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/*
* demod_hapn48.c -- HAPN 4800 baud demodulator (G3RUH)
*
* Copyright (C) 1996
* Thomas Sailer (sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu)
*
* 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.
*/
/* ---------------------------------------------------------------------- */
#include "multimon.h"
#include "filter.h"
#include <math.h>
#include <string.h>
/* ---------------------------------------------------------------------- */
#define FREQ_SAMP 22050
#define BAUD 4800
/* ---------------------------------------------------------------------- */
#define SPHASEINC (0x10000u*BAUD/FREQ_SAMP)
/* ---------------------------------------------------------------------- */
static void hapn48_init(struct demod_state *s)
{
hdlc_init(s);
memset(&s->l1.hapn48, 0, sizeof(s->l1.hapn48));
}
/* ---------------------------------------------------------------------- */
static void hapn48_demod(struct demod_state *s, float *buffer, int length)
{
int cursync;
unsigned int curbit;
for (; length > 0; length--, buffer++) {
s->l1.hapn48.lvlhi *= 0.999;
s->l1.hapn48.lvllo *= 0.999;
if (buffer[1] > s->l1.hapn48.lvlhi)
s->l1.hapn48.lvlhi = buffer[1];
if (buffer[1] < s->l1.hapn48.lvllo)
s->l1.hapn48.lvllo = buffer[1];
cursync = 0;
s->l1.hapn48.shreg = (s->l1.hapn48.shreg << 1) |
(s->l1.hapn48.shreg & 1);
if (buffer[1] > s->l1.hapn48.lvlhi * 0.5) {
s->l1.hapn48.shreg |= 1;
cursync = (buffer[1] > buffer[0] && buffer[1] > buffer[2]);
} else if (buffer[1] < s->l1.hapn48.lvllo * 0.5) {
s->l1.hapn48.shreg &= ~1;
cursync = (buffer[1] < buffer[0] && buffer[1] < buffer[2]);
}
verbprintf(10, "%c", '0' + (s->l1.hapn48.shreg & 1));
s->l1.hapn48.sphase += SPHASEINC;
if (((s->l1.hapn48.shreg >> 1) ^ s->l1.hapn48.shreg) & 1) {
if (s->l1.hapn48.sphase >= 0x8000+SPHASEINC/2)
s->l1.hapn48.sphase -= 0x800;
else
s->l1.hapn48.sphase += 0x800;
}
#if 0
if (cursync) {
if (((s->l1.hapn48.sphase-0x8000)&0xffffu) >= 0x8000+SPHASEINC/2)
s->l1.hapn48.sphase -= 0x800;
else
s->l1.hapn48.sphase += 0x800;
}
#endif
if (s->l1.hapn48.sphase >= 0x10000) {
s->l1.hapn48.sphase &= 0xffff;
curbit = ((s->l1.hapn48.shreg >> 4) ^ s->l1.hapn48.shreg ^ 1) & 1;
verbprintf(9, " %c ", '0'+curbit);
hdlc_rxbit(s, curbit);
}
}
}
/* ---------------------------------------------------------------------- */
const struct demod_param demod_hapn4800 = {
"HAPN4800", FREQ_SAMP, 3, hapn48_init, hapn48_demod
};
/* ---------------------------------------------------------------------- */
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