git.zerfleddert.de Git - proxmark3-svn/blob - armsrc/iso14443b.c

   1 //-----------------------------------------------------------------------------
   2 // Jonathan Westhues, split Nov 2006
   3 //
   4 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
   5 // at your option, any later version. See the LICENSE.txt file for the text of
   6 // the license.
   7 //-----------------------------------------------------------------------------
   8 // Routines to support ISO 14443B. This includes both the reader software and
   9 // the `fake tag' modes.
  10 //-----------------------------------------------------------------------------
  11
  12 #include "proxmark3.h"
  13 #include "apps.h"
  14 #include "util.h"
  15 #include "string.h"
  16
  17 #include "iso14443crc.h"
  18
  19 #define RECEIVE_SAMPLES_TIMEOUT 2000
  20 #define ISO14443B_DMA_BUFFER_SIZE 256
  21
  22 // PCB Block number for APDUs
  23 static uint8_t pcb_blocknum = 0;
  24
  25 //=============================================================================
  26 // An ISO 14443 Type B tag. We listen for commands from the reader, using
  27 // a UART kind of thing that's implemented in software. When we get a
  28 // frame (i.e., a group of bytes between SOF and EOF), we check the CRC.
  29 // If it's good, then we can do something appropriate with it, and send
  30 // a response.
  31 //=============================================================================
  32
  33 //-----------------------------------------------------------------------------
  34 // Code up a string of octets at layer 2 (including CRC, we don't generate
  35 // that here) so that they can be transmitted to the reader. Doesn't transmit
  36 // them yet, just leaves them ready to send in ToSend[].
  37 //-----------------------------------------------------------------------------
  38 static void CodeIso14443bAsTag(const uint8_t *cmd, int len)
  39 {
  40         int i;
  41
  42         ToSendReset();
  43
  44         // Transmit a burst of ones, as the initial thing that lets the
  45         // reader get phase sync. This (TR1) must be > 80/fs, per spec,
  46         // but tag that I've tried (a Paypass) exceeds that by a fair bit,
  47         // so I will too.
  48         for(i = 0; i < 20; i++) {
  49                 ToSendStuffBit(1);
  50                 ToSendStuffBit(1);
  51                 ToSendStuffBit(1);
  52                 ToSendStuffBit(1);
  53         }
  54
  55         // Send SOF.
  56         for(i = 0; i < 10; i++) {
  57                 ToSendStuffBit(0);
  58                 ToSendStuffBit(0);
  59                 ToSendStuffBit(0);
  60                 ToSendStuffBit(0);
  61         }
  62         for(i = 0; i < 2; i++) {
  63                 ToSendStuffBit(1);
  64                 ToSendStuffBit(1);
  65                 ToSendStuffBit(1);
  66                 ToSendStuffBit(1);
  67         }
  68
  69         for(i = 0; i < len; i++) {
  70                 int j;
  71                 uint8_t b = cmd[i];
  72
  73                 // Start bit
  74                 ToSendStuffBit(0);
  75                 ToSendStuffBit(0);
  76                 ToSendStuffBit(0);
  77                 ToSendStuffBit(0);
  78
  79                 // Data bits
  80                 for(j = 0; j < 8; j++) {
  81                         if(b & 1) {
  82                                 ToSendStuffBit(1);
  83                                 ToSendStuffBit(1);
  84                                 ToSendStuffBit(1);
  85                                 ToSendStuffBit(1);
  86                         } else {
  87                                 ToSendStuffBit(0);
  88                                 ToSendStuffBit(0);
  89                                 ToSendStuffBit(0);
  90                                 ToSendStuffBit(0);
  91                         }
  92                         b >>= 1;
  93                 }
  94
  95                 // Stop bit
  96                 ToSendStuffBit(1);
  97                 ToSendStuffBit(1);
  98                 ToSendStuffBit(1);
  99                 ToSendStuffBit(1);
 100         }
 101
 102         // Send EOF.
 103         for(i = 0; i < 10; i++) {
 104                 ToSendStuffBit(0);
 105                 ToSendStuffBit(0);
 106                 ToSendStuffBit(0);
 107                 ToSendStuffBit(0);
 108         }
 109         for(i = 0; i < 2; i++) {
 110                 ToSendStuffBit(1);
 111                 ToSendStuffBit(1);
 112                 ToSendStuffBit(1);
 113                 ToSendStuffBit(1);
 114         }
 115
 116         // Convert from last byte pos to length
 117         ToSendMax++;
 118 }
 119
 120 //-----------------------------------------------------------------------------
 121 // The software UART that receives commands from the reader, and its state
 122 // variables.
 123 //-----------------------------------------------------------------------------
 124 static struct {
 125         enum {
 126                 STATE_UNSYNCD,
 127                 STATE_GOT_FALLING_EDGE_OF_SOF,
 128                 STATE_AWAITING_START_BIT,
 129                 STATE_RECEIVING_DATA
 130         }       state;
 131         uint16_t    shiftReg;
 132         int     bitCnt;
 133         int     byteCnt;
 134         int     byteCntMax;
 135         int     posCnt;
 136         uint8_t   *output;
 137 } Uart;
 138
 139 /* Receive & handle a bit coming from the reader.
 140  *
 141  * This function is called 4 times per bit (every 2 subcarrier cycles).
 142  * Subcarrier frequency fs is 848kHz, 1/fs = 1,18us, i.e. function is called every 2,36us
 143  *
 144  * LED handling:
 145  * LED A -> ON once we have received the SOF and are expecting the rest.
 146  * LED A -> OFF once we have received EOF or are in error state or unsynced
 147  *
 148  * Returns: true if we received a EOF
 149  *          false if we are still waiting for some more
 150  */
 151 static RAMFUNC int Handle14443bUartBit(uint8_t bit)
 152 {
 153         switch(Uart.state) {
 154                 case STATE_UNSYNCD:
 155                         if(!bit) {
 156                                 // we went low, so this could be the beginning
 157                                 // of an SOF
 158                                 Uart.state = STATE_GOT_FALLING_EDGE_OF_SOF;
 159                                 Uart.posCnt = 0;
 160                                 Uart.bitCnt = 0;
 161                         }
 162                         break;
 163
 164                 case STATE_GOT_FALLING_EDGE_OF_SOF:
 165                         Uart.posCnt++;
 166                         if(Uart.posCnt == 2) {  // sample every 4 1/fs in the middle of a bit
 167                                 if(bit) {
 168                                         if(Uart.bitCnt > 9) {
 169                                                 // we've seen enough consecutive
 170                                                 // zeros that it's a valid SOF
 171                                                 Uart.posCnt = 0;
 172                                                 Uart.byteCnt = 0;
 173                                                 Uart.state = STATE_AWAITING_START_BIT;
 174                                                 LED_A_ON(); // Indicate we got a valid SOF
 175                                         } else {
 176                                                 // didn't stay down long enough
 177                                                 // before going high, error
 178                                                 Uart.state = STATE_UNSYNCD;
 179                                         }
 180                                 } else {
 181                                         // do nothing, keep waiting
 182                                 }
 183                                 Uart.bitCnt++;
 184                         }
 185                         if(Uart.posCnt >= 4) Uart.posCnt = 0;
 186                         if(Uart.bitCnt > 12) {
 187                                 // Give up if we see too many zeros without
 188                                 // a one, too.
