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

   1 /*
   2  * LEGIC RF simulation code
   3  *
   4  * (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
   5  */
   6
   7 #include <proxmark3.h>
   8
   9 #include "apps.h"
  10 #include "legicrf.h"
  11 #include "unistd.h"
  12 #include "stdint.h"
  13
  14 static struct legic_frame {
  15         int bits;
  16         uint16_t data;
  17 } current_frame;
  18 AT91PS_TC timer;
  19
  20 static void setup_timer(void)
  21 {
  22         /* Set up Timer 1 to use for measuring time between pulses. Since we're bit-banging
  23          * this it won't be terribly accurate but should be good enough.
  24          */
  25         AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
  26         timer = AT91C_BASE_TC1;
  27         timer->TC_CCR = AT91C_TC_CLKDIS;
  28         timer->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK3;
  29         timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
  30
  31 /* At TIMER_CLOCK3 (MCK/32) */
  32 #define RWD_TIME_1 150     /* RWD_TIME_PAUSE off, 80us on = 100us */
  33 #define RWD_TIME_0 90      /* RWD_TIME_PAUSE off, 40us on = 60us */
  34 #define RWD_TIME_PAUSE 30  /* 20us */
  35 #define RWD_TIME_FUZZ 20   /* rather generous 13us, since the peak detector + hysteresis fuzz quite a bit */
  36 #define TAG_TIME_BIT 150   /* 100us for every bit */
  37 #define TAG_TIME_WAIT 490  /* time from RWD frame end to tag frame start, experimentally determined */
  38
  39 }
  40
  41 #define FUZZ_EQUAL(value, target, fuzz) ((value) > ((target)-(fuzz)) && (value) < ((target)+(fuzz)))
  42
  43 static const struct legic_frame queries[] = {
  44                 {7, 0x55}, /* 1010 101 */
  45 };
  46
  47 static const struct legic_frame responses[] = {
  48                 {6, 0x3b}, /* 1101 11 */
  49 };
  50
  51 /* Send a frame in tag mode, the FPGA must have been set up by
  52  * LegicRfSimulate
  53  */
  54 static void frame_send_tag(uint16_t response, int bits)
  55 {
  56 #if 0
  57         /* Use the SSC to send a response. 8-bit transfers, LSBit first, 100us per bit */
  58 #else
  59         /* Bitbang the response */
  60         AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
  61         AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
  62         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
  63
  64         /* Wait for the frame start */
  65         while(timer->TC_CV < TAG_TIME_WAIT) ;
  66
  67         int i;
  68         for(i=0; i<bits; i++) {
  69                 int nextbit = timer->TC_CV + TAG_TIME_BIT;
  70                 int bit = response & 1;
  71                 response = response >> 1;
  72                 if(bit)
  73                         AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
  74                 else
  75                         AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
  76                 while(timer->TC_CV < nextbit) ;
  77         }
  78         AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
  79 #endif
  80 }
  81
  82 /* Send a frame in reader mode, the FPGA must have been set up by
  83  * LegicRfReader
  84  */
  85 static void frame_send_rwd(uint16_t data, int bits)
  86 {
  87         /* Start clock */
  88         timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
  89         while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
  90
  91         int i;
  92         for(i=0; i<bits; i++) {
  93                 int starttime = timer->TC_CV;
  94                 int pause_end = starttime + RWD_TIME_PAUSE, bit_end;
  95                 int bit = data & 1;
  96                 data = data >> 1;
  97
  98                 if(bit) {
  99                         bit_end = starttime + RWD_TIME_1;
 100                 } else {
 101                         bit_end = starttime + RWD_TIME_0;
 102                 }
 103
 104                 /* RWD_TIME_PAUSE time off, then some time on, so that the complete bit time is
 105                  * RWD_TIME_x, where x is the bit to be transmitted */
 106                 AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
 107                 while(timer->TC_CV < pause_end) ;
 108                 AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
 109                 while(timer->TC_CV < bit_end) ;
 110         }
 111
 112         {
 113                 /* One final pause to mark the end of the frame */
 114                 int pause_end = timer->TC_CV + RWD_TIME_PAUSE;
 115                 AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
 116                 while(timer->TC_CV < pause_end) ;
 117                 AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
 118         }
 119
 120         /* Reset the timer, to measure time until the start of the tag frame */
 121         timer->TC_CCR = AT91C_TC_SWTRG;
 122 }
 123
 124 /* Receive a frame from the card in reader emulation mode, the FPGA and
 125  * timer must have been set up by LegicRfReader and frame_send_rwd.
