]> git.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/legicrf.c
CHG: merged the forum user @jason 's fixes to LEGIC. *UNTESTED*
[proxmark3-svn] / armsrc / legicrf.c
index 5ad1fdf1f0c31895328f089847186405c2fec2cd..a725c0bc596aac7e45b80d7f7f9388f10cf61742 100644 (file)
@@ -325,12 +325,11 @@ static void LegicCommonInit(void) {
        crc_init(&legic_crc, 4, 0x19 >> 1, 0x5, 0);
 }
 
+/* Switch off carrier, make sure tag is reset */
 static void switch_off_tag_rwd(void)
 {
-       /* Switch off carrier, make sure tag is reset */
        AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
        SpinDelay(10);
-
        WDT_HIT();
 }
 /* calculate crc for a legic command */
@@ -372,11 +371,12 @@ int legic_read_byte(int byte_index, int cmd_sz) {
  *  * wait until the tag sends back an ACK ('1' bit unencrypted)
  *  * forward the prng based on the timing
  */
+//int legic_write_byte(int byte, int addr, int addr_sz, int PrngCorrection) {
 int legic_write_byte(int byte, int addr, int addr_sz) {
-    //do not write UID, CRC, DCF
-    if(addr <= 0x06)
+    //do not write UID, CRC
+       if(addr <= 0x04) { 
                return 0;
-
+               }
        //== send write command ==============================
        crc_clear(&legic_crc);
        crc_update(&legic_crc, 0, 1); /* CMD_WRITE */
@@ -390,10 +390,13 @@ int legic_write_byte(int byte, int addr, int addr_sz) {
                    |(0x00    <<0));           //CMD = W
     uint32_t cmd_sz = addr_sz+1+8+4;          //crc+data+cmd
 
-    legic_prng_forward(2); /* we wait anyways */
+    legic_prng_forward(4); /* we wait anyways */
     while(timer->TC_CV < 387) ; /* ~ 258us */
        frame_send_rwd(cmd, cmd_sz);
 
+       AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
+       AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
+
        //== wait for ack ====================================
     int t, old_level=0, edges=0;
     int next_bit_at =0;
@@ -413,7 +416,7 @@ int legic_write_byte(int byte, int addr, int addr_sz) {
                        int c = t/TAG_TIME_BIT;
                        timer->TC_CCR = AT91C_TC_SWTRG;
                        while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
-                       legic_prng_forward(c);
+                       legic_prng_forward(c-1);
                return 0;
         }
     }
@@ -423,6 +426,11 @@ int legic_write_byte(int byte, int addr, int addr_sz) {
 }
 
 int LegicRfReader(int offset, int bytes) {
+       
+       // ice_legic_setup();
+       // ice_legic_select_card();
+       // return 0;
+       
        int byte_index=0, cmd_sz=0, card_sz=0;
 
        LegicCommonInit();
@@ -434,13 +442,18 @@ int LegicRfReader(int offset, int bytes) {
        uint32_t tag_type = perform_setup_phase_rwd(SESSION_IV);
        switch_off_tag_rwd(); //we lose to mutch time with dprintf
        switch(tag_type) {
+               case 0x0d:
+                       DbpString("MIM22 card found, reading card ...");
+            cmd_sz = 6;
+                       card_sz = 22;
+                       break;
                case 0x1d:
-                       DbpString("MIM 256 card found, reading card ...");
+                       DbpString("MIM256 card found, reading card ...");
             cmd_sz = 9;
                        card_sz = 256;
                        break;
                case 0x3d:
-                       DbpString("MIM 1024 card found, reading card ...");
+                       DbpString("MIM1024 card found, reading card ...");
             cmd_sz = 11;
                        card_sz = 1024;
                        break;
@@ -469,7 +482,7 @@ int LegicRfReader(int offset, int bytes) {
                BigBuf[byte_index] = r;
         WDT_HIT();
                byte_index++;
-               if(byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
+               if (byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
        }
        LED_B_OFF();
     LED_C_OFF();
@@ -479,6 +492,47 @@ int LegicRfReader(int offset, int bytes) {
     return 0;
 }
 
+/*int _LegicRfWriter(int bytes, int offset, int addr_sz, uint8_t *BigBuf, int RoundBruteforceValue) {
+       int byte_index=0;
+
+    LED_B_ON();