 189                                 LED_A_OFF();
 190                                 Uart.state = STATE_UNSYNCD;
 191                         }
 192                         break;
 193
 194                 case STATE_AWAITING_START_BIT:
 195                         Uart.posCnt++;
 196                         if(bit) {
 197                                 if(Uart.posCnt > 50/2) {        // max 57us between characters = 49 1/fs, max 3 etus after low phase of SOF = 24 1/fs
 198                                         // stayed high for too long between
 199                                         // characters, error
 200                                         Uart.state = STATE_UNSYNCD;
 201                                 }
 202                         } else {
 203                                 // falling edge, this starts the data byte
 204                                 Uart.posCnt = 0;
 205                                 Uart.bitCnt = 0;
 206                                 Uart.shiftReg = 0;
 207                                 Uart.state = STATE_RECEIVING_DATA;
 208                         }
 209                         break;
 210
 211                 case STATE_RECEIVING_DATA:
 212                         Uart.posCnt++;
 213                         if(Uart.posCnt == 2) {
 214                                 // time to sample a bit
 215                                 Uart.shiftReg >>= 1;
 216                                 if(bit) {
 217                                         Uart.shiftReg |= 0x200;
 218                                 }
 219                                 Uart.bitCnt++;
 220                         }
 221                         if(Uart.posCnt >= 4) {
 222                                 Uart.posCnt = 0;
 223                         }
 224                         if(Uart.bitCnt == 10) {
 225                                 if((Uart.shiftReg & 0x200) && !(Uart.shiftReg & 0x001))
 226                                 {
 227                                         // this is a data byte, with correct
 228                                         // start and stop bits
 229                                         Uart.output[Uart.byteCnt] = (Uart.shiftReg >> 1) & 0xff;
 230                                         Uart.byteCnt++;
 231
 232                                         if(Uart.byteCnt >= Uart.byteCntMax) {
 233                                                 // Buffer overflowed, give up
 234                                                 LED_A_OFF();
 235                                                 Uart.state = STATE_UNSYNCD;
 236                                         } else {
 237                                                 // so get the next byte now
 238                                                 Uart.posCnt = 0;
 239                                                 Uart.state = STATE_AWAITING_START_BIT;
 240                                         }
 241                                 } else if (Uart.shiftReg == 0x000) {
 242                                         // this is an EOF byte
 243                                         LED_A_OFF(); // Finished receiving
 244                                         Uart.state = STATE_UNSYNCD;
 245                                         if (Uart.byteCnt != 0) {
 246                                                 return TRUE;
 247                                         }
 248                                 } else {
 249                                         // this is an error
 250                                         LED_A_OFF();
 251                                         Uart.state = STATE_UNSYNCD;
 252                                 }
 253                         }
 254                         break;
 255
 256                 default:
 257                         LED_A_OFF();
 258                         Uart.state = STATE_UNSYNCD;
 259                         break;
 260         }
 261
 262         return FALSE;
 263 }
 264
 265
 266 static void UartReset()
 267 {
 268         Uart.byteCntMax = MAX_FRAME_SIZE;
 269         Uart.state = STATE_UNSYNCD;
 270         Uart.byteCnt = 0;
 271         Uart.bitCnt = 0;
 272 }
 273
 274
 275 static void UartInit(uint8_t *data)
 276 {
 277         Uart.output = data;
 278         UartReset();
 279 }
 280
 281
 282 //-----------------------------------------------------------------------------
 283 // Receive a command (from the reader to us, where we are the simulated tag),
 284 // and store it in the given buffer, up to the given maximum length. Keeps
 285 // spinning, waiting for a well-framed command, until either we get one
 286 // (returns TRUE) or someone presses the pushbutton on the board (FALSE).
 287 //
 288 // Assume that we're called with the SSC (to the FPGA) and ADC path set
 289 // correctly.
 290 //-----------------------------------------------------------------------------
 291 static int GetIso14443bCommandFromReader(uint8_t *received, uint16_t *len)
 292 {
 293         // Set FPGA mode to "simulated ISO 14443B tag", no modulation (listen
 294         // only, since we are receiving, not transmitting).
 295         // Signal field is off with the appropriate LED
 296         LED_D_OFF();
 297         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
 298
 299         // Now run a `software UART' on the stream of incoming samples.
 300         UartInit(received);
 301
 302         for(;;) {
 303                 WDT_HIT();
 304
 305                 if(BUTTON_PRESS()) return FALSE;
 306
 307                 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 308                         uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
 309                         for(uint8_t mask = 0x80; mask != 0x00; mask >>= 1) {
 310                                 if(Handle14443bUartBit(b & mask)) {
 311                                         *len = Uart.byteCnt;
 312                                         return TRUE;
 313                                 }
 314                         }
 315                 }
 316         }
 317
 318         return FALSE;
 319 }
 320
 321 //-----------------------------------------------------------------------------
 322 // Main loop of simulated tag: receive commands from reader, decide what
 323 // response to send, and send it.
 324 //-----------------------------------------------------------------------------
 325 void SimulateIso14443bTag(void)
 326 {
 327         // the only commands we understand is WUPB, AFI=0, Select All, N=1:
 328         static const uint8_t cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 }; // WUPB
 329         // ... and REQB, AFI=0, Normal Request, N=1:
 330         static const uint8_t cmd2[] = { 0x05, 0x00, 0x00, 0x71, 0xFF }; // REQB
 331         // ... and HLTB
 332         static const uint8_t cmd3[] = { 0x50, 0xff, 0xff, 0xff, 0xff }; // HLTB
 333         // ... and ATTRIB
 334         static const uint8_t cmd4[] = { 0x1D, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}; // ATTRIB
 335
 336         // ... and we always respond with ATQB, PUPI = 820de174, Application Data = 0x20381922,
 337         // supports only 106kBit/s in both directions, max frame size = 32Bytes,
 338         // supports ISO14443-4, FWI=8 (77ms), NAD supported, CID not supported:
 339         static const uint8_t response1[] = {
 340                 0x50, 0x82, 0x0d, 0xe1, 0x74, 0x20, 0x38, 0x19, 0x22,
 341                 0x00, 0x21, 0x85, 0x5e, 0xd7
 342         };
 343         // response to HLTB and ATTRIB
 344         static const uint8_t response2[] = {0x00, 0x78, 0xF0};
 345
 346
 347         FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
 348
 349         clear_trace();
 350         set_tracing(TRUE);
 351
 352         const uint8_t *resp;
 353         uint8_t *respCode;
 354         uint16_t respLen, respCodeLen;
 355
 356         // allocate command receive buffer
 357         BigBuf_free();
 358         uint8_t *receivedCmd = BigBuf_malloc(MAX_FRAME_SIZE);
 359
 360         uint16_t len;
 361         uint16_t cmdsRecvd = 0;
 362
 363         // prepare the (only one) tag answer:
 364         CodeIso14443bAsTag(response1, sizeof(response1));
 365         uint8_t *resp1Code = BigBuf_malloc(ToSendMax);
 366         memcpy(resp1Code, ToSend, ToSendMax);
 367         uint16_t resp1CodeLen = ToSendMax;
 368
 369         // prepare the (other) tag answer:
 370         CodeIso14443bAsTag(response2, sizeof(response2));
 371         uint8_t *resp2Code = BigBuf_malloc(ToSendMax);
 372         memcpy(resp2Code, ToSend, ToSendMax);
 373         uint16_t resp2CodeLen = ToSendMax;
 374
 375         // We need to listen to the high-frequency, peak-detected path.
