cvs.zerfleddert.de Git - proxmark3-svn/blob - armsrc/iso14443.c

   1 //-----------------------------------------------------------------------------
   2 // Routines to support ISO 14443. This includes both the reader software and
   3 // the `fake tag' modes. At the moment only the Type B modulation is
   4 // supported.
   5 // Jonathan Westhues, split Nov 2006
   6 //-----------------------------------------------------------------------------
   7 #include <proxmark3.h>
   8 #include "apps.h"
   9 #include "iso14443crc.h"
  10
  11
  12 //static void GetSamplesFor14443(BOOL weTx, int n);
  13
  14 #define DEMOD_TRACE_SIZE 4096
  15 #define READER_TAG_BUFFER_SIZE 2048
  16 #define TAG_READER_BUFFER_SIZE 2048
  17 #define DMA_BUFFER_SIZE 1024
  18
  19 //=============================================================================
  20 // An ISO 14443 Type B tag. We listen for commands from the reader, using
  21 // a UART kind of thing that's implemented in software. When we get a
  22 // frame (i.e., a group of bytes between SOF and EOF), we check the CRC.
  23 // If it's good, then we can do something appropriate with it, and send
  24 // a response.
  25 //=============================================================================
  26
  27 //-----------------------------------------------------------------------------
  28 // Code up a string of octets at layer 2 (including CRC, we don't generate
  29 // that here) so that they can be transmitted to the reader. Doesn't transmit
  30 // them yet, just leaves them ready to send in ToSend[].
  31 //-----------------------------------------------------------------------------
  32 static void CodeIso14443bAsTag(const BYTE *cmd, int len)
  33 {
  34     int i;
  35
  36     ToSendReset();
  37
  38     // Transmit a burst of ones, as the initial thing that lets the
  39     // reader get phase sync. This (TR1) must be > 80/fs, per spec,
  40     // but tag that I've tried (a Paypass) exceeds that by a fair bit,
  41     // so I will too.
  42     for(i = 0; i < 20; i++) {
  43         ToSendStuffBit(1);
  44         ToSendStuffBit(1);
  45         ToSendStuffBit(1);
  46         ToSendStuffBit(1);
  47     }
  48
  49     // Send SOF.
  50     for(i = 0; i < 10; i++) {
  51         ToSendStuffBit(0);
  52         ToSendStuffBit(0);
  53         ToSendStuffBit(0);
  54         ToSendStuffBit(0);
  55     }
  56     for(i = 0; i < 2; i++) {
  57         ToSendStuffBit(1);
  58         ToSendStuffBit(1);
  59         ToSendStuffBit(1);
  60         ToSendStuffBit(1);
  61     }
  62
  63     for(i = 0; i < len; i++) {
  64         int j;
  65         BYTE b = cmd[i];
  66
  67         // Start bit
  68         ToSendStuffBit(0);
  69         ToSendStuffBit(0);
  70         ToSendStuffBit(0);
  71         ToSendStuffBit(0);
  72
  73         // Data bits
  74         for(j = 0; j < 8; j++) {
  75             if(b & 1) {
  76                 ToSendStuffBit(1);
  77                 ToSendStuffBit(1);
  78                 ToSendStuffBit(1);
  79                 ToSendStuffBit(1);
  80             } else {
  81                 ToSendStuffBit(0);
  82                 ToSendStuffBit(0);
  83                 ToSendStuffBit(0);
  84                 ToSendStuffBit(0);
  85             }
  86             b >>= 1;
  87         }
  88
  89         // Stop bit
  90         ToSendStuffBit(1);
  91         ToSendStuffBit(1);
  92         ToSendStuffBit(1);
  93         ToSendStuffBit(1);
  94     }
  95
  96     // Send SOF.
  97     for(i = 0; i < 10; i++) {
  98         ToSendStuffBit(0);
  99         ToSendStuffBit(0);
 100         ToSendStuffBit(0);
 101         ToSendStuffBit(0);
 102     }
 103     for(i = 0; i < 10; i++) {
 104         ToSendStuffBit(1);
 105         ToSendStuffBit(1);
 106         ToSendStuffBit(1);
 107         ToSendStuffBit(1);
 108     }
 109
 110     // Convert from last byte pos to length
 111     ToSendMax++;
 112
 113     // Add a few more for slop
 114     ToSendMax += 2;
 115 }
 116
 117 //-----------------------------------------------------------------------------
 118 // The software UART that receives commands from the reader, and its state
 119 // variables.
 120 //-----------------------------------------------------------------------------
 121 static struct {
 122     enum {
 123         STATE_UNSYNCD,
 124         STATE_GOT_FALLING_EDGE_OF_SOF,
 125         STATE_AWAITING_START_BIT,
 126         STATE_RECEIVING_DATA,
 127         STATE_ERROR_WAIT
 128     }       state;
 129     WORD    shiftReg;
 130     int     bitCnt;
 131     int     byteCnt;
 132     int     byteCntMax;
 133     int     posCnt;
 134     BYTE   *output;
 135 } Uart;
 136
 137 /* Receive & handle a bit coming from the reader.
 138  *
 139  * LED handling:
 140  * LED A -> ON once we have received the SOF and are expecting the rest.
