
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@ -25,7 +25,6 @@
#include "../common/debug.h"
#include "../common/timer.h"
#include "nmt.h"
#include "dsp.h"
#define MUTE_DURATION 0.300 /* 200ms, and about 95ms for the frame itself */
@ -288,7 +287,8 @@ static void dms_encode_dt(nmt_t *nmt, uint8_t d, uint8_t s, uint8_t n, uint8_t *
#endif
/* render wave form */
dms->frame_length = fsk_render_frame(nmt, frame, 127, dms->frame_spl);
test_dms_frame(frame, 127); // used by test program
dms->frame_length = ffsk_render_frame(&nmt->ffsk, frame, 127, dms->frame_spl);
dms->frame_valid = 1;
dms->frame_pos = 0;
if (dms->frame_length > dms->frame_size) {
@ -335,7 +335,8 @@ static void dms_encode_rr(nmt_t *nmt, uint8_t d, uint8_t s, uint8_t n)
#endif
/* render wave form */
dms->frame_length = fsk_render_frame(nmt, frame, 77, dms->frame_spl);
test_dms_frame(frame, 77); // used by test program
dms->frame_length = ffsk_render_frame(&nmt->ffsk, frame, 77, dms->frame_spl);
dms->frame_valid = 1;
dms->frame_pos = 0;
if (dms->frame_length > dms->frame_size) {
@ -662,7 +663,7 @@ void fsk_receive_bit_dms(nmt_t *nmt, int bit, double quality, double level)
memset(dms->rx_frame_quality, 0, sizeof(dms->rx_frame_quality));
/* set muting of receive path */
nmt->fsk_filter_mute = (int)((double)nmt->sender.samplerate * MUTE_DURATION);
nmt->rx_mute = (int)((double)nmt->sender.samplerate * MUTE_DURATION);
return;
}

2
src/nmt/dms.h
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@ -60,3 +60,5 @@ void dms_send(nmt_t *nmt, const uint8_t *data, int length, int eight_bits);
void dms_all_sent(nmt_t *nmt);
void dms_receive(nmt_t *nmt, const uint8_t *data, int length, int eight_bits);
void test_dms_frame(const char *frame, int length);

260
src/nmt/dsp.c
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@ -59,9 +59,8 @@
#define COMPANDOR_0DB 1.0 /* A level of 0dBm (1.0) shall be unaccected */
#define TX_PEAK_FSK (4200.0 / 1800.0 * 1000.0 / DBM0_DEVIATION)
#define TX_PEAK_SUPER (300.0 / 4015.0 * 1000.0 / DBM0_DEVIATION)
#define BIT_RATE 1200
#define MAX_DISPLAY 1.4 /* something above dBm0 */
#define BIT_RATE 1200 /* baud rate */
#define FILTER_STEPS 0.1 /* step every 1/12000 sec */
#define DIALTONE_HZ 425.0 /* dial tone frequency */
#define TX_PEAK_DIALTONE 0.5 /* dial tone peak FIXME */
#define SUPER_DURATION 0.25 /* duration of supervisory signal measurement */
@ -69,12 +68,6 @@
#define SUPER_DETECT_COUNT 6 /* number of measures to detect supervisory signal */
#define MUTE_DURATION 0.280 /* a tiny bit more than two frames */
/* two signaling tones */
static double fsk_freq[2] = {
1800.0,
1200.0,
};
/* two supervisory tones */
static double super_freq[5] = {
3955.0, /* 0-Signal 1 */
@ -85,48 +78,39 @@ static double super_freq[5] = {
};
/* table for fast sine generation */
static sample_t dsp_tone_bit[2][2][65536]; /* polarity, bit, phase */
static sample_t dsp_sine_super[65536];
static sample_t dsp_sine_dialtone[65536];
/* global init for FSK */
/* global init for FFSK */
void dsp_init(void)
{
int i;
double s;
