An implementation of Analog cellular networks like A-Netz, B-Netz, C-Netz, NMT, AMPS, TACS, JTACS, Radiocom 2000, IMTS, MPT1327, Eurosignal and more http://osmocom-analog.eversberg.eu/
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osmocom-analog/src/dcf77/dcf77.c

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/* implementation of DCF77 transmitter and receiver
*
* (C) 2022 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/>.
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdint.h>
#include <inttypes.h>
#include <stdlib.h>
#include <math.h>
#include "../libdebug/debug.h"
#include "dcf77.h"
double get_time(void);
#define CARRIER_FREQUENCY 77500
#define TEST_FREQUENCY 1000
#define CARRIER_BANDWIDTH 10.0
#define SAMPLE_CLOCK 1000
#define CLOCK_1S 1.0
#define CLOCK_BANDWIDTH 0.1
#define REDUCTION_FACTOR 0.15
#define REDUCTION_TH 0.575
#define TX_LEVEL 0.9
#define level2db(level) (20 * log10(level))
static int fast_math = 0;
static float *sin_tab = NULL, *cos_tab = NULL;
const char *time_zone[4] = { "???", "CEST", "CET", "???" };
const char *week_day[8] = { "???", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun" };
const char *month_name[13] = { "???", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
/* global init */
int dcf77_init(int _fast_math)
{
fast_math = _fast_math;
if (fast_math) {
int i;
sin_tab = calloc(65536+16384, sizeof(*sin_tab));
if (!sin_tab) {
fprintf(stderr, "No mem!\n");
return -ENOMEM;
}
cos_tab = sin_tab + 16384;
/* generate sine and cosine */
for (i = 0; i < 65536+16384; i++)
sin_tab[i] = sin(2.0 * M_PI * (double)i / 65536.0);
}
return 0;
}
/* global exit */
void dcf77_exit(void)
{
if (sin_tab) {
free(sin_tab);
sin_tab = cos_tab = NULL;
}
}
dcf77_t *dcf77_create(int samplerate, int use_tx, int use_rx, int test_tone)
{
dcf77_t *dcf77 = NULL;
dcf77_tx_t *tx;
dcf77_rx_t *rx;
dcf77 = calloc(1, sizeof(*dcf77));
if (!dcf77) {
PDEBUG(DDCF77, DEBUG_ERROR, "No mem!\n");
return NULL;
}
tx = &dcf77->tx;
rx = &dcf77->rx;
/* measurement */
display_wave_init(&dcf77->dispwav, (double)samplerate, "DCF77");
display_measurements_init(&dcf77->dispmeas, samplerate, "DCF77");
/* prepare tx */
if (use_tx) {
tx->enable = 1;
if (fast_math)
tx->phase_360 = 65536.0;
else
tx->phase_360 = 2.0 * M_PI;
/* carrier generation */
tx->carrier_phase_step = tx->phase_360 * (double)CARRIER_FREQUENCY / ((double)samplerate);
tx->test_phase_step = tx->phase_360 * (double)TEST_FREQUENCY / ((double)samplerate);
tx->waves_0 = CARRIER_FREQUENCY / 10;
tx->waves_1 = CARRIER_FREQUENCY / 5;
tx->waves_sec = CARRIER_FREQUENCY;
tx->test_tone = test_tone;
}
/* prepare rx */
if (use_rx) {
rx->enable = 1;
if (fast_math)
rx->phase_360 = 65536.0;
else
rx->phase_360 = 2.0 * M_PI;
/* carrier filter */
rx->carrier_phase_step = rx->phase_360 * (double)CARRIER_FREQUENCY / ((double)samplerate);
/* use fourth order (2 iter) filter, since it is as fast as second order (1 iter) filter */
iir_lowpass_init(&rx->carrier_lp[0], CARRIER_BANDWIDTH, (double)samplerate, 2);
