]> cvs.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/iso14443a.c
fix 'hf iclass replay' (#888)
[proxmark3-svn] / armsrc / iso14443a.c
index 5a27e06b6193b73737b17a9ae40f2ec1e224c9ec..0ca9873bb4e63224d8a4d26f8bd14650ba0091b1 100644 (file)
 
 #include "iso14443a.h"
 
+#include <stdio.h>
+#include <string.h>
 #include "proxmark3.h"
 #include "apps.h"
 #include "util.h"
-#include "string.h"
 #include "cmd.h"
 #include "iso14443crc.h"
 #include "crapto1/crapto1.h"
@@ -24,6 +25,7 @@
 #include "BigBuf.h"
 #include "protocols.h"
 #include "parity.h"
+#include "fpgaloader.h"
 
 typedef struct {
        enum {
@@ -66,7 +68,7 @@ typedef struct {
                // DROP_FIRST_HALF,
                } state;
        uint16_t shiftReg;
-       int16_t  bitCount;
+       int16_t  bitCount;
        uint16_t len;
        uint16_t byteCntMax;
        uint16_t posCnt;
@@ -75,11 +77,13 @@ typedef struct {
        uint8_t  parityLen;
        uint32_t fourBits;
        uint32_t startTime, endTime;
-    uint8_t *output;
+       uint8_t *output;
        uint8_t *parity;
 } tUart;
 
 static uint32_t iso14a_timeout;
+#define MAX_ISO14A_TIMEOUT 524288
+
 int rsamples = 0;
 uint8_t trigger = 0;
 // the block number for the ISO14443-4 PCB
@@ -90,8 +94,8 @@ static uint8_t iso14_pcb_blocknum = 0;
 //
 // minimum time between the start bits of consecutive transfers from reader to tag: 7000 carrier (13.56Mhz) cycles
 #define REQUEST_GUARD_TIME (7000/16 + 1)
-// minimum time between last modulation of tag and next start bit from reader to tag: 1172 carrier cycles 
-#define FRAME_DELAY_TIME_PICC_TO_PCD (1172/16 + 1) 
+// minimum time between last modulation of tag and next start bit from reader to tag: 1172 carrier cycles
+#define FRAME_DELAY_TIME_PICC_TO_PCD (1172/16 + 1)
 // bool LastCommandWasRequest = false;
 
 //
@@ -103,8 +107,8 @@ static uint8_t iso14_pcb_blocknum = 0;
 // 8 ticks until bit_to_arm is assigned from curbit
 // 8*16 ticks for the transfer from FPGA to ARM
 // 4*16 ticks until we measure the time
-// - 8*16 ticks because we measure the time of the previous transfer 
-#define DELAY_AIR2ARM_AS_READER (3 + 16 + 8 + 8*16 + 4*16 - 8*16) 
+// - 8*16 ticks because we measure the time of the previous transfer
+#define DELAY_AIR2ARM_AS_READER (3 + 16 + 8 + 8*16 + 4*16 - 8*16)
 
 // When the PM acts as a reader and is sending, it takes
 // 4*16 ticks until we can write data to the sending hold register
@@ -121,10 +125,10 @@ static uint8_t iso14_pcb_blocknum = 0;
 // 8 ticks until the SSC samples the first data
 // 7*16 ticks to complete the transfer from FPGA to ARM
 // 8 ticks until the next ssp_clk rising edge
-// 4*16 ticks until we measure the time 
-// - 8*16 ticks because we measure the time of the previous transfer 
+// 4*16 ticks until we measure the time
+// - 8*16 ticks because we measure the time of the previous transfer
 #define DELAY_AIR2ARM_AS_TAG (2 + 3 + 8 + 8 + 7*16 + 8 + 4*16 - 8*16)
+
 // The FPGA will report its internal sending delay in
 uint16_t FpgaSendQueueDelay;
 // the 5 first bits are the number of bits buffered in mod_sig_buf
@@ -146,16 +150,16 @@ uint16_t FpgaSendQueueDelay;
 // 8 ticks (on average) until the result is stored in to_arm
 // + the delays in transferring data - which is the same for
 // sniffing reader and tag data and therefore not relevant
-#define DELAY_TAG_AIR2ARM_AS_SNIFFER (3 + 14 + 8) 
+#define DELAY_TAG_AIR2ARM_AS_SNIFFER (3 + 14 + 8)
+
 // When the PM acts as sniffer and is receiving reader data, it takes
-// 2 ticks delay in analogue RF receiver (for the falling edge of the 
+// 2 ticks delay in analogue RF receiver (for the falling edge of the
 // start bit, which marks the start of the communication)
 // 3 ticks A/D conversion
 // 8 ticks on average until the data is stored in to_arm.
 // + the delays in transferring data - which is the same for
 // sniffing reader and tag data and therefore not relevant
-#define DELAY_READER_AIR2ARM_AS_SNIFFER (2 + 3 + 8) 
+#define DELAY_READER_AIR2ARM_AS_SNIFFER (2 + 3 + 8)
 
 //variables used for timing purposes:
 //these are in ssp_clk cycles:
@@ -173,12 +177,12 @@ static uint32_t LastProxToAirDuration;
 // Sequence X: 00001100 drop after half a period
 // Sequence Y: 00000000 no drop
 // Sequence Z: 11000000 drop at start
-#define        SEC_D 0xf0
-#define        SEC_E 0x0f
-#define        SEC_F 0x00
-#define        SEC_X 0x0c
-#define        SEC_Y 0x00
-#define        SEC_Z 0xc0
+#define SEC_D 0xf0
+#define SEC_E 0x0f
+#define SEC_F 0x00
+#define SEC_X 0x0c
+#define SEC_Y 0x00
+#define SEC_Z 0xc0
 
 void iso14a_set_trigger(bool enable) {
        trigger = enable;
@@ -186,33 +190,16 @@ void iso14a_set_trigger(bool enable) {
 
 
 void iso14a_set_timeout(uint32_t timeout) {
-       iso14a_timeout = timeout;
-       if(MF_DBGLEVEL >= 3) Dbprintf("ISO14443A Timeout set to %ld (%dms)", iso14a_timeout, iso14a_timeout / 106);
+       // adjust timeout by FPGA delays and 2 additional ssp_frames to detect SOF
+       iso14a_timeout = timeout + (DELAY_AIR2ARM_AS_READER + DELAY_ARM2AIR_AS_READER)/(16*8) + 2;
+       if(MF_DBGLEVEL >= 3) Dbprintf("ISO14443A Timeout set to %ld (%dms)", timeout, timeout / 106);
 }
 
 
-static void iso14a_set_ATS_timeout(uint8_t *ats) {
-
-       uint8_t tb1;
-       uint8_t fwi; 
-       uint32_t fwt;
-       
-       if (ats[0] > 1) {                                                       // there is a format byte T0
-               if ((ats[1] & 0x20) == 0x20) {                  // there is an interface byte TB(1)
-                       if ((ats[1] & 0x10) == 0x10) {          // there is an interface byte TA(1) preceding TB(1)
-                               tb1 = ats[3];
-                       } else {
-                               tb1 = ats[2];
-                       }
-                       fwi = (tb1 & 0xf0) >> 4;                        // frame waiting indicator (FWI)
-                       fwt = 256 * 16 * (1 << fwi);            // frame waiting time (FWT) in 1/fc
-                       
-                       iso14a_set_timeout(fwt/(8*16));
-               }
-       }
+uint32_t iso14a_get_timeout(void) {
+       return iso14a_timeout - (DELAY_AIR2ARM_AS_READER + DELAY_ARM2AIR_AS_READER)/(16*8) - 2;
 }
 
-
 //-----------------------------------------------------------------------------
 // Generate the parity value for a byte sequence
 //
@@ -227,8 +214,8 @@ void GetParity(const uint8_t *pbtCmd, uint16_t iLen, uint8_t *par)
                // Generate the parity bits
                parityBits |= ((oddparity8(pbtCmd[i])) << (7-paritybit_cnt));
                if (paritybit_cnt == 7) {
-                       par[paritybyte_cnt] = parityBits;       // save 8 Bits parity
-                       parityBits = 0;                                         // and advance to next Parity Byte
+                       par[paritybyte_cnt] = parityBits;   // save 8 Bits parity
+                       parityBits = 0;                     // and advance to next Parity Byte
                        paritybyte_cnt++;
                        paritybit_cnt = 0;
                } else {
@@ -238,7 +225,7 @@ void GetParity(const uint8_t *pbtCmd, uint16_t iLen, uint8_t *par)
 
        // save remaining parity bits
        par[paritybyte_cnt] = parityBits;
-       
+
 }
 
 void AppendCrc14443a(uint8_t* data, int len)
@@ -257,14 +244,14 @@ static void AppendCrc14443b(uint8_t* data, int len)
 //=============================================================================
 // Basics:
 // This decoder is used when the PM3 acts as a tag.
-// The reader will generate "pauses" by temporarily switching of the field. 
-// At the PM3 antenna we will therefore measure a modulated antenna voltage. 
+// The reader will generate "pauses" by temporarily switching of the field.
+// At the PM3 antenna we will therefore measure a modulated antenna voltage.
 // The FPGA does a comparison with a threshold and would deliver e.g.:
 // ........  1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1  .......
 // The Miller decoder needs to identify the following sequences:
-// 2 (or 3) ticks pause followed by 6 (or 5) ticks unmodulated:        pause at beginning - Sequence Z ("start of communication" or a "0")
-// 8 ticks without a modulation:                                                                       no pause - Sequence Y (a "0" or "end of communication" or "no information")
-// 4 ticks unmodulated followed by 2 (or 3) ticks pause:                       pause in second half - Sequence X (a "1")
+// 2 (or 3) ticks pause followed by 6 (or 5) ticks unmodulated:     pause at beginning - Sequence Z ("start of communication" or a "0")
+// 8 ticks without a modulation:                                    no pause - Sequence Y (a "0" or "end of communication" or "no information")
+// 4 ticks unmodulated followed by 2 (or 3) ticks pause:            pause in second half - Sequence X (a "1")
 // Note 1: the bitstream may start at any time. We therefore need to sync.
 // Note 2: the interpretation of Sequence Y and Z depends on the preceding sequence.
 //-----------------------------------------------------------------------------
@@ -287,19 +274,19 @@ static void UartReset()
 {
        Uart.state = STATE_UNSYNCD;
        Uart.bitCount = 0;
-       Uart.len = 0;                                           // number of decoded data bytes
-       Uart.parityLen = 0;                                     // number of decoded parity bytes
-       Uart.shiftReg = 0;                                      // shiftreg to hold decoded data bits
-       Uart.parityBits = 0;                            // holds 8 parity bits
-       Uart.startTime = 0;
-       Uart.endTime = 0;
+       Uart.len = 0;                       // number of decoded data bytes
+       Uart.parityLen = 0;                 // number of decoded parity bytes
+       Uart.shiftReg = 0;                  // shiftreg to hold decoded data bits
+       Uart.parityBits = 0;                // holds 8 parity bits
 }
 
 static void UartInit(uint8_t *data, uint8_t *parity)
 {
        Uart.output = data;
        Uart.parity = parity;
-       Uart.fourBits = 0x00000000;                     // clear the buffer for 4 Bits
+       Uart.fourBits = 0x00000000;         // clear the buffer for 4 Bits
+       Uart.startTime = 0;
+       Uart.endTime = 0;
        UartReset();
 }
 
@@ -308,17 +295,17 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
 {
 
        Uart.fourBits = (Uart.fourBits << 8) | bit;
-       
-       if (Uart.state == STATE_UNSYNCD) {                                                                                      // not yet synced
-       
-               Uart.syncBit = 9999;                                                                                                    // not set
+
+       if (Uart.state == STATE_UNSYNCD) {                                          // not yet synced
+
+               Uart.syncBit = 9999;                                                    // not set
                // The start bit is one ore more Sequence Y followed by a Sequence Z (... 11111111 00x11111). We need to distinguish from
                // Sequence X followed by Sequence Y followed by Sequence Z (111100x1 11111111 00x11111)
-               // we therefore look for a ...xx11111111111100x11111xxxxxx... pattern 
+               // we therefore look for a ...xx11111111111100x11111xxxxxx... pattern
                // (12 '1's followed by 2 '0's, eventually followed by another '0', followed by 5 '1's)
-               #define ISO14443A_STARTBIT_MASK         0x07FFEF80                                                      // mask is    00000111 11111111 11101111 10000000
-               #define ISO14443A_STARTBIT_PATTERN      0x07FF8F80                                                      // pattern is 00000111 11111111 10001111 10000000
-               if              ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 0)) == ISO14443A_STARTBIT_PATTERN >> 0) Uart.syncBit = 7;
+               #define ISO14443A_STARTBIT_MASK     0x07FFEF80                          // mask is    00000111 11111111 11101111 10000000
+               #define ISO14443A_STARTBIT_PATTERN  0x07FF8F80                          // pattern is 00000111 11111111 10001111 10000000
+               if      ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 0)) == ISO14443A_STARTBIT_PATTERN >> 0) Uart.syncBit = 7;
                else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 1)) == ISO14443A_STARTBIT_PATTERN >> 1) Uart.syncBit = 6;
                else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 2)) == ISO14443A_STARTBIT_PATTERN >> 2) Uart.syncBit = 5;
                else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 3)) == ISO14443A_STARTBIT_PATTERN >> 3) Uart.syncBit = 4;
@@ -327,102 +314,107 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
                else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 6)) == ISO14443A_STARTBIT_PATTERN >> 6) Uart.syncBit = 1;
                else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 7)) == ISO14443A_STARTBIT_PATTERN >> 7) Uart.syncBit = 0;
 