PDEBUG(DDSP, DEBUG_DEBUG, "Generating sine table for supervisory signal.\n");
PDEBUG(DDSP, DEBUG_DEBUG, "Generating sine table for supervisory signal and dial tone.\n");
for (i = 0; i < 65536; i++) {
s = sin((double)i / 65536.0 * 2.0 * PI);
/* supervisor sine */
dsp_sine_super[i] = s * TX_PEAK_SUPER;
/* dialtone sine */
dsp_sine_dialtone[i] = s * TX_PEAK_DIALTONE;
/* bit(1) 1 cycle */
dsp_tone_bit[0][1][i] = s * TX_PEAK_FSK;
dsp_tone_bit[1][1][i] = -s * TX_PEAK_FSK;
/* bit(0) 1.5 cycles */
s = sin((double)i / 65536.0 * 3.0 * PI);
dsp_tone_bit[0][0][i] = s * TX_PEAK_FSK;
dsp_tone_bit[1][0][i] = -s * TX_PEAK_FSK;
}
ffsk_global_init(TX_PEAK_FSK);
}
static void fsk_receive_bit(void *inst, int bit, double quality, double level);
/* Init FSK of transceiver */
int dsp_init_sender(nmt_t *nmt, double deviation_factor)
{
sample_t *spl;
double samples_per_bit;
int i;
/* attack (3ms) and recovery time (13.5ms) according to NMT specs */
init_compandor(&nmt->cstate, 8000, 3.0, 13.5, COMPANDOR_0DB);
/* a symbol rate of 1200 Hz, times check interval of FILTER_STEPS */
if (nmt->sender.samplerate < (double)BIT_RATE / (double)FILTER_STEPS) {
PDEBUG(DDSP, DEBUG_ERROR, "Sample rate must be at least 12000 Hz to process FSK+supervisory signal.\n");
return -EINVAL;
}
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Init DSP for Transceiver.\n");
/* set modulation parameters */
@ -135,22 +119,16 @@ int dsp_init_sender(nmt_t *nmt, double deviation_factor)
PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.3f (%.3f KHz deviation @ 1500 Hz)\n", TX_PEAK_FSK * deviation_factor, 3.5 * deviation_factor);
PDEBUG(DDSP, DEBUG_DEBUG, "Using Supervisory level of %.3f (%.3f KHz deviation @ 4015 Hz)\n", TX_PEAK_SUPER * deviation_factor, 0.3 * deviation_factor);
nmt->fsk_samples_per_bit = (double)nmt->sender.samplerate / (double)BIT_RATE;
nmt->fsk_bits_per_sample = 1.0 / nmt->fsk_samples_per_bit;
PDEBUG(DDSP, DEBUG_DEBUG, "Use %.4f samples for full bit duration @ %d.\n", nmt->fsk_samples_per_bit, nmt->sender.samplerate);
/* allocate ring buffers, one bit duration */
nmt->fsk_filter_size = floor(nmt->fsk_samples_per_bit); /* buffer holds one bit (rounded down) */
spl = calloc(1, nmt->fsk_filter_size * sizeof(*spl));
if (!spl) {
PDEBUG(DDSP, DEBUG_ERROR, "No memory!\n");
return -ENOMEM;
/* init ffsk */
if (ffsk_init(&nmt->ffsk, nmt, fsk_receive_bit, nmt->sender.kanal, nmt->sender.samplerate) < 0) {
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "FFSK init failed!\n");
return -EINVAL;
}
nmt->fsk_filter_spl = spl;
nmt->fsk_filter_bit = -1;
/* allocate transmit buffer for a complete frame, add 10 to be safe */
nmt->frame_size = 166.0 * (double)nmt->fsk_samples_per_bit + 10;
samples_per_bit = (double)nmt->sender.samplerate / (double)BIT_RATE;
nmt->frame_size = 166.0 * samples_per_bit + 10;
spl = calloc(nmt->frame_size, sizeof(*spl));
if (!spl) {
PDEBUG(DDSP, DEBUG_ERROR, "No memory!\n");
@ -159,7 +137,7 @@ int dsp_init_sender(nmt_t *nmt, double deviation_factor)
nmt->frame_spl = spl;
/* allocate DMS transmit buffer for a complete frame, add 10 to be safe */