iir_lowpass_init(&rx->carrier_lp[1], CARRIER_BANDWIDTH, (double)samplerate, 2);
/* signal rate */
rx->sample_step = (double)SAMPLE_CLOCK / (double)samplerate;
/* delay buffer */
rx->delay_size = ceil((double)SAMPLE_CLOCK * 0.1);
rx->delay_buffer = calloc(rx->delay_size, sizeof(*rx->delay_buffer));
if (!rx->delay_buffer) {
PDEBUG(DDCF77, DEBUG_ERROR, "No mem!\n");
return NULL;
}
/* count clock signal */
rx->clock_count = -1;
/* measurement parameters */
dcf77->dmp_input_level = display_measurements_add(&dcf77->dispmeas, "Input Level", "%.0f dB", DISPLAY_MEAS_AVG, DISPLAY_MEAS_LEFT, -100.0, 0.0, -INFINITY);
dcf77->dmp_signal_level = display_measurements_add(&dcf77->dispmeas, "Signal Level", "%.0f dB", DISPLAY_MEAS_AVG, DISPLAY_MEAS_LEFT, -100.0, 0.0, -INFINITY);
dcf77->dmp_signal_quality = display_measurements_add(&dcf77->dispmeas, "Signal Qualtiy", "%.0f %%", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 100.0, -INFINITY);
}
if (tx->enable)
PDEBUG(DDCF77, DEBUG_INFO, "DCF77 transmitter has been created.\n");
if (rx->enable)
PDEBUG(DDCF77, DEBUG_INFO, "DCF77 receiver has been created.\n");
return dcf77;
}
void dcf77_destroy(dcf77_t *dcf77)
{
if (dcf77) {
dcf77_rx_t *rx = &dcf77->rx;
free(rx->delay_buffer);
free(dcf77);
}
PDEBUG(DDCF77, DEBUG_INFO, "DCF77 has been destroyed.\n");
}
/* set inital time stamp at the moment the stream starts */
void dcf77_tx_start(dcf77_t *dcf77, time_t timestamp)
{
dcf77_tx_t *tx = &dcf77->tx;
double now;
time_t t;
/* get time stamp */
if (timestamp < 0)
now = get_time();
else
now = timestamp;
t = floor(now);
/* current second within minute */
tx->second = t % 60;
/* time stamp of next minute */
tx->timestamp = t - tx->second + 60;
/* wave within current second */
tx->wave = floor(fmod(now, 1.0) * (double)tx->waves_sec);
/* silence until next second begins */
tx->symbol = 'm'; tx->level = 0;
}
static char tx_symbol(dcf77_t *dcf77, time_t timestamp, int second)
{
dcf77_tx_t *tx = &dcf77->tx;
char symbol;
/* generate frame */
if (second == 0 || !tx->data_frame) {
struct tm *tm;
int isdst_next_hour, wday, zone;
uint64_t frame = 0, p;
timestamp += 3600;
tm = localtime(&timestamp);
timestamp -= 3600;
if (!tm) {
error_tm:
PDEBUG(DDCF77, DEBUG_ERROR, "Failed to get local time of time stamp!\n");
return 'm';
}
isdst_next_hour = tm->tm_isdst;
tm = localtime(&timestamp);
if (!tm)
goto error_tm;
if (tm->tm_wday > 0)
wday = tm->tm_wday;
else
wday = 7;
if (tm->tm_isdst > 0)
zone = 1;
else
zone = 2;
PDEBUG(DDCF77, DEBUG_NOTICE, "The time transmitting: %s %s %d %02d:%02d:00 %s %02d\n", week_day[wday], month_name[tm->tm_mon + 1], tm->tm_mday, tm->tm_hour, tm->tm_min, time_zone[zone], tm->tm_year + 1900);
if ((tm->tm_isdst > 0) != (isdst_next_hour > 0))
frame |= (uint64_t)1 << 16;
if (tm->tm_isdst > 0)
frame |= (uint64_t)1 << 17;
else
frame |= (uint64_t)2 << 17;
frame |= 1 << 20;
frame |= (uint64_t)(tm->tm_min % 10) << 21;
frame |= (uint64_t)(tm->tm_min / 10) << 25;
p = (frame >> 21) & 0x7f;
p = p ^ (p >> 4);
p = p ^ (p >> 2);
p = p ^ (p >> 1);