-               if (Uart.syncBit != 9999) {                                                                                             // found a sync bit
+               if (Uart.syncBit != 9999) {                                             // found a sync bit
                        Uart.startTime = non_real_time?non_real_time:(GetCountSspClk() & 0xfffffff8);
                        Uart.startTime -= Uart.syncBit;
                        Uart.endTime = Uart.startTime;
                        Uart.state = STATE_START_OF_COMMUNICATION;
+                       LED_B_ON();
                }
 
        } else {
 
-               if (IsMillerModulationNibble1(Uart.fourBits >> Uart.syncBit)) {                 
-                       if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) {         // Modulation in both halves - error
+               if (IsMillerModulationNibble1(Uart.fourBits >> Uart.syncBit)) {
+                       if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) {     // Modulation in both halves - error
+                               LED_B_OFF();
                                UartReset();
-                       } else {                                                                                                                        // Modulation in first half = Sequence Z = logic "0"
-                               if (Uart.state == STATE_MILLER_X) {                                                             // error - must not follow after X
+                       } else {                                                            // Modulation in first half = Sequence Z = logic "0"
+                               if (Uart.state == STATE_MILLER_X) {                             // error - must not follow after X
+                                       LED_B_OFF();
                                        UartReset();
                                } else {
                                        Uart.bitCount++;
-                                       Uart.shiftReg = (Uart.shiftReg >> 1);                                           // add a 0 to the shiftreg
+                                       Uart.shiftReg = (Uart.shiftReg >> 1);                       // add a 0 to the shiftreg
                                        Uart.state = STATE_MILLER_Z;
                                        Uart.endTime = Uart.startTime + 8*(9*Uart.len + Uart.bitCount + 1) - 6;
-                                       if(Uart.bitCount >= 9) {                                                                        // if we decoded a full byte (including parity)
+                                       if(Uart.bitCount >= 9) {                                    // if we decoded a full byte (including parity)
                                                Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);
-                                               Uart.parityBits <<= 1;                                                                  // make room for the parity bit
-                                               Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);               // store parity bit
+                                               Uart.parityBits <<= 1;                                  // make room for the parity bit
+                                               Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);       // store parity bit
                                                Uart.bitCount = 0;
                                                Uart.shiftReg = 0;
-                                               if((Uart.len&0x0007) == 0) {                                                    // every 8 data bytes
-                                                       Uart.parity[Uart.parityLen++] = Uart.parityBits;        // store 8 parity bits
+                                               if((Uart.len&0x0007) == 0) {                            // every 8 data bytes
+                                                       Uart.parity[Uart.parityLen++] = Uart.parityBits;    // store 8 parity bits
                                                        Uart.parityBits = 0;
                                                }
                                        }
                                }
                        }
                } else {
-                       if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) {         // Modulation second half = Sequence X = logic "1"
+                       if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) {     // Modulation second half = Sequence X = logic "1"
                                Uart.bitCount++;
-                               Uart.shiftReg = (Uart.shiftReg >> 1) | 0x100;                                   // add a 1 to the shiftreg
+                               Uart.shiftReg = (Uart.shiftReg >> 1) | 0x100;                   // add a 1 to the shiftreg
                                Uart.state = STATE_MILLER_X;
                                Uart.endTime = Uart.startTime + 8*(9*Uart.len + Uart.bitCount + 1) - 2;
-                               if(Uart.bitCount >= 9) {                                                                                // if we decoded a full byte (including parity)
+                               if(Uart.bitCount >= 9) {                                        // if we decoded a full byte (including parity)
                                        Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);
-                                       Uart.parityBits <<= 1;                                                                          // make room for the new parity bit
-                                       Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);                       // store parity bit
+                                       Uart.parityBits <<= 1;                                      // make room for the new parity bit
+                                       Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);           // store parity bit
                                        Uart.bitCount = 0;
                                        Uart.shiftReg = 0;
-                                       if ((Uart.len&0x0007) == 0) {                                                           // every 8 data bytes
-                                               Uart.parity[Uart.parityLen++] = Uart.parityBits;                // store 8 parity bits
+                                       if ((Uart.len&0x0007) == 0) {                               // every 8 data bytes
+                                               Uart.parity[Uart.parityLen++] = Uart.parityBits;        // store 8 parity bits
                                                Uart.parityBits = 0;
                                        }
                                }
-                       } else {                                                                                                                        // no modulation in both halves - Sequence Y
-                               if (Uart.state == STATE_MILLER_Z || Uart.state == STATE_MILLER_Y) {     // Y after logic "0" - End of Communication
+                       } else {                                                            // no modulation in both halves - Sequence Y
+                               if (Uart.state == STATE_MILLER_Z || Uart.state == STATE_MILLER_Y) { // Y after logic "0" - End of Communication
+                                       LED_B_OFF();
                                        Uart.state = STATE_UNSYNCD;
-                                       Uart.bitCount--;                                                                                        // last "0" was part of EOC sequence
-                                       Uart.shiftReg <<= 1;                                                                            // drop it
-                                       if(Uart.bitCount > 0) {                                                                         // if we decoded some bits
-                                               Uart.shiftReg >>= (9 - Uart.bitCount);                                  // right align them
-                                               Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);               // add last byte to the output
-                                               Uart.parityBits <<= 1;                                                                  // add a (void) parity bit
-                                               Uart.parityBits <<= (8 - (Uart.len&0x0007));                    // left align parity bits
-                                               Uart.parity[Uart.parityLen++] = Uart.parityBits;                // and store it
+                                       Uart.bitCount--;                                            // last "0" was part of EOC sequence
+                                       Uart.shiftReg <<= 1;                                        // drop it
+                                       if(Uart.bitCount > 0) {                                     // if we decoded some bits
+                                               Uart.shiftReg >>= (9 - Uart.bitCount);                  // right align them
+                                               Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);       // add last byte to the output
+                                               Uart.parityBits <<= 1;                                  // add a (void) parity bit
+                                               Uart.parityBits <<= (8 - (Uart.len&0x0007));            // left align parity bits
+                                               Uart.parity[Uart.parityLen++] = Uart.parityBits;        // and store it
                                                return true;
-                                       } else if (Uart.len & 0x0007) {                                                         // there are some parity bits to store
-                                               Uart.parityBits <<= (8 - (Uart.len&0x0007));                    // left align remaining parity bits
-                                               Uart.parity[Uart.parityLen++] = Uart.parityBits;                // and store them
+                                       } else if (Uart.len & 0x0007) {                             // there are some parity bits to store
+                                               Uart.parityBits <<= (8 - (Uart.len&0x0007));            // left align remaining parity bits
+                                               Uart.parity[Uart.parityLen++] = Uart.parityBits;        // and store them
                                        }
                                        if (Uart.len) {
-                                               return true;                                                                                    // we are finished with decoding the raw data sequence
+                                               return true;                                            // we are finished with decoding the raw data sequence
                                        } else {
-                                               UartReset();                                                                                    // Nothing received - start over
+                                               UartReset();                                            // Nothing received - start over
                                        }
                                }
-                               if (Uart.state == STATE_START_OF_COMMUNICATION) {                               // error - must not follow directly after SOC
+                               if (Uart.state == STATE_START_OF_COMMUNICATION) {               // error - must not follow directly after SOC
+                                       LED_B_OFF();
                                        UartReset();
-                               } else {                                                                                                                // a logic "0"
+                               } else {                                                        // a logic "0"
                                        Uart.bitCount++;
-                                       Uart.shiftReg = (Uart.shiftReg >> 1);                                           // add a 0 to the shiftreg
+                                       Uart.shiftReg = (Uart.shiftReg >> 1);                       // add a 0 to the shiftreg
                                        Uart.state = STATE_MILLER_Y;
-                                       if(Uart.bitCount >= 9) {                                                                        // if we decoded a full byte (including parity)
+                                       if(Uart.bitCount >= 9) {                                    // if we decoded a full byte (including parity)
                                                Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);
-                                               Uart.parityBits <<= 1;                                                                  // make room for the parity bit
-                                               Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);               // store parity bit
+                                               Uart.parityBits <<= 1;                                  // make room for the parity bit
+                                               Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);       // store parity bit
                                                Uart.bitCount = 0;
                                                Uart.shiftReg = 0;
-                                               if ((Uart.len&0x0007) == 0) {                                                   // every 8 data bytes
-                                                       Uart.parity[Uart.parityLen++] = Uart.parityBits;        // store 8 parity bits
+                                               if ((Uart.len&0x0007) == 0) {                           // every 8 data bytes
+                                                       Uart.parity[Uart.parityLen++] = Uart.parityBits;    // store 8 parity bits
                                                        Uart.parityBits = 0;
                                                }
                                        }
                                }
                        }
                }
-                       
-       } 
 
-    return false;      // not finished yet, need more data
+       }
+
+       return false;   // not finished yet, need more data
 }
 
 
@@ -436,10 +428,10 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
 // at the reader antenna will be modulated as well. The FPGA detects the modulation for us and would deliver e.g. the following:
 // ........ 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .......
 // The Manchester decoder needs to identify the following sequences:
-// 4 ticks modulated followed by 4 ticks unmodulated:  Sequence D = 1 (also used as "start of communication")
-// 4 ticks unmodulated followed by 4 ticks modulated:  Sequence E = 0
-// 8 ticks unmodulated:                                                                        Sequence F = end of communication
-// 8 ticks modulated:                                                                  A collision. Save the collision position and treat as Sequence D
+// 4 ticks modulated followed by 4 ticks unmodulated:   Sequence D = 1 (also used as "start of communication")
+// 4 ticks unmodulated followed by 4 ticks modulated:   Sequence E = 0
+// 8 ticks unmodulated:                                 Sequence F = end of communication
+// 8 ticks modulated:                                   A collision. Save the collision position and treat as Sequence D
 // Note 1: the bitstream may start at any time. We therefore need to sync.
 // Note 2: parameter offset is used to determine the position of the parity bits (required for the anticollision command only)
 static tDemod Demod;
@@ -458,12 +450,12 @@ const bool Mod_Manchester_LUT[] = {
 static void DemodReset()
 {
        Demod.state = DEMOD_UNSYNCD;
-       Demod.len = 0;                                          // number of decoded data bytes
+       Demod.len = 0;                      // number of decoded data bytes
        Demod.parityLen = 0;
-       Demod.shiftReg = 0;                                     // shiftreg to hold decoded data bits
-       Demod.parityBits = 0;                           // 
-       Demod.collisionPos = 0;                         // Position of collision bit
-       Demod.twoBits = 0xffff;                         // buffer for 2 Bits
+       Demod.shiftReg = 0;                 // shiftreg to hold decoded data bits
+       Demod.parityBits = 0;               //
+       Demod.collisionPos = 0;             // Position of collision bit
+       Demod.twoBits = 0xffff;             // buffer for 2 Bits
        Demod.highCnt = 0;
        Demod.startTime = 0;
        Demod.endTime = 0;
@@ -481,18 +473,18 @@ static RAMFUNC int ManchesterDecoding(uint8_t bit, uint16_t offset, uint32_t non
 {
 
        Demod.twoBits = (Demod.twoBits << 8) | bit;
-       
+
        if (Demod.state == DEMOD_UNSYNCD) {
 
-               if (Demod.highCnt < 2) {                                                                                        // wait for a stable unmodulated signal
+               if (Demod.highCnt < 2) {                                            // wait for a stable unmodulated signal
                        if (Demod.twoBits == 0x0000) {
                                Demod.highCnt++;
                        } else {
                                Demod.highCnt = 0;
                        }
                } else {
-                       Demod.syncBit = 0xFFFF;                 // not set
-                       if              ((Demod.twoBits & 0x7700) == 0x7000) Demod.syncBit = 7; 
+                       Demod.syncBit = 0xFFFF;         // not set
+                       if      ((Demod.twoBits & 0x7700) == 0x7000) Demod.syncBit = 7;
                        else if ((Demod.twoBits & 0x3B80) == 0x3800) Demod.syncBit = 6;
                        else if ((Demod.twoBits & 0x1DC0) == 0x1C00) Demod.syncBit = 5;
                        else if ((Demod.twoBits & 0x0EE0) == 0x0E00) Demod.syncBit = 4;
@@ -503,72 +495,74 @@ static RAMFUNC int ManchesterDecoding(uint8_t bit, uint16_t offset, uint32_t non
                        if (Demod.syncBit != 0xFFFF) {
                                Demod.startTime = non_real_time?non_real_time:(GetCountSspClk() & 0xfffffff8);
                                Demod.startTime -= Demod.syncBit;
-                               Demod.bitCount = offset;                        // number of decoded data bits
+                               Demod.bitCount = offset;            // number of decoded data bits
                                Demod.state = DEMOD_MANCHESTER_DATA;
+                               LED_C_ON();
                        }
                }
 
