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fixed bug in ASKbiphaseDemod()
[proxmark3-svn] / armsrc / iso15693.c
diff --git a/armsrc/iso15693.c b/armsrc/iso15693.c
index e36baad2a9688f17f9679f88c3be6ffd6cbd782c..e352437524a029f6f951f1143407634fe49d0cdd 100644 (file)
--- a/armsrc/iso15693.c
+++ b/armsrc/iso15693.c
@@ -1,71 +1,103 @@
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
-// Routines to support ISO 15693. This includes both the reader software and
-// the `fake tag' modes, but at the moment I've implemented only the reader
-// stuff, and that barely.
 // Jonathan Westhues, split Nov 2006
 // Jonathan Westhues, split Nov 2006
+// Modified by Greg Jones, Jan 2009
+// Modified by Adrian Dabrowski "atrox", Mar-Sept 2010,Oct 2011
+// Modified by piwi, Oct 2018 
+//
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file for the text of
+// the license.
+//-----------------------------------------------------------------------------
+// Routines to support ISO 15693. This includes both the reader software and
+// the `fake tag' modes.
+//-----------------------------------------------------------------------------
 
 
-// Modified by Greg Jones, Jan 2009 to perform modulation onboard in arm rather than on PC
-// Also added additional reader commands (SELECT, READ etc.)
-
+// The ISO 15693 describes two transmission modes from reader to tag, and four
+// transmission modes from tag to reader. As of Oct 2018 this code supports
+// both reader modes and the high speed variant with one subcarrier from card to reader.
+// As long as the card fully support ISO 15693 this is no problem, since the
+// reader chooses both data rates, but some non-standard tags do not. 
+// For card simulation, the code supports both high and low speed modes with one subcarrier.
+//
+// VCD (reader) -> VICC (tag)
+// 1 out of 256:
+//     data rate: 1,66 kbit/s (fc/8192)
+//     used for long range
+// 1 out of 4:
+//     data rate: 26,48 kbit/s (fc/512)
+//     used for short range, high speed
+//
+// VICC (tag) -> VCD (reader)
+// Modulation:
+//             ASK / one subcarrier (423,75 khz)
+//             FSK / two subcarriers (423,75 khz && 484,28 khz)
+// Data Rates / Modes:
+//     low ASK: 6,62 kbit/s
+//     low FSK: 6.67 kbit/s
+//     high ASK: 26,48 kbit/s
+//     high FSK: 26,69 kbit/s
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
-#include <proxmark3.h>
+
+
+// Random Remarks:
+// *) UID is always used "transmission order" (LSB), which is reverse to display order
+
+// TODO / BUGS / ISSUES:
+// *) signal decoding is unable to detect collisions.
+// *) add anti-collision support for inventory-commands
+// *) read security status of a block
+// *) sniffing and simulation do not support two subcarrier modes.
+// *) remove or refactor code under "deprecated"
+// *) document all the functions
+
+#include "iso15693.h"
+
+#include "proxmark3.h"
+#include "util.h"
 #include "apps.h"
 #include "apps.h"
+#include "string.h"
+#include "iso15693tools.h"
+#include "protocols.h"
+#include "cmd.h"
+#include "BigBuf.h"
+#include "fpgaloader.h"
 
 
-// FROM winsrc\prox.h //////////////////////////////////
 #define arraylen(x) (sizeof(x)/sizeof((x)[0]))
 
 #define arraylen(x) (sizeof(x)/sizeof((x)[0]))
 
