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/* ISO14443A Miller decoder 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_buffer.h"
#include "cmd.h"
#if 0
// With debugging
#define MILLER_DEBUG_STRING DumpStringToUSB
#define MILLER_DEBUG_UINT DumpUIntToUSB
#else
// Without debugging
#define MILLER_DEBUG_STRING(...) if(0){(void)__VA_ARGS__;}
#define MILLER_DEBUG_UINT(...) if(0){(void)__VA_ARGS__;}
#endif
#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
static const int BITSAMPLE_MASK = ~(~0 << OVERSAMPLING_RATE);
int iso14443a_decode_miller(iso14443_frame *frame,
const ssc_dma_rx_buffer_t * const 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;
u_int32_t sample = 0;
u_int8_t *sample_8=0;
u_int16_t *sample_16=0;
u_int32_t *sample_32=0;
switch(buffer->reception_mode->transfersize_pdc) {
case 8: sample_8 = ((u_int8_t*)buffer->data); break;
case 16: sample_16 = ((u_int16_t*)buffer->data); break;
case 32: sample_32 = ((u_int32_t*)buffer->data); break;
}
for(i=0; i<buffer->len_transfers && bit != BIT_ENDMARKER; i++) {
MILLER_DEBUG_STRING(" ");
switch(buffer->reception_mode->transfersize_pdc) {
case 8: sample = *sample_8++; break;
case 16: sample = *sample_16++; break;
case 32: sample = *sample_32++; break;
}
MILLER_DEBUG_UINT(sample);
for(j=0; j<buffer->reception_mode->transfersize_ssc && bit != BIT_ENDMARKER; j+=OVERSAMPLING_RATE) {
MILLER_DEBUG_STRING(".");
int bitsample = (sample>>j) & BITSAMPLE_MASK;
switch(bitsample) {
case SEQ_X: current_seq = SEQUENCE_X; MILLER_DEBUG_STRING("X"); break;
case SEQ_Y: current_seq = SEQUENCE_Y; MILLER_DEBUG_STRING("Y"); break;
case SEQ_Z: current_seq = SEQUENCE_Z; MILLER_DEBUG_STRING("Z"); break;
default: MILLER_DEBUG_UINT(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;
MILLER_DEBUG_STRING("!");
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;
MILLER_DEBUG_STRING(" ");
MILLER_DEBUG_UINT(frame->numbytes);
MILLER_DEBUG_STRING(" bytes, ");
MILLER_DEBUG_UINT(frame->numbits);
MILLER_DEBUG_STRING(" bits ");
return 0;
}
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