+       perform_setup_phase_rwd(SESSION_IV);
+    //legic_prng_forward(2);
+       while(byte_index < bytes) {
+               int r;
+
+               //check if the DCF should be changed
+               if ( (offset == 0x05) && (bytes == 0x02) ) {
+                       //write DCF in reverse order (addr 0x06 before 0x05)
+                       r = legic_write_byte(BigBuf[(0x06-byte_index)], (0x06-byte_index), addr_sz, RoundBruteforceValue);
+                       //legic_prng_forward(1);
+                       if(r == 0) {
+                               byte_index++;
+                               r = legic_write_byte(BigBuf[(0x06-byte_index)], (0x06-byte_index), addr_sz, RoundBruteforceValue);
+                       }
+                       //legic_prng_forward(1);
+               }
+               else {
+                       r = legic_write_byte(BigBuf[byte_index+offset], byte_index+offset, addr_sz, RoundBruteforceValue);
+               }
+               if((r != 0) || BUTTON_PRESS()) {
+                       Dbprintf("operation aborted @ 0x%03.3x", byte_index);
+       switch_off_tag_rwd();
+                       LED_B_OFF();
+                       LED_C_OFF();
+                       return -1;
+               }
+
+        WDT_HIT();
+               byte_index++;
+        if(byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
+       }
+    LED_B_OFF();
+    LED_C_OFF();
+    DbpString("write successful");
+    return 0;
+}*/
+
 void LegicRfWriter(int bytes, int offset) {
        int byte_index=0, addr_sz=0;
        uint8_t *BigBuf = BigBuf_get_addr();
@@ -489,32 +543,56 @@ void LegicRfWriter(int bytes, int offset) {
        uint32_t tag_type = perform_setup_phase_rwd(SESSION_IV);
        switch_off_tag_rwd();
        switch(tag_type) {
+               case 0x0d:
+                       if(offset+bytes > 22) {
+                               Dbprintf("Error: can not write to 0x%03.3x on MIM22", offset+bytes);
+                               return;
+                       }
+                       addr_sz = 5;
+                       Dbprintf("MIM22 card found, writing 0x%02.2x - 0x%02.2x ...", offset, offset+bytes);
+                       break;
                case 0x1d:
                        if(offset+bytes > 0x100) {
-                               Dbprintf("Error: can not write to 0x%03.3x on MIM 256", offset+bytes);
+                               Dbprintf("Error: can not write to 0x%03.3x on MIM256", offset+bytes);
                                return;
                        }
                        addr_sz = 8;
-                       Dbprintf("MIM 256 card found, writing 0x%02.2x - 0x%02.2x ...", offset, offset+bytes);
+                       Dbprintf("MIM256 card found, writing 0x%02.2x - 0x%02.2x ...", offset, offset+bytes);
                        break;
                case 0x3d:
                        if(offset+bytes > 0x400) {
-                       Dbprintf("Error: can not write to 0x%03.3x on MIM 1024", offset+bytes);
+                       Dbprintf("Error: can not write to 0x%03.3x on MIM1024", offset+bytes);
                        return;
                }
                        addr_sz = 10;
-                       Dbprintf("MIM 1024 card found, writing 0x%03.3x - 0x%03.3x ...", offset, offset+bytes);
+                       Dbprintf("MIM1024 card found, writing 0x%03.3x - 0x%03.3x ...", offset, offset+bytes);
                        break;
                default:
                        Dbprintf("No or unknown card found, aborting");
             return;
        }
 
+#if 1
     LED_B_ON();
        perform_setup_phase_rwd(SESSION_IV);
-    legic_prng_forward(2);
+
        while(byte_index < bytes) {
-               int r = legic_write_byte(BigBuf[byte_index+offset], byte_index+offset, addr_sz);
+               int r;
+
+               //check if the DCF should be changed
+               if ( ((byte_index+offset) == 0x05) && (bytes >= 0x02) ) {
+                       //write DCF in reverse order (addr 0x06 before 0x05)
+                       r = legic_write_byte(BigBuf[(0x06-byte_index)], (0x06-byte_index), addr_sz);
+
+                       // write second byte on success...
