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/*****************************************************************************/
/*
* dcfmod.c -- Linux soundcard DCF77 signal generator (modulator).
*
* Copyright (C) 1996 Thomas Sailer (sailer@ife.ee.ethz.ch)
* Swiss Federal Institute of Technology (ETH), Electronics Lab
*
* 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 2 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
/*****************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <string.h>
#include "dcf77.h"
/* --------------------------------------------------------------------- */
#define FILTER
/* --------------------------------------------------------------------- */
static struct modulator_state {
unsigned int car_inc;
unsigned int pn_inc;
unsigned int sec_inc;
int cur_bit;
int cur_pn;
unsigned int ph_sec;
unsigned int ph_car;
unsigned int ph_pn;
unsigned int pn_cnt;
unsigned int pn_st;
#ifdef FILTER
#define FILTER_N 32
#define FILTER_MASK (FILTER_N-1)
struct filter_state {
int state[FILTER_N];
unsigned int ptr;
} f;
#endif /* FILTER */
} m;
/* --------------------------------------------------------------------- */
static void dcf_init(unsigned int sample_rate)
{
memset(&m, 0, sizeof(m));
m.car_inc = 0x1000000ULL * CARRIER_FREQ / sample_rate;
m.pn_inc = 0x10000ULL * PN_FREQ / sample_rate;
m.sec_inc = 0x1000000 / sample_rate;
}
/* --------------------------------------------------------------------- */
#ifdef FILTER
static const int filt_coeff[2*FILTER_N] = {
465, 48, -33, -1295, -736, 221, -503, -1930,
-2095, -684, 101, -1922, -4702, -3117, 4111, 11188,
11188, 4111, -3117, -4702, -1922, 101, -684, -2095,
-1930, -503, 221, -736, -1295, -33, 48, 465,
465, 48, -33, -1295, -736, 221, -503, -1930,
-2095, -684, 101, -1922, -4702, -3117, 4111, 11188,
11188, 4111, -3117, -4702, -1922, 101, -684, -2095,
-1930, -503, 221, -736, -1295, -33, 48, 465
};
extern __inline__ short calc_filter(short new)
{
const int *c = filt_coeff + FILTER_N;
int *s = m.f.state;
int sum = 0;
unsigned int u;
m.f.state[m.f.ptr++] = new;
m.f.ptr &= FILTER_MASK;
c -= m.f.ptr;
for (u = 0; u < FILTER_N; u++, c++, s++)
sum += (*c) * (*s);
sum >>= 16;
return sum;
}
#endif /* FILTER */
/* --------------------------------------------------------------------- */
static void dcf_mod(short *s, unsigned int n)
{
short sp;
for (; n > 0; n--, s++) {
if ((m.ph_sec < 0x1000000*1/10 && m.cur_bit == 0) ||
(m.ph_sec < 0x1000000*2/10 && m.cur_bit > 0))
sp = COS(m.ph_car) >> 2;
else if (m.ph_sec >= 0x1000000*2/10 && m.pn_cnt < PN_LENGTH) {
sp = COS(m.ph_car + m.cur_pn);
m.ph_pn += m.pn_inc;
if (m.ph_pn >= 0x10000) {
m.ph_pn &= 0xffff;
m.pn_cnt++;
m.cur_pn = ((m.cur_bit ^ PN(m.pn_cnt) ^ !lsb_mode) & 1) ?
0x1000000*PN_MOD_IDX : -0x1000000*PN_MOD_IDX;
}
} else
sp = COS(m.ph_car);
#ifdef FILTER
*s = calc_filter(sp);
#else /* FILTER */
*s = sp;
#endif /* FILTER */
m.ph_car = (m.ph_car + m.car_inc) & 0xffffffu;
m.ph_sec += m.sec_inc;
if (m.ph_sec >= 0x1000000) {
m.ph_sec &= 0xffffffu;
m.pn_st = 0;
m.pn_cnt = 0;
m.ph_pn = 0;
m.cur_bit = timeenc_getbit();
m.cur_pn = ((m.cur_bit ^ PN(0) ^ !lsb_mode) & 1) ?
0x1000000*PN_MOD_IDX : -0x1000000*PN_MOD_IDX;
}
}
}
/* --------------------------------------------------------------------- */
const struct modulator dcf77_modulator = { "DCF77 modulator", dcf_init, dcf_mod };
/* --------------------------------------------------------------------- */
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