 141  * LED A -> OFF once we have received EOF or are in error state or unsynced
 142  *
 143  * Returns: true if we received a EOF
 144  *          false if we are still waiting for some more
 145  */
 146 static BOOL Handle14443UartBit(int bit)
 147 {
 148     switch(Uart.state) {
 149         case STATE_UNSYNCD:
 150                 LED_A_OFF();
 151             if(!bit) {
 152                 // we went low, so this could be the beginning
 153                 // of an SOF
 154                 Uart.state = STATE_GOT_FALLING_EDGE_OF_SOF;
 155                 Uart.posCnt = 0;
 156                 Uart.bitCnt = 0;
 157             }
 158             break;
 159
 160         case STATE_GOT_FALLING_EDGE_OF_SOF:
 161             Uart.posCnt++;
 162             if(Uart.posCnt == 2) {
 163                 if(bit) {
 164                     if(Uart.bitCnt >= 10) {
 165                         // we've seen enough consecutive
 166                         // zeros that it's a valid SOF
 167                         Uart.posCnt = 0;
 168                         Uart.byteCnt = 0;
 169                         Uart.state = STATE_AWAITING_START_BIT;
 170                         LED_A_ON(); // Indicate we got a valid SOF
 171                     } else {
 172                         // didn't stay down long enough
 173                         // before going high, error
 174                         Uart.state = STATE_ERROR_WAIT;
 175                     }
 176                 } else {
 177                     // do nothing, keep waiting
 178                 }
 179                 Uart.bitCnt++;
 180             }
 181             if(Uart.posCnt >= 4) Uart.posCnt = 0;
 182             if(Uart.bitCnt > 14) {
 183                 // Give up if we see too many zeros without
 184                 // a one, too.
 185                 Uart.state = STATE_ERROR_WAIT;
 186             }
 187             break;
 188
 189         case STATE_AWAITING_START_BIT:
 190             Uart.posCnt++;
 191             if(bit) {
 192                 if(Uart.posCnt > 25) {
 193                     // stayed high for too long between
 194                     // characters, error
 195                     Uart.state = STATE_ERROR_WAIT;
 196                 }
 197             } else {
 198                 // falling edge, this starts the data byte
 199                 Uart.posCnt = 0;
 200                 Uart.bitCnt = 0;
 201                 Uart.shiftReg = 0;
 202                 Uart.state = STATE_RECEIVING_DATA;
 203                 LED_A_ON(); // Indicate we're receiving
 204             }
 205             break;
 206
 207         case STATE_RECEIVING_DATA:
 208             Uart.posCnt++;
 209             if(Uart.posCnt == 2) {
 210                 // time to sample a bit
 211                 Uart.shiftReg >>= 1;
 212                 if(bit) {
 213                     Uart.shiftReg |= 0x200;
 214                 }
 215                 Uart.bitCnt++;
 216             }
 217             if(Uart.posCnt >= 4) {
 218                 Uart.posCnt = 0;
 219             }
 220             if(Uart.bitCnt == 10) {
 221                 if((Uart.shiftReg & 0x200) && !(Uart.shiftReg & 0x001))
 222                 {
 223                     // this is a data byte, with correct
 224                     // start and stop bits
 225                     Uart.output[Uart.byteCnt] = (Uart.shiftReg >> 1) & 0xff;
 226                     Uart.byteCnt++;
 227
 228                     if(Uart.byteCnt >= Uart.byteCntMax) {
 229                         // Buffer overflowed, give up
 230                         Uart.posCnt = 0;
 231                         Uart.state = STATE_ERROR_WAIT;
 232                     } else {
 233                         // so get the next byte now
 234                         Uart.posCnt = 0;
 235                         Uart.state = STATE_AWAITING_START_BIT;
 236                     }
 237                 } else if(Uart.shiftReg == 0x000) {
 238                     // this is an EOF byte
 239                         LED_A_OFF(); // Finished receiving
 240                     return TRUE;
 241                 } else {
 242                     // this is an error
 243                     Uart.posCnt = 0;
 244                     Uart.state = STATE_ERROR_WAIT;
 245                 }
 246             }
 247             break;
 248
 249         case STATE_ERROR_WAIT:
 250             // We're all screwed up, so wait a little while
 251             // for whatever went wrong to finish, and then
 252             // start over.
 253             Uart.posCnt++;
 254             if(Uart.posCnt > 10) {
 255                 Uart.state = STATE_UNSYNCD;
 256             }
 257             break;
 258
 259         default:
 260             Uart.state = STATE_UNSYNCD;
 261             break;
 262     }
 263
 264     if (Uart.state == STATE_ERROR_WAIT) LED_A_OFF(); // Error
 265
 266     return FALSE;
 267 }
 268
 269 //-----------------------------------------------------------------------------
 270 // Receive a command (from the reader to us, where we are the simulated tag),
 271 // and store it in the given buffer, up to the given maximum length. Keeps
 272 // spinning, waiting for a well-framed command, until either we get one
 273 // (returns TRUE) or someone presses the pushbutton on the board (FALSE).
 274 //
 275 // Assume that we're called with the SSC (to the FPGA) and ADC path set
 276 // correctly.
 277 //-----------------------------------------------------------------------------
 278 static BOOL GetIso14443CommandFromReader(BYTE *received, int *len, int maxLen)
 279 {
 280     BYTE mask;
 281     int i, bit;
 282
 283     // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
 284     // only, since we are receiving, not transmitting).
 285     // Signal field is off with the appropriate LED
 286     LED_D_OFF();
 287     FpgaWriteConfWord(
 288         FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
 289
 290
 291     // Now run a `software UART' on the stream of incoming samples.
 292     Uart.output = received;
 293     Uart.byteCntMax = maxLen;
 294     Uart.state = STATE_UNSYNCD;
 295
 296     for(;;) {
 297         WDT_HIT();
 298
 299         if(BUTTON_PRESS()) return FALSE;
 300
 301         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 302             AT91C_BASE_SSC->SSC_THR = 0x00;
 303         }
 304         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 305             BYTE b = (BYTE)AT91C_BASE_SSC->SSC_RHR;
 306
 307             mask = 0x80;
 308             for(i = 0; i < 8; i++, mask >>= 1) {
 309                 bit = (b & mask);
 310                 if(Handle14443UartBit(bit)) {
 311                     *len = Uart.byteCnt;
 312                     return TRUE;
 313                 }
 314             }
 315         }
 316     }
 317 }
 318
 319 //-----------------------------------------------------------------------------
 320 // Main loop of simulated tag: receive commands from reader, decide what
 321 // response to send, and send it.