+                       if(r == 0) {
+                               byte_index++;
+                               r = legic_write_byte(BigBuf[(0x06-byte_index)], (0x06-byte_index), addr_sz);
+                       }
+               }
+               else {
+                       r = legic_write_byte(BigBuf[byte_index+offset], byte_index+offset, addr_sz);
+               }
                if((r != 0) || BUTTON_PRESS()) {
                        Dbprintf("operation aborted @ 0x%03.3x", byte_index);
                        switch_off_tag_rwd();
@@ -522,6 +600,76 @@ void LegicRfWriter(int bytes, int offset) {
                        LED_C_OFF();
                        return;
                }
+
+        WDT_HIT();
+               byte_index++;
+        if(byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
+       }
+    LED_B_OFF();
+    LED_C_OFF();
+    DbpString("write successful");
+#else
+       for(byte_index = -2; byte_index < 200; byte_index++)
+       {
+               Dbprintf("+ Try RndValue %d...", byte_index);
+               if(_LegicRfWriter(bytes, offset, addr_sz, BigBuf, byte_index) == 0)
+                       break;
+       }
+#endif
+
+}
+
+void LegicRfRawWriter(int offset, int byte) {
+       int byte_index=0, addr_sz=0;
+       
+       LegicCommonInit();
+       
+       DbpString("setting up legic card");
+       uint32_t tag_type = perform_setup_phase_rwd(SESSION_IV);
+       switch_off_tag_rwd();
+       switch(tag_type) {
+               case 0x0d:
+                       if(offset > 22) {
+                               Dbprintf("Error: can not write to 0x%03.3x on MIM22", offset);
+                               return;
+                       }
+                       addr_sz = 5;
+                       Dbprintf("MIM22 card found, writing at addr 0x%02.2x - value 0x%02.2x ...", offset, byte);
+                       break;
+               case 0x1d:
+                       if(offset > 0x100) {
+                               Dbprintf("Error: can not write to 0x%03.3x on MIM256", offset);
+                               return;
+                       }
+                       addr_sz = 8;
+                       Dbprintf("MIM256 card found, writing at addr 0x%02.2x - value 0x%02.2x ...", offset, byte);
+                       break;
+               case 0x3d:
+                       if(offset > 0x400) {
+                       Dbprintf("Error: can not write to 0x%03.3x on MIM1024", offset);
+                       return;
+               }
+                       addr_sz = 10;
+                       Dbprintf("MIM1024 card found, writing at addr 0x%03.3x - value 0x%03.3x ...", offset, byte);
+                       break;
+               default:
+                       Dbprintf("No or unknown card found, aborting");
+            return;
+       }
+       Dbprintf("integer value: %d offset: %d  addr_sz: %d", byte, offset, addr_sz);
+    LED_B_ON();
+       perform_setup_phase_rwd(SESSION_IV);
+    //legic_prng_forward(2);
+               
+       int r = legic_write_byte(byte, offset, addr_sz);
+               
+       if((r != 0) || BUTTON_PRESS()) {
+               Dbprintf("operation aborted @ 0x%03.3x (%1d)", byte_index, r);
+               switch_off_tag_rwd();
+               LED_B_OFF();
+               LED_C_OFF();
+               return;
+                       
         WDT_HIT();
                byte_index++;
         if(byte_index & 0x10) LED_C_ON(); else LED_C_OFF();
@@ -756,3 +904,757 @@ void LegicRfSimulate(int phase, int frame, int reqresp)
    LED_C_OFF();
 }
 
+
+//-----------------------------------------------------------------------------
+//-----------------------------------------------------------------------------
+
+
+//-----------------------------------------------------------------------------
+// Code up a string of octets at layer 2 (including CRC, we don't generate
+// that here) so that they can be transmitted to the reader. Doesn't transmit
+// them yet, just leaves them ready to send in ToSend[].
+//-----------------------------------------------------------------------------
+// static void CodeLegicAsTag(const uint8_t *cmd, int len)
+// {
+       // int i;
+
+       // ToSendReset();
+
+       // // Transmit a burst of ones, as the initial thing that lets the
+       // // reader get phase sync. This (TR1) must be > 80/fs, per spec,
+       // // but tag that I've tried (a Paypass) exceeds that by a fair bit,
+       // // so I will too.
+       // for(i = 0; i < 20; i++) {
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+       // }
+
+       // // Send SOF.
+       // for(i = 0; i < 10; i++) {
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+       // }
+       // for(i = 0; i < 2; i++) {
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+       // }
+
+       // for(i = 0; i < len; i++) {
+               // int j;
+               // uint8_t b = cmd[i];
+
+               // // Start bit
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+
+               // // Data bits
+               // for(j = 0; j < 8; j++) {
+                       // if(b & 1) {
+                               // ToSendStuffBit(1);
+                               // ToSendStuffBit(1);
+                               // ToSendStuffBit(1);
+                               // ToSendStuffBit(1);
+                       // } else {
+                               // ToSendStuffBit(0);
+                               // ToSendStuffBit(0);
+                               // ToSendStuffBit(0);
+                               // ToSendStuffBit(0);
+                       // }
+                       // b >>= 1;
+               // }
+
+               // // Stop bit
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+       // }
+
+       // // Send EOF.