        } else {
 
-               if (IsManchesterModulationNibble1(Demod.twoBits >> Demod.syncBit)) {            // modulation in first half
-                       if (IsManchesterModulationNibble2(Demod.twoBits >> Demod.syncBit)) {    // ... and in second half = collision
+               if (IsManchesterModulationNibble1(Demod.twoBits >> Demod.syncBit)) {        // modulation in first half
+                       if (IsManchesterModulationNibble2(Demod.twoBits >> Demod.syncBit)) {    // ... and in second half = collision
                                if (!Demod.collisionPos) {
                                        Demod.collisionPos = (Demod.len << 3) + Demod.bitCount;
                                }
-                       }                                                                                                                       // modulation in first half only - Sequence D = 1
+                       }                                                           // modulation in first half only - Sequence D = 1
                        Demod.bitCount++;
-                       Demod.shiftReg = (Demod.shiftReg >> 1) | 0x100;                         // in both cases, add a 1 to the shiftreg
-                       if(Demod.bitCount == 9) {                                                                       // if we decoded a full byte (including parity)
+                       Demod.shiftReg = (Demod.shiftReg >> 1) | 0x100;             // in both cases, add a 1 to the shiftreg
+                       if(Demod.bitCount == 9) {                                   // if we decoded a full byte (including parity)
                                Demod.output[Demod.len++] = (Demod.shiftReg & 0xff);
-                               Demod.parityBits <<= 1;                                                                 // make room for the parity bit
-                               Demod.parityBits |= ((Demod.shiftReg >> 8) & 0x01);     // store parity bit
+                               Demod.parityBits <<= 1;                                 // make room for the parity bit
+                               Demod.parityBits |= ((Demod.shiftReg >> 8) & 0x01);     // store parity bit
                                Demod.bitCount = 0;
                                Demod.shiftReg = 0;
-                               if((Demod.len&0x0007) == 0) {                                                   // every 8 data bytes
-                                       Demod.parity[Demod.parityLen++] = Demod.parityBits;     // store 8 parity bits
+                               if((Demod.len&0x0007) == 0) {                           // every 8 data bytes
+                                       Demod.parity[Demod.parityLen++] = Demod.parityBits; // store 8 parity bits
                                        Demod.parityBits = 0;
                                }
                        }
                        Demod.endTime = Demod.startTime + 8*(9*Demod.len + Demod.bitCount + 1) - 4;
-               } else {                                                                                                                // no modulation in first half
-                       if (IsManchesterModulationNibble2(Demod.twoBits >> Demod.syncBit)) {    // and modulation in second half = Sequence E = 0
+               } else {                                                        // no modulation in first half
+                       if (IsManchesterModulationNibble2(Demod.twoBits >> Demod.syncBit)) {    // and modulation in second half = Sequence E = 0
                                Demod.bitCount++;
-                               Demod.shiftReg = (Demod.shiftReg >> 1);                                 // add a 0 to the shiftreg
-                               if(Demod.bitCount >= 9) {                                                               // if we decoded a full byte (including parity)
+                               Demod.shiftReg = (Demod.shiftReg >> 1);                 // add a 0 to the shiftreg
+                               if(Demod.bitCount >= 9) {                               // if we decoded a full byte (including parity)
                                        Demod.output[Demod.len++] = (Demod.shiftReg & 0xff);
-                                       Demod.parityBits <<= 1;                                                         // make room for the new parity bit
+                                       Demod.parityBits <<= 1;                             // make room for the new parity bit
                                        Demod.parityBits |= ((Demod.shiftReg >> 8) & 0x01); // store parity bit
                                        Demod.bitCount = 0;
                                        Demod.shiftReg = 0;
-                                       if ((Demod.len&0x0007) == 0) {                                          // every 8 data bytes
-                                               Demod.parity[Demod.parityLen++] = Demod.parityBits;     // store 8 parity bits1
+                                       if ((Demod.len&0x0007) == 0) {                      // every 8 data bytes
+                                               Demod.parity[Demod.parityLen++] = Demod.parityBits; // store 8 parity bits1
                                                Demod.parityBits = 0;
                                        }
                                }
                                Demod.endTime = Demod.startTime + 8*(9*Demod.len + Demod.bitCount + 1);
-                       } else {                                                                                                        // no modulation in both halves - End of communication
-                               if(Demod.bitCount > 0) {                                                                // there are some remaining data bits
-                                       Demod.shiftReg >>= (9 - Demod.bitCount);                        // right align the decoded bits
-                                       Demod.output[Demod.len++] = Demod.shiftReg & 0xff;      // and add them to the output
-                                       Demod.parityBits <<= 1;                                                         // add a (void) parity bit
-                                       Demod.parityBits <<= (8 - (Demod.len&0x0007));          // left align remaining parity bits
-                                       Demod.parity[Demod.parityLen++] = Demod.parityBits;     // and store them
+                       } else {                                                    // no modulation in both halves - End of communication
+                               LED_C_OFF();
+                               if(Demod.bitCount > 0) {                                // there are some remaining data bits
+                                       Demod.shiftReg >>= (9 - Demod.bitCount);            // right align the decoded bits
+                                       Demod.output[Demod.len++] = Demod.shiftReg & 0xff;  // and add them to the output
+                                       Demod.parityBits <<= 1;                             // add a (void) parity bit
+                                       Demod.parityBits <<= (8 - (Demod.len&0x0007));      // left align remaining parity bits
+                                       Demod.parity[Demod.parityLen++] = Demod.parityBits; // and store them
                                        return true;
-                               } else if (Demod.len & 0x0007) {                                                // there are some parity bits to store
-                                       Demod.parityBits <<= (8 - (Demod.len&0x0007));          // left align remaining parity bits
-                                       Demod.parity[Demod.parityLen++] = Demod.parityBits;     // and store them
+                               } else if (Demod.len & 0x0007) {                        // there are some parity bits to store
+                                       Demod.parityBits <<= (8 - (Demod.len&0x0007));      // left align remaining parity bits
+                                       Demod.parity[Demod.parityLen++] = Demod.parityBits; // and store them
                                }
                                if (Demod.len) {
-                                       return true;                                                                            // we are finished with decoding the raw data sequence
-                               } else {                                                                                                // nothing received. Start over
+                                       return true;                                        // we are finished with decoding the raw data sequence
+                               } else {                                                // nothing received. Start over
                                        DemodReset();
                                }
                        }
                }
-                       
-       } 
 
-    return false;      // not finished yet, need more data
+       }
+
+       return false;   // not finished yet, need more data
 }
 
 //=============================================================================
@@ -585,8 +579,9 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
        // param:
        // bit 0 - trigger from first card answer
        // bit 1 - trigger from first reader 7-bit request
-       
+
        LEDsoff();
+       LED_A_ON();
 
        iso14443a_setup(FPGA_HF_ISO14443A_SNIFFER);
 
@@ -597,11 +592,11 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
        // The command (reader -> tag) that we're receiving.
        uint8_t *receivedCmd = BigBuf_malloc(MAX_FRAME_SIZE);
        uint8_t *receivedCmdPar = BigBuf_malloc(MAX_PARITY_SIZE);
-       
+
        // The response (tag -> reader) that we're receiving.
        uint8_t *receivedResponse = BigBuf_malloc(MAX_FRAME_SIZE);
        uint8_t *receivedResponsePar = BigBuf_malloc(MAX_PARITY_SIZE);
-       
+
        // The DMA buffer, used to stream samples from the FPGA
        uint8_t *dmaBuf = BigBuf_malloc(DMA_BUFFER_SIZE);
 
@@ -615,31 +610,30 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
        int dataLen = 0;
        bool TagIsActive = false;
        bool ReaderIsActive = false;
-       
+
        // Set up the demodulator for tag -> reader responses.
        DemodInit(receivedResponse, receivedResponsePar);
-       
+
        // Set up the demodulator for the reader -> tag commands
        UartInit(receivedCmd, receivedCmdPar);
-       
+
        // Setup and start DMA.
        FpgaSetupSscDma((uint8_t *)dmaBuf, DMA_BUFFER_SIZE);
-       
+
        // We won't start recording the frames that we acquire until we trigger;
        // a good trigger condition to get started is probably when we see a
        // response from the tag.
        // triggered == false -- to wait first for card
-       bool triggered = !(param & 0x03); 
-       
+       bool triggered = !(param & 0x03);
+
        // And now we loop, receiving samples.
-       for(uint32_t rsamples = 0; true; ) {
+       for (uint32_t rsamples = 0; true; ) {
 
-               if(BUTTON_PRESS()) {
+               if (BUTTON_PRESS()) {
                        DbpString("cancelled by button");
                        break;
                }
 
-               LED_A_ON();
                WDT_HIT();
 
                int register readBufDataP = data - dmaBuf;
@@ -671,24 +665,21 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
                        AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;
                }
 
-               LED_A_OFF();
-               
-               if (rsamples & 0x01) {                          // Need two samples to feed Miller and Manchester-Decoder
+               if (rsamples & 0x01) {              // Need two samples to feed Miller and Manchester-Decoder
 
-                       if(!TagIsActive) {              // no need to try decoding reader data if the tag is sending
+                       if(!TagIsActive) {      // no need to try decoding reader data if the tag is sending
                                uint8_t readerdata = (previous_data & 0xF0) | (*data >> 4);
                                if (MillerDecoding(readerdata, (rsamples-1)*4)) {
-                                       LED_C_ON();
-
                                        // check - if there is a short 7bit request from reader
-                                       if ((!triggered) && (param & 0x02) && (Uart.len == 1) && (Uart.bitCount == 7)) triggered = true;
-
+                                       if ((!triggered) && (param & 0x02) && (Uart.len == 1) && (Uart.bitCount == 7)) {
+                                               triggered = true;
+                                       }
                                        if(triggered) {
-                                               if (!LogTrace(receivedCmd, 
-                                                                               Uart.len, 
+                                               if (!LogTrace(receivedCmd,
+                                                                               Uart.len,
                                                                                Uart.startTime*16 - DELAY_READER_AIR2ARM_AS_SNIFFER,
                                                                                Uart.endTime*16 - DELAY_READER_AIR2ARM_AS_SNIFFER,
-                                                                               Uart.parity, 
+                                                                               Uart.parity,
                                                                                true)) break;
                                        }
                                        /* And ready to receive another command. */
@@ -696,32 +687,25 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
                                        /* And also reset the demod code, which might have been */
                                        /* false-triggered by the commands from the reader. */
                                        DemodReset();
-                                       LED_B_OFF();
                                }
                                ReaderIsActive = (Uart.state != STATE_UNSYNCD);
                        }
 
-                       if(!ReaderIsActive) {           // no need to try decoding tag data if the reader is sending - and we cannot afford the time
+                       if (!ReaderIsActive) {      // no need to try decoding tag data if the reader is sending - and we cannot afford the time
                                uint8_t tagdata = (previous_data << 4) | (*data & 0x0F);
-                               if(ManchesterDecoding(tagdata, 0, (rsamples-1)*4)) {
-                                       LED_B_ON();
-
-                                       if (!LogTrace(receivedResponse, 
-                                                                       Demod.len, 
-                                                                       Demod.startTime*16 - DELAY_TAG_AIR2ARM_AS_SNIFFER, 
+                               if (ManchesterDecoding(tagdata, 0, (rsamples-1)*4)) {
+                                       if (!LogTrace(receivedResponse,
+                                                                       Demod.len,
+                                                                       Demod.startTime*16 - DELAY_TAG_AIR2ARM_AS_SNIFFER,
                                                                        Demod.endTime*16 - DELAY_TAG_AIR2ARM_AS_SNIFFER,
                                                                        Demod.parity,
                                                                        false)) break;
-
                                        if ((!triggered) && (param & 0x01)) triggered = true;
-
                                        // And ready to receive another response.
                                        DemodReset();
                                        // And reset the Miller decoder including itS (now outdated) input buffer
                                        UartInit(receivedCmd, receivedCmdPar);
-
-                                       LED_C_OFF();
-                               } 
+                               }
                                TagIsActive = (Demod.state != DEMOD_UNSYNCD);
                        }
                }
@@ -734,12 +718,12 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
                }
        } // main cycle
 
-       DbpString("COMMAND FINISHED");
-
        FpgaDisableSscDma();
+       LEDsoff();
+
+       DbpString("COMMAND FINISHED");
        Dbprintf("maxDataLen=%d, Uart.state=%x, Uart.len=%d", maxDataLen, Uart.state, Uart.len);
        Dbprintf("traceLen=%d, Uart.output[0]=%08x", BigBuf_get_traceLen(), (uint32_t)Uart.output[0]);
-       LEDsoff();
 }
 
 //-----------------------------------------------------------------------------
@@ -758,16 +742,16 @@ static void CodeIso14443aAsTagPar(const uint8_t *cmd, uint16_t len, uint8_t *par
        ToSendStuffBit(0);
        ToSendStuffBit(0);
        ToSendStuffBit(0);
-       
+
        // Send startbit
        ToSend[++ToSendMax] = SEC_D;
        LastProxToAirDuration = 8 * ToSendMax - 4;
 
-       for(uint16_t i = 0; i < len; i++) {
+       for (uint16_t i = 0; i < len; i++) {
                uint8_t b = cmd[i];
 
                // Data bits
-               for(uint16_t j = 0; j < 8; j++) {
+               for (uint16_t j = 0; j < 8; j++) {
                        if(b & 1) {
                                ToSend[++ToSendMax] = SEC_D;
                        } else {
@@ -814,7 +798,7 @@ static void Code4bitAnswerAsTag(uint8_t cmd)
        ToSend[++ToSendMax] = SEC_D;
 
        uint8_t b = cmd;
-       for(i = 0; i < 4; i++) {
+       for (i = 0; i < 4; i++) {
                if(b & 1) {
                        ToSend[++ToSendMax] = SEC_D;
                        LastProxToAirDuration = 8 * ToSendMax - 4;
@@ -855,7 +839,7 @@ static void FixLastReaderTraceTime(uint32_t tag_StartTime) {
        LastReaderTraceTime[3] = (reader_StartTime >> 24) & 0xff;
 }
 
-       
+
 static void EmLogTraceTag(uint8_t *tag_data, uint16_t tag_len, uint8_t *tag_Parity, uint32_t ProxToAirDuration) {
        uint32_t tag_StartTime = LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_TAG;
        uint32_t tag_EndTime = (LastTimeProxToAirStart + ProxToAirDuration)*16 + DELAY_ARM2AIR_AS_TAG;
@@ -871,40 +855,39 @@ static void EmLogTraceTag(uint8_t *tag_data, uint16_t tag_len, uint8_t *tag_Pari
 //-----------------------------------------------------------------------------
 static int GetIso14443aCommandFromReader(uint8_t *received, uint8_t *parity, int *len)
 {
-    // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
-    // only, since we are receiving, not transmitting).
-    // Signal field is off with the appropriate LED
-    LED_D_OFF();
-    FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_LISTEN);
+       // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
+       // only, since we are receiving, not transmitting).
+       // Signal field is off with the appropriate LED
+       LED_D_OFF();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_LISTEN);
 