-//-----------------------------------------------------------------------------
-// Map a sequence of octets (~layer 2 command) into the set of bits to feed
-// to the FPGA, to transmit that command to the tag.
-//-----------------------------------------------------------------------------
-
-       // The sampling rate is 106.353 ksps/s, for T = 18.8 us
-
-       // SOF defined as
-       // 1) Unmodulated time of 56.64us
-       // 2) 24 pulses of 423.75khz
-       // 3) logic '1' (unmodulated for 18.88us followed by 8 pulses of 423.75khz)
-
-       static const int FrameSOF[] = {
-               -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-               -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-                1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
-                1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
-               -1, -1, -1, -1,
-               -1, -1, -1, -1,
-                1,  1,  1,  1,
-                1,  1,  1,  1
-       };
-       static const int Logic0[] = {
-                1,  1,  1,  1,
-                1,  1,  1,  1,
-               -1, -1, -1, -1,
-               -1, -1, -1, -1
-       };
-       static const int Logic1[] = {
-               -1, -1, -1, -1,
-               -1, -1, -1, -1,
-                1,  1,  1,  1,
-                1,  1,  1,  1
-       };
-
-       // EOF defined as
-       // 1) logic '0' (8 pulses of 423.75khz followed by unmodulated for 18.88us)
-       // 2) 24 pulses of 423.75khz
-       // 3) Unmodulated time of 56.64us
-
-       static const int FrameEOF[] = {
-                1,  1,  1,  1,
-                1,  1,  1,  1,
-               -1, -1, -1, -1,
-               -1, -1, -1, -1,
-                1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
-                1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
-               -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-               -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
-       };
-
-static void CodeIso15693AsReader(BYTE *cmd, int n)
+static int DEBUG = 0;
+
+///////////////////////////////////////////////////////////////////////
+// ISO 15693 Part 2 - Air Interface
+// This section basicly contains transmission and receiving of bits
+///////////////////////////////////////////////////////////////////////
+
+#define Crc(data,datalen)     Iso15693Crc(data,datalen)
+#define AddCrc(data,datalen)  Iso15693AddCrc(data,datalen)
+#define sprintUID(target,uid)  Iso15693sprintUID(target,uid)
+
+// buffers
+#define ISO15693_DMA_BUFFER_SIZE        2048 // must be a power of 2
+#define ISO15693_MAX_RESPONSE_LENGTH     36 // allows read single block with the maximum block size of 256bits. Read multiple blocks not supported yet
+#define ISO15693_MAX_COMMAND_LENGTH      45 // allows write single block with the maximum block size of 256bits. Write multiple blocks not supported yet
+
+// timing. Delays in SSP_CLK ticks. 
+// SSP_CLK runs at 13,56MHz / 32 = 423.75kHz when simulating a tag
+#define DELAY_READER_TO_ARM_SIM           8
+#define DELAY_ARM_TO_READER_SIM           1
+#define DELAY_ISO15693_VCD_TO_VICC_SIM    132  // 132/423.75kHz = 311.5us from end of command EOF to start of tag response
+//SSP_CLK runs at 13.56MHz / 4 = 3,39MHz when acting as reader
+#define DELAY_ISO15693_VCD_TO_VICC_READER 1056 // 1056/3,39MHz = 311.5us from end of command EOF to start of tag response
+#define DELAY_ISO15693_VICC_TO_VCD_READER 1017 // 1017/3.39MHz = 300us between end of tag response and next reader command
+
+// ---------------------------
+// Signal Processing
+// ---------------------------
+
+// prepare data using "1 out of 4" code for later transmission
+// resulting data rate is 26.48 kbit/s (fc/512)
+// cmd ... data
+// n ... length of data
+static void CodeIso15693AsReader(uint8_t *cmd, int n)
 {
        int i, j;
 
 {
        int i, j;
 
@@ -76,6 +108,7 @@ static void CodeIso15693AsReader(BYTE *cmd, int n)
                ToSendStuffBit(1);
        }
 
                ToSendStuffBit(1);
        }
 
+       // SOF for 1of4
        ToSendStuffBit(0);
        ToSendStuffBit(1);
        ToSendStuffBit(1);
        ToSendStuffBit(0);
        ToSendStuffBit(1);
        ToSendStuffBit(1);
@@ -131,981 +164,1580 @@ static void CodeIso15693AsReader(BYTE *cmd, int n)
                        }
                }
        }
                        }
                }
        }
+       // EOF
        ToSendStuffBit(1);
        ToSendStuffBit(1);
        ToSendStuffBit(0);
        ToSendStuffBit(1);
 
        ToSendStuffBit(1);
        ToSendStuffBit(1);
        ToSendStuffBit(0);
        ToSendStuffBit(1);
 
-       // And slack at the end, too.
-       for(i = 0; i < 24; i++) {
+       // Fill remainder of last byte with 1
+       for(i = 0; i < 4; i++) {
                ToSendStuffBit(1);
        }
                ToSendStuffBit(1);
        }
+       
+       ToSendMax++;
 }
 
 }
 
-//-----------------------------------------------------------------------------
-// The CRC used by ISO 15693.
-//-----------------------------------------------------------------------------
-static WORD Crc(BYTE *v, int n)
+// encode data using "1 out of 256" scheme
+// data rate is 1,66 kbit/s (fc/8192)
+// is designed for more robust communication over longer distances
+static void CodeIso15693AsReader256(uint8_t *cmd, int n)
 {
 {
-       DWORD reg;
        int i, j;
 
        int i, j;
 