 322 //-----------------------------------------------------------------------------
 323 void SimulateIso14443Tag(void)
 324 {
 325     static const BYTE cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
 326     static const BYTE response1[] = {
 327         0x50, 0x82, 0x0d, 0xe1, 0x74, 0x20, 0x38, 0x19, 0x22,
 328         0x00, 0x21, 0x85, 0x5e, 0xd7
 329     };
 330
 331     BYTE *resp;
 332     int respLen;
 333
 334     BYTE *resp1 = (((BYTE *)BigBuf) + 800);
 335     int resp1Len;
 336
 337     BYTE *receivedCmd = (BYTE *)BigBuf;
 338     int len;
 339
 340     int i;
 341
 342     int cmdsRecvd = 0;
 343
 344     memset(receivedCmd, 0x44, 400);
 345
 346     CodeIso14443bAsTag(response1, sizeof(response1));
 347     memcpy(resp1, ToSend, ToSendMax); resp1Len = ToSendMax;
 348
 349     // We need to listen to the high-frequency, peak-detected path.
 350     SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 351     FpgaSetupSsc();
 352
 353     cmdsRecvd = 0;
 354
 355     for(;;) {
 356         BYTE b1, b2;
 357
 358         if(!GetIso14443CommandFromReader(receivedCmd, &len, 100)) {
 359                 Dbprintf("button pressed, received %d commands", cmdsRecvd);
 360                 break;
 361         }
 362
 363         // Good, look at the command now.
 364
 365         if(len == sizeof(cmd1) && memcmp(receivedCmd, cmd1, len)==0) {
 366             resp = resp1; respLen = resp1Len;
 367         } else {
 368             Dbprintf("new cmd from reader: len=%d, cmdsRecvd=%d", len, cmdsRecvd);
 369             // And print whether the CRC fails, just for good measure
 370             ComputeCrc14443(CRC_14443_B, receivedCmd, len-2, &b1, &b2);
 371             if(b1 != receivedCmd[len-2] || b2 != receivedCmd[len-1]) {
 372                 // Not so good, try again.
 373                 DbpString("+++CRC fail");
 374             } else {
 375                 DbpString("CRC passes");
 376             }
 377             break;
 378         }
 379
 380         memset(receivedCmd, 0x44, 32);
 381
 382         cmdsRecvd++;
 383
 384         if(cmdsRecvd > 0x30) {
 385             DbpString("many commands later...");
 386             break;
 387         }
 388
 389         if(respLen <= 0) continue;
 390
 391         // Modulate BPSK
 392         // Signal field is off with the appropriate LED
 393         LED_D_OFF();
 394         FpgaWriteConfWord(
 395                 FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_BPSK);
 396         AT91C_BASE_SSC->SSC_THR = 0xff;
 397         FpgaSetupSsc();
 398
 399         // Transmit the response.
 400         i = 0;
 401         for(;;) {
 402             if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 403                 BYTE b = resp[i];
 404
 405                 AT91C_BASE_SSC->SSC_THR = b;
 406
 407                 i++;
 408                 if(i > respLen) {
 409                     break;
 410                 }
 411             }
 412             if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 413                 volatile BYTE b = (BYTE)AT91C_BASE_SSC->SSC_RHR;
 414                 (void)b;
 415             }
 416         }
 417     }
 418 }
 419
 420 //=============================================================================
 421 // An ISO 14443 Type B reader. We take layer two commands, code them
 422 // appropriately, and then send them to the tag. We then listen for the
 423 // tag's response, which we leave in the buffer to be demodulated on the
 424 // PC side.
 425 //=============================================================================
 426
 427 static struct {
 428     enum {
 429         DEMOD_UNSYNCD,
 430         DEMOD_PHASE_REF_TRAINING,
 431         DEMOD_AWAITING_FALLING_EDGE_OF_SOF,
 432         DEMOD_GOT_FALLING_EDGE_OF_SOF,
 433         DEMOD_AWAITING_START_BIT,
 434         DEMOD_RECEIVING_DATA,
 435         DEMOD_ERROR_WAIT
 436     }       state;
 437     int     bitCount;
 438     int     posCount;
 439     int     thisBit;
 440     int     metric;
 441     int     metricN;
 442     WORD    shiftReg;
 443     BYTE   *output;
 444     int     len;
 445     int     sumI;
 446     int     sumQ;
 447 } Demod;
 448
 449 /*
 450  * Handles reception of a bit from the tag
 451  *
 452  * LED handling:
 453  * LED C -> ON once we have received the SOF and are expecting the rest.
 454  * LED C -> OFF once we have received EOF or are unsynced
 455  *
 456  * Returns: true if we received a EOF
 457  *          false if we are still waiting for some more
 458  *
 459  */
 460 static BOOL Handle14443SamplesDemod(int ci, int cq)
 461 {
 462     int v;
 463
 464     // The soft decision on the bit uses an estimate of just the
 465     // quadrant of the reference angle, not the exact angle.