nmt->dms.frame_size = 127.0 * (double)nmt->fsk_samples_per_bit + 10;
nmt->dms.frame_size = 127.0 * samples_per_bit + 10;
spl = calloc(nmt->dms.frame_size, sizeof(*spl));
if (!spl) {
PDEBUG(DDSP, DEBUG_ERROR, "No memory!\n");
@ -176,12 +154,6 @@ int dsp_init_sender(nmt_t *nmt, double deviation_factor)
}
nmt->super_filter_spl = spl;
/* count symbols */
for (i = 0; i < 2; i++)
audio_goertzel_init(&nmt->fsk_goertzel[i], fsk_freq[i], nmt->sender.samplerate);
nmt->fsk_phaseshift65536 = 65536.0 / nmt->fsk_samples_per_bit;
PDEBUG(DDSP, DEBUG_DEBUG, "fsk_phaseshift = %.4f\n", nmt->fsk_phaseshift65536);
/* count supervidory tones */
for (i = 0; i < 5; i++) {
audio_goertzel_init(&nmt->super_goertzel[i], super_freq[i], nmt->sender.samplerate);
@ -207,6 +179,8 @@ void dsp_cleanup_sender(nmt_t *nmt)
{
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Cleanup DSP for Transceiver.\n");
ffsk_cleanup(&nmt->ffsk);
if (nmt->frame_spl) {
free(nmt->frame_spl);
nmt->frame_spl = NULL;
@ -215,10 +189,6 @@ void dsp_cleanup_sender(nmt_t *nmt)
free(nmt->dms.frame_spl);
nmt->dms.frame_spl = NULL;
}
if (nmt->fsk_filter_spl) {
free(nmt->fsk_filter_spl);
nmt->fsk_filter_spl = NULL;
}
if (nmt->super_filter_spl) {
free(nmt->super_filter_spl);
nmt->super_filter_spl = NULL;
@ -226,29 +196,38 @@ void dsp_cleanup_sender(nmt_t *nmt)
}
/* Check for SYNC bits, then collect data bits */
static void fsk_receive_bit(nmt_t *nmt, int bit, double quality, double level)
static void fsk_receive_bit(void *inst, int bit, double quality, double level)
{
double frames_elapsed;
nmt_t *nmt = (nmt_t *)inst;
uint64_t frames_elapsed;
int i;
/* normalize FSK level */
level /= TX_PEAK_FSK;
nmt->rx_bits_count++;
if (nmt->dms_call)
fsk_receive_bit_dms(nmt, bit, quality, level);
// printf("bit=%d quality=%.4f\n", bit, quality);
if (!nmt->fsk_filter_in_sync) {
nmt->fsk_filter_sync = (nmt->fsk_filter_sync << 1) | bit;
if (!nmt->rx_in_sync) {
nmt->rx_sync = (nmt->rx_sync << 1) | bit;
/* level and quality */
nmt->fsk_filter_level[nmt->fsk_filter_count & 0xff] = level;
nmt->fsk_filter_quality[nmt->fsk_filter_count & 0xff] = quality;
nmt->fsk_filter_count++;
nmt->rx_level[nmt->rx_count & 0xff] = level;
nmt->rx_quality[nmt->rx_count & 0xff] = quality;
nmt->rx_count++;
/* check if pattern 1010111100010010 matches */
if (nmt->fsk_filter_sync != 0xaf12)
if (nmt->rx_sync != 0xaf12)
return;
/* average level and quality */
level = quality = 0;
for (i = 0; i < 16; i++) {
level += nmt->fsk_filter_level[(nmt->fsk_filter_count - 1 - i) & 0xff];
quality += nmt->fsk_filter_quality[(nmt->fsk_filter_count - 1 - i) & 0xff];
level += nmt->rx_level[(nmt->rx_count - 1 - i) & 0xff];
quality += nmt->rx_quality[(nmt->rx_count - 1 - i) & 0xff];
}
level /= 16.0; quality /= 16.0;
// printf("sync (level = %.2f, quality = %.2f\n", level, quality);
@ -262,114 +241,38 @@ static void fsk_receive_bit(nmt_t *nmt, int bit, double quality, double level)
nmt->rx_bits_count_current = nmt->rx_bits_count - 26.0;
/* rest sync register */
nmt->fsk_filter_sync = 0;
nmt->fsk_filter_in_sync = 1;
nmt->fsk_filter_count = 0;
nmt->rx_sync = 0;
nmt->rx_in_sync = 1;