 376         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 377         FpgaSetupSsc();
 378
 379         cmdsRecvd = 0;
 380
 381         for(;;) {
 382
 383                 if(!GetIso14443bCommandFromReader(receivedCmd, &len)) {
 384                         Dbprintf("button pressed, received %d commands", cmdsRecvd);
 385                         break;
 386                 }
 387
 388                 if (tracing) {
 389                         uint8_t parity[MAX_PARITY_SIZE];
 390                         LogTrace(receivedCmd, len, 0, 0, parity, TRUE);
 391                 }
 392
 393                 // Good, look at the command now.
 394                 if ( (len == sizeof(cmd1) && memcmp(receivedCmd, cmd1, len) == 0)
 395                         || (len == sizeof(cmd2) && memcmp(receivedCmd, cmd2, len) == 0) ) {
 396                         resp = response1;
 397                         respLen = sizeof(response1);
 398                         respCode = resp1Code;
 399                         respCodeLen = resp1CodeLen;
 400                 } else if ( (len == sizeof(cmd3) && receivedCmd[0] == cmd3[0])
 401                         || (len == sizeof(cmd4) && receivedCmd[0] == cmd4[0]) ) {
 402                         resp = response2;
 403                         respLen = sizeof(response2);
 404                         respCode = resp2Code;
 405                         respCodeLen = resp2CodeLen;
 406                 } else {
 407                         Dbprintf("new cmd from reader: len=%d, cmdsRecvd=%d", len, cmdsRecvd);
 408                         // And print whether the CRC fails, just for good measure
 409                         uint8_t b1, b2;
 410                         if (len >= 3){ // if crc exists
 411                                 ComputeCrc14443(CRC_14443_B, receivedCmd, len-2, &b1, &b2);
 412                                 if(b1 != receivedCmd[len-2] || b2 != receivedCmd[len-1]) {
 413                                         // Not so good, try again.
 414                                         DbpString("+++CRC fail");
 415
 416                                 } else {
 417                                         DbpString("CRC passes");
 418                                 }
 419                         }
 420                         //get rid of compiler warning
 421                         respCodeLen = 0;
 422                         resp = response1;
 423                         respLen = 0;
 424                         respCode = resp1Code;
 425                         //don't crash at new command just wait and see if reader will send other new cmds.
 426                         //break;
 427                 }
 428
 429                 cmdsRecvd++;
 430
 431                 if(cmdsRecvd > 0x30) {
 432                         DbpString("many commands later...");
 433                         break;
 434                 }
 435
 436                 if(respCodeLen <= 0) continue;
 437
 438                 // Modulate BPSK
 439                 // Signal field is off with the appropriate LED
 440                 LED_D_OFF();
 441                 FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_BPSK);
 442                 AT91C_BASE_SSC->SSC_THR = 0xff;
 443                 FpgaSetupSsc();
 444
 445                 // Transmit the response.
 446                 uint16_t i = 0;
 447                 for(;;) {
 448                         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 449                                 uint8_t b = respCode[i];
 450
 451                                 AT91C_BASE_SSC->SSC_THR = b;
 452
 453                                 i++;
 454                                 if(i > respCodeLen) {
 455                                         break;
 456                                 }
 457                         }
 458                         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 459                                 volatile uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
 460                                 (void)b;
 461                         }
 462                 }
 463
 464                 // trace the response:
 465                 if (tracing) {
 466                         uint8_t parity[MAX_PARITY_SIZE];
 467                         LogTrace(resp, respLen, 0, 0, parity, FALSE);
 468                 }
 469
 470         }
 471 }
 472
 473 //=============================================================================
 474 // An ISO 14443 Type B reader. We take layer two commands, code them
 475 // appropriately, and then send them to the tag. We then listen for the
 476 // tag's response, which we leave in the buffer to be demodulated on the
 477 // PC side.
 478 //=============================================================================
 479
 480 static struct {
 481         enum {
 482                 DEMOD_UNSYNCD,
 483                 DEMOD_PHASE_REF_TRAINING,
 484                 DEMOD_AWAITING_FALLING_EDGE_OF_SOF,
 485                 DEMOD_GOT_FALLING_EDGE_OF_SOF,
 486                 DEMOD_AWAITING_START_BIT,
 487                 DEMOD_RECEIVING_DATA
 488         }       state;
 489         int     bitCount;
 490         int     posCount;
 491         int     thisBit;
 492 /* this had been used to add RSSI (Received Signal Strength Indication) to traces. Currently not implemented.
 493         int     metric;
 494         int     metricN;
 495 */
 496         uint16_t    shiftReg;
 497         uint8_t   *output;
 498         int     len;
 499         int     sumI;
 500         int     sumQ;
 501 } Demod;
 502
 503 /*
 504  * Handles reception of a bit from the tag
 505  *
 506  * This function is called 2 times per bit (every 4 subcarrier cycles).
 507  * Subcarrier frequency fs is 848kHz, 1/fs = 1,18us, i.e. function is called every 4,72us
 508  *
 509  * LED handling:
 510  * LED C -> ON once we have received the SOF and are expecting the rest.
 511  * LED C -> OFF once we have received EOF or are unsynced
 512  *
 513  * Returns: true if we received a EOF
 514  *          false if we are still waiting for some more
 515  *
 516  */
 517 static RAMFUNC int Handle14443bSamplesDemod(int ci, int cq)
 518 {
 519         int v;
 520
 521 // The soft decision on the bit uses an estimate of just the
 522 // quadrant of the reference angle, not the exact angle.