 466 #define MAKE_SOFT_DECISION() { \
 467         if(Demod.sumI > 0) { \
 468             v = ci; \
 469         } else { \
 470             v = -ci; \
 471         } \
 472         if(Demod.sumQ > 0) { \
 473             v += cq; \
 474         } else { \
 475             v -= cq; \
 476         } \
 477     }
 478
 479     switch(Demod.state) {
 480         case DEMOD_UNSYNCD:
 481             v = ci;
 482             if(v < 0) v = -v;
 483             if(cq > 0) {
 484                 v += cq;
 485             } else {
 486                 v -= cq;
 487             }
 488             if(v > 40) {
 489                 Demod.posCount = 0;
 490                 Demod.state = DEMOD_PHASE_REF_TRAINING;
 491                 Demod.sumI = 0;
 492                 Demod.sumQ = 0;
 493             }
 494             break;
 495
 496         case DEMOD_PHASE_REF_TRAINING:
 497             if(Demod.posCount < 8) {
 498                 Demod.sumI += ci;
 499                 Demod.sumQ += cq;
 500             } else if(Demod.posCount > 100) {
 501                 // error, waited too long
 502                 Demod.state = DEMOD_UNSYNCD;
 503             } else {
 504                 MAKE_SOFT_DECISION();
 505                 if(v < 0) {
 506                     Demod.state = DEMOD_AWAITING_FALLING_EDGE_OF_SOF;
 507                     Demod.posCount = 0;
 508                 }
 509             }
 510             Demod.posCount++;
 511             break;
 512
 513         case DEMOD_AWAITING_FALLING_EDGE_OF_SOF:
 514             MAKE_SOFT_DECISION();
 515             if(v < 0) {
 516                 Demod.state = DEMOD_GOT_FALLING_EDGE_OF_SOF;
 517                 Demod.posCount = 0;
 518             } else {
 519                 if(Demod.posCount > 100) {
 520                     Demod.state = DEMOD_UNSYNCD;
 521                 }
 522             }
 523             Demod.posCount++;
 524             break;
 525
 526         case DEMOD_GOT_FALLING_EDGE_OF_SOF:
 527             MAKE_SOFT_DECISION();
 528             if(v > 0) {
 529                 if(Demod.posCount < 12) {
 530                     Demod.state = DEMOD_UNSYNCD;
 531                 } else {
 532                         LED_C_ON(); // Got SOF
 533                     Demod.state = DEMOD_AWAITING_START_BIT;
 534                     Demod.posCount = 0;
 535                     Demod.len = 0;
 536                     Demod.metricN = 0;
 537                     Demod.metric = 0;
 538                 }
 539             } else {
 540                 if(Demod.posCount > 100) {
 541                     Demod.state = DEMOD_UNSYNCD;
 542                 }
 543             }
 544             Demod.posCount++;
 545             break;
 546
 547         case DEMOD_AWAITING_START_BIT:
 548             MAKE_SOFT_DECISION();
 549             if(v > 0) {
 550                 if(Demod.posCount > 10) {
 551                     Demod.state = DEMOD_UNSYNCD;
 552                 }
 553             } else {
 554                 Demod.bitCount = 0;
 555                 Demod.posCount = 1;
 556                 Demod.thisBit = v;
 557                 Demod.shiftReg = 0;
 558                 Demod.state = DEMOD_RECEIVING_DATA;
 559             }
 560             break;
 561
 562         case DEMOD_RECEIVING_DATA:
 563             MAKE_SOFT_DECISION();
 564             if(Demod.posCount == 0) {
 565                 Demod.thisBit = v;
 566                 Demod.posCount = 1;
 567             } else {
 568                 Demod.thisBit += v;
 569
 570                 if(Demod.thisBit > 0) {
 571                     Demod.metric += Demod.thisBit;
 572                 } else {
 573                     Demod.metric -= Demod.thisBit;
 574                 }
 575                 (Demod.metricN)++;
 576
 577                 Demod.shiftReg >>= 1;
 578                 if(Demod.thisBit > 0) {
 579                     Demod.shiftReg |= 0x200;
 580                 }
 581
 582                 Demod.bitCount++;
 583                 if(Demod.bitCount == 10) {
 584                     WORD s = Demod.shiftReg;
 585                     if((s & 0x200) && !(s & 0x001)) {
 586                         BYTE b = (s >> 1);
 587                         Demod.output[Demod.len] = b;
 588                         Demod.len++;
 589                         Demod.state = DEMOD_AWAITING_START_BIT;
 590                     } else if(s == 0x000) {
 591                         // This is EOF
 592                         LED_C_OFF();
 593                         return TRUE;
 594                         Demod.state = DEMOD_UNSYNCD;
 595                     } else {
 596                         Demod.state = DEMOD_UNSYNCD;
 597                     }
 598                 }
 599                 Demod.posCount = 0;
 600             }
 601             break;
 602
 603         default:
 604             Demod.state = DEMOD_UNSYNCD;
 605             break;
 606     }
 607
 608     if (Demod.state == DEMOD_UNSYNCD) LED_C_OFF(); // Not synchronized...
 609     return FALSE;
 610 }
 611
 612 /*
 613  *  Demodulate the samples we received from the tag
 614  *  weTx: set to 'TRUE' if we behave like a reader
 615  *        set to 'FALSE' if we behave like a snooper
 616  *  quiet: set to 'TRUE' to disable debug output
 617  */
 618 static void GetSamplesFor14443Demod(BOOL weTx, int n, BOOL quiet)
 619 {
 620     int max = 0;
 621     BOOL gotFrame = FALSE;
 622
 623 //#   define DMA_BUFFER_SIZE 8
 624     SBYTE *dmaBuf;
 625
 626     int lastRxCounter;
 627     SBYTE *upTo;
 628
 629     int ci, cq;
 630
 631     int samples = 0;
 632
 633     // Clear out the state of the "UART" that receives from the tag.
 634     memset(BigBuf, 0x44, 400);
 635     Demod.output = (BYTE *)BigBuf;
 636     Demod.len = 0;
 637     Demod.state = DEMOD_UNSYNCD;
 638
 639     // And the UART that receives from the reader
 640     Uart.output = (((BYTE *)BigBuf) + 1024);
 641     Uart.byteCntMax = 100;
 642     Uart.state = STATE_UNSYNCD;
 643
 644     // Setup for the DMA.