-       reg = 0xffff;
+       ToSendReset();
+
+       // Give it a bit of slack at the beginning
+       for(i = 0; i < 24; i++) {
+               ToSendStuffBit(1);
+       }
+
+       // SOF for 1of256
+       ToSendStuffBit(0);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(0);
+
        for(i = 0; i < n; i++) {
        for(i = 0; i < n; i++) {
-               reg = reg ^ ((DWORD)v[i]);
-               for (j = 0; j < 8; j++) {
-                       if (reg & 0x0001) {
-                               reg = (reg >> 1) ^ 0x8408;
+               for (j = 0; j<=255; j++) {
+                       if (cmd[i]==j) {
+                               ToSendStuffBit(1);
+                               ToSendStuffBit(0);
                        } else {
                        } else {
-                               reg = (reg >> 1);
+                               ToSendStuffBit(1);
+                               ToSendStuffBit(1);
                        }
                }
        }
                        }
                }
        }
+       // EOF
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(0);
+       ToSendStuffBit(1);
 
 
-       return ~reg;
-}
+       // Fill remainder of last byte with 1
+       for(i = 0; i < 4; i++) {
+               ToSendStuffBit(1);
+       }
 
 
-char *strcat(char *dest, const char *src)
-{
-       size_t dest_len = strlen(dest);
-       size_t i;
- 
-       for (i = 0 ; src[i] != '\0' ; i++)
-               dest[dest_len + i] = src[i];
-       dest[dest_len + i] = '\0';
- 
-       return dest;
+       ToSendMax++;
 }
 
 }
 
-////////////////////////////////////////// code to do 'itoa'
 
 
-/* reverse:  reverse string s in place */
-void reverse(char s[])
+static void CodeIso15693AsTag(uint8_t *cmd, int n)
 {
 {
-    int c, i, j;
+       ToSendReset();
 
 
-    for (i = 0, j = strlen(s)-1; i<j; i++, j--) {
-        c = s[i];
-        s[i] = s[j];
-        s[j] = c;
-    }
+       // SOF
+       ToSendStuffBit(0);
+       ToSendStuffBit(0);
+       ToSendStuffBit(0);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(0);
+       ToSendStuffBit(1);
+
+       // data
+       for(int i = 0; i < n; i++) {
+               for(int j = 0; j < 8; j++) {
+                       if ((cmd[i] >> j) & 0x01) {
+                                       ToSendStuffBit(0);
+                                       ToSendStuffBit(1);
+                       } else {
+                                       ToSendStuffBit(1);
+                                       ToSendStuffBit(0);
+                       }
+               }
+       }
+
+       // EOF
+       ToSendStuffBit(1);
+       ToSendStuffBit(0);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(1);
+       ToSendStuffBit(0);
+       ToSendStuffBit(0);
+       ToSendStuffBit(0);
+
+       ToSendMax++;
 }
 
 }
 
-/* itoa:  convert n to characters in s */
-void itoa(int n, char s[])
+
+// Transmit the command (to the tag) that was placed in cmd[].
+static void TransmitTo15693Tag(const uint8_t *cmd, int len, uint32_t start_time)
 {
 {
-    int i, sign;
-
-    if ((sign = n) < 0)  /* record sign */
-        n = -n;          /* make n positive */
-    i = 0;
-    do {       /* generate digits in reverse order */
-        s[i++] = n % 10 + '0';   /* get next digit */
-    } while ((n /= 10) > 0);     /* delete it */
-    if (sign < 0)
-        s[i++] = '-';
-    s[i] = '\0';
-    reverse(s);
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_MODE_SEND_FULL_MOD);
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
+
+       while (GetCountSspClk() < start_time) ;
+
+       LED_B_ON();
+       for(int c = 0; c < len; c++) {
+               uint8_t data = cmd[c];
+               for (int i = 0; i < 8; i++) {
+                       uint16_t send_word = (data & 0x80) ? 0x0000 : 0xffff;
+                       while (!(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY))) ;
+                       AT91C_BASE_SSC->SSC_THR = send_word;
+                       while (!(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY))) ;
+                       AT91C_BASE_SSC->SSC_THR = send_word;
+                       data <<= 1;
+               }
+               WDT_HIT();
+       }
+       LED_B_OFF();
 }
 