-    // Now run a `software UART' on the stream of incoming samples.
+       // Now run a `software UART' on the stream of incoming samples.
        UartInit(received, parity);
 
        // clear RXRDY:
-    uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+       uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+
+       for (;;) {
+               WDT_HIT();
 
-    for(;;) {
-        WDT_HIT();
+               if(BUTTON_PRESS()) return false;
 
-        if(BUTTON_PRESS()) return false;
-               
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-            b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+                       b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
                        if(MillerDecoding(b, 0)) {
                                *len = Uart.len;
                                EmLogTraceReader();
                                return true;
                        }
-               }
-    }
+               }
+       }
 }
 
 
-static int EmSend4bitEx(uint8_t resp, bool correctionNeeded);
 int EmSend4bit(uint8_t resp);
-static int EmSendCmdExPar(uint8_t *resp, uint16_t respLen, bool correctionNeeded, uint8_t *par);
-int EmSendCmdEx(uint8_t *resp, uint16_t respLen, bool correctionNeeded);
-int EmSendPrecompiledCmd(tag_response_info_t *response_info, bool correctionNeeded);
+static int EmSendCmdExPar(uint8_t *resp, uint16_t respLen, uint8_t *par);
+int EmSendCmd(uint8_t *resp, uint16_t respLen);
+int EmSendPrecompiledCmd(tag_response_info_t *response_info);
 
 
 static bool prepare_tag_modulation(tag_response_info_t* response_info, size_t max_buffer_size) {
@@ -918,32 +901,32 @@ static bool prepare_tag_modulation(tag_response_info_t* response_info, size_t ma
        // ----------- +
        //    166 bytes, since every bit that needs to be send costs us a byte
        //
+
+
   // Prepare the tag modulation bits from the message
   GetParity(response_info->response, response_info->response_n, &(response_info->par));
   CodeIso14443aAsTagPar(response_info->response,response_info->response_n, &(response_info->par));
-  
+
   // Make sure we do not exceed the free buffer space
   if (ToSendMax > max_buffer_size) {
-    Dbprintf("Out of memory, when modulating bits for tag answer:");
-    Dbhexdump(response_info->response_n, response_info->response, false);
-    return false;
+       Dbprintf("Out of memory, when modulating bits for tag answer:");
+       Dbhexdump(response_info->response_n, response_info->response, false);
+       return false;
   }
-  
+
   // Copy the byte array, used for this modulation to the buffer position
   memcpy(response_info->modulation, ToSend, ToSendMax);
-  
+
   // Store the number of bytes that were used for encoding/modulation and the time needed to transfer them
   response_info->modulation_n = ToSendMax;
   response_info->ProxToAirDuration = LastProxToAirDuration;
-  
+
   return true;
 }
 
 
 // "precompile" responses. There are 7 predefined responses with a total of 28 bytes data to transmit.
-// Coded responses need one byte per bit to transfer (data, parity, start, stop, correction) 
+// Coded responses need one byte per bit to transfer (data, parity, start, stop, correction)
 // 28 * 8 data bits, 28 * 1 parity bits, 7 start bits, 7 stop bits, 7 correction bits for the modulation
 // -> need 273 bytes buffer
 #define ALLOCATED_TAG_MODULATION_BUFFER_SIZE 273
@@ -952,15 +935,15 @@ bool prepare_allocated_tag_modulation(tag_response_info_t* response_info, uint8_
 
   // Retrieve and store the current buffer index
   response_info->modulation = *buffer;
-  
+
   // Forward the prepare tag modulation function to the inner function
   if (prepare_tag_modulation(response_info, *max_buffer_size)) {
-    // Update the free buffer offset and the remaining buffer size
-    *buffer += ToSendMax;
+       // Update the free buffer offset and the remaining buffer size
+       *buffer += ToSendMax;
        *max_buffer_size -= ToSendMax;
-    return true;
+       return true;
   } else {
-    return false;
+       return false;
   }
 }
 
@@ -974,7 +957,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
 
        // The first response contains the ATQA (note: bytes are transmitted in reverse order).
        uint8_t response1[2];
-       
+
        switch (tagType) {
                case 1: { // MIFARE Classic
                        // Says: I am Mifare 1k - original line
@@ -1005,19 +988,19 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                        response1[0] = 0x01;
                        response1[1] = 0x0f;
                        sak = 0x01;
-               } break;                
+               } break;
                default: {
                        Dbprintf("Error: unkown tagtype (%d)",tagType);
                        return;
                } break;
        }
-       
+
        // The second response contains the (mandatory) first 24 bits of the UID
        uint8_t response2[5] = {0x00};
 
        // Check if the uid uses the (optional) part
        uint8_t response2a[5] = {0x00};
-       
+
        if (uid_2nd) {
                response2[0] = 0x88;
                num_to_bytes(uid_1st,3,response2+1);
@@ -1048,8 +1031,8 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
        ComputeCrc14443(CRC_14443_A, response3a, 1, &response3a[1], &response3a[2]);
 
        uint8_t response5[] = { 0x00, 0x00, 0x00, 0x00 }; // Very random tag nonce
-       uint8_t response6[] = { 0x04, 0x58, 0x80, 0x02, 0x00, 0x00 }; // dummy ATS (pseudo-ATR), answer to RATS: 
-       // Format byte = 0x58: FSCI=0x08 (FSC=256), TA(1) and TC(1) present, 
+       uint8_t response6[] = { 0x04, 0x58, 0x80, 0x02, 0x00, 0x00 }; // dummy ATS (pseudo-ATR), answer to RATS:
+       // Format byte = 0x58: FSCI=0x08 (FSC=256), TA(1) and TC(1) present,
        // TA(1) = 0x80: different divisors not supported, DR = 1, DS = 1
        // TB(1) = not present. Defaults: FWI = 4 (FWT = 256 * 16 * 2^4 * 1/fc = 4833us), SFGI = 0 (SFG = 256 * 16 * 2^0 * 1/fc = 302us)
        // TC(1) = 0x02: CID supported, NAD not supported
@@ -1078,7 +1061,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                .modulation = dynamic_modulation_buffer,
                .modulation_n = 0
        };
-  
+
        // We need to listen to the high-frequency, peak-detected path.
        iso14443a_setup(FPGA_HF_ISO14443A_TAGSIM_LISTEN);
 
@@ -1114,7 +1097,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
        tag_response_info_t* p_response;
 
        LED_A_ON();
-       for(;;) {
+       for (;;) {
                // Clean receive command buffer
                if(!GetIso14443aCommandFromReader(receivedCmd, receivedCmdPar, &len)) {
                        DbpString("Button press");
@@ -1122,32 +1105,32 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                }
 
                p_response = NULL;
-               
+
                // Okay, look at the command now.
                lastorder = order;
                if(receivedCmd[0] == 0x26) { // Received a REQUEST
                        p_response = &responses[0]; order = 1;
                } else if(receivedCmd[0] == 0x52) { // Received a WAKEUP
                        p_response = &responses[0]; order = 6;
-               } else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x93) {   // Received request for UID (cascade 1)
+               } else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x93) {   // Received request for UID (cascade 1)
                        p_response = &responses[1]; order = 2;
-               } else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x95) {   // Received request for UID (cascade 2)
+               } else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x95) {   // Received request for UID (cascade 2)
                        p_response = &responses[2]; order = 20;
-               } else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x93) {   // Received a SELECT (cascade 1)
+               } else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x93) {   // Received a SELECT (cascade 1)
                        p_response = &responses[3]; order = 3;
-               } else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x95) {   // Received a SELECT (cascade 2)
+               } else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x95) {   // Received a SELECT (cascade 2)
                        p_response = &responses[4]; order = 30;
-               } else if(receivedCmd[0] == 0x30) {     // Received a (plain) READ
-                       EmSendCmdEx(data+(4*receivedCmd[1]),16,false);
+               } else if(receivedCmd[0] == 0x30) { // Received a (plain) READ
+                       EmSendCmd(data+(4*receivedCmd[1]),16);
                        // Dbprintf("Read request from reader: %x %x",receivedCmd[0],receivedCmd[1]);
                        // We already responded, do not send anything with the EmSendCmd14443aRaw() that is called below
                        p_response = NULL;
-               } else if(receivedCmd[0] == 0x50) {     // Received a HALT
+               } else if(receivedCmd[0] == 0x50) { // Received a HALT
                        p_response = NULL;
-               } else if(receivedCmd[0] == 0x60 || receivedCmd[0] == 0x61) {   // Received an authentication request
+               } else if(receivedCmd[0] == 0x60 || receivedCmd[0] == 0x61) {   // Received an authentication request
                        p_response = &responses[5]; order = 7;
-               } else if(receivedCmd[0] == 0xE0) {     // Received a RATS request
-                       if (tagType == 1 || tagType == 2) {     // RATS not supported
+               } else if(receivedCmd[0] == 0xE0) { // Received a RATS request
+                       if (tagType == 1 || tagType == 2) { // RATS not supported
                                EmSend4bit(CARD_NACK_NA);
                                p_response = NULL;
                        } else {
@@ -1181,7 +1164,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                                  dynamic_response_info.response[0] = receivedCmd[0] ^ 0x11;
                                  dynamic_response_info.response_n = 2;
                                } break;
-                                 
+
                                case 0xBA: { //
                                  memcpy(dynamic_response_info.response,"\xAB\x00",2);
                                  dynamic_response_info.response_n = 2;
@@ -1201,7 +1184,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                                        dynamic_response_info.response_n = 0;
                                } break;
                        }
-      
+
                        if (dynamic_response_info.response_n > 0) {
                                // Copy the CID from the reader query
                                dynamic_response_info.response[1] = receivedCmd[1];
@@ -1209,7 +1192,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                                // Add CRC bytes, always used in ISO 14443A-4 compliant cards
                                AppendCrc14443a(dynamic_response_info.response,dynamic_response_info.response_n);
                                dynamic_response_info.response_n += 2;
-        
+
                                if (prepare_tag_modulation(&dynamic_response_info,DYNAMIC_MODULATION_BUFFER_SIZE) == false) {
                                        Dbprintf("Error preparing tag response");
                                        break;
@@ -1231,10 +1214,10 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
                cmdsRecvd++;
 
                if (p_response != NULL) {
-                       EmSendPrecompiledCmd(p_response, receivedCmd[0] == 0x52);
+                       EmSendPrecompiledCmd(p_response);
                }
-               
-               if (!tracing) {
+
+               if (!get_tracing()) {
                        Dbprintf("Trace Full. Simulation stopped.");
                        break;
                }
@@ -1253,7 +1236,7 @@ static void PrepareDelayedTransfer(uint16_t delay)
        uint8_t bitmask = 0;
        uint8_t bits_to_shift = 0;
        uint8_t bits_shifted = 0;
-       
+
        delay &= 0x07;
        if (delay) {
                for (uint16_t i = 0; i < delay; i++) {
@@ -1274,37 +1257,38 @@ static void PrepareDelayedTransfer(uint16_t delay)
 // Transmit the command (to the tag) that was placed in ToSend[].
 // Parameter timing:
 // if NULL: transfer at next possible time, taking into account
-//                     request guard time and frame delay time
-// if == 0:    transfer immediately and return time of transfer
+//          request guard time, startup frame guard time and frame delay time
+// if == 0: transfer immediately and return time of transfer
 // if != 0: delay transfer until time specified
 //-------------------------------------------------------------------------------------
 static void TransmitFor14443a(const uint8_t *cmd, uint16_t len, uint32_t *timing)
 {
-       
+       LED_B_ON();
+       LED_D_ON();
        FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
 
        uint32_t ThisTransferTime = 0;
 
        if (timing) {
-               if(*timing == 0) {                                                                              // Measure time
+               if(*timing == 0) {                                      // Measure time
                        *timing = (GetCountSspClk() + 8) & 0xfffffff8;
                } else {
-                       PrepareDelayedTransfer(*timing & 0x00000007);           // Delay transfer (fine tuning - up to 7 MF clock ticks)
+                       PrepareDelayedTransfer(*timing & 0x00000007);       // Delay transfer (fine tuning - up to 7 MF clock ticks)
                }
                if(MF_DBGLEVEL >= 4 && GetCountSspClk() >= (*timing & 0xfffffff8)) Dbprintf("TransmitFor14443a: Missed timing");
-               while(GetCountSspClk() < (*timing & 0xfffffff8));               // Delay transfer (multiple of 8 MF clock ticks)
+               while (GetCountSspClk() < (*timing & 0xfffffff8));      // Delay transfer (multiple of 8 MF clock ticks)
                LastTimeProxToAirStart = *timing;
        } else {
                ThisTransferTime = ((MAX(NextTransferTime, GetCountSspClk()) & 0xfffffff8) + 8);
-               while(GetCountSspClk() < ThisTransferTime);
+               while (GetCountSspClk() < ThisTransferTime);
                LastTimeProxToAirStart = ThisTransferTime;
        }
-       
+
        // clear TXRDY
        AT91C_BASE_SSC->SSC_THR = SEC_Y;
 
        uint16_t c = 0;
-       for(;;) {
+       for (;;) {
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
                        AT91C_BASE_SSC->SSC_THR = cmd[c];
                        c++;
@@ -1313,8 +1297,9 @@ static void TransmitFor14443a(const uint8_t *cmd, uint16_t len, uint32_t *timing
                        }
                }
        }
-       
+
        NextTransferTime = MAX(NextTransferTime, LastTimeProxToAirStart + REQUEST_GUARD_TIME);
+       LED_B_OFF();
 }
 