+       // for(i = 0; i < 10; i++) {
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+               // ToSendStuffBit(0);
+       // }
+       // for(i = 0; i < 2; i++) {
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+               // ToSendStuffBit(1);
+       // }
+
+       // // Convert from last byte pos to length
+       // ToSendMax++;
+// }
+
+//-----------------------------------------------------------------------------
+// The software UART that receives commands from the reader, and its state
+// variables.
+//-----------------------------------------------------------------------------
+static struct {
+       enum {
+               STATE_UNSYNCD,
+               STATE_GOT_FALLING_EDGE_OF_SOF,
+               STATE_AWAITING_START_BIT,
+               STATE_RECEIVING_DATA
+       }       state;
+       uint16_t shiftReg;
+       int     bitCnt;
+       int     byteCnt;
+       int     byteCntMax;
+       int     posCnt;
+       uint8_t *output;
+} Uart;
+
+/* Receive & handle a bit coming from the reader.
+ *
+ * This function is called 4 times per bit (every 2 subcarrier cycles).
+ * Subcarrier frequency fs is 212kHz, 1/fs = 4,72us, i.e. function is called every 9,44us
+ *
+ * LED handling:
+ * LED A -> ON once we have received the SOF and are expecting the rest.
+ * LED A -> OFF once we have received EOF or are in error state or unsynced
+ *
+ * Returns: true if we received a EOF
+ *          false if we are still waiting for some more
+ */
+// static RAMFUNC int HandleLegicUartBit(uint8_t bit)
+// {
+       // switch(Uart.state) {
+               // case STATE_UNSYNCD:
+                       // if(!bit) {
+                               // // we went low, so this could be the beginning of an SOF
+                               // Uart.state = STATE_GOT_FALLING_EDGE_OF_SOF;
+                               // Uart.posCnt = 0;
+                               // Uart.bitCnt = 0;
+                       // }
+                       // break;
+
+               // case STATE_GOT_FALLING_EDGE_OF_SOF:
+                       // Uart.posCnt++;
+                       // if(Uart.posCnt == 2) {       // sample every 4 1/fs in the middle of a bit
+                               // if(bit) {
+                                       // if(Uart.bitCnt > 9) {
+                                               // // we've seen enough consecutive
+                                               // // zeros that it's a valid SOF
+                                               // Uart.posCnt = 0;
+                                               // Uart.byteCnt = 0;
+                                               // Uart.state = STATE_AWAITING_START_BIT;
+                                               // LED_A_ON(); // Indicate we got a valid SOF
+                                       // } else {
+                                               // // didn't stay down long enough
+                                               // // before going high, error
+                                               // Uart.state = STATE_UNSYNCD;
+                                       // }
+                               // } else {
+                                       // // do nothing, keep waiting
+                               // }
+                               // Uart.bitCnt++;
+                       // }
+                       // if(Uart.posCnt >= 4) Uart.posCnt = 0;
+                       // if(Uart.bitCnt > 12) {
+                               // // Give up if we see too many zeros without
+                               // // a one, too.
+                               // LED_A_OFF();
+                               // Uart.state = STATE_UNSYNCD;
+                       // }
+                       // break;
+
+               // case STATE_AWAITING_START_BIT:
+                       // Uart.posCnt++;
+                       // if(bit) {
+                               // if(Uart.posCnt > 50/2) {     // max 57us between characters = 49 1/fs, max 3 etus after low phase of SOF = 24 1/fs
+                                       // // stayed high for too long between
+                                       // // characters, error
+                                       // Uart.state = STATE_UNSYNCD;
+                               // }
+                       // } else {
+                               // // falling edge, this starts the data byte
+                               // Uart.posCnt = 0;
+                               // Uart.bitCnt = 0;
+                               // Uart.shiftReg = 0;
+                               // Uart.state = STATE_RECEIVING_DATA;
+                       // }
+                       // break;
+
+               // case STATE_RECEIVING_DATA:
+                       // Uart.posCnt++;
+                       // if(Uart.posCnt == 2) {
+                               // // time to sample a bit
+                               // Uart.shiftReg >>= 1;
+                               // if(bit) {
+                                       // Uart.shiftReg |= 0x200;
+                               // }
+                               // Uart.bitCnt++;
+                       // }
+                       // if(Uart.posCnt >= 4) {
+                               // Uart.posCnt = 0;
+                       // }
+                       // if(Uart.bitCnt == 10) {
+                               // if((Uart.shiftReg & 0x200) && !(Uart.shiftReg & 0x001))
+                               // {
+                                       // // this is a data byte, with correct