 645     dmaBuf = (SBYTE *)(BigBuf + 32);
 646     upTo = dmaBuf;
 647     lastRxCounter = DMA_BUFFER_SIZE;
 648     FpgaSetupSscDma((BYTE *)dmaBuf, DMA_BUFFER_SIZE);
 649
 650     // Signal field is ON with the appropriate LED:
 651         if (weTx) LED_D_ON(); else LED_D_OFF();
 652     // And put the FPGA in the appropriate mode
 653     FpgaWriteConfWord(
 654         FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
 655         (weTx ? 0 : FPGA_HF_READER_RX_XCORR_SNOOP));
 656
 657     for(;;) {
 658         int behindBy = lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR;
 659         if(behindBy > max) max = behindBy;
 660
 661         while(((lastRxCounter-AT91C_BASE_PDC_SSC->PDC_RCR) & (DMA_BUFFER_SIZE-1))
 662                     > 2)
 663         {
 664             ci = upTo[0];
 665             cq = upTo[1];
 666             upTo += 2;
 667             if(upTo - dmaBuf > DMA_BUFFER_SIZE) {
 668                 upTo -= DMA_BUFFER_SIZE;
 669                 AT91C_BASE_PDC_SSC->PDC_RNPR = (DWORD)upTo;
 670                 AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;
 671             }
 672             lastRxCounter -= 2;
 673             if(lastRxCounter <= 0) {
 674                 lastRxCounter += DMA_BUFFER_SIZE;
 675             }
 676
 677             samples += 2;
 678
 679             Handle14443UartBit(1);
 680             Handle14443UartBit(1);
 681
 682             if(Handle14443SamplesDemod(ci, cq)) {
 683                 gotFrame = 1;
 684             }
 685         }
 686
 687         if(samples > 2000) {
 688             break;
 689         }
 690     }
 691     AT91C_BASE_PDC_SSC->PDC_PTCR = AT91C_PDC_RXTDIS;
 692     if (!quiet) Dbprintf("%x %x %x", max, gotFrame, Demod.len);
 693 }
 694
 695 //-----------------------------------------------------------------------------
 696 // Read the tag's response. We just receive a stream of slightly-processed
 697 // samples from the FPGA, which we will later do some signal processing on,
 698 // to get the bits.
 699 //-----------------------------------------------------------------------------
 700 /*static void GetSamplesFor14443(BOOL weTx, int n)
 701 {
 702     BYTE *dest = (BYTE *)BigBuf;
 703     int c;
 704
 705     FpgaWriteConfWord(
 706         FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
 707         (weTx ? 0 : FPGA_HF_READER_RX_XCORR_SNOOP));
 708
 709     c = 0;
 710     for(;;) {
 711         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 712             AT91C_BASE_SSC->SSC_THR = 0x43;
 713         }
 714         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 715             SBYTE b;
 716             b = (SBYTE)AT91C_BASE_SSC->SSC_RHR;
 717
 718             dest[c++] = (BYTE)b;
 719
 720             if(c >= n) {
 721                 break;
 722             }
 723         }
 724     }
 725 }*/
 726
 727 //-----------------------------------------------------------------------------
 728 // Transmit the command (to the tag) that was placed in ToSend[].
 729 //-----------------------------------------------------------------------------
 730 static void TransmitFor14443(void)
 731 {
 732     int c;
 733
 734     FpgaSetupSsc();
 735
 736     while(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 737         AT91C_BASE_SSC->SSC_THR = 0xff;
 738     }
 739
 740     // Signal field is ON with the appropriate Red LED
 741         LED_D_ON();
 742         // Signal we are transmitting with the Green LED
 743         LED_B_ON();
 744         FpgaWriteConfWord(
 745         FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
 746
 747     for(c = 0; c < 10;) {
 748         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 749             AT91C_BASE_SSC->SSC_THR = 0xff;
 750             c++;
 751         }
 752         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 753             volatile DWORD r = AT91C_BASE_SSC->SSC_RHR;
 754             (void)r;
 755         }
 756         WDT_HIT();
 757     }
 758
 759     c = 0;
 760     for(;;) {
 761         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
 762             AT91C_BASE_SSC->SSC_THR = ToSend[c];
 763             c++;
 764             if(c >= ToSendMax) {
 765                 break;
 766             }
 767         }
 768         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
 769             volatile DWORD r = AT91C_BASE_SSC->SSC_RHR;
 770             (void)r;
 771         }
 772         WDT_HIT();
 773     }
 774     LED_B_OFF(); // Finished sending
 775 }
 776
 777 //-----------------------------------------------------------------------------
 778 // Code a layer 2 command (string of octets, including CRC) into ToSend[],
 779 // so that it is ready to transmit to the tag using TransmitFor14443().
 780 //-----------------------------------------------------------------------------
 781 void CodeIso14443bAsReader(const BYTE *cmd, int len)
 782 {
 783     int i, j;
 784     BYTE b;
 785
 786     ToSendReset();
 787
 788     // Establish initial reference level
 789     for(i = 0; i < 40; i++) {
 790         ToSendStuffBit(1);
 791     }
 792     // Send SOF
 793     for(i = 0; i < 10; i++) {
 794         ToSendStuffBit(0);
 795     }
 796
 797     for(i = 0; i < len; i++) {
 798         // Stop bits/EGT
 799         ToSendStuffBit(1);
 800         ToSendStuffBit(1);
 801         // Start bit
 802         ToSendStuffBit(0);
 803         // Data bits
 804         b = cmd[i];
 805         for(j = 0; j < 8; j++) {
 806             if(b & 1) {
 807                 ToSendStuffBit(1);
 808             } else {
 809                 ToSendStuffBit(0);
 810             }
 811             b >>= 1;
 812         }
 813     }
 814     // Send EOF
 815     ToSendStuffBit(1);
 816     for(i = 0; i < 10; i++) {
 817         ToSendStuffBit(0);
 818     }
 819     for(i = 0; i < 8; i++) {
 820         ToSendStuffBit(1);
 821     }
 822
 823     // And then a little more, to make sure that the last character makes
 824     // it out before we switch to rx mode.
 825     for(i = 0; i < 24; i++) {
 826         ToSendStuffBit(1);
 827     }
 828
 829     // Convert from last character reference to length
 830     ToSendMax++;
 831 }
 832
 833 //-----------------------------------------------------------------------------
 834 // Read an ISO 14443 tag. We send it some set of commands, and record the
 835 // responses.