 
@@ -1407,175 +1392,182 @@ static void CodeIso14443aBitsAsReaderPar(const uint8_t *cmd, uint16_t bits, cons
 //-----------------------------------------------------------------------------
 int EmGetCmd(uint8_t *received, uint16_t *len, uint8_t *parity)
 {
+       uint32_t field_off_time = -1;
+       uint32_t samples = 0;
+       int ret = 0;
+       uint8_t b = 0;;
+       uint8_t dmaBuf[DMA_BUFFER_SIZE];
+       uint8_t *upTo = dmaBuf;
+
        *len = 0;
 
-       uint32_t timer = 0, vtime = 0;
-       int analogCnt = 0;
-       int analogAVG = 0;
+       // Run a 'software UART' on the stream of incoming samples.
+       UartInit(received, parity);
+
+       // start ADC
+       AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
+
+       // Ensure that the FPGA Delay Queue is empty before we switch to TAGSIM_LISTEN
+       while (GetCountSspClk() < LastTimeProxToAirStart + LastProxToAirDuration + (FpgaSendQueueDelay>>3) - 8 - 3) /* wait */ ;
 
        // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
        // only, since we are receiving, not transmitting).
-       // Signal field is off with the appropriate LED
-       LED_D_OFF();
        FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_LISTEN);
 
-       // Set ADC to read field strength
-       AT91C_BASE_ADC->ADC_CR = AT91C_ADC_SWRST;
-       AT91C_BASE_ADC->ADC_MR =
-                               ADC_MODE_PRESCALE(63) |
-                               ADC_MODE_STARTUP_TIME(1) |
-                               ADC_MODE_SAMPLE_HOLD_TIME(15);
-       AT91C_BASE_ADC->ADC_CHER = ADC_CHANNEL(ADC_CHAN_HF);
-       // start ADC
-       AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
-       
-       // Now run a 'software UART' on the stream of incoming samples.
-       UartInit(received, parity);
+       // clear receive register, measure time of next transfer
+       uint32_t temp = AT91C_BASE_SSC->SSC_RHR; (void) temp;
+       while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY)) ;
+       uint32_t start_time = GetCountSspClk() & 0xfffffff8;
+
+       // Setup and start DMA.
+       FpgaSetupSscDma(dmaBuf, DMA_BUFFER_SIZE);
 
-       // Clear RXRDY:
-    uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
-       
        for(;;) {
-               WDT_HIT();
+               uint16_t behindBy = ((uint8_t*)AT91C_BASE_PDC_SSC->PDC_RPR - upTo) & (DMA_BUFFER_SIZE-1);
+
+               if (behindBy == 0) continue;
 
-               if (BUTTON_PRESS()) return 1;
-
-               // test if the field exists
-               if (AT91C_BASE_ADC->ADC_SR & ADC_END_OF_CONVERSION(ADC_CHAN_HF)) {
-                       analogCnt++;
-                       analogAVG += AT91C_BASE_ADC->ADC_CDR[ADC_CHAN_HF];
-                       AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
-                       if (analogCnt >= 32) {
-                               if ((MAX_ADC_HF_VOLTAGE * (analogAVG / analogCnt) >> 10) < MF_MINFIELDV) {
-                                       vtime = GetTickCount();
-                                       if (!timer) timer = vtime;
-                                       // 50ms no field --> card to idle state
-                                       if (vtime - timer > 50) return 2;
-                               } else
-                                       if (timer) timer = 0;
-                               analogCnt = 0;
-                               analogAVG = 0;
+               b = *upTo++;
+
+               if(upTo >= dmaBuf + DMA_BUFFER_SIZE) {                   // we have read all of the DMA buffer content.
+                       upTo = dmaBuf;                                       // start reading the circular buffer from the beginning
+                       if(behindBy > (9*DMA_BUFFER_SIZE/10)) {
+                               Dbprintf("About to blow circular buffer - aborted! behindBy=%d", behindBy);
+                               ret = 1;
+                               break;
                        }
                }
+               if (AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_ENDRX)) {        // DMA Counter Register had reached 0, already rotated.
+                       AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) dmaBuf;    // refresh the DMA Next Buffer and
+                       AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;      // DMA Next Counter registers
+               }
 
-               // receive and test the miller decoding
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-            b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
-                       if(MillerDecoding(b, 0)) {
-                               *len = Uart.len;
-                               EmLogTraceReader();
-                               return 0;
+               if (BUTTON_PRESS()) {
+                       ret = 1;
+                       break;
+               }
+
+               // check reader's HF field
+               if (AT91C_BASE_ADC->ADC_SR & ADC_END_OF_CONVERSION(ADC_CHAN_HF_LOW)) {
+                       if ((MAX_ADC_HF_VOLTAGE_LOW * AT91C_BASE_ADC->ADC_CDR[ADC_CHAN_HF_LOW]) >> 10 < MF_MINFIELDV) {
+                               if (GetTickCount() - field_off_time > 50) {
+                                       ret = 2; // reader has switched off HF field for more than 50ms. Timeout
+                                       break;
+                               }
+                       } else {
+                               field_off_time = GetTickCount(); // HF field is still there. Reset timer
                        }
-        }
+                       AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START; // restart ADC
+               }
+
+               if (MillerDecoding(b, start_time + samples*8)) {
+                       *len = Uart.len;
+                       EmLogTraceReader();
+                       ret = 0;
+                       break;
+               }
 
+               samples++;
        }
+
+       FpgaDisableSscDma();
+       return ret;
 }
 
 
-static int EmSendCmd14443aRaw(uint8_t *resp, uint16_t respLen, bool correctionNeeded)
+static int EmSendCmd14443aRaw(uint8_t *resp, uint16_t respLen)
 {
+       LED_C_ON();
+
        uint8_t b;
        uint16_t i = 0;
-       
+       bool correctionNeeded;
+
        // Modulate Manchester
        FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_MOD);
 
        // include correction bit if necessary
-       if (Uart.parityBits & 0x01) {
-               correctionNeeded = true;
+       if (Uart.bitCount == 7)
+       {
+               // Short tags (7 bits) don't have parity, determine the correct value from MSB
+               correctionNeeded = Uart.output[0] & 0x40;
+       }
+       else
+       {
+               // Look at the last parity bit
+               correctionNeeded = Uart.parity[(Uart.len-1)/8] & (0x80 >> ((Uart.len-1) & 7));
        }
-       if(correctionNeeded) {
+
+       if (correctionNeeded) {
                // 1236, so correction bit needed
                i = 0;
        } else {
                i = 1;
        }
 
-       // clear receiving shift register and holding register
-       while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
+       // clear receiving shift register and holding register
        b = AT91C_BASE_SSC->SSC_RHR; (void) b;
-       while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
+       while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
        b = AT91C_BASE_SSC->SSC_RHR; (void) b;
-       
+
        // wait for the FPGA to signal fdt_indicator == 1 (the FPGA is ready to queue new data in its delay line)
-       for (uint16_t j = 0; j < 5; j++) {      // allow timeout - better late than never
-               while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
+       for (uint16_t j = 0; j < 5; j++) {  // allow timeout - better late than never
+               while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
                if (AT91C_BASE_SSC->SSC_RHR) break;
        }
 
        LastTimeProxToAirStart = (GetCountSspClk() & 0xfffffff8) + (correctionNeeded?8:0);
 
        // send cycle
-       for(; i < respLen; ) {
+       for (; i < respLen; ) {
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
                        AT91C_BASE_SSC->SSC_THR = resp[i++];
                        FpgaSendQueueDelay = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
                }
-       
+
                if(BUTTON_PRESS()) {
                        break;
                }
        }
 
-       // Ensure that the FPGA Delay Queue is empty before we switch to TAGSIM_LISTEN again:
-       uint8_t fpga_queued_bits = FpgaSendQueueDelay >> 3;
-       for (i = 0; i < fpga_queued_bits/8; ) {
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       AT91C_BASE_SSC->SSC_THR = SEC_F;
-                       FpgaSendQueueDelay = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
-                       i++;
-               }
-       }
-
+       LED_C_OFF();
        return 0;
 }
 
 
-static int EmSend4bitEx(uint8_t resp, bool correctionNeeded){
+int EmSend4bit(uint8_t resp){
        Code4bitAnswerAsTag(resp);
-       int res = EmSendCmd14443aRaw(ToSend, ToSendMax, correctionNeeded);
-       // do the tracing for the previous reader request and this tag answer:
+       int res = EmSendCmd14443aRaw(ToSend, ToSendMax);
+       // Log this tag answer and fix timing of previous reader command:
        EmLogTraceTag(&resp, 1, NULL, LastProxToAirDuration);
        return res;
 }
 
 
-int EmSend4bit(uint8_t resp){
-       return EmSend4bitEx(resp, false);
-}
-
-
-static int EmSendCmdExPar(uint8_t *resp, uint16_t respLen, bool correctionNeeded, uint8_t *par){
+static int EmSendCmdExPar(uint8_t *resp, uint16_t respLen, uint8_t *par){
        CodeIso14443aAsTagPar(resp, respLen, par);
-       int res = EmSendCmd14443aRaw(ToSend, ToSendMax, correctionNeeded);
-       // do the tracing for the previous reader request and this tag answer:
+       int res = EmSendCmd14443aRaw(ToSend, ToSendMax);
+       // Log this tag answer and fix timing of previous reader command:
        EmLogTraceTag(resp, respLen, par, LastProxToAirDuration);
        return res;
 }
 
 
-int EmSendCmdEx(uint8_t *resp, uint16_t respLen, bool correctionNeeded){
-       uint8_t par[MAX_PARITY_SIZE];
-       GetParity(resp, respLen, par);
-       return EmSendCmdExPar(resp, respLen, correctionNeeded, par);
-}
-
-
 int EmSendCmd(uint8_t *resp, uint16_t respLen){
        uint8_t par[MAX_PARITY_SIZE];
        GetParity(resp, respLen, par);
-       return EmSendCmdExPar(resp, respLen, false, par);
+       return EmSendCmdExPar(resp, respLen, par);
 }
 
 
 int EmSendCmdPar(uint8_t *resp, uint16_t respLen, uint8_t *par){
-       return EmSendCmdExPar(resp, respLen, false, par);
+       return EmSendCmdExPar(resp, respLen, par);
 }
 
 
-int EmSendPrecompiledCmd(tag_response_info_t *response_info, bool correctionNeeded) {
-       int ret = EmSendCmd14443aRaw(response_info->modulation, response_info->modulation_n, correctionNeeded);
-       // do the tracing for the previous reader request and this tag answer:
+int EmSendPrecompiledCmd(tag_response_info_t *response_info) {
+       int ret = EmSendCmd14443aRaw(response_info->modulation, response_info->modulation_n);
+       // Log this tag answer and fix timing of previous reader command:
        EmLogTraceTag(response_info->response, response_info->response_n, &(response_info->par), response_info->ProxToAirDuration);
        return ret;
 }
@@ -1589,21 +1581,21 @@ int EmSendPrecompiledCmd(tag_response_info_t *response_info, bool correctionNeed
 static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receivedResponsePar, uint16_t offset)
 {
        uint32_t c;
-       
+
        // Set FPGA mode to "reader listen mode", no modulation (listen
        // only, since we are receiving, not transmitting).
        // Signal field is on with the appropriate LED
        LED_D_ON();
        FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_LISTEN);
-       
+
        // Now get the answer from the card
        DemodInit(receivedResponse, receivedResponsePar);
 
        // clear RXRDY:
-    uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+       uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
 
        c = 0;
-       for(;;) {
+       for (;;) {
                WDT_HIT();
 
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
@@ -1612,7 +1604,7 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receive
                                NextTransferTime = MAX(NextTransferTime, Demod.endTime - (DELAY_AIR2ARM_AS_READER + DELAY_ARM2AIR_AS_READER)/16 + FRAME_DELAY_TIME_PICC_TO_PCD);
                                return true;
                        } else if (c++ > iso14a_timeout && Demod.state == DEMOD_UNSYNCD) {
-                               return false; 
+                               return false;
                        }
                }
        }
@@ -1622,16 +1614,14 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receive
 void ReaderTransmitBitsPar(uint8_t* frame, uint16_t bits, uint8_t *par, uint32_t *timing)
 {
        CodeIso14443aBitsAsReaderPar(frame, bits, par);
-  
+
        // Send command to tag
        TransmitFor14443a(ToSend, ToSendMax, timing);
        if(trigger)
                LED_A_ON();
-  
+
        // Log reader command in trace buffer
-       if (tracing) {
-               LogTrace(frame, nbytes(bits), LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_READER, (LastTimeProxToAirStart + LastProxToAirDuration)*16 + DELAY_ARM2AIR_AS_READER, par, true);
-       }
+       LogTrace(frame, nbytes(bits), LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_READER, (LastTimeProxToAirStart + LastProxToAirDuration)*16 + DELAY_ARM2AIR_AS_READER, par, true);
 }
 
 
@@ -1662,9 +1652,7 @@ void ReaderTransmit(uint8_t* frame, uint16_t len, uint32_t *timing)
 static int ReaderReceiveOffset(uint8_t* receivedAnswer, uint16_t offset, uint8_t *parity)
 {
        if (!GetIso14443aAnswerFromTag(receivedAnswer, parity, offset)) return false;
-       if (tracing) {
-               LogTrace(receivedAnswer, Demod.len, Demod.startTime*16 - DELAY_AIR2ARM_AS_READER, Demod.endTime*16 - DELAY_AIR2ARM_AS_READER, parity, false);
-       }
+       LogTrace(receivedAnswer, Demod.len, Demod.startTime*16 - DELAY_AIR2ARM_AS_READER, Demod.endTime*16 - DELAY_AIR2ARM_AS_READER, parity, false);
        return Demod.len;
 }
 