 523 #define MAKE_SOFT_DECISION() { \
 524                 if(Demod.sumI > 0) { \
 525                         v = ci; \
 526                 } else { \
 527                         v = -ci; \
 528                 } \
 529                 if(Demod.sumQ > 0) { \
 530                         v += cq; \
 531                 } else { \
 532                         v -= cq; \
 533                 } \
 534         }
 535
 536 #define SUBCARRIER_DETECT_THRESHOLD     8
 537
 538 // Subcarrier amplitude v = sqrt(ci^2 + cq^2), approximated here by abs(ci) + abs(cq)
 539 /* #define CHECK_FOR_SUBCARRIER() { \
 540                 v = ci; \
 541                 if(v < 0) v = -v; \
 542                 if(cq > 0) { \
 543                         v += cq; \
 544                 } else { \
 545                         v -= cq; \
 546                 } \
 547         }
 548  */
 549 // Subcarrier amplitude v = sqrt(ci^2 + cq^2), approximated here by max(abs(ci),abs(cq)) + 1/2*min(abs(ci),abs(cq)))
 550
 551         //note: couldn't we just use MAX(ABS(ci),ABS(cq)) + (MIN(ABS(ci),ABS(cq))/2) from common.h - marshmellow
 552 #define CHECK_FOR_SUBCARRIER() { \
 553                 v = MAX(ABS(ci),ABS(cq)) + (MIN(ABS(ci),ABS(cq))/2); \
 554         }
 555                 /*
 556                 if(ci < 0) { \
 557                         if(cq < 0) { \ // ci < 0, cq < 0
 558                                 if (cq < ci) { \
 559                                         v = -cq - (ci >> 1); \
 560                                 } else { \
 561                                         v = -ci - (cq >> 1); \
 562                                 } \
 563                         } else {        \ // ci < 0, cq >= 0
 564                                 if (cq < -ci) { \
 565                                         v = -ci + (cq >> 1); \
 566                                 } else { \
 567                                         v = cq - (ci >> 1); \
 568                                 } \
 569                         } \
 570                 } else { \
 571                         if(cq < 0) { \ // ci >= 0, cq < 0
 572                                 if (-cq < ci) { \
 573                                         v = ci - (cq >> 1); \
 574                                 } else { \
 575                                         v = -cq + (ci >> 1); \
 576                                 } \
 577                         } else {        \ // ci >= 0, cq >= 0
 578                                 if (cq < ci) { \
 579                                         v = ci + (cq >> 1); \
 580                                 } else { \
 581                                         v = cq + (ci >> 1); \
 582                                 } \
 583                         } \
 584                 } \
 585         }
 586                 */
 587
 588         switch(Demod.state) {
 589                 case DEMOD_UNSYNCD:
 590                         CHECK_FOR_SUBCARRIER();
 591                         if(v > SUBCARRIER_DETECT_THRESHOLD) {   // subcarrier detected
 592                                 Demod.state = DEMOD_PHASE_REF_TRAINING;
 593                                 Demod.sumI = ci;
 594                                 Demod.sumQ = cq;
 595                                 Demod.posCount = 1;
 596                                 }
 597                         break;
 598
 599                 case DEMOD_PHASE_REF_TRAINING:
 600                         if(Demod.posCount < 8) {
 601                                 CHECK_FOR_SUBCARRIER();
 602                                 if (v > SUBCARRIER_DETECT_THRESHOLD) {
 603                                         // set the reference phase (will code a logic '1') by averaging over 32 1/fs.
 604                                         // note: synchronization time > 80 1/fs
 605                                         Demod.sumI += ci;
 606                                         Demod.sumQ += cq;
 607                                         Demod.posCount++;
 608                                 } else {                // subcarrier lost
 609                                         Demod.state = DEMOD_UNSYNCD;
 610                                 }
 611                         } else {
 612                                 Demod.state = DEMOD_AWAITING_FALLING_EDGE_OF_SOF;
 613                         }
 614                         break;
 615
 616                 case DEMOD_AWAITING_FALLING_EDGE_OF_SOF:
 617                         MAKE_SOFT_DECISION();
 618                         if(v < 0) {     // logic '0' detected
 619                                 Demod.state = DEMOD_GOT_FALLING_EDGE_OF_SOF;
 620                                 Demod.posCount = 0;     // start of SOF sequence
 621                         } else {
 622                                 if(Demod.posCount > 200/4) {    // maximum length of TR1 = 200 1/fs
 623                                         Demod.state = DEMOD_UNSYNCD;
 624                                 }
 625                         }
 626                         Demod.posCount++;
 627                         break;
 628
 629                 case DEMOD_GOT_FALLING_EDGE_OF_SOF:
 630                         Demod.posCount++;
 631                         MAKE_SOFT_DECISION();
 632                         if(v > 0) {
 633                                 if(Demod.posCount < 9*2) { // low phase of SOF too short (< 9 etu). Note: spec is >= 10, but FPGA tends to "smear" edges
 634                                         Demod.state = DEMOD_UNSYNCD;
 635                                 } else {
 636                                         LED_C_ON(); // Got SOF
 637                                         Demod.state = DEMOD_AWAITING_START_BIT;
 638                                         Demod.posCount = 0;
 639                                         Demod.len = 0;
 640 /* this had been used to add RSSI (Received Signal Strength Indication) to traces. Currently not implemented.
 641                                         Demod.metricN = 0;
 642                                         Demod.metric = 0;
 643 */
 644                                 }
 645                         } else {
 646                                 if(Demod.posCount > 12*2) { // low phase of SOF too long (> 12 etu)
 647                                         Demod.state = DEMOD_UNSYNCD;
 648                                         LED_C_OFF();
 649                                 }
 650                         }
 651                         break;
 652
 653                 case DEMOD_AWAITING_START_BIT:
 654                         Demod.posCount++;
 655                         MAKE_SOFT_DECISION();
 656                         if(v > 0) {
 657                                 if(Demod.posCount > 3*2) {              // max 19us between characters = 16 1/fs, max 3 etu after low phase of SOF = 24 1/fs
 658                                         Demod.state = DEMOD_UNSYNCD;
 659                                         LED_C_OFF();
 660                                 }
 661                         } else {                                                        // start bit detected
 662                                 Demod.bitCount = 0;
 663                                 Demod.posCount = 1;                             // this was the first half
 664                                 Demod.thisBit = v;
 665                                 Demod.shiftReg = 0;
 666                                 Demod.state = DEMOD_RECEIVING_DATA;
 667                         }
 668                         break;
 669
 670                 case DEMOD_RECEIVING_DATA:
 671                         MAKE_SOFT_DECISION();
 672                         if(Demod.posCount == 0) {                       // first half of bit
 673                                 Demod.thisBit = v;
 674                                 Demod.posCount = 1;
 675                         } else {                                                        // second half of bit
 676                                 Demod.thisBit += v;
 677
 678 /* this had been used to add RSSI (Received Signal Strength Indication) to traces. Currently not implemented.