 836 // The command name is misleading, it actually decodes the reponse in HEX
 837 // into the output buffer (read the result using hexsamples, not hisamples)
 838 //-----------------------------------------------------------------------------
 839 void AcquireRawAdcSamplesIso14443(DWORD parameter)
 840 {
 841     BYTE cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
 842
 843     // Make sure that we start from off, since the tags are stateful;
 844     // confusing things will happen if we don't reset them between reads.
 845     FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
 846     LED_D_OFF();
 847     SpinDelay(200);
 848
 849     SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 850     FpgaSetupSsc();
 851
 852     // Now give it time to spin up.
 853     // Signal field is on with the appropriate LED
 854     LED_D_ON();
 855     FpgaWriteConfWord(
 856         FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
 857     SpinDelay(200);
 858
 859     CodeIso14443bAsReader(cmd1, sizeof(cmd1));
 860     TransmitFor14443();
 861 //    LED_A_ON();
 862     GetSamplesFor14443Demod(TRUE, 2000, FALSE);
 863 //    LED_A_OFF();
 864 }
 865
 866 //-----------------------------------------------------------------------------
 867 // Read a SRI512 ISO 14443 tag.
 868 //
 869 // SRI512 tags are just simple memory tags, here we're looking at making a dump
 870 // of the contents of the memory. No anticollision algorithm is done, we assume
 871 // we have a single tag in the field.
 872 //
 873 // I tried to be systematic and check every answer of the tag, every CRC, etc...
 874 //-----------------------------------------------------------------------------
 875 void ReadSRI512Iso14443(DWORD parameter)
 876 {
 877      ReadSTMemoryIso14443(parameter,0x0F);
 878 }
 879 void ReadSRIX4KIso14443(DWORD parameter)
 880 {
 881      ReadSTMemoryIso14443(parameter,0x7F);
 882 }
 883
 884 void ReadSTMemoryIso14443(DWORD parameter,DWORD dwLast)
 885 {
 886     BYTE i = 0x00;
 887
 888     // Make sure that we start from off, since the tags are stateful;
 889     // confusing things will happen if we don't reset them between reads.
 890     LED_D_OFF();
 891     FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
 892     SpinDelay(200);
 893
 894     SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 895     FpgaSetupSsc();
 896
 897     // Now give it time to spin up.
 898     // Signal field is on with the appropriate LED
 899     LED_D_ON();
 900     FpgaWriteConfWord(
 901         FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
 902     SpinDelay(200);
 903
 904     // First command: wake up the tag using the INITIATE command
 905     BYTE cmd1[] = { 0x06, 0x00, 0x97, 0x5b};
 906     CodeIso14443bAsReader(cmd1, sizeof(cmd1));
 907     TransmitFor14443();
 908 //    LED_A_ON();
 909     GetSamplesFor14443Demod(TRUE, 2000,TRUE);
 910 //    LED_A_OFF();
 911
 912     if (Demod.len == 0) {
 913         DbpString("No response from tag");
 914         return;
 915     } else {
 916         Dbprintf("Randomly generated UID from tag (+ 2 byte CRC): %x %x %x",
 917                 Demod.output[0], Demod.output[1],Demod.output[2]);
 918     }
 919     // There is a response, SELECT the uid
 920     DbpString("Now SELECT tag:");
 921     cmd1[0] = 0x0E; // 0x0E is SELECT
 922     cmd1[1] = Demod.output[0];
 923     ComputeCrc14443(CRC_14443_B, cmd1, 2, &cmd1[2], &cmd1[3]);
 924     CodeIso14443bAsReader(cmd1, sizeof(cmd1));
 925     TransmitFor14443();
 926 //    LED_A_ON();
 927     GetSamplesFor14443Demod(TRUE, 2000,TRUE);
 928 //    LED_A_OFF();
 929     if (Demod.len != 3) {
 930         Dbprintf("Expected 3 bytes from tag, got %d", Demod.len);
 931         return;
 932     }
 933     // Check the CRC of the answer:
 934     ComputeCrc14443(CRC_14443_B, Demod.output, 1 , &cmd1[2], &cmd1[3]);
 935     if(cmd1[2] != Demod.output[1] || cmd1[3] != Demod.output[2]) {
 936         DbpString("CRC Error reading select response.");
 937         return;
 938     }
 939     // Check response from the tag: should be the same UID as the command we just sent:
 940     if (cmd1[1] != Demod.output[0]) {
 941         Dbprintf("Bad response to SELECT from Tag, aborting: %x %x", cmd1[1], Demod.output[0]);
 942         return;
 943     }
 944     // Tag is now selected,
 945     // First get the tag's UID:
 946     cmd1[0] = 0x0B;
 947     ComputeCrc14443(CRC_14443_B, cmd1, 1 , &cmd1[1], &cmd1[2]);
 948     CodeIso14443bAsReader(cmd1, 3); // Only first three bytes for this one
 949     TransmitFor14443();
 950 //    LED_A_ON();
 951     GetSamplesFor14443Demod(TRUE, 2000,TRUE);
 952 //    LED_A_OFF();
 953     if (Demod.len != 10) {
 954         Dbprintf("Expected 10 bytes from tag, got %d", Demod.len);
 955         return;
 956     }
 957     // The check the CRC of the answer (use cmd1 as temporary variable):
 958     ComputeCrc14443(CRC_14443_B, Demod.output, 8, &cmd1[2], &cmd1[3]);
 959            if(cmd1[2] != Demod.output[8] || cmd1[3] != Demod.output[9]) {
 960         Dbprintf("CRC Error reading block! - Below: expected, got %x %x",
 961                 (cmd1[2]<<8)+cmd1[3], (Demod.output[8]<<8)+Demod.output[9]);
 962         // Do not return;, let's go on... (we should retry, maybe ?)