+                                       // // start and stop bits
+                                       // Uart.output[Uart.byteCnt] = (Uart.shiftReg >> 1) & 0xff;
+                                       // Uart.byteCnt++;
+
+                                       // if(Uart.byteCnt >= Uart.byteCntMax) {
+                                               // // Buffer overflowed, give up
+                                               // LED_A_OFF();
+                                               // Uart.state = STATE_UNSYNCD;
+                                       // } else {
+                                               // // so get the next byte now
+                                               // Uart.posCnt = 0;
+                                               // Uart.state = STATE_AWAITING_START_BIT;
+                                       // }
+                               // } else if (Uart.shiftReg == 0x000) {
+                                       // // this is an EOF byte
+                                       // LED_A_OFF(); // Finished receiving
+                                       // Uart.state = STATE_UNSYNCD;
+                                       // if (Uart.byteCnt != 0) {
+                                       // return TRUE;
+                                       // }
+                               // } else {
+                                       // // this is an error
+                                       // LED_A_OFF();
+                                       // Uart.state = STATE_UNSYNCD;
+                               // }
+                       // }
+                       // break;
+
+               // default:
+                       // LED_A_OFF();
+                       // Uart.state = STATE_UNSYNCD;
+                       // break;
+       // }
+
+       // return FALSE;
+// }
+
+
+static void UartReset()
+{
+       Uart.byteCntMax = MAX_FRAME_SIZE;
+       Uart.state = STATE_UNSYNCD;
+       Uart.byteCnt = 0;
+       Uart.bitCnt = 0;
+       Uart.posCnt = 0;
+       memset(Uart.output, 0x00, MAX_FRAME_SIZE);
+}
+
+// static void UartInit(uint8_t *data)
+// {
+       // Uart.output = data;
+       // UartReset();
+// }
+
+//=============================================================================
+// An LEGIC reader. We take layer two commands, code them
+// appropriately, and then send them to the tag. We then listen for the
+// tag's response, which we leave in the buffer to be demodulated on the
+// PC side.
+//=============================================================================
+
+static struct {
+       enum {
+               DEMOD_UNSYNCD,
+               DEMOD_PHASE_REF_TRAINING,
+               DEMOD_AWAITING_FALLING_EDGE_OF_SOF,
+               DEMOD_GOT_FALLING_EDGE_OF_SOF,
+               DEMOD_AWAITING_START_BIT,
+               DEMOD_RECEIVING_DATA
+       }       state;
+       int     bitCount;
+       int     posCount;
+       int     thisBit;
+       uint16_t  shiftReg;
+       uint8_t   *output;
+       int     len;
+       int     sumI;
+       int     sumQ;
+} Demod;
+
+/*
+ * Handles reception of a bit from the tag
+ *
+ * This function is called 2 times per bit (every 4 subcarrier cycles).
+ * Subcarrier frequency fs is 212kHz, 1/fs = 4,72us, i.e. function is called every 9,44us
+ *
+ * LED handling:
+ * LED C -> ON once we have received the SOF and are expecting the rest.
+ * LED C -> OFF once we have received EOF or are unsynced
+ *
+ * Returns: true if we received a EOF
+ *          false if we are still waiting for some more
+ *
+ */
+
+ #ifndef SUBCARRIER_DETECT_THRESHOLD
+ # define SUBCARRIER_DETECT_THRESHOLD  8
+ #endif
+ // Subcarrier amplitude v = sqrt(ci^2 + cq^2), approximated here by max(abs(ci),abs(cq)) + 1/2*min(abs(ci),abs(cq)))
+#ifndef CHECK_FOR_SUBCARRIER
+# define CHECK_FOR_SUBCARRIER() { v = MAX(ai, aq) + MIN(halfci, halfcq); }
+#endif
+
+// The soft decision on the bit uses an estimate of just the
+// quadrant of the reference angle, not the exact angle.
+// Subcarrier amplitude v = sqrt(ci^2 + cq^2), approximated here by max(abs(ci),abs(cq)) + 1/2*min(abs(ci),abs(cq)))
+#define MAKE_SOFT_DECISION() { \
+               if(Demod.sumI > 0) \
+                       v = ci; \
+               else \
+                       v = -ci; \
+               \
+               if(Demod.sumQ > 0) \
+                       v += cq; \
+               else \
+                       v -= cq; \
+               \
+       }
+
+static RAMFUNC int HandleLegicSamplesDemod(int ci, int cq)
+{
+       int v = 0;
+       int ai = ABS(ci);
+       int aq = ABS(cq);
+       int halfci = (ai >> 1);
+       int halfcq = (aq >> 1);
+
+       switch(Demod.state) {
+               case DEMOD_UNSYNCD:
+                       
+                       CHECK_FOR_SUBCARRIER()
+                       
+                       if(v > SUBCARRIER_DETECT_THRESHOLD) {   // subcarrier detected
+                               Demod.state = DEMOD_PHASE_REF_TRAINING;
+                               Demod.sumI = ci;
+                               Demod.sumQ = cq;
+                               Demod.posCount = 1;
+                       }
+                       break;
+
+               case DEMOD_PHASE_REF_TRAINING:
+                       if(Demod.posCount < 8) {
+                       
+                               CHECK_FOR_SUBCARRIER()
+                               
+                               if (v > SUBCARRIER_DETECT_THRESHOLD) {
+                                       // set the reference phase (will code a logic '1') by averaging over 32 1/fs.