nmt->rx_count = 0;
/* set muting of receive path */
nmt->fsk_filter_mute = (int)((double)nmt->sender.samplerate * MUTE_DURATION);
nmt->rx_mute = (int)((double)nmt->sender.samplerate * MUTE_DURATION);
return;
}
/* read bits */
nmt->fsk_filter_frame[nmt->fsk_filter_count] = bit + '0';
nmt->fsk_filter_level[nmt->fsk_filter_count] = level;
nmt->fsk_filter_quality[nmt->fsk_filter_count] = quality;
if (++nmt->fsk_filter_count != 140)
nmt->rx_frame[nmt->rx_count] = bit + '0';
nmt->rx_level[nmt->rx_count] = level;
nmt->rx_quality[nmt->rx_count] = quality;
if (++nmt->rx_count != 140)
return;
/* end of frame */
nmt->fsk_filter_frame[140] = '\0';
nmt->fsk_filter_in_sync = 0;
nmt->rx_frame[140] = '\0';
nmt->rx_in_sync = 0;
/* average level and quality */
level = quality = 0;
for (i = 0; i < 140; i++) {
level += nmt->fsk_filter_level[i];
quality += nmt->fsk_filter_quality[i];
level += nmt->rx_level[i];
quality += nmt->rx_quality[i];
}
level /= 140.0; quality /= 140.0;
/* send telegramm */
frames_elapsed = (nmt->rx_bits_count_current - nmt->rx_bits_count_last) / 166.0;
frames_elapsed = (nmt->rx_bits_count_current - nmt->rx_bits_count_last + 83) / 166; /* round to nearest frame */
/* convert level so that received level at TX_PEAK_FSK results in 1.0 (100%) */
nmt_receive_frame(nmt, nmt->fsk_filter_frame, quality, level, frames_elapsed);
}
//#define DEBUG_MODULATOR
//#define DEBUG_FILTER
//#define DEBUG_QUALITY
/* Filter one chunk of audio an detect tone, quality and loss of signal.
* The chunk is a window of 1/1200s. This window slides over audio stream
* and is processed every 1/12000s. (one step) */
static inline void fsk_decode_step(nmt_t *nmt, int pos)
{
double level, result[2], softbit, quality;
int max;
sample_t *spl;
int bit;
max = nmt->fsk_filter_size;
spl = nmt->fsk_filter_spl;
/* count time in bits */
nmt->rx_bits_count += FILTER_STEPS;
level = audio_level(spl, max);
/* limit level to prevent division by zero */
if (level < 0.001)
level = 0.001;
audio_goertzel(nmt->fsk_goertzel, spl, max, pos, result, 2);
/* calculate soft bit from both frequencies */
softbit = (result[1] / level - result[0] / level + 1.0) / 2.0;
//printf("%.3f: %.3f\n", level, softbit);
/* scale it, since both filters overlap by some percent */
#define MIN_QUALITY 0.33
softbit = (softbit - MIN_QUALITY) / (1.0 - MIN_QUALITY - MIN_QUALITY);
#ifdef DEBUG_FILTER
// printf("|%s", debug_amplitude(result[0]/level));
// printf("|%s| low=%.3f high=%.3f level=%d\n", debug_amplitude(result[1]/level), result[0]/level, result[1]/level, (int)level);
printf("|%s| softbit=%.3f\n", debug_amplitude(softbit), softbit);
#endif
if (softbit > 1)
softbit = 1;
if (softbit < 0)
softbit = 0;
if (softbit > 0.5)
bit = 1;
else
bit = 0;
if (nmt->fsk_filter_bit != bit) {
/* if we have a bit change, reset sample counter to one half bit duration */
#ifdef DEBUG_FILTER
puts("bit change");
#endif
nmt->fsk_filter_bit = bit;
nmt->fsk_filter_sample = 5;
} else if (--nmt->fsk_filter_sample == 0) {
/* if sample counter bit reaches 0, we reset sample counter to one bit duration */
#ifdef DEBUG_FILTER