 679                                 if(Demod.thisBit > 0) {
 680                                         Demod.metric += Demod.thisBit;
 681                                 } else {
 682                                         Demod.metric -= Demod.thisBit;
 683                                 }
 684                                 (Demod.metricN)++;
 685 */
 686
 687                                 Demod.shiftReg >>= 1;
 688                                 if(Demod.thisBit > 0) { // logic '1'
 689                                         Demod.shiftReg |= 0x200;
 690                                 }
 691
 692                                 Demod.bitCount++;
 693                                 if(Demod.bitCount == 10) {
 694                                         uint16_t s = Demod.shiftReg;
 695                                         if((s & 0x200) && !(s & 0x001)) { // stop bit == '1', start bit == '0'
 696                                                 uint8_t b = (s >> 1);
 697                                                 Demod.output[Demod.len] = b;
 698                                                 Demod.len++;
 699                                                 Demod.state = DEMOD_AWAITING_START_BIT;
 700                                         } else {
 701                                                 Demod.state = DEMOD_UNSYNCD;
 702                                                 LED_C_OFF();
 703                                                 if(s == 0x000) {
 704                                                         // This is EOF (start, stop and all data bits == '0'
 705                                                         return TRUE;
 706                                                 }
 707                                         }
 708                                 }
 709                                 Demod.posCount = 0;
 710                         }
 711                         break;
 712
 713                 default:
 714                         Demod.state = DEMOD_UNSYNCD;
 715                         LED_C_OFF();
 716                         break;
 717         }
 718
 719         return FALSE;
 720 }
 721
 722
 723 static void DemodReset()
 724 {
 725         // Clear out the state of the "UART" that receives from the tag.
 726         Demod.len = 0;
 727         Demod.state = DEMOD_UNSYNCD;
 728         Demod.posCount = 0;
 729         memset(Demod.output, 0x00, MAX_FRAME_SIZE);
 730 }
 731
 732
 733 static void DemodInit(uint8_t *data)
 734 {
 735         Demod.output = data;
 736         DemodReset();
 737 }
 738
 739
 740 /*
 741  *  Demodulate the samples we received from the tag, also log to tracebuffer
 742  *  quiet: set to 'TRUE' to disable debug output
 743  */
 744 static void GetSamplesFor14443bDemod(int n, bool quiet)
 745 {
 746         int max = 0;
 747         bool gotFrame = FALSE;
 748         int lastRxCounter, ci, cq, samples = 0;
 749
 750         // Allocate memory from BigBuf for some buffers
 751         // free all previous allocations first
 752         BigBuf_free();
 753
 754         // The response (tag -> reader) that we're receiving.
 755         uint8_t *receivedResponse = BigBuf_malloc(MAX_FRAME_SIZE);
 756
 757         // The DMA buffer, used to stream samples from the FPGA
 758         int8_t *dmaBuf = (int8_t*) BigBuf_malloc(ISO14443B_DMA_BUFFER_SIZE);
 759
 760         // Set up the demodulator for tag -> reader responses.
 761         DemodInit(receivedResponse);
 762
 763         // Setup and start DMA.
 764         FpgaSetupSscDma((uint8_t*) dmaBuf, ISO14443B_DMA_BUFFER_SIZE);
 765
 766         int8_t *upTo = dmaBuf;
 767         lastRxCounter = ISO14443B_DMA_BUFFER_SIZE;
 768
 769         // Signal field is ON with the appropriate LED:
 770         LED_D_ON();
 771         // And put the FPGA in the appropriate mode
 772         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
 773
 774         for(;;) {
 775                 int behindBy = lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR;
 776                 if(behindBy > max) max = behindBy;
 777
 778                 while(((lastRxCounter-AT91C_BASE_PDC_SSC->PDC_RCR) & (ISO14443B_DMA_BUFFER_SIZE-1)) > 2) {
 779                         ci = upTo[0];
 780                         cq = upTo[1];
 781                         upTo += 2;
 782                         if(upTo >= dmaBuf + ISO14443B_DMA_BUFFER_SIZE) {
 783                                 upTo = dmaBuf;
 784                                 AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) upTo;
 785                                 AT91C_BASE_PDC_SSC->PDC_RNCR = ISO14443B_DMA_BUFFER_SIZE;
 786                         }
 787                         lastRxCounter -= 2;
 788                         if(lastRxCounter <= 0) {
 789                                 lastRxCounter += ISO14443B_DMA_BUFFER_SIZE;
 790                         }
 791
 792                         samples += 2;
 793
 794                         if(Handle14443bSamplesDemod(ci, cq)) {
 795                                 gotFrame = TRUE;
 796                                 break;
 797                         }
 798                 }
 799
 800                 if(samples > n || gotFrame) {
 801                         break;
 802                 }
 803         }
 804
 805         AT91C_BASE_PDC_SSC->PDC_PTCR = AT91C_PDC_RXTDIS;
 806
 807         if (!quiet) Dbprintf("max behindby = %d, samples = %d, gotFrame = %d, Demod.len = %d, Demod.sumI = %d, Demod.sumQ = %d", max, samples, gotFrame, Demod.len, Demod.sumI, Demod.sumQ);
 808         //Tracing
 809         if (tracing && Demod.len > 0) {
 810                 uint8_t parity[MAX_PARITY_SIZE];
 811                 LogTrace(Demod.output, Demod.len, 0, 0, parity, FALSE);
 812         }
 813 }
 814
 815
 816 //-----------------------------------------------------------------------------
 817 // Transmit the command (to the tag) that was placed in ToSend[].
 818 //-----------------------------------------------------------------------------
 819 static void TransmitFor14443b(void)
 820 {
 821         int c;
 822
 823         FpgaSetupSsc();
 824
 825         while(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 826                 AT91C_BASE_SSC->SSC_THR = 0xff;
 827         }
 828
 829         // Signal field is ON with the appropriate Red LED
 830         LED_D_ON();
 831         // Signal we are transmitting with the Green LED
 832         LED_B_ON();
 833         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
 834
 835         for(c = 0; c < 10;) {
 836                 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 837                         AT91C_BASE_SSC->SSC_THR = 0xff;
 838                         c++;
 839                 }
 840                 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 841                         volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
 842                         (void)r;
 843                 }
 844                 WDT_HIT();
 845         }
 846
 847         c = 0;
 848         for(;;) {
 849                 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 850                         AT91C_BASE_SSC->SSC_THR = ToSend[c];
 851                         c++;
 852                         if(c >= ToSendMax) {
 853                                 break;
 854                         }
 855                 }
 856                 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 857                         volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
 858                         (void)r;
 859                 }
 860                 WDT_HIT();
 861         }
 862         LED_B_OFF(); // Finished sending
 863 }
 864
 865
 866 //-----------------------------------------------------------------------------
 867 // Code a layer 2 command (string of octets, including CRC) into ToSend[],
 868 // so that it is ready to transmit to the tag using TransmitFor14443b().