@@ -1672,20 +1660,70 @@ static int ReaderReceiveOffset(uint8_t* receivedAnswer, uint16_t offset, uint8_t
 int ReaderReceive(uint8_t *receivedAnswer, uint8_t *parity)
 {
        if (!GetIso14443aAnswerFromTag(receivedAnswer, parity, 0)) return false;
-       if (tracing) {
-               LogTrace(receivedAnswer, Demod.len, Demod.startTime*16 - DELAY_AIR2ARM_AS_READER, Demod.endTime*16 - DELAY_AIR2ARM_AS_READER, parity, false);
-       }
+       LogTrace(receivedAnswer, Demod.len, Demod.startTime*16 - DELAY_AIR2ARM_AS_READER, Demod.endTime*16 - DELAY_AIR2ARM_AS_READER, parity, false);
        return Demod.len;
 }
 
+
+static void iso14a_set_ATS_times(uint8_t *ats) {
+
+       uint8_t tb1;
+       uint8_t fwi, sfgi;
+       uint32_t fwt, sfgt;
+
+       if (ats[0] > 1) {                           // there is a format byte T0
+               if ((ats[1] & 0x20) == 0x20) {          // there is an interface byte TB(1)
+                       if ((ats[1] & 0x10) == 0x10) {      // there is an interface byte TA(1) preceding TB(1)
+                               tb1 = ats[3];
+                       } else {
+                               tb1 = ats[2];
+                       }
+                       fwi = (tb1 & 0xf0) >> 4;            // frame waiting time integer (FWI)
+                       if (fwi != 15) {
+                               fwt = 256 * 16 * (1 << fwi);    // frame waiting time (FWT) in 1/fc
+                               iso14a_set_timeout(fwt/(8*16));
+                       }
+                       sfgi = tb1 & 0x0f;                  // startup frame guard time integer (SFGI)
+                       if (sfgi != 0 && sfgi != 15) {
+                               sfgt = 256 * 16 * (1 << sfgi);  // startup frame guard time (SFGT) in 1/fc
+                               NextTransferTime = MAX(NextTransferTime, Demod.endTime + (sfgt - DELAY_AIR2ARM_AS_READER - DELAY_ARM2AIR_AS_READER)/16);
+                       }
+               }
+       }
+}
+
+
+static int GetATQA(uint8_t *resp, uint8_t *resp_par) {
+
+#define WUPA_RETRY_TIMEOUT  10  // 10ms
+       uint8_t wupa[]       = { 0x52 };  // 0x26 - REQA  0x52 - WAKE-UP
+
+       uint32_t save_iso14a_timeout = iso14a_get_timeout();
+       iso14a_set_timeout(1236/(16*8)+1);      // response to WUPA is expected at exactly 1236/fc. No need to wait longer.
+
+       uint32_t start_time = GetTickCount();
+       int len;
+
+       // we may need several tries if we did send an unknown command or a wrong authentication before...
+       do {
+               // Broadcast for a card, WUPA (0x52) will force response from all cards in the field
+               ReaderTransmitBitsPar(wupa, 7, NULL, NULL);
+               // Receive the ATQA
+               len = ReaderReceive(resp, resp_par);
+       } while (len == 0 && GetTickCount() <= start_time + WUPA_RETRY_TIMEOUT);
+
+       iso14a_set_timeout(save_iso14a_timeout);
+       return len;
+}
+
+
 // performs iso14443a anticollision (optional) and card select procedure
 // fills the uid and cuid pointer unless NULL
 // fills the card info record unless NULL
-// if anticollision is false, then the UID must be provided in uid_ptr[] 
+// if anticollision is false, then the UID must be provided in uid_ptr[]
 // and num_cascades must be set (1: 4 Byte UID, 2: 7 Byte UID, 3: 10 Byte UID)
 // requests ATS unless no_rats is true
 int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, uint32_t *cuid_ptr, bool anticollision, uint8_t num_cascades, bool no_rats) {
-       uint8_t wupa[]       = { 0x52 };  // 0x26 - REQA  0x52 - WAKE-UP
        uint8_t sel_all[]    = { 0x93,0x20 };
        uint8_t sel_uid[]    = { 0x93,0x70,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
        uint8_t rats[]       = { 0xE0,0x80,0x00,0x00 }; // FSD=256, FSDI=8, CID=0
@@ -1705,11 +1743,9 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                p_hi14a_card->ats_len = 0;
        }
 
-       // Broadcast for a card, WUPA (0x52) will force response from all cards in the field
-    ReaderTransmitBitsPar(wupa, 7, NULL, NULL);
-       
-       // Receive the ATQA
-       if(!ReaderReceive(resp, resp_par)) return 0;
+       if (!GetATQA(resp, resp_par)) {
+               return 0;
+       }
 
        if(p_hi14a_card) {
                memcpy(p_hi14a_card->atqa, resp, 2);
@@ -1726,40 +1762,44 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
        if ((resp[0] & 0x1F) == 0) {
                return 3;
        }
-       
+
        // OK we will select at least at cascade 1, lets see if first byte of UID was 0x88 in
        // which case we need to make a cascade 2 request and select - this is a long UID
-       // While the UID is not complete, the 3nd bit (from the right) is set in the SAK.
-       for(; sak & 0x04; cascade_level++) {
+       // While the UID is not complete, the 3rd bit (from the right) is set in the SAK.
+       for (; sak & 0x04; cascade_level++) {
                // SELECT_* (L1: 0x93, L2: 0x95, L3: 0x97)
                sel_uid[0] = sel_all[0] = 0x93 + cascade_level * 2;
 
                if (anticollision) {
                        // SELECT_ALL
                        ReaderTransmit(sel_all, sizeof(sel_all), NULL);
-                       if (!ReaderReceive(resp, resp_par)) return 0;
+                       if (!ReaderReceive(resp, resp_par)) {
+                               return 0;
+                       }
 
-                       if (Demod.collisionPos) {                       // we had a collision and need to construct the UID bit by bit
+                       if (Demod.collisionPos) {           // we had a collision and need to construct the UID bit by bit
                                memset(uid_resp, 0, 4);
                                uint16_t uid_resp_bits = 0;
                                uint16_t collision_answer_offset = 0;
                                // anti-collision-loop:
                                while (Demod.collisionPos) {
                                        Dbprintf("Multiple tags detected. Collision after Bit %d", Demod.collisionPos);
-                                       for (uint16_t i = collision_answer_offset; i < Demod.collisionPos; i++, uid_resp_bits++) {      // add valid UID bits before collision point
+                                       for (uint16_t i = collision_answer_offset; i < Demod.collisionPos; i++, uid_resp_bits++) {  // add valid UID bits before collision point
                                                uint16_t UIDbit = (resp[i/8] >> (i % 8)) & 0x01;
                                                uid_resp[uid_resp_bits / 8] |= UIDbit << (uid_resp_bits % 8);
                                        }
-                                       uid_resp[uid_resp_bits/8] |= 1 << (uid_resp_bits % 8);                                  // next time select the card(s) with a 1 in the collision position
+                                       uid_resp[uid_resp_bits/8] |= 1 << (uid_resp_bits % 8);                  // next time select the card(s) with a 1 in the collision position
                                        uid_resp_bits++;
                                        // construct anticollosion command:
-                                       sel_uid[1] = ((2 + uid_resp_bits/8) << 4) | (uid_resp_bits & 0x07);     // length of data in bytes and bits
+                                       sel_uid[1] = ((2 + uid_resp_bits/8) << 4) | (uid_resp_bits & 0x07);     // length of data in bytes and bits
                                        for (uint16_t i = 0; i <= uid_resp_bits/8; i++) {
                                                sel_uid[2+i] = uid_resp[i];
                                        }
                                        collision_answer_offset = uid_resp_bits%8;
                                        ReaderTransmitBits(sel_uid, 16 + uid_resp_bits, NULL);
-                                       if (!ReaderReceiveOffset(resp, collision_answer_offset, resp_par)) return 0;
+                                       if (!ReaderReceiveOffset(resp, collision_answer_offset, resp_par)) {
+                                               return 0;
+                                       }
                                }
                                // finally, add the last bits and BCC of the UID
                                for (uint16_t i = collision_answer_offset; i < (Demod.len-1)*8; i++, uid_resp_bits++) {
@@ -1767,7 +1807,7 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                                        uid_resp[uid_resp_bits/8] |= UIDbit << (uid_resp_bits % 8);
                                }
 
-                       } else {                // no collision, use the response to SELECT_ALL as current uid
+                       } else {        // no collision, use the response to SELECT_ALL as current uid
                                memcpy(uid_resp, resp, 4);
                        }
                } else {
@@ -1786,23 +1826,25 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                }
 
                // Construct SELECT UID command
-               sel_uid[1] = 0x70;                                                                                                      // transmitting a full UID (1 Byte cmd, 1 Byte NVB, 4 Byte UID, 1 Byte BCC, 2 Bytes CRC)
-               memcpy(sel_uid+2, uid_resp, 4);                                                                         // the UID received during anticollision, or the provided UID
-               sel_uid[6] = sel_uid[2] ^ sel_uid[3] ^ sel_uid[4] ^ sel_uid[5];         // calculate and add BCC
-               AppendCrc14443a(sel_uid, 7);                                                                            // calculate and add CRC
+               sel_uid[1] = 0x70;                                                  // transmitting a full UID (1 Byte cmd, 1 Byte NVB, 4 Byte UID, 1 Byte BCC, 2 Bytes CRC)
+               memcpy(sel_uid+2, uid_resp, 4);                                     // the UID received during anticollision, or the provided UID
+               sel_uid[6] = sel_uid[2] ^ sel_uid[3] ^ sel_uid[4] ^ sel_uid[5];     // calculate and add BCC
+               AppendCrc14443a(sel_uid, 7);                                        // calculate and add CRC
                ReaderTransmit(sel_uid, sizeof(sel_uid), NULL);
 
                // Receive the SAK
-               if (!ReaderReceive(resp, resp_par)) return 0;
+               if (!ReaderReceive(resp, resp_par)) {
+                       return 0;
+               }
                sak = resp[0];
-       
+
                // Test if more parts of the uid are coming
                if ((sak & 0x04) /* && uid_resp[0] == 0x88 */) {
                        // Remove first byte, 0x88 is not an UID byte, it CT, see page 3 of:
                        // http://www.nxp.com/documents/application_note/AN10927.pdf
                        uid_resp[0] = uid_resp[1];
                        uid_resp[1] = uid_resp[2];
-                       uid_resp[2] = uid_resp[3]; 
+                       uid_resp[2] = uid_resp[3];
                        uid_resp_len = 3;
                }
 
@@ -1821,14 +1863,16 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
        }
 
        // PICC compilant with iso14443a-4 ---> (SAK & 0x20 != 0)
-       if( (sak & 0x20) == 0) return 2; 
+       if( (sak & 0x20) == 0) return 2;
 
        if (!no_rats) {
                // Request for answer to select
                AppendCrc14443a(rats, 2);
                ReaderTransmit(rats, sizeof(rats), NULL);
 
-               if (!(len = ReaderReceive(resp, resp_par))) return 0;
+               if (!(len = ReaderReceive(resp, resp_par))) {
+                       return 0;
+               }
 
                if(p_hi14a_card) {
                        memcpy(p_hi14a_card->ats, resp, len);
@@ -1838,17 +1882,18 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                // reset the PCB block number
                iso14_pcb_blocknum = 0;
 
-               // set default timeout based on ATS
-               iso14a_set_ATS_timeout(resp);
+               // set default timeout and delay next transfer based on ATS
+               iso14a_set_ATS_times(resp);
+
        }
-       return 1;       
+       return 1;
 }
 
 
 void iso14443a_setup(uint8_t fpga_minor_mode) {
        FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
        // Set up the synchronous serial port
-       FpgaSetupSsc();
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_ISO14443A);
        // connect Demodulated Signal to ADC:
        SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
@@ -1861,39 +1906,124 @@ void iso14443a_setup(uint8_t fpga_minor_mode) {
        }
        FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | fpga_minor_mode);
 
+       // Set ADC to read field strength
+       AT91C_BASE_ADC->ADC_CR = AT91C_ADC_SWRST;
+       AT91C_BASE_ADC->ADC_MR =
+                               ADC_MODE_PRESCALE(63) |
+                               ADC_MODE_STARTUP_TIME(1) |
+                               ADC_MODE_SAMPLE_HOLD_TIME(15);
+       AT91C_BASE_ADC->ADC_CHER = ADC_CHANNEL(ADC_CHAN_HF_LOW);
+
        // Start the timer
        StartCountSspClk();
-       
+
        DemodReset();
        UartReset();
+       LastTimeProxToAirStart = 0;
+       FpgaSendQueueDelay = 0;
+       LastProxToAirDuration = 20; // arbitrary small value. Avoid lock in EmGetCmd()
        NextTransferTime = 2*DELAY_ARM2AIR_AS_READER;
        iso14a_set_timeout(1060); // 10ms default
 }
 