puts("sample");
#endif
// quality = result[bit] / level;
if (softbit > 0.5)
quality = softbit * 2.0 - 1.0;
else
quality = 1.0 - softbit * 2.0;
#ifdef DEBUG_QUALITY
printf("|%s| quality=%.2f ", debug_amplitude(softbit), quality);
printf("|%s|\n", debug_amplitude(quality));
#endif
/* adjust level, so a peak level becomes 100% */
fsk_receive_bit(nmt, bit, quality, level / 0.63662 / TX_PEAK_FSK);
if (nmt->dms_call)
fsk_receive_bit_dms(nmt, bit, quality, level / 0.63662 / TX_PEAK_FSK);
nmt->fsk_filter_sample = 10;
}
nmt_receive_frame(nmt, nmt->rx_frame, quality, level, frames_elapsed);
}
/* compare supervisory signal against noise floor on 3900 Hz */
@ -425,7 +328,6 @@ void sender_receive(sender_t *sender, sample_t *samples, int length)
nmt_t *nmt = (nmt_t *) sender;
sample_t *spl;
int max, pos;
double step, bps;
int i;
/* write received samples to decode buffer */
@ -442,34 +344,15 @@ void sender_receive(sender_t *sender, sample_t *samples, int length)
}
nmt->super_filter_pos = pos;
/* write received samples to decode buffer */
max = nmt->fsk_filter_size;
pos = nmt->fsk_filter_pos;
step = nmt->fsk_filter_step;
bps = nmt->fsk_bits_per_sample;
spl = nmt->fsk_filter_spl;
ffsk_receive(&nmt->ffsk, samples, length);
/* muting audio while receiving frame */
for (i = 0; i < length; i++) {
#ifdef DEBUG_MODULATOR
printf("|%s|\n", debug_amplitude((double)samples[i] / TX_PEAK_FSK / 2.0));
#endif
/* write into ring buffer */
spl[pos++] = samples[i];
if (pos == max)
pos = 0;
/* muting audio while receiving frame */
if (nmt->fsk_filter_mute && !nmt->sender.loopback) {
if (nmt->rx_mute && !nmt->sender.loopback) {
samples[i] = 0;
nmt->fsk_filter_mute--;
}
/* if 1/10th of a bit duration is reached, decode buffer */
step += bps;
if (step >= FILTER_STEPS) {
step -= FILTER_STEPS;
fsk_decode_step(nmt, pos);
nmt->rx_mute--;
}
}
nmt->fsk_filter_step = step;
nmt->fsk_filter_pos = pos;
if ((nmt->dsp_mode == DSP_MODE_AUDIO || nmt->dsp_mode == DSP_MODE_DTMF)
&& nmt->trans && nmt->trans->callref) {
@ -494,35 +377,6 @@ void sender_receive(sender_t *sender, sample_t *samples, int length)
nmt->sender.rxbuf_pos = 0;
}
/* render frame */
int fsk_render_frame(nmt_t *nmt, const char *frame, int length, sample_t *sample)
{
int bit, polarity;
double phaseshift, phase;
int count = 0, i;
polarity = nmt->fsk_polarity;
phaseshift = nmt->fsk_phaseshift65536;
phase = nmt->fsk_phase65536;
for (i = 0; i < length; i++) {
bit = (frame[i] == '1');
do {
*sample++ = dsp_tone_bit[polarity][bit][(uint16_t)phase];
count++;
phase += phaseshift;
} while (phase < 65536.0);
phase -= 65536.0;
/* flip polarity when we have 1.5 sine waves */
if (bit == 0)
polarity = 1 - polarity;
}
nmt->fsk_phase65536 = phase;
nmt->fsk_polarity = polarity;
/* return number of samples created for frame */
return count;
}
static int fsk_frame(nmt_t *nmt, sample_t *samples, int length)
{
const char *frame;
@ -539,7 +393,7 @@ next_frame:
return length;
}
/* render frame */
nmt->frame_length = fsk_render_frame(nmt, frame, 166, nmt->frame_spl);
nmt->frame_length = ffsk_render_frame(&nmt->ffsk, frame, 166, nmt->frame_spl);
