forked from EliasOenal/multimon-ng
-
Notifications
You must be signed in to change notification settings - Fork 0
/
demod_poc5.c
97 lines (84 loc) · 2.91 KB
/
demod_poc5.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
/*
* demod_poc5.c -- 512 baud POCSAG demodulator
*
* Copyright (C) 1996
* Thomas Sailer (sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu)
*
* POCSAG (Post Office Code Standard Advisory Group)
* Radio Paging Decoder
*
* 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 512
#define SUBSAMP 5
#define FILTLEN 1
/* ---------------------------------------------------------------------- */
#define SPHASEINC (0x10000u*BAUD*SUBSAMP/FREQ_SAMP)
/* ---------------------------------------------------------------------- */
static void poc5_init(struct demod_state *s)
{
pocsag_init(s);
memset(&s->l1.poc5, 0, sizeof(s->l1.poc5));
}
/* ---------------------------------------------------------------------- */
static void poc5_demod(struct demod_state *s, buffer_t buffer, int length)
{
if (s->l1.poc5.subsamp) {
int numfill = SUBSAMP - s->l1.poc5.subsamp;
if (length < numfill) {
s->l1.poc5.subsamp += length;
return;
}
buffer.fbuffer += numfill;
length -= numfill;
s->l1.poc5.subsamp = 0;
}
for (; length >= SUBSAMP; length -= SUBSAMP, buffer.fbuffer += SUBSAMP) {
s->l1.poc5.dcd_shreg <<= 1;
s->l1.poc5.dcd_shreg |= ((*buffer.fbuffer) > 0);
verbprintf(10, "%c", '0'+(s->l1.poc5.dcd_shreg & 1));
/*
* check if transition
*/
if ((s->l1.poc5.dcd_shreg ^ (s->l1.poc5.dcd_shreg >> 1)) & 1) {
if (s->l1.poc5.sphase < (0x8000u-(SPHASEINC/2)))
s->l1.poc5.sphase += SPHASEINC/8;
else
s->l1.poc5.sphase -= SPHASEINC/8;
}
s->l1.poc5.sphase += SPHASEINC;
if (s->l1.poc5.sphase >= 0x10000u) {
s->l1.poc5.sphase &= 0xffffu;
pocsag_rxbit(s, s->l1.poc5.dcd_shreg & 1);
}
}
s->l1.poc5.subsamp = length;
}
static void poc5_deinit(struct demod_state *s)
{
pocsag_deinit(s);
}
/* ---------------------------------------------------------------------- */
const struct demod_param demod_poc5 = {
"POCSAG512", true, FREQ_SAMP, FILTLEN, poc5_init, poc5_demod, poc5_deinit
};
/* ---------------------------------------------------------------------- */