+                                       // note: synchronization time > 80 1/fs
+                                       Demod.sumI += ci;
+                                       Demod.sumQ += cq;
+                                       ++Demod.posCount;
+                               } else {
+                                       // subcarrier lost
+                                       Demod.state = DEMOD_UNSYNCD;
+                               }
+                       } else {
+                               Demod.state = DEMOD_AWAITING_FALLING_EDGE_OF_SOF;
+                       }
+                       break;
+
+               case DEMOD_AWAITING_FALLING_EDGE_OF_SOF:
+
+                       MAKE_SOFT_DECISION()
+
+                       //Dbprintf("ICE: %d %d %d %d %d", v, Demod.sumI, Demod.sumQ, ci, cq );
+                       // logic '0' detected
+                       if (v <= 0) {
+                               
+                               Demod.state = DEMOD_GOT_FALLING_EDGE_OF_SOF;
+                       
+                               // start of SOF sequence
+                               Demod.posCount = 0;
+                       } else {
+                               // maximum length of TR1 = 200 1/fs
+                               if(Demod.posCount > 25*2) Demod.state = DEMOD_UNSYNCD;
+                       }
+                       ++Demod.posCount;
+                       break;
+
+               case DEMOD_GOT_FALLING_EDGE_OF_SOF:
+                       ++Demod.posCount;
+
+                       MAKE_SOFT_DECISION()
+
+                       if(v > 0) {
+                               // low phase of SOF too short (< 9 etu). Note: spec is >= 10, but FPGA tends to "smear" edges
+                               if(Demod.posCount < 10*2) { 
+                                       Demod.state = DEMOD_UNSYNCD;
+                               } else {
+                                       LED_C_ON(); // Got SOF
+                                       Demod.state = DEMOD_AWAITING_START_BIT;
+                                       Demod.posCount = 0;
+                                       Demod.len = 0;
+                               }
+                       } else {
+                               // low phase of SOF too long (> 12 etu)
+                               if(Demod.posCount > 13*2) { 
+                                       Demod.state = DEMOD_UNSYNCD;
+                                       LED_C_OFF();
+                               }
+                       }
+                       break;
+
+               case DEMOD_AWAITING_START_BIT:
+                       ++Demod.posCount;
+                       
+                       MAKE_SOFT_DECISION()
+                       
+                       if(v > 0) {
+                               // max 19us between characters = 16 1/fs, max 3 etu after low phase of SOF = 24 1/fs
+                               if(Demod.posCount > 3*2) { 
+                                       Demod.state = DEMOD_UNSYNCD;
+                                       LED_C_OFF();
+                               }
+                       } else {
+                               // start bit detected
+                               Demod.bitCount = 0;
+                               Demod.posCount = 1;                             // this was the first half
+                               Demod.thisBit = v;
+                               Demod.shiftReg = 0;
+                               Demod.state = DEMOD_RECEIVING_DATA;
+                       }
+                       break;
+
+               case DEMOD_RECEIVING_DATA:
+               
+                       MAKE_SOFT_DECISION()
+                       
+                       if(Demod.posCount == 0) {
+                               // first half of bit
+                               Demod.thisBit = v;
+                               Demod.posCount = 1;
+                       } else {
+                               // second half of bit
+                               Demod.thisBit += v;
+                               Demod.shiftReg >>= 1;
+                               // logic '1'
+                               if(Demod.thisBit > 0) 
+                                       Demod.shiftReg |= 0x200;
+                               
+                               ++Demod.bitCount;
+                               
+                               if(Demod.bitCount == 10) {
+                                       
+                                       uint16_t s = Demod.shiftReg;
+                                       
+                                       if((s & 0x200) && !(s & 0x001)) { 
+                                               // stop bit == '1', start bit == '0'
+                                               uint8_t b = (s >> 1);
+                                               Demod.output[Demod.len] = b;
+                                               ++Demod.len;
+                                               Demod.state = DEMOD_AWAITING_START_BIT;
+                                       } else {
+                                               Demod.state = DEMOD_UNSYNCD;
+                                               LED_C_OFF();
+                                               
+                                               if(s == 0x000) {
+                                                       // This is EOF (start, stop and all data bits == '0'
+                                                       return TRUE;
+                                               }
+                                       }
+                               }
+                               Demod.posCount = 0;
+                       }
+                       break;
+
+               default:
+                       Demod.state = DEMOD_UNSYNCD;
+                       LED_C_OFF();
+                       break;
+       }
+       return FALSE;
+}
+
+// Clear out the state of the "UART" that receives from the tag.
