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/* ISO14443A Miller decoder for OpenPICC
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* (C) 2007 by Henryk Plötz <henryk@ploetzli.ch>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#include <openpicc.h>
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#include <FreeRTOS.h>
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#include <string.h>
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#include "iso14443_layer3a.h"
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#include "usb_print.h"
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#include "ssc_buffer.h"
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#include "cmd.h"
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#if 0
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// With debugging
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#define MILLER_DEBUG_STRING DumpStringToUSB
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#define MILLER_DEBUG_UINT DumpUIntToUSB
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#else
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// Without debugging
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#define MILLER_DEBUG_STRING(...) if(0){(void)__VA_ARGS__;}
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#define MILLER_DEBUG_UINT(...) if(0){(void)__VA_ARGS__;}
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#endif
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#ifdef FOUR_TIMES_OVERSAMPLING
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#define OVERSAMPLING_RATE 4
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/* definitions for four-times oversampling */
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#define SEQ_X 0x4
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#define SEQ_Y 0x0
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#define SEQ_Z 0x1
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#else
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#define OVERSAMPLING_RATE 2
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#define SEQ_X 0x2
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#define SEQ_Y 0x0
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#define SEQ_Z 0x1
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#endif
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enum miller_sequence {
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SEQUENCE_X,
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SEQUENCE_Y,
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SEQUENCE_Z,
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};
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#define BIT_ENDMARKER -1
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static const int BITSAMPLE_MASK = ~(~0 << OVERSAMPLING_RATE);
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int iso14443a_decode_miller(iso14443_frame *frame,
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const ssc_dma_rx_buffer_t * const buffer)
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{
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u_int32_t i,j;
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signed int bit = 0, last_bit = ISO14443A_LAST_BIT_NONE, next_to_last_bit = ISO14443A_LAST_BIT_NONE;
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enum miller_sequence current_seq;
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unsigned int bitpos = 0;
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memset(frame, 0, sizeof(*frame));
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frame->type = TYPE_A;
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frame->parameters.a.parity = GIVEN_PARITY;
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u_int32_t sample = 0;
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u_int8_t *sample_8=0;
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u_int16_t *sample_16=0;
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u_int32_t *sample_32=0;
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switch(buffer->reception_mode->transfersize_pdc) {
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case 8: sample_8 = ((u_int8_t*)buffer->data); break;
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case 16: sample_16 = ((u_int16_t*)buffer->data); break;
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case 32: sample_32 = ((u_int32_t*)buffer->data); break;
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}
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for(i=0; i<buffer->len_transfers && bit != BIT_ENDMARKER; i++) {
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MILLER_DEBUG_STRING(" ");
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switch(buffer->reception_mode->transfersize_pdc) {
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case 8: sample = *sample_8++; break;
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case 16: sample = *sample_16++; break;
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case 32: sample = *sample_32++; break;
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}
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MILLER_DEBUG_UINT(sample);
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for(j=0; j<buffer->reception_mode->transfersize_ssc && bit != BIT_ENDMARKER; j+=OVERSAMPLING_RATE) {
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MILLER_DEBUG_STRING(".");
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int bitsample = (sample>>j) & BITSAMPLE_MASK;
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switch(bitsample) {
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case SEQ_X: current_seq = SEQUENCE_X; MILLER_DEBUG_STRING("X"); break;
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case SEQ_Y: current_seq = SEQUENCE_Y; MILLER_DEBUG_STRING("Y"); break;
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case SEQ_Z: current_seq = SEQUENCE_Z; MILLER_DEBUG_STRING("Z"); break;
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default: MILLER_DEBUG_UINT(bitsample); current_seq = SEQUENCE_Y;
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}
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switch(current_seq) {
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case SEQUENCE_X:
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bit = 1; break;
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case SEQUENCE_Y: /* Fall-through to SEQUENCE_Z */
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if(last_bit == 0) {
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bit = BIT_ENDMARKER;
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MILLER_DEBUG_STRING("!");
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break;
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}
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case SEQUENCE_Z:
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bit = 0; break;
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}
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switch(bit) {
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case BIT_ENDMARKER:
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bitpos-=2; /* Subtract this sequence and the previous sequence (which was a 0) */
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frame->parameters.a.last_bit = next_to_last_bit;
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break;
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case 0: /* Fall-through */
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case 1: {
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int bytepos = bitpos/9;
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if(bitpos % 9 == 8) { /* Parity bit */
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frame->parity[ bytepos/8 ] |= (bit<<(bytepos%8));
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} else {
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frame->data[ bytepos ] |= (bit<<(bitpos%9));
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}
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}
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}
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next_to_last_bit = last_bit;
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last_bit = bit;
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bitpos++;
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}
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}
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frame->numbytes = bitpos/9;
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frame->numbits = bitpos%9;
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MILLER_DEBUG_STRING(" ");
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MILLER_DEBUG_UINT(frame->numbytes);
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MILLER_DEBUG_STRING(" bytes, ");
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MILLER_DEBUG_UINT(frame->numbits);
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MILLER_DEBUG_STRING(" bits ");
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return 0;
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}
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