nmt->frame_pos = 0;
if (nmt->frame_length > nmt->frame_size) {
PDEBUG_CHAN(DDSP, DEBUG_ERROR, "Frame exceeds buffer, please fix!\n");

1
src/nmt/dsp.h
View File

@ -2,7 +2,6 @@
void dsp_init(void);
int dsp_init_sender(nmt_t *nmt, double deviation_factor);
void dsp_cleanup_sender(nmt_t *nmt);
int fsk_render_frame(nmt_t *nmt, const char *frame, int length, sample_t *sample);
void nmt_set_dsp_mode(nmt_t *nmt, enum dsp_mode mode);
void super_reset(nmt_t *nmt);

3
src/nmt/main.c
View File

@ -427,3 +427,6 @@ fail:
return 0;
}
// dummy, will be replaced by DMS test program
void test_dms_frame(const char __attribute__((unused)) *frame, int __attribute__((unused)) length) {}

4
src/nmt/nmt.c
View File

@ -1527,7 +1527,7 @@ static void tx_active(nmt_t *nmt, frame_t *frame)
* general handlers to call sub handling
*/
void nmt_receive_frame(nmt_t *nmt, const char *bits, double quality, double level, double frames_elapsed)
void nmt_receive_frame(nmt_t *nmt, const char *bits, double quality, double level, int frames_elapsed)
{
frame_t frame;
int rc;
@ -1541,7 +1541,7 @@ void nmt_receive_frame(nmt_t *nmt, const char *bits, double quality, double leve
}
/* frame counter */
nmt->rx_frame_count += (int)(frames_elapsed + 0.5);
nmt->rx_frame_count += frames_elapsed;
PDEBUG_CHAN(DNMT, (nmt->sender.loopback) ? DEBUG_NOTICE : DEBUG_DEBUG, "Received frame %s\n", nmt_frame_name(frame.mt));

37
src/nmt/nmt.h
View File

@ -1,8 +1,8 @@
#include "../common/goertzel.h"
#include "../common/sender.h"
#include "../common/compandor.h"
#include "../common/dtmf.h"
#include "../common/call.h"
#include "../common/ffsk.h"
#include "dms.h"
#include "sms.h"
@ -96,40 +96,29 @@ typedef struct nmt {
/* dsp states */
enum dsp_mode dsp_mode; /* current mode: audio, durable tone 0 or 1, paging */
double fsk_samples_per_bit; /* number of samples for one bit (1200 Baud) */
double fsk_bits_per_sample; /* fraction of a bit per sample */
ffsk_t ffsk; /* ffsk processing */
int super_samples; /* number of samples in buffer for supervisory detection */
goertzel_t fsk_goertzel[2]; /* filter for fsk decoding */
goertzel_t super_goertzel[5]; /* filter for supervisory decoding */
int fsk_polarity; /* current polarity state of bit */
sample_t *fsk_filter_spl; /* array to hold ring buffer for bit decoding */
int fsk_filter_size; /* size of ring buffer */
int fsk_filter_pos; /* position to write next sample */
double fsk_filter_step; /* counts bit duration, to trigger decoding every 10th bit */
int fsk_filter_bit; /* last bit state, so we detect a bit change */
int fsk_filter_sample; /* count until it is time to sample bit */
uint16_t fsk_filter_sync; /* shift register to detect sync */
int fsk_filter_in_sync; /* if we are in sync and receive bits */
int fsk_filter_mute; /* mute count down after sync */
char fsk_filter_frame[141]; /* receive frame (one extra byte to terminate string) */
int fsk_filter_count; /* next bit to receive */
double fsk_filter_level[256]; /* level infos */
double fsk_filter_quality[256];/* quality infos */