 126  *
 127  * The LEGIC RF protocol from card to reader does not include explicit
 128  * frame start/stop information or length information. The reader must
 129  * know beforehand how many bits it wants to receive. (Notably: a card
 130  * sending a stream of 0-bits is indistinguishable from no card present.)
 131  *
 132  * Receive methodology: There is a fancy correlator in hi_read_rx_xcorr, but
 133  * I'm not smart enough to use it. Instead I have patched hi_read_tx to output
 134  * the ADC signal with hysteresis on SSP_DIN. Bit-bang that signal and look
 135  * for edges. Count the edges in each bit interval. If they are approximately
 136  * 0 this was a 0-bit, if they are approximately equal to the number of edges
 137  * expected for a 212kHz subcarrier, this was a 1-bit. For timing we use the
 138  * timer that's still running from frame_send_rwd in order to get a synchronization
 139  * with the frame that we just sent.
 140  *
 141  * FIXME: Because we're relying on the hysteresis to just do the right thing
 142  * the range is severely reduced (and you'll probably also need a good antenna).
 143  * So this should be fixed some time in the future for a proper receiver.
 144  */
 145 static void frame_receive_rwd(struct legic_frame * const f, int bits)
 146 {
 147         uint16_t the_bit = 1;  /* Use a bitmask to save on shifts */
 148         uint16_t data=0;
 149         int i, old_level=0, edges=0;
 150         int next_bit_at = TAG_TIME_WAIT;
 151
 152
 153         if(bits > 16)
 154                 bits = 16;
 155
 156         AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
 157         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
 158
 159         while(timer->TC_CV < next_bit_at) ;
 160         next_bit_at += TAG_TIME_BIT;
 161
 162         for(i=0; i<bits; i++) {
 163                 edges = 0;
 164                 while(timer->TC_CV < next_bit_at) {
 165                         int level = (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
 166                         if(level != old_level)
 167                                 edges++;
 168                         old_level = level;
 169                 }
 170                 next_bit_at += TAG_TIME_BIT;
 171
 172                 if(edges > 20 && edges < 60) { /* expected are 42 edges */
 173                         data |= the_bit;
 174                 }
 175
 176
 177                 the_bit <<= 1;
 178         }
 179
 180         f->data = data;
 181         f->bits = bits;
 182 }
 183
 184 /* Figure out a response to a frame in tag mode */
 185 static void frame_respond_tag(struct legic_frame const * const f)
 186 {
 187         LED_D_ON();
 188         int i, r_size;
 189         uint16_t r_data;
 190
 191         for(i=0; i<sizeof(queries)/sizeof(queries[0]); i++) {
 192                 if(f->bits == queries[i].bits && f->data == queries[i].data) {
 193                         r_data = responses[i].data;
 194                         r_size = responses[i].bits;
 195                         break;
 196                 }
 197         }
 198
 199         if(r_size != 0) {
 200                 frame_send_tag(r_data, r_size);
 201                 LED_A_ON();
 202         } else {
 203                 LED_A_OFF();
 204         }
 205
 206         LED_D_OFF();
 207 }
 208
 209 static void frame_append_bit(struct legic_frame * const f, int bit)
 210 {
 211         if(f->bits >= 15)
 212                 return; /* Overflow, won't happen */
 213         f->data |= (bit<<f->bits);
 214         f->bits++;
 215 }
 216
 217 static int frame_is_empty(struct legic_frame const * const f)
 218 {
 219         return( f->bits <= 4 );
 220 }
 221
 222 /* Handle (whether to respond) a frame in tag mode */
 223 static void frame_handle_tag(struct legic_frame const * const f)
 224 {
 225         if(f->bits == 6) {
 226                 /* Short path */
 227                 return;
 228         }
 229         if( !frame_is_empty(f) ) {
 230                 frame_respond_tag(f);
 231         }
 232 }
 233
 234 static void frame_clean(struct legic_frame * const f)
 235 {
 236         f->data = 0;
 237         f->bits = 0;
 238 }
 239
 240 enum emit_mode {
 241         EMIT_RWD, /* Emit in tag simulation mode, e.g. the source is the RWD */
 242         EMIT_TAG  /* Emit in reader simulation mode, e.g. the source is the TAG */
 243 };
 244 static void emit(enum emit_mode mode, int bit)
 245 {
 246         if(bit == -1) {
 247                 if(mode == EMIT_RWD) {
 248                         frame_handle_tag(&current_frame);
 249                 }
 250                 frame_clean(&current_frame);
 251         } else if(bit == 0) {
 252                 frame_append_bit(&current_frame, 0);
 253         } else if(bit == 1) {
 254                 frame_append_bit(&current_frame, 1);
 255         }
 256 }
 257
 258 void LegicRfSimulate(void)
 259 {
 260         /* ADC path high-frequency peak detector, FPGA in high-frequency simulator mode,
 261          * modulation mode set to 212kHz subcarrier. We are getting the incoming raw
 262          * envelope waveform on DIN and should send our response on DOUT.