-
-int iso14_apdu(uint8_t *cmd, uint16_t cmd_len, void *data) {
+/* Peter Fillmore 2015
+Added card id field to the function
+ info from ISO14443A standard
+b1 = Block Number
+b2 = RFU (always 1)
+b3 = depends on block
+b4 = Card ID following if set to 1
+b5 = depends on block type
+b6 = depends on block type
+b7,b8 = block type.
+Coding of I-BLOCK:
+b8 b7 b6 b5 b4 b3 b2 b1
+0  0  0  x  x  x  1  x
+b5 = chaining bit
+Coding of R-block:
+b8 b7 b6 b5 b4 b3 b2 b1
+1  0  1  x  x  0  1  x
+b5 = ACK/NACK
+Coding of S-block:
+b8 b7 b6 b5 b4 b3 b2 b1
+1  1  x  x  x  0  1  0
+b5,b6 = 00 - DESELECT
+               11 - WTX
+*/
+int iso14_apdu(uint8_t *cmd, uint16_t cmd_len, bool send_chaining, void *data, uint8_t *res) {
        uint8_t parity[MAX_PARITY_SIZE];
-       uint8_t real_cmd[cmd_len+4];
-       real_cmd[0] = 0x0a; //I-Block
-       // put block number into the PCB
-       real_cmd[0] |= iso14_pcb_blocknum;
-       real_cmd[1] = 0x00; //CID: 0 //FIXME: allow multiple selected cards
-       memcpy(real_cmd+2, cmd, cmd_len);
-       AppendCrc14443a(real_cmd,cmd_len+2);
-       ReaderTransmit(real_cmd, cmd_len+4, NULL);
+       uint8_t real_cmd[cmd_len + 4];
+
+       if (cmd_len) {
+               // ISO 14443 APDU frame: PCB [CID] [NAD] APDU CRC PCB=0x02
+               real_cmd[0] = 0x02; // bnr,nad,cid,chn=0; i-block(0x00)
+               if (send_chaining) {
+                       real_cmd[0] |= 0x10;
+               }
+               // put block number into the PCB
+               real_cmd[0] |= iso14_pcb_blocknum;
+               memcpy(real_cmd + 1, cmd, cmd_len);
+       } else {
+               // R-block. ACK
+               real_cmd[0] = 0xA2; // r-block + ACK
+               real_cmd[0] |= iso14_pcb_blocknum;
+       }
+       AppendCrc14443a(real_cmd, cmd_len + 1);
+
+       ReaderTransmit(real_cmd, cmd_len + 3, NULL);
+
        size_t len = ReaderReceive(data, parity);
        uint8_t *data_bytes = (uint8_t *) data;
-       if (!len)
+
+       if (!len) {
                return 0; //DATA LINK ERROR
-       // if we received an I- or R(ACK)-Block with a block number equal to the
-       // current block number, toggle the current block number
-       else if (len >= 4 // PCB+CID+CRC = 4 bytes
-                && ((data_bytes[0] & 0xC0) == 0 // I-Block
-                    || (data_bytes[0] & 0xD0) == 0x80) // R-Block with ACK bit set to 0
-                && (data_bytes[0] & 0x01) == iso14_pcb_blocknum) // equal block numbers
-       {
-               iso14_pcb_blocknum ^= 1;
+       } else {
+               // S-Block WTX
+               while (len && ((data_bytes[0] & 0xF2) == 0xF2)) {
+                       uint32_t save_iso14a_timeout = iso14a_get_timeout();
+                       // temporarily increase timeout
+                       iso14a_set_timeout(MAX((data_bytes[1] & 0x3f) * save_iso14a_timeout, MAX_ISO14A_TIMEOUT));
+                       // Transmit WTX back
+                       // byte1 - WTXM [1..59]. command FWT=FWT*WTXM
+                       data_bytes[1] = data_bytes[1] & 0x3f; // 2 high bits mandatory set to 0b
+                       // now need to fix CRC.
+                       AppendCrc14443a(data_bytes, len - 2);
+                       // transmit S-Block
+                       ReaderTransmit(data_bytes, len, NULL);
+                       // retrieve the result again (with increased timeout)
+                       len = ReaderReceive(data, parity);
+                       data_bytes = data;
+                       // restore timeout
+                       iso14a_set_timeout(save_iso14a_timeout);
+               }
+
+               // if we received an I- or R(ACK)-Block with a block number equal to the
+               // current block number, toggle the current block number
+               if (len >= 3 // PCB+CRC = 3 bytes
+                        && ((data_bytes[0] & 0xC0) == 0 // I-Block
+                                || (data_bytes[0] & 0xD0) == 0x80) // R-Block with ACK bit set to 0
+                        && (data_bytes[0] & 0x01) == iso14_pcb_blocknum) // equal block numbers
+               {
+                       iso14_pcb_blocknum ^= 1;
+               }
+
+               // if we received I-block with chaining we need to send ACK and receive another block of data
+               if (res)
+                       *res = data_bytes[0];
+
+               // crc check
+               if (len >= 3 && !CheckCrc14443(CRC_14443_A, data_bytes, len)) {
+                       return -1;
+               }
+
+       }
+
+       if (len) {
+               // cut frame byte
+               len -= 1;
+               // memmove(data_bytes, data_bytes + 1, len);
+               for (int i = 0; i < len; i++)
+                       data_bytes[i] = data_bytes[i + 1];
        }
 
        return len;
@@ -1915,20 +2045,19 @@ void ReaderIso14443a(UsbCommand *c)
        byte_t buf[USB_CMD_DATA_SIZE] = {0};
        uint8_t par[MAX_PARITY_SIZE];
        bool cantSELECT = false;
-  
-       if(param & ISO14A_CONNECT) {
-               clear_trace();
-       }
 
        set_tracing(true);
 
+       if(param & ISO14A_CLEAR_TRACE) {
+               clear_trace();
+       }
+
        if(param & ISO14A_REQUEST_TRIGGER) {
                iso14a_set_trigger(true);
        }
 
        if(param & ISO14A_CONNECT) {
                LED_A_ON();
-               clear_trace();
                iso14443a_setup(FPGA_HF_ISO14443A_READER_LISTEN);
                if(!(param & ISO14A_NO_SELECT)) {
                        iso14a_card_select_t *card = (iso14a_card_select_t*)buf;
@@ -1939,7 +2068,7 @@ void ReaderIso14443a(UsbCommand *c)
                                // 1 - all is OK with ATS, 2 - without ATS
                                cantSELECT = true;
                        }
-                       
+                       FpgaDisableTracing();
                        LED_B_ON();
                        cmd_send(CMD_ACK,arg0,card->uidlen,0,buf,sizeof(iso14a_card_select_t));
                        LED_B_OFF();
@@ -1951,9 +2080,11 @@ void ReaderIso14443a(UsbCommand *c)
        }
 
        if(param & ISO14A_APDU && !cantSELECT) {
-               arg0 = iso14_apdu(cmd, len, buf);
+               uint8_t res;
+               arg0 = iso14_apdu(cmd, len, (param & ISO14A_SEND_CHAINING), buf, &res);
+               FpgaDisableTracing();
                LED_B_ON();
-               cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
+               cmd_send(CMD_ACK, arg0, res, 0, buf, sizeof(buf));
                LED_B_OFF();
        }
 
@@ -1967,32 +2098,33 @@ void ReaderIso14443a(UsbCommand *c)
                        len += 2;
                        if (lenbits) lenbits += 16;
                }
-               if(lenbits>0) {                         // want to send a specific number of bits (e.g. short commands)
+               if(lenbits>0) {             // want to send a specific number of bits (e.g. short commands)
                        if(param & ISO14A_TOPAZMODE) {
                                int bits_to_send = lenbits;
                                uint16_t i = 0;
-                               ReaderTransmitBitsPar(&cmd[i++], MIN(bits_to_send, 7), NULL, NULL);             // first byte is always short (7bits) and no parity
+                               ReaderTransmitBitsPar(&cmd[i++], MIN(bits_to_send, 7), NULL, NULL);     // first byte is always short (7bits) and no parity
                                bits_to_send -= 7;
                                while (bits_to_send > 0) {
-                                       ReaderTransmitBitsPar(&cmd[i++], MIN(bits_to_send, 8), NULL, NULL);     // following bytes are 8 bit and no parity
+                                       ReaderTransmitBitsPar(&cmd[i++], MIN(bits_to_send, 8), NULL, NULL); // following bytes are 8 bit and no parity
                                        bits_to_send -= 8;
                                }
                        } else {
                                GetParity(cmd, lenbits/8, par);
-                               ReaderTransmitBitsPar(cmd, lenbits, par, NULL);                                                 // bytes are 8 bit with odd parity
+                               ReaderTransmitBitsPar(cmd, lenbits, par, NULL);                         // bytes are 8 bit with odd parity
                        }
-               } else {                                        // want to send complete bytes only
+               } else {                    // want to send complete bytes only
                        if(param & ISO14A_TOPAZMODE) {
                                uint16_t i = 0;
-                               ReaderTransmitBitsPar(&cmd[i++], 7, NULL, NULL);                                                // first byte: 7 bits, no paritiy
+                               ReaderTransmitBitsPar(&cmd[i++], 7, NULL, NULL);                        // first byte: 7 bits, no paritiy
                                while (i < len) {
-                                       ReaderTransmitBitsPar(&cmd[i++], 8, NULL, NULL);                                        // following bytes: 8 bits, no paritiy
+                                       ReaderTransmitBitsPar(&cmd[i++], 8, NULL, NULL);                    // following bytes: 8 bits, no paritiy
                                }
                        } else {
-                               ReaderTransmit(cmd,len, NULL);                                                                                  // 8 bits, odd parity
+                               ReaderTransmit(cmd,len, NULL);                                          // 8 bits, odd parity
                        }
                }
                arg0 = ReaderReceive(buf, par);
+               FpgaDisableTracing();
 
                LED_B_ON();
                cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
@@ -2024,14 +2156,14 @@ static int32_t dist_nt(uint32_t nt1, uint32_t nt2) {
 
        nttmp1 = nt1;
        nttmp2 = nt2;
-       
+
        for (i = 1; i < 32768; i++) {
                nttmp1 = prng_successor(nttmp1, 1);
                if (nttmp1 == nt2) return i;
                nttmp2 = prng_successor(nttmp2, 1);
                if (nttmp2 == nt1) return -i;
                }
-       
+
        return(-99999); // either nt1 or nt2 are invalid nonces
 }
 
@@ -2052,19 +2184,17 @@ void ReaderMifare(bool first_try)
        uint8_t receivedAnswer[MAX_MIFARE_FRAME_SIZE];
        uint8_t receivedAnswerPar[MAX_MIFARE_PARITY_SIZE];
 
-       if (first_try) { 
-               iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
-       }
-       
+       iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
+
        // free eventually allocated BigBuf memory. We want all for tracing.
        BigBuf_free();
-       
+
        clear_trace();
        set_tracing(true);
 
-       byte_t nt_diff = 0;
-       uint8_t par[1] = {0};   // maximum 8 Bytes to be sent here, 1 byte parity is therefore enough
-       static byte_t par_low = 0;
+       uint8_t nt_diff = 0;
+       uint8_t par[1] = {0};   // maximum 8 Bytes to be sent here, 1 byte parity is therefore enough
+       static uint8_t par_low = 0;
        bool led_on = true;
        uint8_t uid[10]  ={0};
        uint32_t cuid;
@@ -2072,11 +2202,11 @@ void ReaderMifare(bool first_try)
        uint32_t nt = 0;
        uint32_t previous_nt = 0;
        static uint32_t nt_attacked = 0;
-       byte_t par_list[8] = {0x00};
-       byte_t ks_list[8] = {0x00};
+       uint8_t par_list[8] = {0x00};
+       uint8_t ks_list[8] = {0x00};
 
        #define PRNG_SEQUENCE_LENGTH  (1 << 16);
-       static uint32_t sync_time;
+       uint32_t sync_time = GetCountSspClk() & 0xfffffff8;
        static int32_t sync_cycles;
        int catch_up_cycles = 0;
        int last_catch_up = 0;
@@ -2084,12 +2214,11 @@ void ReaderMifare(bool first_try)
        uint16_t consecutive_resyncs = 0;
        int isOK = 0;
 
-       if (first_try) { 
+       if (first_try) {
                mf_nr_ar3 = 0;
-               sync_time = GetCountSspClk() & 0xfffffff8;
-               sync_cycles = PRNG_SEQUENCE_LENGTH;                                                     // theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the tag nonces).
+               par[0] = par_low = 0;
+               sync_cycles = PRNG_SEQUENCE_LENGTH;                         // theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the tag nonces).
                nt_attacked = 0;
-               par[0] = 0;
        }
        else {
                // we were unsuccessful on a previous call. Try another READER nonce (first 3 parity bits remain the same)
@@ -2101,12 +2230,13 @@ void ReaderMifare(bool first_try)
        LED_A_ON();
        LED_B_OFF();
        LED_C_OFF();
-       
 
-       #define MAX_UNEXPECTED_RANDOM   4               // maximum number of unexpected (i.e. real) random numbers when trying to sync. Then give up.
-       #define MAX_SYNC_TRIES                  32
-       #define NUM_DEBUG_INFOS                 8               // per strategy
-       #define MAX_STRATEGY                    3
+
+       #define MAX_UNEXPECTED_RANDOM   4       // maximum number of unexpected (i.e. real) random numbers when trying to sync. Then give up.
+       #define MAX_SYNC_TRIES          32
+       #define SYNC_TIME_BUFFER        16      // if there is only SYNC_TIME_BUFFER left before next planned sync, wait for next PRNG cycle
+       #define NUM_DEBUG_INFOS         8       // per strategy
+       #define MAX_STRATEGY            3
        uint16_t unexpected_random = 0;
        uint16_t sync_tries = 0;
        int16_t debug_info_nr = -1;
@@ -2114,9 +2244,9 @@ void ReaderMifare(bool first_try)
        int32_t debug_info[MAX_STRATEGY][NUM_DEBUG_INFOS];
        uint32_t select_time;
        uint32_t halt_time;
-       
-       for(uint16_t i = 0; true; i++) {
-               
+
+       for (uint16_t i = 0; true; i++) {
+
                LED_C_ON();
                WDT_HIT();
 