 869 //-----------------------------------------------------------------------------
 870 static void CodeIso14443bAsReader(const uint8_t *cmd, int len)
 871 {
 872         int i, j;
 873         uint8_t b;
 874
 875         ToSendReset();
 876
 877         // Establish initial reference level
 878         for(i = 0; i < 40; i++) {
 879                 ToSendStuffBit(1);
 880         }
 881         // Send SOF
 882         for(i = 0; i < 10; i++) {
 883                 ToSendStuffBit(0);
 884         }
 885
 886         for(i = 0; i < len; i++) {
 887                 // Stop bits/EGT
 888                 ToSendStuffBit(1);
 889                 ToSendStuffBit(1);
 890                 // Start bit
 891                 ToSendStuffBit(0);
 892                 // Data bits
 893                 b = cmd[i];
 894                 for(j = 0; j < 8; j++) {
 895                         if(b & 1) {
 896                                 ToSendStuffBit(1);
 897                         } else {
 898                                 ToSendStuffBit(0);
 899                         }
 900                         b >>= 1;
 901                 }
 902         }
 903         // Send EOF
 904         ToSendStuffBit(1);
 905         for(i = 0; i < 10; i++) {
 906                 ToSendStuffBit(0);
 907         }
 908         for(i = 0; i < 8; i++) {
 909                 ToSendStuffBit(1);
 910         }
 911
 912         // And then a little more, to make sure that the last character makes
 913         // it out before we switch to rx mode.
 914         for(i = 0; i < 24; i++) {
 915                 ToSendStuffBit(1);
 916         }
 917
 918         // Convert from last character reference to length
 919         ToSendMax++;
 920 }
 921
 922
 923 /**
 924   Convenience function to encode, transmit and trace iso 14443b comms
 925   **/
 926 static void CodeAndTransmit14443bAsReader(const uint8_t *cmd, int len)
 927 {
 928         CodeIso14443bAsReader(cmd, len);
 929         TransmitFor14443b();
 930         if (tracing) {
 931                 uint8_t parity[MAX_PARITY_SIZE];
 932                 LogTrace(cmd,len, 0, 0, parity, TRUE);
 933         }
 934 }
 935
 936 /* Sends an APDU to the tag
 937  * TODO: check CRC and preamble
 938  */
 939 int iso14443b_apdu(uint8_t const *message, size_t message_length, uint8_t *response)
 940 {
 941         uint8_t message_frame[message_length + 4];
 942         // PCB
 943         message_frame[0] = 0x0A | pcb_blocknum;
 944         pcb_blocknum ^= 1;
 945         // CID
 946         message_frame[1] = 0;
 947         // INF
 948         memcpy(message_frame + 2, message, message_length);
 949         // EDC (CRC)
 950         ComputeCrc14443(CRC_14443_B, message_frame, message_length + 2, &message_frame[message_length + 2], &message_frame[message_length + 3]);
 951         // send
 952         CodeAndTransmit14443bAsReader(message_frame, message_length + 4);
 953         // get response
 954         GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT*100, TRUE);
 955         if(Demod.len < 3)
 956         {
 957                 return 0;
 958         }
 959         // TODO: Check CRC
 960         // copy response contents
 961         if(response != NULL)
 962         {
 963                 memcpy(response, Demod.output, Demod.len);
 964         }
 965         return Demod.len;
 966 }
 967
 968 /* Perform the ISO 14443 B Card Selection procedure
 969  * Currently does NOT do any collision handling.
 970  * It expects 0-1 cards in the device's range.
 971  * TODO: Support multiple cards (perform anticollision)
 972  * TODO: Verify CRC checksums
 973  */
 974 int iso14443b_select_card()
 975 {
 976         // WUPB command (including CRC)
 977         // Note: WUPB wakes up all tags, REQB doesn't wake up tags in HALT state
 978         static const uint8_t wupb[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
 979         // ATTRIB command (with space for CRC)
 980         uint8_t attrib[] = { 0x1D, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00};
 981
 982         // first, wake up the tag
 983         CodeAndTransmit14443bAsReader(wupb, sizeof(wupb));
 984         GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
 985         // ATQB too short?
 986         if (Demod.len < 14)
 987         {
 988                 return 2;
 989         }
 990
 991     // select the tag
 992     // copy the PUPI to ATTRIB
 993     memcpy(attrib + 1, Demod.output + 1, 4);
 994     /* copy the protocol info from ATQB (Protocol Info -> Protocol_Type) into
 995     ATTRIB (Param 3) */
 996     attrib[7] = Demod.output[10] & 0x0F;
 997     ComputeCrc14443(CRC_14443_B, attrib, 9, attrib + 9, attrib + 10);
 998     CodeAndTransmit14443bAsReader(attrib, sizeof(attrib));
 999     GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
1000     // Answer to ATTRIB too short?
1001     if(Demod.len < 3)
1002         {
1003                 return 2;
1004         }
1005         // reset PCB block number
1006         pcb_blocknum = 0;
1007         return 1;
1008 }
1009
1010 // Set up ISO 14443 Type B communication (similar to iso14443a_setup)
1011 void iso14443b_setup() {
1012         FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
1013         // Set up the synchronous serial port
1014         FpgaSetupSsc();
1015         // connect Demodulated Signal to ADC:
1016         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
1017
1018         // Signal field is on with the appropriate LED
1019     LED_D_ON();
1020         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
1021
1022         // Start the timer
1023         StartCountSspClk();
1024
1025         DemodReset();
1026         UartReset();
1027 }
1028
1029 //-----------------------------------------------------------------------------
1030 // Read a SRI512 ISO 14443B tag.
1031 //
1032 // SRI512 tags are just simple memory tags, here we're looking at making a dump
1033 // of the contents of the memory. No anticollision algorithm is done, we assume
1034 // we have a single tag in the field.
1035 //
1036 // I tried to be systematic and check every answer of the tag, every CRC, etc...
1037 //-----------------------------------------------------------------------------
1038 void ReadSTMemoryIso14443b(uint32_t dwLast)
1039 {
1040         uint8_t i = 0x00;
1041
1042         FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
1043         // Make sure that we start from off, since the tags are stateful;
1044         // confusing things will happen if we don't reset them between reads.
1045         LED_D_OFF();
1046         FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
1047         SpinDelay(200);
1048
1049         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
1050         FpgaSetupSsc();
1051
1052         // Now give it time to spin up.