 963     }
 964     Dbprintf("Tag UID (64 bits): %08x %08x",
 965         (Demod.output[7]<<24) + (Demod.output[6]<<16) + (Demod.output[5]<<8) + Demod.output[4],
 966         (Demod.output[3]<<24) + (Demod.output[2]<<16) + (Demod.output[1]<<8) + Demod.output[0]);
 967
 968     // Now loop to read all 16 blocks, address from 0 to 15
 969     DbpString("Tag memory dump, block 0 to 15");
 970     cmd1[0] = 0x08;
 971     i = 0x00;
 972     dwLast++;
 973     for (;;) {
 974            if (i == dwLast) {
 975                     DbpString("System area block (0xff):");
 976                     i = 0xff;
 977             }
 978             cmd1[1] = i;
 979             ComputeCrc14443(CRC_14443_B, cmd1, 2, &cmd1[2], &cmd1[3]);
 980             CodeIso14443bAsReader(cmd1, sizeof(cmd1));
 981             TransmitFor14443();
 982 //          LED_A_ON();
 983             GetSamplesFor14443Demod(TRUE, 2000,TRUE);
 984 //          LED_A_OFF();
 985             if (Demod.len != 6) { // Check if we got an answer from the tag
 986                 DbpString("Expected 6 bytes from tag, got less...");
 987                 return;
 988             }
 989             // The check the CRC of the answer (use cmd1 as temporary variable):
 990             ComputeCrc14443(CRC_14443_B, Demod.output, 4, &cmd1[2], &cmd1[3]);
 991             if(cmd1[2] != Demod.output[4] || cmd1[3] != Demod.output[5]) {
 992                 Dbprintf("CRC Error reading block! - Below: expected, got %x %x",
 993                         (cmd1[2]<<8)+cmd1[3], (Demod.output[4]<<8)+Demod.output[5]);
 994                 // Do not return;, let's go on... (we should retry, maybe ?)
 995             }
 996             // Now print out the memory location:
 997             Dbprintf("Address=%x, Contents=%x, CRC=%x", i,
 998                 (Demod.output[3]<<24) + (Demod.output[2]<<16) + (Demod.output[1]<<8) + Demod.output[0],
 999                 (Demod.output[4]<<8)+Demod.output[5]);
1000             if (i == 0xff) {
1001                 break;
1002             }
1003             i++;
1004     }
1005 }
1006
1007
1008 //=============================================================================
1009 // Finally, the `sniffer' combines elements from both the reader and
1010 // simulated tag, to show both sides of the conversation.
1011 //=============================================================================
1012
1013 //-----------------------------------------------------------------------------
1014 // Record the sequence of commands sent by the reader to the tag, with
1015 // triggering so that we start recording at the point that the tag is moved
1016 // near the reader.
1017 //-----------------------------------------------------------------------------
1018 /*
1019  * Memory usage for this function, (within BigBuf)
1020  * 0-4095 : Demodulated samples receive (4096 bytes) - DEMOD_TRACE_SIZE
1021  * 4096-6143 : Last Received command, 2048 bytes (reader->tag) - READER_TAG_BUFFER_SIZE
1022  * 6144-8191 : Last Received command, 2048 bytes(tag->reader) - TAG_READER_BUFFER_SIZE
1023  * 8192-9215 : DMA Buffer, 1024 bytes (samples) - DMA_BUFFER_SIZE
1024  */
1025 void SnoopIso14443(void)
1026 {
1027     // We won't start recording the frames that we acquire until we trigger;
1028     // a good trigger condition to get started is probably when we see a
1029     // response from the tag.
1030     BOOL triggered = FALSE;
1031
1032     // The command (reader -> tag) that we're working on receiving.
1033     BYTE *receivedCmd = (BYTE *)(BigBuf) + DEMOD_TRACE_SIZE;
1034     // The response (tag -> reader) that we're working on receiving.
1035     BYTE *receivedResponse = (BYTE *)(BigBuf) + DEMOD_TRACE_SIZE + READER_TAG_BUFFER_SIZE;
1036
1037     // As we receive stuff, we copy it from receivedCmd or receivedResponse
1038     // into trace, along with its length and other annotations.
1039     BYTE *trace = (BYTE *)BigBuf;
1040     int traceLen = 0;
1041
1042     // The DMA buffer, used to stream samples from the FPGA.
1043     SBYTE *dmaBuf = (SBYTE *)(BigBuf) + DEMOD_TRACE_SIZE + READER_TAG_BUFFER_SIZE + TAG_READER_BUFFER_SIZE;
1044     int lastRxCounter;
1045     SBYTE *upTo;
1046     int ci, cq;
1047     int maxBehindBy = 0;
1048
1049     // Count of samples received so far, so that we can include timing
1050     // information in the trace buffer.
1051     int samples = 0;
1052
1053     // Initialize the trace buffer
1054     memset(trace, 0x44, DEMOD_TRACE_SIZE);
1055
1056     // Set up the demodulator for tag -> reader responses.
1057     Demod.output = receivedResponse;
1058     Demod.len = 0;
1059     Demod.state = DEMOD_UNSYNCD;
1060
1061     // And the reader -> tag commands
1062     memset(&Uart, 0, sizeof(Uart));
1063     Uart.output = receivedCmd;
1064     Uart.byteCntMax = 100;
1065     Uart.state = STATE_UNSYNCD;
1066
1067         // Print some debug information about the buffer sizes
1068         Dbprintf("Snooping buffers initialized:");
1069         Dbprintf("  Trace: %i bytes", DEMOD_TRACE_SIZE);
1070         Dbprintf("  Reader -> tag: %i bytes", READER_TAG_BUFFER_SIZE);
1071         Dbprintf("  tag -> Reader: %i bytes", TAG_READER_BUFFER_SIZE);
1072         Dbprintf("  DMA: %i bytes", DMA_BUFFER_SIZE);
1073
1074         // Use a counter for blinking the LED
1075         long ledCount=0;
1076         long ledFlashAt=200000;
1077
1078     // And put the FPGA in the appropriate mode
1079     // Signal field is off with the appropriate LED
1080     LED_D_OFF();
1081     FpgaWriteConfWord(
1082         FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
1083         FPGA_HF_READER_RX_XCORR_SNOOP);
1084     SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
1085
1086     // Setup for the DMA.
