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/* 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 "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 u_int8_t *sample_buf, const u_int16_t sample_buf_len)
{
signed int i, j, bit = 0, last_bit = -1;
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<sample_buf_len && bit != BIT_ENDMARKER; i++) {
DumpStringToUSB(" ");
DumpUIntToUSB(sample_buf[i]);
for(j=0; j<(signed)(sizeof(sample_buf[0])*8)/OVERSAMPLING_RATE && bit != BIT_ENDMARKER; j++) {
DumpStringToUSB(".");
int sample = (sample_buf[i]>>(j*OVERSAMPLING_RATE)) & ~(~0 << OVERSAMPLING_RATE);
switch(sample) {
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(sample); 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) */
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));
}
}
}
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;
}
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