 }
 
-//////////////////////////////////////// END 'itoa' CODE
 
 //-----------------------------------------------------------------------------
 
 //-----------------------------------------------------------------------------
-// Encode (into the ToSend buffers) an identify request, which is the first
-// thing that you must send to a tag to get a response.
+// Transmit the tag response (to the reader) that was placed in cmd[].
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
-static void BuildIdentifyRequest(void)
+static void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t start_time, bool slow)
 {
 {
-       BYTE cmd[5];
+       // don't use the FPGA_HF_SIMULATOR_MODULATE_424K_8BIT minor mode. It would spoil GetCountSspClk()
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_424K);
 
 
-       WORD crc;
-       // one sub-carrier, inventory, 1 slot, fast rate
-       // AFI is at bit 5 (1<<4) when doing an INVENTORY
-       cmd[0] = (1 << 2) | (1 << 5) | (1 << 1);
-       // inventory command code
-       cmd[1] = 0x01;
-       // no mask
-       cmd[2] = 0x00;
-       //Now the CRC
-       crc = Crc(cmd, 3);
-       cmd[3] = crc & 0xff;
-       cmd[4] = crc >> 8;
-
-       CodeIso15693AsReader(cmd, sizeof(cmd));
-}
+       uint8_t shift_delay = start_time & 0x00000007;
+       uint8_t bitmask = 0x00;
+       for (int i = 0; i < shift_delay; i++) {
+               bitmask |= (0x01 << i);
+       }
 
 
-static void __attribute__((unused)) BuildSysInfoRequest(BYTE *uid)
-{
-       BYTE cmd[12];
+       while (GetCountSspClk() < (start_time & 0xfffffff8)) ;
 
 
-       WORD crc;
-       // If we set the Option_Flag in this request, the VICC will respond with the secuirty status of the block
-       // followed by teh block data
-       // one sub-carrier, inventory, 1 slot, fast rate
-       cmd[0] =  (1 << 5) | (1 << 1); // no SELECT bit
-       // System Information command code
-       cmd[1] = 0x2B;
-       // UID may be optionally specified here
-       // 64-bit UID
-       cmd[2] = 0x32;
-       cmd[3]= 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05;
-       cmd[9]= 0xe0; // always e0 (not exactly unique)
-       //Now the CRC
-       crc = Crc(cmd, 10); // the crc needs to be calculated over 2 bytes
-       cmd[10] = crc & 0xff;
-       cmd[11] = crc >> 8;
+       AT91C_BASE_SSC->SSC_THR = 0x00; // clear TXRDY
 
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
+       LED_C_ON();
+       uint8_t bits_to_shift = 0x00;
+    for(size_t c = 0; c <= len; c++) {
+               uint8_t bits_to_send = bits_to_shift << (8 - shift_delay) | (c==len?0x00:cmd[c]) >> shift_delay;
+               bits_to_shift = cmd[c] & bitmask;
+               for (int i = 7; i >= 0; i--) {
+                       for (int j = 0; j < (slow?4:1); ) {
+                               if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
+                                       if (bits_to_send >> i & 0x01) {
+                                               AT91C_BASE_SSC->SSC_THR = 0xff;
+                                       } else {
+                                               AT91C_BASE_SSC->SSC_THR = 0x00;
+                                       }
+                                       j++;
+                               }
+                               WDT_HIT();
+                       }
+        }
+    }
+       LED_C_OFF();
 }
 