frame |= (uint64_t)(p & 1) << 28;
frame |= (uint64_t)(tm->tm_hour % 10) << 29;
frame |= (uint64_t)(tm->tm_hour / 10) << 33;
p = (frame >> 29) & 0x3f;
p = p ^ (p >> 4);
p = p ^ (p >> 2);
p = p ^ (p >> 1);
frame |= (uint64_t)(p & 1) << 35;
frame |= (uint64_t)(tm->tm_mday % 10) << 36;
frame |= (uint64_t)(tm->tm_mday / 10) << 40;
frame |= (uint64_t)(wday) << 42;
frame |= (uint64_t)((tm->tm_mon + 1) % 10) << 45;
frame |= (uint64_t)((tm->tm_mon + 1) / 10) << 49;
frame |= (uint64_t)(tm->tm_year % 10) << 50;
frame |= (uint64_t)((tm->tm_year / 10) % 10) << 54;
p = (frame >> 36) & 0x3fffff;
p = p ^ (p >> 16);
p = p ^ (p >> 8);
p = p ^ (p >> 4);
p = p ^ (p >> 2);
p = p ^ (p >> 1);
frame |= (uint64_t)(p & 1) << 58;
tx->data_frame = frame;
}
if (second == 59)
symbol = 'm';
else symbol = ((tx->data_frame >> second) & 1) + '0';
PDEBUG(DDSP, DEBUG_DEBUG, "Trasmitting symbol '%c' (Bit %d)\n", symbol, second);
return symbol;
}
void dcf77_encode(dcf77_t *dcf77, sample_t *samples, int length)
{
dcf77_tx_t *tx = &dcf77->tx;
double carrier_phase, test_phase;
int i;
if (!tx->enable) {
memset(samples, 0, sizeof(*samples) * length);
return;
}
carrier_phase = tx->carrier_phase;
test_phase = tx->test_phase;
for (i = 0; i < length; i++) {
if (fast_math)
samples[i] = sin_tab[(uint16_t)carrier_phase] * tx->level;
else
samples[i] = sin(carrier_phase) * tx->level;
carrier_phase += tx->carrier_phase_step;
if (carrier_phase >= tx->phase_360) {
carrier_phase -= tx->phase_360;
tx->wave++;
if (tx->wave >= tx->waves_sec) {
tx->wave -= tx->waves_sec;
if (++tx->second == 60) {
tx->second = 0;
tx->timestamp += 60;
}
tx->symbol = tx_symbol(dcf77, tx->timestamp, tx->second);
}
switch (tx->symbol) {
case '0':
if (tx->wave < tx->waves_0)
tx->level = TX_LEVEL * REDUCTION_FACTOR;
else
tx->level = TX_LEVEL;
break;
case '1':
if (tx->wave < tx->waves_1)
tx->level = TX_LEVEL * REDUCTION_FACTOR;
else
tx->level = TX_LEVEL;
break;
case 'm':
tx->level = TX_LEVEL;
break;
}
if (tx->test_tone)
tx->level *= 0.9; /* 90 % */
}
if (tx->test_tone) {
if (fast_math)
samples[i] += sin_tab[(uint16_t)test_phase] * tx->level / 10.0; /* 10 % */
else
samples[i] += sin(test_phase) * tx->level / 10.0; /* 10 % */
if (test_phase >= tx->phase_360)
test_phase -= tx->phase_360;
test_phase += tx->test_phase_step;
}
}
tx->carrier_phase = carrier_phase;
tx->test_phase = test_phase;
}
static void rx_frame(uint64_t frame)
{
int zone;
int minute_one, minute_ten, minute = -1;
int hour_one, hour_ten, hour = -1;
int day_one, day_ten, day = -1;
int wday = -1;
int month_one, month_ten, month = -1;
int year_one, year_ten, year = -1;
uint64_t p;
PDEBUG(DFRAME, DEBUG_INFO, "Bit 0 is '0'? : %s\n", ((frame >> 0) & 1) ? "no" : "yes");
PDEBUG(DFRAME, DEBUG_INFO, "Bits 1..14 : 0x%04x\n", (int)(frame >> 1) & 0x3fff);
PDEBUG(DFRAME, DEBUG_INFO, "Call Bit : %d\n", (int)(frame >> 15) & 1);
PDEBUG(DFRAME, DEBUG_INFO, "Change Time Zone : %s\n", ((frame >> 16) & 1) ? "yes" : "no");
zone = ((frame >> 17) & 3);
PDEBUG(DFRAME, DEBUG_INFO, "Time Zone : %s\n", time_zone[zone]);