sample_t *super_filter_spl; /* array with sample buffer for supervisory detection */
int super_filter_pos; /* current sample position in filter_spl */
double super_phaseshift65536[4];/* how much the phase of sine wave changes per sample */
double super_phase65536; /* current phase */
double dial_phaseshift65536; /* how much the phase of sine wave changes per sample */
double dial_phase65536; /* current phase */
double fsk_phaseshift65536; /* how much the phase of fsk synbol changes per sample */
double fsk_phase65536; /* current phase */
uint16_t rx_sync; /* shift register to detect sync */
int rx_in_sync; /* if we are in sync and receive bits */
int rx_mute; /* mute count down after sync */
char rx_frame[141]; /* receive frame (one extra byte to terminate string) */
int rx_count; /* next bit to receive */
double rx_level[256]; /* level infos */
double rx_quality[256]; /* quality infos */
sample_t *frame_spl; /* samples to store a complete rendered frame */
int frame_size; /* total size of sample buffer */
int frame_length; /* current length of data in sample buffer */
int frame_pos; /* current sample position in frame_spl */
double rx_bits_count; /* sample counter */
double rx_bits_count_current; /* sample counter of current frame */
double rx_bits_count_last; /* sample counter of last frame */
uint64_t rx_bits_count; /* sample counter */
uint64_t rx_bits_count_current; /* sample counter of current frame */
uint64_t rx_bits_count_last; /* sample counter of last frame */
int super_detected; /* current detection state flag */
int super_detect_count; /* current number of consecutive detections/losses */
@ -149,7 +138,7 @@ int nmt_create(int nmt_system, const char *country, int channel, enum nmt_chan_t
void nmt_check_channels(int nmt_system);
void nmt_destroy(sender_t *sender);
void nmt_go_idle(nmt_t *nmt);
void nmt_receive_frame(nmt_t *nmt, const char *bits, double quality, double level, double frames_elapsed);
void nmt_receive_frame(nmt_t *nmt, const char *bits, double quality, double level, int frames_elapsed);
const char *nmt_get_frame(nmt_t *nmt);
void nmt_rx_super(nmt_t *nmt, int tone, double quality);
void timeout_mt_paging(struct transaction *trans);

10
src/test/test_dms.c
View File

@ -56,14 +56,12 @@ void dms_all_sent(nmt_t *nmt)
}
/* receive bits from DMS */
int fsk_render_frame(nmt_t *nmt, const char *frame, int length, sample_t *sample)
void test_dms_frame(const char *frame, int length)
{
printf("(getting %d bits from DMS layer)\n", length);
memcpy(current_bits, frame, length);
current_bit_count = length;
return nmt->fsk_samples_per_bit * length;
}
nmt_t *alloc_nmt(void)
@ -71,9 +69,11 @@ nmt_t *alloc_nmt(void)
nmt_t *nmt;
nmt = calloc(sizeof(*nmt), 1);
nmt->sender.samplerate = 40 * 1200;
dms_init_sender(nmt);
nmt->fsk_samples_per_bit = 40;
nmt->dms.frame_size = nmt->fsk_samples_per_bit * 127 + 10;
ffsk_global_init(1.0);
ffsk_init(&nmt->ffsk, nmt, NULL, 1, nmt->sender.samplerate);
nmt->dms.frame_size = nmt->ffsk.samples_per_bit * 127 + 10;
nmt->dms.frame_spl = calloc(nmt->dms.frame_size, sizeof(nmt->dms.frame_spl[0]));
dms_reset(nmt);