 }
 
-static void BuildSelectRequest( BYTE uid[])
+
+//=============================================================================
+// An ISO 15693 decoder for tag responses (one subcarrier only).
+// Uses cross correlation to identify each bit and EOF.
+// This function is called 8 times per bit (every 2 subcarrier cycles).
+// Subcarrier frequency fs is 424kHz, 1/fs = 2,36us,
+// i.e. function is called every 4,72us
+// LED handling:
+//    LED C -> ON once we have received the SOF and are expecting the rest.
+//    LED C -> OFF once we have received EOF or are unsynced
+//
+// Returns: true if we received a EOF
+//          false if we are still waiting for some more
+//=============================================================================
+
+#define NOISE_THRESHOLD    160      // don't try to correlate noise
+
+typedef struct DecodeTag {
+       enum {
+               STATE_TAG_SOF_LOW,
+               STATE_TAG_SOF_HIGH,
+               STATE_TAG_SOF_HIGH_END,
+               STATE_TAG_RECEIVING_DATA,
+               STATE_TAG_EOF
+       }         state;
+       int       bitCount;
+       int       posCount;
+       enum {
+               LOGIC0,
+               LOGIC1,
+               SOF_PART1,
+               SOF_PART2
+       }         lastBit;
+       uint16_t  shiftReg;
+       uint16_t  max_len;
+       uint8_t   *output;
+       int       len;
+       int       sum1, sum2;
+} DecodeTag_t;
+
+
+static int inline __attribute__((always_inline)) Handle15693SamplesFromTag(uint16_t amplitude, DecodeTag_t *DecodeTag)
 {
 {
+       switch(DecodeTag->state) {
+               case STATE_TAG_SOF_LOW: 
+                       // waiting for 12 times low (11 times low is accepted as well)
+                       if (amplitude < NOISE_THRESHOLD) {
+                               DecodeTag->posCount++;
+                       } else {
+                               if (DecodeTag->posCount > 10) {
+                                       DecodeTag->posCount = 1;
+                                       DecodeTag->sum1 = 0;
+                                       DecodeTag->state = STATE_TAG_SOF_HIGH;
+                               } else {
+                                       DecodeTag->posCount = 0;
+                               }
+                       }
+                       break;
+                       
+               case STATE_TAG_SOF_HIGH:
+                       // waiting for 10 times high. Take average over the last 8
+                       if (amplitude > NOISE_THRESHOLD) {
+                               DecodeTag->posCount++;
+                               if (DecodeTag->posCount > 2) {
+                                       DecodeTag->sum1 += amplitude; // keep track of average high value
+                               }
+                               if (DecodeTag->posCount == 10) {
+                                       DecodeTag->sum1 >>= 4;        // calculate half of average high value (8 samples)
+                                       DecodeTag->state = STATE_TAG_SOF_HIGH_END;
+                               }
+                       } else { // high phase was too short
+                               DecodeTag->posCount = 1;
+                               DecodeTag->state = STATE_TAG_SOF_LOW;
+                       }
+                       break;
 
 
-//     uid[6]=0x31;  // this is getting ignored - the uid array is not happening...
-       BYTE cmd[12];
+               case STATE_TAG_SOF_HIGH_END:
+                       // waiting for a falling edge
+                       if (amplitude < DecodeTag->sum1) {   // signal drops below 50% average high: a falling edge
+                               DecodeTag->lastBit = SOF_PART1;  // detected 1st part of SOF (12 samples low and 12 samples high)
+                               DecodeTag->shiftReg = 0;
+                               DecodeTag->bitCount = 0;
+                               DecodeTag->len = 0;
+                               DecodeTag->sum1 = amplitude;
+                               DecodeTag->sum2 = 0;
+                               DecodeTag->posCount = 2;
+                               DecodeTag->state = STATE_TAG_RECEIVING_DATA;
+                               LED_C_ON();
+                       } else {
+                               DecodeTag->posCount++;
+                               if (DecodeTag->posCount > 13) { // high phase too long
+                                       DecodeTag->posCount = 0;
+                                       DecodeTag->state = STATE_TAG_SOF_LOW;
+                                       LED_C_OFF();
+                               }
+                       }
+                       break;
 