PDEBUG(DFRAME, DEBUG_INFO, "Add Leap Second : %s\n", ((frame >> 19) & 1) ? "yes" : "no");
PDEBUG(DFRAME, DEBUG_INFO, "Bit 20 is '1'? : %s\n", ((frame >> 20) & 1) ? "yes" : "no");
minute_one = (frame >> 21 & 0xf);
minute_ten = ((frame >> 25) & 0x7);
p = (frame >> 21) & 0xff;
p = p ^ (p >> 4);
p = p ^ (p >> 2);
p = p ^ (p >> 1);
if (minute_one > 9 || minute_ten > 5 || (p & 1))
PDEBUG(DFRAME, DEBUG_INFO, "Minute : ???\n");
else {
minute = minute_ten * 10 + minute_one;
PDEBUG(DFRAME, DEBUG_INFO, "Minute : %02d\n", minute);
}
hour_one = (frame >> 29 & 0xf);
hour_ten = ((frame >> 33) & 0x3);
p = (frame >> 29) & 0x7f;
p = p ^ (p >> 4);
p = p ^ (p >> 2);
p = p ^ (p >> 1);
if (hour_one > 9 || hour_ten > 2 || (hour_ten == 2 && hour_one > 3) || (p & 1))
PDEBUG(DFRAME, DEBUG_INFO, "Hour : ???\n");
else {
hour = hour_ten * 10 + hour_one;
PDEBUG(DFRAME, DEBUG_INFO, "Hour : %02d\n", hour);
}
day_one = (frame >> 36 & 0xf);
day_ten = ((frame >> 40) & 0x3);
wday = (frame >> 42 & 0x7);
month_one = (frame >> 45 & 0xf);
month_ten = ((frame >> 49) & 0x1);
year_one = (frame >> 50 & 0xf);
year_ten = ((frame >> 54) & 0xf);
p = (frame >> 36) & 0x7fffff;
p = p ^ (p >> 16);
p = p ^ (p >> 8);
p = p ^ (p >> 4);
p = p ^ (p >> 2);
p = p ^ (p >> 1);
if (day_one > 9 || day_ten > 3 || (day_ten == 3 && day_one > 1) || (day_ten == 0 && day_one == 0) || (p & 1))
PDEBUG(DFRAME, DEBUG_INFO, "Day : ???\n");
else {
day = day_ten * 10 + day_one;
PDEBUG(DFRAME, DEBUG_INFO, "Day : %d\n", day);
}
if (wday < 1 || wday > 7 || (p & 1)) {
PDEBUG(DFRAME, DEBUG_INFO, "Week Day : ???\n");
wday = -1;
} else
PDEBUG(DFRAME, DEBUG_INFO, "Week Day : %s\n", week_day[wday]);
if (month_one > 9 || month_ten > 1 || (month_ten == 1 && month_one > 2) || (month_ten == 0 && month_one == 0) || (p & 1))
PDEBUG(DFRAME, DEBUG_INFO, "Month : ???\n");
else {
month = month_ten * 10 + month_one;
PDEBUG(DFRAME, DEBUG_INFO, "Month : %d\n", month);
}
if (year_one > 9 || year_ten > 9 || (p & 1))
PDEBUG(DFRAME, DEBUG_INFO, "Year : ???\n");
else {
year = year_ten * 10 + year_one;
PDEBUG(DFRAME, DEBUG_INFO, "Year : %02d\n", year);
}
if (minute >= 0 && hour >= 0 && day >= 0 && wday >= 0 && month >= 0 && year >= 0)
PDEBUG(DDCF77, DEBUG_NOTICE, "The received time is: %s %s %d %02d:%02d:00 %s 20%02d\n", week_day[wday], month_name[month], day, hour, minute, time_zone[zone], year);
else
PDEBUG(DDCF77, DEBUG_NOTICE, "The received time is invalid!\n");
}
static void rx_symbol(dcf77_t *dcf77, char symbol)
{
dcf77_rx_t *rx = &dcf77->rx;
PDEBUG(DDSP, DEBUG_DEBUG, "Received symbol '%c'\n", symbol);
if (!rx->data_receive) {
if (symbol == 'm') {
PDEBUG(DDSP, DEBUG_INFO, "Reception of frame has started\n");
rx->data_receive = 1;
rx->data_index = 0;
}
} else {
if (symbol == 'm') {
if (rx->data_index == 59) {
rx->data_string[rx->data_index] = '\0';
rx->data_index = 0;
PDEBUG(DDSP, DEBUG_INFO, "Received complete frame: %s (0x%016" PRIx64 ")\n", rx->data_string, rx->data_frame);
rx_frame(rx->data_frame);
} else {
PDEBUG(DDSP, DEBUG_INFO, "Short read, frame too short\n");