1087     FpgaSetupSsc();
1088     upTo = dmaBuf;
1089     lastRxCounter = DMA_BUFFER_SIZE;
1090     FpgaSetupSscDma((BYTE *)dmaBuf, DMA_BUFFER_SIZE);
1091     // And now we loop, receiving samples.
1092     for(;;) {
1093                 // Blink the LED while Snooping
1094                 ledCount++;
1095                 if (ledCount == ledFlashAt) {
1096                         LED_D_ON();
1097                 }
1098                 if (ledCount >= 2*ledFlashAt) {
1099                         LED_D_OFF();
1100                         ledCount=0;
1101                 }
1102
1103         int behindBy = (lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR) &
1104                                 (DMA_BUFFER_SIZE-1);
1105         if(behindBy > maxBehindBy) {
1106             maxBehindBy = behindBy;
1107             if(behindBy > (DMA_BUFFER_SIZE-2)) { // TODO: understand whether we can increase/decrease as we want or not?
1108                 Dbprintf("blew circular buffer! behindBy=%x", behindBy);
1109                 goto done;
1110             }
1111         }
1112         if(behindBy < 2) continue;
1113
1114         ci = upTo[0];
1115         cq = upTo[1];
1116         upTo += 2;
1117         lastRxCounter -= 2;
1118         if(upTo - dmaBuf > DMA_BUFFER_SIZE) {
1119             upTo -= DMA_BUFFER_SIZE;
1120             lastRxCounter += DMA_BUFFER_SIZE;
1121             AT91C_BASE_PDC_SSC->PDC_RNPR = (DWORD) upTo;
1122             AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;
1123         }
1124
1125         samples += 2;
1126
1127 #define HANDLE_BIT_IF_BODY \
1128             if(triggered) { \
1129                                 ledFlashAt=30000; \
1130                 trace[traceLen++] = ((samples >>  0) & 0xff); \
1131                 trace[traceLen++] = ((samples >>  8) & 0xff); \
1132                 trace[traceLen++] = ((samples >> 16) & 0xff); \
1133                 trace[traceLen++] = ((samples >> 24) & 0xff); \
1134                 trace[traceLen++] = 0; \
1135                 trace[traceLen++] = 0; \
1136                 trace[traceLen++] = 0; \
1137                 trace[traceLen++] = 0; \
1138                 trace[traceLen++] = Uart.byteCnt; \
1139                 memcpy(trace+traceLen, receivedCmd, Uart.byteCnt); \
1140                 traceLen += Uart.byteCnt; \
1141                 if(traceLen > 1000) break; \
1142             } \
1143             /* And ready to receive another command. */ \
1144             memset(&Uart, 0, sizeof(Uart)); \
1145             Uart.output = receivedCmd; \
1146             Uart.byteCntMax = 100; \
1147             Uart.state = STATE_UNSYNCD; \
1148             /* And also reset the demod code, which might have been */ \
1149             /* false-triggered by the commands from the reader. */ \
1150             memset(&Demod, 0, sizeof(Demod)); \
1151             Demod.output = receivedResponse; \
1152             Demod.state = DEMOD_UNSYNCD; \
1153
1154         if(Handle14443UartBit(ci & 1)) {
1155             HANDLE_BIT_IF_BODY
1156         }
1157         if(Handle14443UartBit(cq & 1)) {
1158             HANDLE_BIT_IF_BODY
1159         }
1160
1161         if(Handle14443SamplesDemod(ci, cq)) {
1162             // timestamp, as a count of samples
1163             trace[traceLen++] = ((samples >>  0) & 0xff);
1164             trace[traceLen++] = ((samples >>  8) & 0xff);
1165             trace[traceLen++] = ((samples >> 16) & 0xff);
1166             trace[traceLen++] = 0x80 | ((samples >> 24) & 0xff);
1167             // correlation metric (~signal strength estimate)
1168             if(Demod.metricN != 0) {
1169                 Demod.metric /= Demod.metricN;
1170             }
1171             trace[traceLen++] = ((Demod.metric >>  0) & 0xff);
1172             trace[traceLen++] = ((Demod.metric >>  8) & 0xff);
1173             trace[traceLen++] = ((Demod.metric >> 16) & 0xff);
1174             trace[traceLen++] = ((Demod.metric >> 24) & 0xff);
1175             // length
1176             trace[traceLen++] = Demod.len;
1177             memcpy(trace+traceLen, receivedResponse, Demod.len);
1178             traceLen += Demod.len;
1179             if(traceLen > DEMOD_TRACE_SIZE) {
1180                                 DbpString("Reached trace limit");
1181                                 goto done;
1182                         }
1183
1184             triggered = TRUE;
1185
1186             // And ready to receive another response.
1187             memset(&Demod, 0, sizeof(Demod));
1188             Demod.output = receivedResponse;
1189             Demod.state = DEMOD_UNSYNCD;
1190         }
1191                 WDT_HIT();
1192
1193         if(BUTTON_PRESS()) {
1194             DbpString("cancelled");
1195             goto done;
1196         }
1197     }
1198
1199 done:
1200         LED_D_OFF();
1201     AT91C_BASE_PDC_SSC->PDC_PTCR = AT91C_PDC_RXTDIS;
1202         DbpString("Snoop statistics:");
1203     Dbprintf("  Max behind by: %i", maxBehindBy);
1204         Dbprintf("  Uart State: %x", Uart.state);
1205         Dbprintf("  Uart ByteCnt: %i", Uart.byteCnt);
1206         Dbprintf("  Uart ByteCntMax: %i", Uart.byteCntMax);
1207         Dbprintf("  Trace length: %i", traceLen);
1208 }