+static void DemodReset() {
+       Demod.len = 0;
+       Demod.state = DEMOD_UNSYNCD;
+       Demod.posCount = 0;
+       Demod.sumI = 0;
+       Demod.sumQ = 0;
+       Demod.bitCount = 0;
+       Demod.thisBit = 0;
+       Demod.shiftReg = 0;
+       memset(Demod.output, 0x00, MAX_FRAME_SIZE);
+}
+
+static void DemodInit(uint8_t *data) {
+       Demod.output = data;
+       DemodReset();
+}
+
+/*
+ *  Demodulate the samples we received from the tag, also log to tracebuffer
+ *  quiet: set to 'TRUE' to disable debug output
+ */
+ #define LEGIC_DMA_BUFFER_SIZE 256
+static void GetSamplesForLegicDemod(int n, bool quiet)
+{
+       int max = 0;
+       bool gotFrame = FALSE;
+       int lastRxCounter = LEGIC_DMA_BUFFER_SIZE;
+       int     ci, cq, samples = 0;
+
+       BigBuf_free();
+
+       // And put the FPGA in the appropriate mode
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_QUARTER_FREQ);
+
+       // The response (tag -> reader) that we're receiving.
+       // Set up the demodulator for tag -> reader responses.
+       DemodInit(BigBuf_malloc(MAX_FRAME_SIZE));
+       
+       // The DMA buffer, used to stream samples from the FPGA
+       int8_t *dmaBuf = (int8_t*) BigBuf_malloc(LEGIC_DMA_BUFFER_SIZE);
+       int8_t *upTo = dmaBuf;
+
+       // Setup and start DMA.
+       if ( !FpgaSetupSscDma((uint8_t*) dmaBuf, LEGIC_DMA_BUFFER_SIZE) ){
+               if (MF_DBGLEVEL > 1) Dbprintf("FpgaSetupSscDma failed. Exiting"); 
+               return;
+       }       
+
+       // Signal field is ON with the appropriate LED:
+       LED_D_ON();
+       for(;;) {
+               int behindBy = lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR;
+               if(behindBy > max) max = behindBy;
+
+               while(((lastRxCounter-AT91C_BASE_PDC_SSC->PDC_RCR) & (LEGIC_DMA_BUFFER_SIZE-1)) > 2) {
+                       ci = upTo[0];
+                       cq = upTo[1];
+                       upTo += 2;
+                       if(upTo >= dmaBuf + LEGIC_DMA_BUFFER_SIZE) {
+                               upTo = dmaBuf;
+                               AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) upTo;
+                               AT91C_BASE_PDC_SSC->PDC_RNCR = LEGIC_DMA_BUFFER_SIZE;
+                       }
+                       lastRxCounter -= 2;
+                       if(lastRxCounter <= 0)
+                               lastRxCounter = LEGIC_DMA_BUFFER_SIZE;
+
+                       samples += 2;
+
+                       gotFrame = HandleLegicSamplesDemod(ci , cq );
+                       if ( gotFrame )
+                               break;
+               }
+
+               if(samples > n || gotFrame)
+                       break;
+       }
+
+       FpgaDisableSscDma();
+
+       if (!quiet && Demod.len == 0) {
+               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
+               );
+       }
+
+       //Tracing
+       if (Demod.len > 0) {
+               uint8_t parity[MAX_PARITY_SIZE] = {0x00};
+               LogTrace(Demod.output, Demod.len, 0, 0, parity, FALSE);
+       }
+}
+//-----------------------------------------------------------------------------
+// Transmit the command (to the tag) that was placed in ToSend[].