rx->data_index = 0;
}
} else {
if (rx->data_index == 59) {
PDEBUG(DDSP, DEBUG_INFO, "Long read, frame too long\n");
rx->data_receive = 0;
} else {
rx->data_string[rx->data_index++] = symbol;
rx->data_frame >>= 1;
rx->data_frame |= (uint64_t)(symbol & 1) << 58;
}
}
}
}
//#define DEBUG_SAMPLE
void dcf77_decode(dcf77_t *dcf77, sample_t *samples, int length)
{
dcf77_rx_t *rx = &dcf77->rx;
sample_t I[length], Q[length];
double phase, level, delayed_level, reduction, quality;
int i;
display_wave(&dcf77->dispwav, samples, length, 1.0);
if (!rx->enable)
return;
/* rotate spectrum */
phase = rx->carrier_phase;
for (i = 0; i < length; i++) {
/* mix with carrier frequency */
if (fast_math) {
I[i] = cos_tab[(uint16_t)phase] * samples[i];
Q[i] = sin_tab[(uint16_t)phase] * samples[i];
} else {
I[i] = cos(phase) * samples[i];
Q[i] = sin(phase) * samples[i];
}
phase += rx->carrier_phase_step;
if (phase >= rx->phase_360)
phase -= rx->phase_360;
}
rx->carrier_phase = phase;
level = sqrt(I[0] * I[0] + Q[0] * Q[0]);
if (level > 0.0) // don't average with level of 0.0 (-inf dB)
display_measurements_update(dcf77->dmp_input_level, level2db(level), 0.0);
/* filter carrier */
iir_process(&rx->carrier_lp[0], I, length);
iir_process(&rx->carrier_lp[1], Q, length);
for (i = 0; i < length; i++) {
rx->sample_counter += rx->sample_step;
if (rx->sample_counter >= 1.0) {
rx->sample_counter -= 1.0;
/* level */
level = sqrt(I[i] * I[i] + Q[i] * Q[i]);
if (level > 0.0) // don't average with level of 0.0 (-inf dB)
display_measurements_update(dcf77->dmp_signal_level, level2db(level), 0.0);
#ifdef DEBUG_SAMPLE
printf("%s amplitude= %.6f\n", debug_amplitude(level/rx->value_level), level/rx->value_level);
#endif
/* delay sample */
delayed_level = rx->delay_buffer[rx->delay_index];
rx->delay_buffer[rx->delay_index] = level;
if (++rx->delay_index == rx->delay_size)
rx->delay_index = 0;
if (rx->clock_count < 0 || rx->clock_count > 900) {
if (level / delayed_level < REDUCTION_TH)
rx->clock_count = 0;
}
if (rx->clock_count >= 0) {
if (rx->clock_count == 0) {
#ifdef DEBUG_SAMPLE
puts("got clock");
#endif
rx->value_level = delayed_level;
}
if (rx->clock_count == 50) {
#ifdef DEBUG_SAMPLE
puts("*short*");
#endif
rx->value_short = level;
reduction = rx->value_short / rx->value_level;
if (reduction < REDUCTION_TH) {
#ifdef DEBUG_SAMPLE
printf("reduction is %.3f\n", reduction);
#endif
if (reduction < REDUCTION_FACTOR)
reduction = REDUCTION_FACTOR;
quality = 1.0 - (reduction - REDUCTION_FACTOR) / (REDUCTION_TH - REDUCTION_FACTOR);
display_measurements_update(dcf77->dmp_signal_quality, quality * 100.0, 0.0);
}
}
if (rx->clock_count == 150) {
#ifdef DEBUG_SAMPLE
puts("*long*");
#endif
rx->value_long = level;
if (rx->value_long / rx->value_level < REDUCTION_TH)
rx_symbol(dcf77, '1');
else
rx_symbol(dcf77, '0');
}
if (rx->clock_count == 1100) {
#ifdef DEBUG_SAMPLE
puts("*missing clock*");
#endif
rx->clock_count = -1;
rx_symbol(dcf77, 'm');
}
}
if (rx->clock_count >= 0)
rx->clock_count++;
}
}
}