 
-       WORD crc;
-       // one sub-carrier, inventory, 1 slot, fast rate
-       //cmd[0] = (1 << 2) | (1 << 5) | (1 << 1);      // INVENTROY FLAGS
-       cmd[0] = (1 << 4) | (1 << 5) | (1 << 1);        // Select and addressed FLAGS
-       // SELECT command code
-       cmd[1] = 0x25;
-       // 64-bit UID
-//     cmd[2] = uid[0];//0x32;
-//     cmd[3]= uid[1];//0x4b;
-//     cmd[4] = uid[2];//0x03;
-//     cmd[5] = uid[3];//0x01;
-//     cmd[6] = uid[4];//0x00;
-//     cmd[7] = uid[5];//0x10;
-//     cmd[8] = uid[6];//0x05;
-       cmd[2] = 0x32;//
-       cmd[3] = 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05; // infineon?
+               case STATE_TAG_RECEIVING_DATA:
+                       if (DecodeTag->posCount == 1) {
+                               DecodeTag->sum1 = 0;
+                               DecodeTag->sum2 = 0;
+                       }
+                       if (DecodeTag->posCount <= 4) {
+                               DecodeTag->sum1 += amplitude;
+                       } else {
+                               DecodeTag->sum2 += amplitude;
+                       }
+                       if (DecodeTag->posCount == 8) {
+                               int32_t corr_1 = DecodeTag->sum2 - DecodeTag->sum1;
+                               int32_t corr_0 = -corr_1;
+                               int32_t corr_EOF = (DecodeTag->sum1 + DecodeTag->sum2) / 2;
+                               if (corr_EOF > corr_0 && corr_EOF > corr_1) {
+                                       if (DecodeTag->lastBit == LOGIC0) {  // this was already part of EOF
+                                               DecodeTag->state = STATE_TAG_EOF;
+                                       } else {
+                                               DecodeTag->posCount = 0;
+                                               DecodeTag->state = STATE_TAG_SOF_LOW;
+                                               LED_C_OFF();
+                                       }
+                               } else if (corr_1 > corr_0) {
+                                       // logic 1
+                                       if (DecodeTag->lastBit == SOF_PART1) { // still part of SOF
+                                               DecodeTag->lastBit = SOF_PART2;    // SOF completed
+                                       } else {
+                                               DecodeTag->lastBit = LOGIC1;
+                                               DecodeTag->shiftReg >>= 1;
+                                               DecodeTag->shiftReg |= 0x80;
+                                               DecodeTag->bitCount++;
+                                               if (DecodeTag->bitCount == 8) {
+                                                       DecodeTag->output[DecodeTag->len] = DecodeTag->shiftReg;
+                                                       DecodeTag->len++;
+                                                       if (DecodeTag->len > DecodeTag->max_len) {
+                                                               // buffer overflow, give up
+                                                               DecodeTag->posCount = 0;
+                                                               DecodeTag->state = STATE_TAG_SOF_LOW;
+                                                               LED_C_OFF();
+                                                       }
+                                                       DecodeTag->bitCount = 0;
+                                                       DecodeTag->shiftReg = 0;
+                                               }
+                                       }
+                               } else {
+                                       // logic 0
+                                       if (DecodeTag->lastBit == SOF_PART1) { // incomplete SOF
+                                               DecodeTag->posCount = 0;
+                                               DecodeTag->state = STATE_TAG_SOF_LOW;
+                                               LED_C_OFF();
+                                       } else {
+                                               DecodeTag->lastBit = LOGIC0;
+                                               DecodeTag->shiftReg >>= 1;
+                                               DecodeTag->bitCount++;
+                                               if (DecodeTag->bitCount == 8) {
+                                                       DecodeTag->output[DecodeTag->len] = DecodeTag->shiftReg;
+                                                       DecodeTag->len++;
+                                                       if (DecodeTag->len > DecodeTag->max_len) {
+                                                               // buffer overflow, give up
+                                                               DecodeTag->posCount = 0;
+                                                               DecodeTag->state = STATE_TAG_SOF_LOW;
+                                                               LED_C_OFF();
+                                                       }
+                                                       DecodeTag->bitCount = 0;
+                                                       DecodeTag->shiftReg = 0;
+                                               }
+                                       }
+                               }
+                               DecodeTag->posCount = 0;
+                       }
+                       DecodeTag->posCount++;
+                       break;
 
 
-       cmd[9]= 0xe0; // always e0 (not exactly unique)
+               case STATE_TAG_EOF:
+                       if (DecodeTag->posCount == 1) {
+                               DecodeTag->sum1 = 0;
+                               DecodeTag->sum2 = 0;
+                       }
+                       if (DecodeTag->posCount <= 4) {
+                               DecodeTag->sum1 += amplitude;
+                       } else {
+                               DecodeTag->sum2 += amplitude;
+                       }
+                       if (DecodeTag->posCount == 8) {
+                               int32_t corr_1 = DecodeTag->sum2 - DecodeTag->sum1;
+                               int32_t corr_0 = -corr_1;
+                               int32_t corr_EOF = (DecodeTag->sum1 + DecodeTag->sum2) / 2;
+                               if (corr_EOF > corr_0 || corr_1 > corr_0) {
+                                       DecodeTag->posCount = 0;
+                                       DecodeTag->state = STATE_TAG_SOF_LOW;
+                                       LED_C_OFF();
+                               } else {
+                                       LED_C_OFF();
+                                       return true;
+                               }
+                       }
+                       DecodeTag->posCount++;
+                       break;
 