1053         // Signal field is on with the appropriate LED
1054         LED_D_ON();
1055         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
1056         SpinDelay(200);
1057
1058         clear_trace();
1059         set_tracing(TRUE);
1060
1061         // First command: wake up the tag using the INITIATE command
1062         uint8_t cmd1[] = {0x06, 0x00, 0x97, 0x5b};
1063         CodeAndTransmit14443bAsReader(cmd1, sizeof(cmd1));
1064         GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
1065
1066         if (Demod.len == 0) {
1067                 DbpString("No response from tag");
1068                 return;
1069         } else {
1070                 Dbprintf("Randomly generated Chip ID (+ 2 byte CRC): %02x %02x %02x",
1071                                 Demod.output[0], Demod.output[1], Demod.output[2]);
1072         }
1073
1074         // There is a response, SELECT the uid
1075         DbpString("Now SELECT tag:");
1076         cmd1[0] = 0x0E; // 0x0E is SELECT
1077         cmd1[1] = Demod.output[0];
1078         ComputeCrc14443(CRC_14443_B, cmd1, 2, &cmd1[2], &cmd1[3]);
1079         CodeAndTransmit14443bAsReader(cmd1, sizeof(cmd1));
1080         GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
1081         if (Demod.len != 3) {
1082                 Dbprintf("Expected 3 bytes from tag, got %d", Demod.len);
1083                 return;
1084         }
1085         // Check the CRC of the answer:
1086         ComputeCrc14443(CRC_14443_B, Demod.output, 1 , &cmd1[2], &cmd1[3]);
1087         if(cmd1[2] != Demod.output[1] || cmd1[3] != Demod.output[2]) {
1088                 DbpString("CRC Error reading select response.");
1089                 return;
1090         }
1091         // Check response from the tag: should be the same UID as the command we just sent:
1092         if (cmd1[1] != Demod.output[0]) {
1093                 Dbprintf("Bad response to SELECT from Tag, aborting: %02x %02x", cmd1[1], Demod.output[0]);
1094                 return;
1095         }
1096
1097         // Tag is now selected,
1098         // First get the tag's UID:
1099         cmd1[0] = 0x0B;
1100         ComputeCrc14443(CRC_14443_B, cmd1, 1 , &cmd1[1], &cmd1[2]);
1101         CodeAndTransmit14443bAsReader(cmd1, 3); // Only first three bytes for this one
1102         GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
1103         if (Demod.len != 10) {
1104                 Dbprintf("Expected 10 bytes from tag, got %d", Demod.len);
1105                 return;
1106         }
1107         // The check the CRC of the answer (use cmd1 as temporary variable):
1108         ComputeCrc14443(CRC_14443_B, Demod.output, 8, &cmd1[2], &cmd1[3]);
1109         if(cmd1[2] != Demod.output[8] || cmd1[3] != Demod.output[9]) {
1110                 Dbprintf("CRC Error reading block! Expected: %04x got: %04x",
1111                                 (cmd1[2]<<8)+cmd1[3], (Demod.output[8]<<8)+Demod.output[9]);
1112                 // Do not return;, let's go on... (we should retry, maybe ?)
1113         }
1114         Dbprintf("Tag UID (64 bits): %08x %08x",
1115                         (Demod.output[7]<<24) + (Demod.output[6]<<16) + (Demod.output[5]<<8) + Demod.output[4],
1116                         (Demod.output[3]<<24) + (Demod.output[2]<<16) + (Demod.output[1]<<8) + Demod.output[0]);
1117
1118         // Now loop to read all 16 blocks, address from 0 to last block
1119         Dbprintf("Tag memory dump, block 0 to %d", dwLast);
1120         cmd1[0] = 0x08;
1121         i = 0x00;
1122         dwLast++;
1123         for (;;) {
1124                 if (i == dwLast) {
1125                         DbpString("System area block (0xff):");
1126                         i = 0xff;
1127                 }
1128                 cmd1[1] = i;
1129                 ComputeCrc14443(CRC_14443_B, cmd1, 2, &cmd1[2], &cmd1[3]);
1130                 CodeAndTransmit14443bAsReader(cmd1, sizeof(cmd1));
1131                 GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
1132                 if (Demod.len != 6) { // Check if we got an answer from the tag
1133                         DbpString("Expected 6 bytes from tag, got less...");
1134                         return;
1135                 }
1136                 // The check the CRC of the answer (use cmd1 as temporary variable):
1137                 ComputeCrc14443(CRC_14443_B, Demod.output, 4, &cmd1[2], &cmd1[3]);
1138                 if(cmd1[2] != Demod.output[4] || cmd1[3] != Demod.output[5]) {
1139                         Dbprintf("CRC Error reading block! Expected: %04x got: %04x",
1140                                         (cmd1[2]<<8)+cmd1[3], (Demod.output[4]<<8)+Demod.output[5]);
1141                         // Do not return;, let's go on... (we should retry, maybe ?)
1142                 }
1143                 // Now print out the memory location:
1144                 Dbprintf("Address=%02x, Contents=%08x, CRC=%04x", i,
1145                                 (Demod.output[3]<<24) + (Demod.output[2]<<16) + (Demod.output[1]<<8) + Demod.output[0],
1146                                 (Demod.output[4]<<8)+Demod.output[5]);
1147                 if (i == 0xff) {
1148                         break;
1149                 }
1150                 i++;
1151         }
1152 }
1153
1154
1155 //=============================================================================
1156 // Finally, the `sniffer' combines elements from both the reader and
1157 // simulated tag, to show both sides of the conversation.
1158 //=============================================================================
1159
1160 //-----------------------------------------------------------------------------
1161 // Record the sequence of commands sent by the reader to the tag, with
1162 // triggering so that we start recording at the point that the tag is moved
1163 // near the reader.
1164 //-----------------------------------------------------------------------------
1165 /*
1166  * Memory usage for this function, (within BigBuf)
1167  * Last Received command (reader->tag) - MAX_FRAME_SIZE
1168  * Last Received command (tag->reader) - MAX_FRAME_SIZE
1169  * DMA Buffer - ISO14443B_DMA_BUFFER_SIZE
1170  * Demodulated samples received - all the rest
1171  */
1172 void RAMFUNC SnoopIso14443b(void)
1173 {
1174         // We won't start recording the frames that we acquire until we trigger;
1175         // a good trigger condition to get started is probably when we see a
1176         // response from the tag.
1177         int triggered = TRUE;                   // TODO: set and evaluate trigger condition
1178
1179         FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
1180         BigBuf_free();
1181
1182         clear_trace();
1183         set_tracing(TRUE);
1184
1185         // The DMA buffer, used to stream samples from the FPGA
1186         int8_t *dmaBuf = (int8_t*) BigBuf_malloc(ISO14443B_DMA_BUFFER_SIZE);
1187         int lastRxCounter;
1188         int8_t *upTo;
1189         int ci, cq;
1190         int maxBehindBy = 0;
1191
1192         // Count of samples received so far, so that we can include timing
1193         // information in the trace buffer.