@@ -2125,7 +2255,7 @@ void ReaderMifare(bool first_try)
                        isOK = -1;
                        break;
                }
-               
+
                if (strategy == 2) {
                        // test with additional hlt command
                        halt_time = 0;
@@ -2142,9 +2272,9 @@ void ReaderMifare(bool first_try)
                        iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
                        SpinDelay(100);
                }
-               
+
                if(!iso14443a_select_card(uid, NULL, &cuid, true, 0, true)) {
-                       if (MF_DBGLEVEL >= 1)   Dbprintf("Mifare: Can't select card");
+                       if (MF_DBGLEVEL >= 1)   Dbprintf("Mifare: Can't select card");
                        continue;
                }
                select_time = GetCountSspClk();
@@ -2154,17 +2284,17 @@ void ReaderMifare(bool first_try)
                        sync_time = (sync_time & 0xfffffff8) + sync_cycles + catch_up_cycles;
                        catch_up_cycles = 0;
 
-                       // if we missed the sync time already, advance to the next nonce repeat
-                       while(GetCountSspClk() > sync_time) {
+                       // if we missed the sync time already or are about to miss it, advance to the next nonce repeat
+                       while(sync_time < GetCountSspClk() + SYNC_TIME_BUFFER) {
                                elapsed_prng_sequences++;
                                sync_time = (sync_time & 0xfffffff8) + sync_cycles;
                        }
 
-                       // Transmit MIFARE_CLASSIC_AUTH at synctime. Should result in returning the same tag nonce (== nt_attacked) 
+                       // Transmit MIFARE_CLASSIC_AUTH at synctime. Should result in returning the same tag nonce (== nt_attacked)
                        ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
                } else {
                        // collect some information on tag nonces for debugging:
-                       #define DEBUG_FIXED_SYNC_CYCLES PRNG_SEQUENCE_LENGTH
+                       #define DEBUG_FIXED_SYNC_CYCLES PRNG_SEQUENCE_LENGTH
                        if (strategy == 0) {
                                // nonce distances at fixed time after card select:
                                sync_time = select_time + DEBUG_FIXED_SYNC_CYCLES;
@@ -2179,11 +2309,11 @@ void ReaderMifare(bool first_try)
                                sync_time = DEBUG_FIXED_SYNC_CYCLES;
                        }
                        ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
-               }                       
+               }
 
                // Receive the (4 Byte) "random" nonce
                if (!ReaderReceive(receivedAnswer, receivedAnswerPar)) {
-                       if (MF_DBGLEVEL >= 1)   Dbprintf("Mifare: Couldn't receive tag nonce");
+                       if (MF_DBGLEVEL >= 1)   Dbprintf("Mifare: Couldn't receive tag nonce");
                        continue;
                  }
 
@@ -2201,17 +2331,17 @@ void ReaderMifare(bool first_try)
                                if (nt_distance == -99999) { // invalid nonce received
                                        unexpected_random++;
                                        if (unexpected_random > MAX_UNEXPECTED_RANDOM) {
-                                               isOK = -3;              // Card has an unpredictable PRNG. Give up      
+                                               isOK = -3;      // Card has an unpredictable PRNG. Give up
                                                break;
                                        } else {
-                                               continue;               // continue trying...
+                                               continue;       // continue trying...
                                        }
                                }
                                if (++sync_tries > MAX_SYNC_TRIES) {
                                        if (strategy > MAX_STRATEGY || MF_DBGLEVEL < 3) {
-                                               isOK = -4;                      // Card's PRNG runs at an unexpected frequency or resets unexpectedly
+                                               isOK = -4;          // Card's PRNG runs at an unexpected frequency or resets unexpectedly
                                                break;
-                                       } else {                                // continue for a while, just to collect some debug info
+                                       } else {                // continue for a while, just to collect some debug info
                                                debug_info[strategy][debug_info_nr] = nt_distance;
                                                debug_info_nr++;
                                                if (debug_info_nr == NUM_DEBUG_INFOS) {
@@ -2232,9 +2362,9 @@ void ReaderMifare(bool first_try)
                        }
                }
 
-               if ((nt != nt_attacked) && nt_attacked) {       // we somehow lost sync. Try to catch up again...
+               if ((nt != nt_attacked) && nt_attacked) {   // we somehow lost sync. Try to catch up again...
                        catch_up_cycles = -dist_nt(nt_attacked, nt);
-                       if (catch_up_cycles == 99999) {                 // invalid nonce received. Don't resync on that one.
+                       if (catch_up_cycles == 99999) {         // invalid nonce received. Don't resync on that one.
                                catch_up_cycles = 0;
                                continue;
                        }
@@ -2244,12 +2374,12 @@ void ReaderMifare(bool first_try)
                        }
                        else {
                                last_catch_up = catch_up_cycles;
-                           consecutive_resyncs = 0;
+                               consecutive_resyncs = 0;
                        }
                        if (consecutive_resyncs < 3) {
                                if (MF_DBGLEVEL >= 3) Dbprintf("Lost sync in cycle %d. nt_distance=%d. Consecutive Resyncs = %d. Trying one time catch up...\n", i, -catch_up_cycles, consecutive_resyncs);
                        }
-                       else {  
+                       else {
                                sync_cycles = sync_cycles + catch_up_cycles;
                                if (MF_DBGLEVEL >= 3) Dbprintf("Lost sync in cycle %d for the fourth time consecutively (nt_distance = %d). Adjusting sync_cycles to %d.\n", i, -catch_up_cycles, sync_cycles);
                                last_catch_up = 0;
@@ -2258,13 +2388,13 @@ void ReaderMifare(bool first_try)
                        }
                        continue;
                }
+
                consecutive_resyncs = 0;
-               
+
                // Receive answer. This will be a 4 Bit NACK when the 8 parity bits are OK after decoding
                if (ReaderReceive(receivedAnswer, receivedAnswerPar)) {
-                       catch_up_cycles = 8;    // the PRNG is delayed by 8 cycles due to the NAC (4Bits = 0x05 encrypted) transfer
-       
+                       catch_up_cycles = 8;    // the PRNG is delayed by 8 cycles due to the NAC (4Bits = 0x05 encrypted) transfer
+
                        if (nt_diff == 0) {
                                par_low = par[0] & 0xE0; // there is no need to check all parities for other nt_diff. Parity Bits for mf_nr_ar[0..2] won't change
                        }
@@ -2288,7 +2418,7 @@ void ReaderMifare(bool first_try)
                        if (nt_diff == 0 && first_try)
                        {
                                par[0]++;
-                               if (par[0] == 0x00) {           // tried all 256 possible parities without success. Card doesn't send NACK.
+                               if (par[0] == 0x00) {       // tried all 256 possible parities without success. Card doesn't send NACK.
                                        isOK = -2;
                                        break;
                                }
@@ -2304,21 +2434,23 @@ void ReaderMifare(bool first_try)
        if (isOK == -4) {
                if (MF_DBGLEVEL >= 3) {
                        for (uint16_t i = 0; i <= MAX_STRATEGY; i++) {
-                               for(uint16_t j = 0; j < NUM_DEBUG_INFOS; j++) {
+                               for (uint16_t j = 0; j < NUM_DEBUG_INFOS; j++) {
                                        Dbprintf("collected debug info[%d][%d] = %d", i, j, debug_info[i][j]);
                                }
                        }
                }
        }
-       
-       byte_t buf[28];
+
+       FpgaDisableTracing();
+
+       uint8_t buf[32];
        memcpy(buf + 0,  uid, 4);
        num_to_bytes(nt, 4, buf + 4);
        memcpy(buf + 8,  par_list, 8);
        memcpy(buf + 16, ks_list, 8);
-       memcpy(buf + 24, mf_nr_ar, 4);
-               
-       cmd_send(CMD_ACK, isOK, 0, 0, buf, 28);
+       memcpy(buf + 24, mf_nr_ar, 8);
+
+       cmd_send(CMD_ACK, isOK, 0, 0, buf, 32);
 
        // Thats it...
        FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
@@ -2329,8 +2461,8 @@ void ReaderMifare(bool first_try)
 
 
 //-----------------------------------------------------------------------------
-// MIFARE sniffer. 
-// 
+// MIFARE sniffer.
+//
 //-----------------------------------------------------------------------------
 void RAMFUNC SniffMifare(uint8_t param) {
        // param:
@@ -2339,6 +2471,8 @@ void RAMFUNC SniffMifare(uint8_t param) {
 
        // C(red) A(yellow) B(green)
        LEDsoff();
+       LED_A_ON();
+
        // init trace buffer
        clear_trace();
        set_tracing(true);
@@ -2374,26 +2508,23 @@ void RAMFUNC SniffMifare(uint8_t param) {
        // Setup for the DMA.
        FpgaSetupSscDma((uint8_t *)dmaBuf, DMA_BUFFER_SIZE); // set transfer address and number of bytes. Start transfer.
 
-       LED_D_OFF();
-       
        // init sniffer
        MfSniffInit();
 
        // And now we loop, receiving samples.
-       for(uint32_t sniffCounter = 0; true; ) {
-       
+       for (uint32_t sniffCounter = 0; true; ) {
+
                if(BUTTON_PRESS()) {
-                       DbpString("cancelled by button");
+                       DbpString("Canceled by button.");
                        break;
                }
 
-               LED_A_ON();
                WDT_HIT();
-               
-               if ((sniffCounter & 0x0000FFFF) == 0) { // from time to time
+
+               if ((sniffCounter & 0x0000FFFF) == 0) { // from time to time
                        // check if a transaction is completed (timeout after 2000ms).
                        // if yes, stop the DMA transfer and send what we have so far to the client
-                       if (MfSniffSend(2000)) {                        
+                       if (MfSniffSend(2000)) {
                                // Reset everything - we missed some sniffed data anyway while the DMA was stopped
                                sniffCounter = 0;
                                data = dmaBuf;
@@ -2403,17 +2534,17 @@ void RAMFUNC SniffMifare(uint8_t param) {
                                FpgaSetupSscDma((uint8_t *)dmaBuf, DMA_BUFFER_SIZE); // set transfer address and number of bytes. Start transfer.
                        }
                }
-               
-               int register readBufDataP = data - dmaBuf;      // number of bytes we have processed so far
+
+               int register readBufDataP = data - dmaBuf;  // number of bytes we have processed so far
                int register dmaBufDataP = DMA_BUFFER_SIZE - AT91C_BASE_PDC_SSC->PDC_RCR; // number of bytes already transferred
-               if (readBufDataP <= dmaBufDataP){                       // we are processing the same block of data which is currently being transferred
-                       dataLen = dmaBufDataP - readBufDataP;   // number of bytes still to be processed
-               } else {                                                                        
+               if (readBufDataP <= dmaBufDataP){           // we are processing the same block of data which is currently being transferred
+                       dataLen = dmaBufDataP - readBufDataP;   // number of bytes still to be processed
+               } else {
                        dataLen = DMA_BUFFER_SIZE - readBufDataP + dmaBufDataP; // number of bytes still to be processed
                }
                // test for length of buffer
-               if(dataLen > maxDataLen) {                                      // we are more behind than ever...
-                       maxDataLen = dataLen;                                   
+               if(dataLen > maxDataLen) {                  // we are more behind than ever...
+                       maxDataLen = dataLen;
                        if(dataLen > (9 * DMA_BUFFER_SIZE / 10)) {
                                Dbprintf("blew circular buffer! dataLen=0x%x", dataLen);
                                break;
@@ -2433,29 +2564,26 @@ void RAMFUNC SniffMifare(uint8_t param) {
                        AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;
                }
 
-               LED_A_OFF();
-               
                if (sniffCounter & 0x01) {
 
-                       if(!TagIsActive) {              // no need to try decoding tag data if the reader is sending
+                       if(!TagIsActive) {      // no need to try decoding tag data if the reader is sending
                                uint8_t readerdata = (previous_data & 0xF0) | (*data >> 4);
                                if(MillerDecoding(readerdata, (sniffCounter-1)*4)) {
-                                       LED_C_INV();
+
                                        if (MfSniffLogic(receivedCmd, Uart.len, Uart.parity, Uart.bitCount, true)) break;
 
                                        /* And ready to receive another command. */
                                        UartInit(receivedCmd, receivedCmdPar);
-                                       
+
                                        /* And also reset the demod code */
                                        DemodReset();
                                }
                                ReaderIsActive = (Uart.state != STATE_UNSYNCD);
                        }
-                       
-                       if(!ReaderIsActive) {           // no need to try decoding tag data if the reader is sending
+
+                       if(!ReaderIsActive) {       // no need to try decoding tag data if the reader is sending
                                uint8_t tagdata = (previous_data << 4) | (*data & 0x0F);
                                if(ManchesterDecoding(tagdata, 0, (sniffCounter-1)*4)) {
-                                       LED_C_INV();
 
                                        if (MfSniffLogic(receivedResponse, Demod.len, Demod.parity, Demod.bitCount, false)) break;
 
@@ -2477,11 +2605,13 @@ void RAMFUNC SniffMifare(uint8_t param) {
 
        } // main cycle
 
-       DbpString("COMMAND FINISHED");
-
+       FpgaDisableTracing();
        FpgaDisableSscDma();
+       LEDsoff();
+
+       DbpString("COMMAND FINISHED.");
+
        MfSniffEnd();
-       
+
        Dbprintf("maxDataLen=%x, Uart.state=%x, Uart.len=%x", maxDataLen, Uart.state, Uart.len);
-       LEDsoff();
 }
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