 263          *
 264          * The LEGIC RF protocol is pulse-pause-encoding from reader to card, so we'll
 265          * measure the time between two rising edges on DIN, and no encoding on the
 266          * subcarrier from card to reader, so we'll just shift out our verbatim data
 267          * on DOUT, 1 bit is 100us. The time from reader to card frame is still unclear,
 268          * seems to be 300us-ish.
 269          */
 270         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 271         FpgaSetupSsc();
 272         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_212K);
 273
 274         /* Bitbang the receiver */
 275         AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
 276         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
 277
 278         setup_timer();
 279
 280         int old_level = 0;
 281         int active = 0;
 282
 283         while(!BUTTON_PRESS()) {
 284                 int level = !!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
 285                 int time = timer->TC_CV;
 286
 287                 if(level != old_level) {
 288                         if(level == 1) {
 289                                 timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
 290                                 if(FUZZ_EQUAL(time, RWD_TIME_1, RWD_TIME_FUZZ)) {
 291                                         /* 1 bit */
 292                                         emit(EMIT_RWD, 1);
 293                                         active = 1;
 294                                         LED_B_ON();
 295                                 } else if(FUZZ_EQUAL(time, RWD_TIME_0, RWD_TIME_FUZZ)) {
 296                                         /* 0 bit */
 297                                         emit(EMIT_RWD, 0);
 298                                         active = 1;
 299                                         LED_B_ON();
 300                                 } else if(active) {
 301                                         /* invalid */
 302                                         emit(EMIT_RWD, -1);
 303                                         active = 0;
 304                                         LED_B_OFF();
 305                                 }
 306                         }
 307                 }
 308
 309                 if(time >= (RWD_TIME_1+RWD_TIME_FUZZ) && active) {
 310                         /* Frame end */
 311                         emit(EMIT_RWD, -1);
 312                         active = 0;
 313                         LED_B_OFF();
 314                 }
 315
 316                 if(time >= (20*RWD_TIME_1) && (timer->TC_SR & AT91C_TC_CLKSTA)) {
 317                         timer->TC_CCR = AT91C_TC_CLKDIS;
 318                 }
 319
 320
 321                 old_level = level;
 322                 WDT_HIT();
 323         }
 324 }
 325
 326 void LegicRfReader(void)
 327 {
 328         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 329         FpgaSetupSsc();
 330         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
 331
 332         /* Bitbang the transmitter */
 333         AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
 334         AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
 335         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
 336
 337         setup_timer();
 338
 339         while(!BUTTON_PRESS()) {
 340                 /* Switch on carrier and let the tag charge for 1ms */
 341                 AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
 342                 SpinDelay(1);
 343
 344                 LED_A_ON();
 345                 frame_send_rwd(queries[0].data, queries[0].bits);
 346                 LED_A_OFF();
 347
 348                 frame_clean(&current_frame);
 349                 LED_B_ON();
 350                 frame_receive_rwd(&current_frame, responses[0].bits);
 351                 LED_B_OFF();
 352
 353                 /* Switch off carrier, make sure tag is reset */
 354                 AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
 355                 SpinDelay(10);
 356
 357                 WDT_HIT();
 358         }
 359
 360 }