+//-----------------------------------------------------------------------------
+static void TransmitForLegic(void)
+{
+       int c;
+
+       FpgaSetupSsc();
+       
+       while(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY))
+               AT91C_BASE_SSC->SSC_THR = 0xff;
+
+       // Signal field is ON with the appropriate Red LED
+       LED_D_ON();
+
+       // Signal we are transmitting with the Green LED
+       LED_B_ON();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
+       
+       for(c = 0; c < 10;) {
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                       AT91C_BASE_SSC->SSC_THR = 0xff;
+                       c++;
+               }
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+                       volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
+                       (void)r;
+               }
+               WDT_HIT();
+       }
+
+       c = 0;
+       for(;;) {
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                       AT91C_BASE_SSC->SSC_THR = ToSend[c];
+                       legic_prng_forward(1); // forward the lfsr 
+                       c++;
+                       if(c >= ToSendMax) {
+                               break;
+                       }
+               }
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+                       volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
+                       (void)r;
+               }
+               WDT_HIT();
+       }
+       LED_B_OFF();
+}
+
+
+//-----------------------------------------------------------------------------
+// Code a layer 2 command (string of octets, including CRC) into ToSend[],
+// so that it is ready to transmit to the tag using TransmitForLegic().
+//-----------------------------------------------------------------------------
+static void CodeLegicBitsAsReader(const uint8_t *cmd, int bits)
+{
+       int i, j;
+       uint8_t b;
+
+       ToSendReset();
+
+       // Send SOF
+       for(i = 0; i < 7; i++) {
+               ToSendStuffBit(1);
+       }
+
+       for(i = 0; i < bits; i++) {
+               // Start bit
+               ToSendStuffBit(0);
+
+               // Data bits
+               b = cmd[i];
+               for(j = 0; j < 8; j++) {
+                       if(b & 1) {
+                               ToSendStuffBit(1);
+                       } else {
+                               ToSendStuffBit(0);
+                       }
+                       b >>= 1;
+               }
+       }
+       
+       // Convert from last character reference to length
+       ++ToSendMax;
+}
+
+/**
+  Convenience function to encode, transmit and trace Legic comms
+  **/
+static void CodeAndTransmitLegicAsReader(const uint8_t *cmd, int bits)
+{
+       CodeLegicBitsAsReader(cmd, bits);
+       TransmitForLegic();
+       if (tracing) {
+               uint8_t parity[1] = {0x00};
+               LogTrace(cmd, bits, 0, 0, parity, TRUE);
+       }
+}
+
+int ice_legic_select_card()
+{
+       //int cmd_size=0, card_size=0;
+       uint8_t wakeup[] = { 0x7F};
+       uint8_t getid[] = {0x19};
+
+       legic_prng_init(SESSION_IV);
+
+       // first, wake up the tag, 7bits
+       CodeAndTransmitLegicAsReader(wakeup, 7);
+
+       GetSamplesForLegicDemod(1000, TRUE);
+
+       // frame_clean(&current_frame);
+       //frame_receive_rwd(&current_frame, 6, 1);
+
+       legic_prng_forward(1); /* we wait anyways */
+       
+       //while(timer->TC_CV < 387) ; /* ~ 258us */
+       //frame_send_rwd(0x19, 6);
+       CodeAndTransmitLegicAsReader(getid, sizeof(getid));
+       GetSamplesForLegicDemod(1000, TRUE);
+
+       //if (Demod.len < 14) return 2; 
+       Dbprintf("CARD TYPE: %02x  LEN: %d", Demod.output[0], Demod.len);
+
+       switch(Demod.output[0]) {
+               case 0x1d:
+                       DbpString("MIM 256 card found");
+            // cmd_size = 9;
+                       // card_size = 256;
+                       break;
+               case 0x3d:
+                       DbpString("MIM 1024 card found");
+            // cmd_size = 11;
+                       // card_size = 1024;
+                       break;
+               default:
+                       return -1;
+       }
+       
+       // if(bytes == -1)
+               // bytes = card_size;
+
+       // if(bytes + offset >= card_size)
+               // bytes = card_size - offset;  
+       
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       set_tracing(FALSE);
+       return 1;
+}
+
+// Set up LEGIC communication
+void ice_legic_setup() {
+
+       // standard things.
+       FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+       BigBuf_free(); BigBuf_Clear_ext(false);
+       clear_trace();
+       set_tracing(TRUE);
+       DemodReset();
+       UartReset();
+       
+       // Set up the synchronous serial port
+       FpgaSetupSsc();
+
+       // connect Demodulated Signal to ADC:
+       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+
+       // Signal field is on with the appropriate LED
+    LED_D_ON();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
+       SpinDelay(200);
+       // Start the timer
+       //StartCountSspClk();
+       
+       // initalize CRC 
+       crc_init(&legic_crc, 4, 0x19 >> 1, 0x5, 0);
+
+       // initalize prng
+       legic_prng_init(0);
+}
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