summaryrefslogtreecommitdiff
path: root/openpicc/application/iso14443a_miller.c
blob: a17a6e82ef25e5fc0727523f8e79bbe6577c424c (plain)
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
/* ISO14443A Manchester encoder for OpenPICC
 * (C) 2007 by Henryk Plötz <henryk@ploetzli.ch>
 *
 *  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
 *
 */

#include <openpicc.h>
#include <FreeRTOS.h>

#include <string.h>

#include "iso14443_layer3a.h"
#include "usb_print.h"
#include "ssc_picc.h"
#include "cmd.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

enum miller_sequence {
	SEQUENCE_X,
	SEQUENCE_Y,
	SEQUENCE_Z,
};

#define BIT_ENDMARKER -1

int iso14443a_decode_miller(iso14443_frame *frame, 
	const ssc_dma_rx_buffer_t *buffer)
{
	u_int32_t i,j;
	signed int bit = 0, last_bit = ISO14443A_LAST_BIT_NONE, next_to_last_bit = ISO14443A_LAST_BIT_NONE;
	enum miller_sequence current_seq;
	unsigned int bitpos = 0;
	
	memset(frame, 0, sizeof(*frame));
	frame->type = TYPE_A;
	frame->parameters.a.parity = GIVEN_PARITY;
	
	for(i=0; i<buffer->len_transfers && bit != BIT_ENDMARKER; i++) {
		u_int32_t sample = 0;
		DumpStringToUSB(" ");
		switch(buffer->reception_mode->transfersize_pdc) {
			case 8:  sample = ((u_int8_t*)buffer->data)[i];  break;
			case 16: sample = ((u_int16_t*)buffer->data)[i]; break;
			case 32: sample = ((u_int32_t*)buffer->data)[i]; break;
		}
		DumpUIntToUSB(sample);
		for(j=0; j<buffer->reception_mode->transfersize_ssc/OVERSAMPLING_RATE && bit != BIT_ENDMARKER; j++) {
			DumpStringToUSB(".");
			int bitsample = (sample>>(j*OVERSAMPLING_RATE)) & ~(~0 << OVERSAMPLING_RATE);
			switch(bitsample) {
				case SEQ_X: current_seq = SEQUENCE_X; DumpStringToUSB("X"); break;
				case SEQ_Y: current_seq = SEQUENCE_Y; DumpStringToUSB("Y"); break;
				case SEQ_Z: current_seq = SEQUENCE_Z; DumpStringToUSB("Z"); break;
				default: DumpUIntToUSB(bitsample); current_seq = SEQUENCE_Y;
			}
			
			switch(current_seq) {
				case SEQUENCE_X:
					bit = 1; break;
				case SEQUENCE_Y: /* Fall-through to SEQUENCE_Z */
					if(last_bit == 0) {
						bit = BIT_ENDMARKER;
						DumpStringToUSB("!");
						break;
					}
				case SEQUENCE_Z:
					bit = 0; break;
			}
			
			switch(bit) {
				case BIT_ENDMARKER:
					bitpos-=2; /* Subtract this sequence and the previous sequence (which was a 0) */
					frame->parameters.a.last_bit = next_to_last_bit;
					break;
				case 0: /* Fall-through */
				case 1: {
					int bytepos = bitpos/9;
					if(bitpos % 9 == 8) { /* Parity bit */
						frame->parity[ bytepos/8 ] |= (bit<<(bytepos%8));
					} else {
						frame->data[ bytepos ] |= (bit<<(bitpos%9));
					}
				}
			}
			
			next_to_last_bit = last_bit;
			last_bit = bit;
			bitpos++;
		}
	}
	
	frame->numbytes = bitpos/9;
	frame->numbits = bitpos%9;
	DumpStringToUSB(" ");
	DumpUIntToUSB(frame->numbytes);
	DumpStringToUSB(" bytes, ");
	DumpUIntToUSB(frame->numbits);
	DumpStringToUSB(" bits ");
	
	return 0;
}
personal git repositories of Harald Welte. Your mileage may vary