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
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/*
* ISO14443A modified Miller decoder for OpenPICC
* (C) 2006 by Harald Welte <hwelte@hmw-consulting.de>
*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/*
* LSB First LSB hex
* Sequence X 0010 0100 0x4
* Sequence Y 0000 0000 0x0
* Sequence Z 1000 0001 0x1
*
* Logic 1 Sequence X
* Logic 0 Sequence Y with two exceptions:
* - if there are more contiguous 0, Z used from second one
* - if the first bit after SOF is 0, sequence Z used for all contig 0's
* SOF Sequence Z
* EOF Logic 0 followed by Sequence Y
*
* cmd hex bits symbols hex (quad-sampled)
*
* REQA 0x26 S 0110010 E Z ZXXYZXY ZY 0x10410441
* WUPA 0x52 S 0100101 E Z ZXYZXYX YY 0x04041041
*
* SOF is 'eaten' by SSC start condition (Compare 0). Remaining bits are
* mirrored, e.g. samples for LSB of first byte are & 0xf
*
*/
#include <sys/types.h>
#include "openpicc.h"
#include "dbgu.h"
#include "decoder.h"
#include "iso14443_layer3a.h"
#ifdef FOUR_TIMES_OVERSAMPLING
#define OVERSAMPLING_RATE 4
/* definitions for four-times oversampling */
#define SEQ_X 0x4
#define SEQ_Y 0x0
#define SEQ_Z 0x1
#else
#define OVERSAMPLING_RATE 2
#define SEQ_X 0x2
#define SEQ_Y 0x0
#define SEQ_Z 0x1
#endif
/* decode a single sampled bit */
static inline u_int8_t miller_decode_sampled_bit(u_int32_t sampled_bit)
{
switch (sampled_bit) {
case SEQ_X:
return 1;
break;
case SEQ_Z:
case SEQ_Y:
return 0;
break;
default:
DEBUGP("unknown sequence sample `%x' ", sampled_bit);
return 2;
break;
}
}
/* decode a single 32bit data sample of an 8bit miller encoded word */
static int miller_decode_sample(u_int32_t sample, u_int8_t *data)
{
u_int8_t ret = 0;
unsigned int i;
for (i = 0; i < sizeof(sample)/OVERSAMPLING_RATE; i++) {
u_int8_t bit = miller_decode_sampled_bit(sample & 0xf);
if (bit == 1)
ret |= 1;
/* else do nothing since ret was initialized with 0 */
/* skip shifting in case of last data bit */
if (i == sizeof(sample)/OVERSAMPLING_RATE)
break;
sample = sample >> OVERSAMPLING_RATE;
ret = ret << 1;
}
*data = ret;
return ret;
}
static u_int32_t get_next_bytesample(struct decoder_state *ms,
u_int8_t *parity_sample)
{
u_int32_t ret = 0;
/* get remaining bits from the current word */
ret = *(ms->buf32) >> ms->bit_ofs;
/* move to next word */
ms->buf32++;
/* if required, get remaining bits from next word */
if (ms->bit_ofs)
ret |= *(ms->buf32) << (32 - ms->bit_ofs);
*parity_sample = (*(ms->buf32) >> ms->bit_ofs & 0xf);
/* increment bit offset (modulo 32) */
ms->bit_ofs = (ms->bit_ofs + OVERSAMPLING_RATE) % 32;
return ret;
}
struct decoder_algo miller_decoder = {
.oversampling_rate = OVERSAMPLING_RATE,
.bits_per_sampled_char = 9 * OVERSAMPLING_RATE,
.bytesample_mask = 0xffffffff,
.decode_sample = &miller_decode_sample,
.get_next_bytesample = &get_next_bytesample,
};
|
