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 /* Figure out a response to a frame in tag mode */
  83 static void frame_respond_tag(struct legic_frame const * const f)
  84 {
  85         LED_D_ON();
  86         int i, r_size;
  87         uint16_t r_data;
  88
  89         for(i=0; i<sizeof(queries)/sizeof(queries[0]); i++) {
  90                 if(f->bits == queries[i].bits && f->data == queries[i].data) {
  91                         r_data = responses[i].data;
  92                         r_size = responses[i].bits;
  93                         break;
  94                 }
  95         }
  96
  97         if(r_size != 0) {
  98                 frame_send_tag(r_data, r_size);
  99                 LED_A_ON();
 100         } else {
 101                 LED_A_OFF();
 102         }
 103
 104         LED_D_OFF();
 105 }
 106
 107 static void frame_append_bit(struct legic_frame * const f, int bit)
 108 {
 109         if(f->bits >= 15)
 110                 return; /* Overflow, won't happen */
 111         f->data |= (bit<<f->bits);
 112         f->bits++;
 113 }
 114
 115 static int frame_is_empty(struct legic_frame const * const f)
 116 {
 117         return( f->bits <= 4 );
 118 }
 119
 120 /* Handle (whether to respond) a frame in tag mode */
 121 static void frame_handle_tag(struct legic_frame const * const f)
 122 {
 123         if(f->bits == 6) {
 124                 /* Short path */
 125                 return;
 126         }
 127         if( !frame_is_empty(f) ) {
 128                 frame_respond_tag(f);
 129         }
 130 }
 131
 132 static void frame_clean(struct legic_frame * const f)
 133 {
 134         f->data = 0;
 135         f->bits = 0;
 136 }
 137
 138 enum emit_mode {
 139         EMIT_RWD, /* Emit in tag simulation mode, e.g. the source is the RWD */
 140         EMIT_TAG  /* Emit in reader simulation mode, e.g. the source is the TAG */
 141 };
 142 static void emit(enum emit_mode mode, int bit)
 143 {
 144         if(bit == -1) {
 145                 if(mode == EMIT_RWD) {
 146                         frame_handle_tag(&current_frame);
 147                 }
 148                 frame_clean(&current_frame);
 149         } else if(bit == 0) {
 150                 frame_append_bit(&current_frame, 0);
 151         } else if(bit == 1) {
 152                 frame_append_bit(&current_frame, 1);
 153         }
 154 }
 155
 156 void LegicRfSimulate(void)
 157 {
 158         /* ADC path high-frequency peak detector, FPGA in high-frequency simulator mode,
 159          * modulation mode set to 212kHz subcarrier. We are getting the incoming raw
 160          * envelope waveform on DIN and should send our response on DOUT.
 161          *
 162          * The LEGIC RF protocol is pulse-pause-encoding from reader to card, so we'll
 163          * measure the time between two rising edges on DIN, and no encoding on the
 164          * subcarrier from card to reader, so we'll just shift out our verbatim data
 165          * on DOUT, 1 bit is 100us. The time from reader to card frame is still unclear,
 166          * seems to be 300us-ish.
 167          */
 168         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 169         FpgaSetupSsc();
 170         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_212K);
 171
 172         /* Bitbang the receiver */
 173         AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
 174         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
 175
 176         setup_timer();
 177
 178         int old_level = 0;
 179         int active = 0;
 180
 181         while(!BUTTON_PRESS()) {
 182                 int level = !!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
 183                 int time = timer->TC_CV;
 184
 185                 if(level != old_level) {
 186                         if(level == 1) {
 187                                 timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
 188                                 if(FUZZ_EQUAL(time, RWD_TIME_1, RWD_TIME_FUZZ)) {
 189                                         /* 1 bit */
 190                                         emit(EMIT_RWD, 1);
 191                                         active = 1;
 192                                         LED_B_ON();
 193                                 } else if(FUZZ_EQUAL(time, RWD_TIME_0, RWD_TIME_FUZZ)) {
 194                                         /* 0 bit */
 195                                         emit(EMIT_RWD, 0);
 196                                         active = 1;
 197                                         LED_B_ON();
 198                                 } else if(active) {
 199                                         /* invalid */
 200                                         emit(EMIT_RWD, -1);
 201                                         active = 0;
 202                                         LED_B_OFF();
 203                                 }
 204                         }
 205                 }
 206
 207                 if(time >= (RWD_TIME_1+RWD_TIME_FUZZ) && active) {
 208                         /* Frame end */
 209                         emit(EMIT_RWD, -1);
 210                         active = 0;
 211                         LED_B_OFF();
 212                 }
 213
 214                 if(time >= (20*RWD_TIME_1) && (timer->TC_SR & AT91C_TC_CLKSTA)) {
 215                         timer->TC_CCR = AT91C_TC_CLKDIS;
 216                 }
 217
 218
 219                 old_level = level;
 220                 WDT_HIT();
 221         }
 222 }