1194         int samples = 0;
1195
1196         DemodInit(BigBuf_malloc(MAX_FRAME_SIZE));
1197         UartInit(BigBuf_malloc(MAX_FRAME_SIZE));
1198
1199         // Print some debug information about the buffer sizes
1200         Dbprintf("Snooping buffers initialized:");
1201         Dbprintf("  Trace: %i bytes", BigBuf_max_traceLen());
1202         Dbprintf("  Reader -> tag: %i bytes", MAX_FRAME_SIZE);
1203         Dbprintf("  tag -> Reader: %i bytes", MAX_FRAME_SIZE);
1204         Dbprintf("  DMA: %i bytes", ISO14443B_DMA_BUFFER_SIZE);
1205
1206         // Signal field is off, no reader signal, no tag signal
1207         LEDsoff();
1208
1209         // And put the FPGA in the appropriate mode
1210         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ | FPGA_HF_READER_RX_XCORR_SNOOP);
1211         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
1212
1213         // Setup for the DMA.
1214         FpgaSetupSsc();
1215         upTo = dmaBuf;
1216         lastRxCounter = ISO14443B_DMA_BUFFER_SIZE;
1217         FpgaSetupSscDma((uint8_t*) dmaBuf, ISO14443B_DMA_BUFFER_SIZE);
1218         uint8_t parity[MAX_PARITY_SIZE];
1219
1220         bool TagIsActive = FALSE;
1221         bool ReaderIsActive = FALSE;
1222
1223         // And now we loop, receiving samples.
1224         for(;;) {
1225                 int behindBy = (lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR) &
1226                                                                 (ISO14443B_DMA_BUFFER_SIZE-1);
1227                 if(behindBy > maxBehindBy) {
1228                         maxBehindBy = behindBy;
1229                 }
1230
1231                 if(behindBy < 2) continue;
1232
1233                 ci = upTo[0];
1234                 cq = upTo[1];
1235                 upTo += 2;
1236                 lastRxCounter -= 2;
1237                 if(upTo >= dmaBuf + ISO14443B_DMA_BUFFER_SIZE) {
1238                         upTo = dmaBuf;
1239                         lastRxCounter += ISO14443B_DMA_BUFFER_SIZE;
1240                         AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) dmaBuf;
1241                         AT91C_BASE_PDC_SSC->PDC_RNCR = ISO14443B_DMA_BUFFER_SIZE;
1242                         WDT_HIT();
1243                         if(behindBy > (9*ISO14443B_DMA_BUFFER_SIZE/10)) { // TODO: understand whether we can increase/decrease as we want or not?
1244                                 Dbprintf("blew circular buffer! behindBy=%d", behindBy);
1245                                 break;
1246                         }
1247                         if(!tracing) {
1248                                 DbpString("Reached trace limit");
1249                                 break;
1250                         }
1251                         if(BUTTON_PRESS()) {
1252                                 DbpString("cancelled");
1253                                 break;
1254                         }
1255                 }
1256
1257                 samples += 2;
1258
1259                 if (!TagIsActive) {                                                     // no need to try decoding reader data if the tag is sending
1260                         if(Handle14443bUartBit(ci & 0x01)) {
1261                                 if(triggered && tracing) {
1262                                         LogTrace(Uart.output, Uart.byteCnt, samples, samples, parity, TRUE);
1263                                 }
1264                                 /* And ready to receive another command. */
1265                                 UartReset();
1266                                 /* And also reset the demod code, which might have been */
1267                                 /* false-triggered by the commands from the reader. */
1268                                 DemodReset();
1269                         }
1270                         if(Handle14443bUartBit(cq & 0x01)) {
1271                                 if(triggered && tracing) {
1272                                         LogTrace(Uart.output, Uart.byteCnt, samples, samples, parity, TRUE);
1273                                 }
1274                                 /* And ready to receive another command. */
1275                                 UartReset();
1276                                 /* And also reset the demod code, which might have been */
1277                                 /* false-triggered by the commands from the reader. */
1278                                 DemodReset();
1279                         }
1280                         ReaderIsActive = (Uart.state > STATE_GOT_FALLING_EDGE_OF_SOF);
1281                 }
1282
1283                 if(!ReaderIsActive) {                                           // no need to try decoding tag data if the reader is sending - and we cannot afford the time
1284                         if(Handle14443bSamplesDemod(ci | 0x01, cq | 0x01)) {
1285
1286                                 //Use samples as a time measurement
1287                                 if(tracing)
1288                                 {
1289                                         uint8_t parity[MAX_PARITY_SIZE];
1290                                         LogTrace(Demod.output, Demod.len, samples, samples, parity, FALSE);
1291                                 }
1292                                 triggered = TRUE;
1293
1294                                 // And ready to receive another response.
1295                                 DemodReset();
1296                         }
1297                         TagIsActive = (Demod.state > DEMOD_GOT_FALLING_EDGE_OF_SOF);
1298                 }
1299
1300         }
1301
1302         FpgaDisableSscDma();
1303         LEDsoff();
1304         AT91C_BASE_PDC_SSC->PDC_PTCR = AT91C_PDC_RXTDIS;
1305         DbpString("Snoop statistics:");
1306         Dbprintf("  Max behind by: %i", maxBehindBy);
1307         Dbprintf("  Uart State: %x", Uart.state);
1308         Dbprintf("  Uart ByteCnt: %i", Uart.byteCnt);
1309         Dbprintf("  Uart ByteCntMax: %i", Uart.byteCntMax);
1310         Dbprintf("  Trace length: %i", BigBuf_get_traceLen());
1311 }
1312
1313
1314 /*
1315  * Send raw command to tag ISO14443B
1316  * @Input
1317  * datalen     len of buffer data
1318  * recv        bool when true wait for data from tag and send to client
1319  * powerfield  bool leave the field on when true
1320  * data        buffer with byte to send
1321  *
1322  * @Output
1323  * none
1324  *
1325  */
1326 void SendRawCommand14443B(uint32_t datalen, uint32_t recv, uint8_t powerfield, uint8_t data[])
1327 {
1328         FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
1329         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
1330         FpgaSetupSsc();
1331
1332         if (datalen){
1333                 set_tracing(TRUE);
1334
1335                 CodeAndTransmit14443bAsReader(data, datalen);
1336
1337                 if(recv) {
1338                         GetSamplesFor14443bDemod(RECEIVE_SAMPLES_TIMEOUT, TRUE);
1339                         uint16_t iLen = MIN(Demod.len, USB_CMD_DATA_SIZE);
1340                         cmd_send(CMD_ACK, iLen, 0, 0, Demod.output, iLen);
1341                 }
1342         }
1343
1344         if(!powerfield) {
1345                 FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
1346                 LED_D_OFF();
1347         }
1348 }
1349