 
-//     DbpIntegers(cmd[8],cmd[7],cmd[6]);
-       // Now the CRC
-       crc = Crc(cmd, 10); // the crc needs to be calculated over 10 bytes
-       cmd[10] = crc & 0xff;
-       cmd[11] = crc >> 8;
+       }
 
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
+       return false;
 }
 
 }
 
-static void __attribute__((unused)) BuildReadBlockRequest(BYTE *uid, BYTE blockNumber )
+
+static void DecodeTagInit(DecodeTag_t *DecodeTag, uint8_t *data, uint16_t max_len)
 {
 {
-       BYTE cmd[13];
+       DecodeTag->posCount = 0;
+       DecodeTag->state = STATE_TAG_SOF_LOW;
+       DecodeTag->output = data;
+       DecodeTag->max_len = max_len;
+}
 
 
-       WORD crc;
-       // If we set the Option_Flag in this request, the VICC will respond with the secuirty status of the block
-       // followed by teh block data
-       // one sub-carrier, inventory, 1 slot, fast rate
-       cmd[0] = (1 << 6)| (1 << 5) | (1 << 1); // no SELECT bit
-       // READ BLOCK command code
-       cmd[1] = 0x20;
-       // UID may be optionally specified here
-       // 64-bit UID
-       cmd[2] = 0x32;
-       cmd[3]= 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05;
-       cmd[9]= 0xe0; // always e0 (not exactly unique)
-       // Block number to read
-       cmd[10] = blockNumber;//0x00;
-       //Now the CRC
-       crc = Crc(cmd, 11); // the crc needs to be calculated over 2 bytes
-       cmd[11] = crc & 0xff;
-       cmd[12] = crc >> 8;
 
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
+static void DecodeTagReset(DecodeTag_t *DecodeTag)
+{
+       DecodeTag->posCount = 0;
+       DecodeTag->state = STATE_TAG_SOF_LOW;
 }
 
 }
 
-static void __attribute__((unused)) BuildReadMultiBlockRequest(BYTE *uid)
+
+/*
+ *  Receive and decode the tag response, also log to tracebuffer
+ */
+static int GetIso15693AnswerFromTag(uint8_t* response, uint16_t max_len, int timeout)
 {
 {
-       BYTE cmd[14];
+       int samples = 0;
+       bool gotFrame = false;
 
 
-       WORD crc;
-       // If we set the Option_Flag in this request, the VICC will respond with the secuirty status of the block
-       // followed by teh block data
-       // one sub-carrier, inventory, 1 slot, fast rate
-       cmd[0] =  (1 << 5) | (1 << 1); // no SELECT bit
-       // READ Multi BLOCK command code
-       cmd[1] = 0x23;
-       // UID may be optionally specified here
-       // 64-bit UID
-       cmd[2] = 0x32;
-       cmd[3]= 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05;
-       cmd[9]= 0xe0; // always e0 (not exactly unique)
-       // First Block number to read
-       cmd[10] = 0x00;
-       // Number of Blocks to read
-       cmd[11] = 0x2f; // read quite a few
-       //Now the CRC
-       crc = Crc(cmd, 12); // the crc needs to be calculated over 2 bytes
-       cmd[12] = crc & 0xff;
-       cmd[13] = crc >> 8;
+       uint16_t *dmaBuf = (uint16_t*)BigBuf_malloc(ISO15693_DMA_BUFFER_SIZE*sizeof(uint16_t));
+       
+       // the Decoder data structure
+       DecodeTag_t DecodeTag = { 0 };
+       DecodeTagInit(&DecodeTag, response, max_len);
 
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
-}
+       // wait for last transfer to complete
+       while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
 
 
-static void __attribute__((unused)) BuildArbitraryRequest(BYTE *uid,BYTE CmdCode)
-{
-       BYTE cmd[14];
+       // And put the FPGA in the appropriate mode
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_SUBCARRIER_424_KHZ | FPGA_HF_READER_MODE_RECEIVE_AMPLITUDE);
 
 
-       WORD crc;
-       // If we set the Option_Flag in this request, the VICC will respond with the secuirty status of the block
-       // followed by teh block data
-       // one sub-carrier, inventory, 1 slot, fast rate
-       cmd[0] =   (1 << 5) | (1 << 1); // no SELECT bit
-       // READ BLOCK command code
-       cmd[1] = CmdCode;
-       // UID may be optionally specified here
-       // 64-bit UID
-       cmd[2] = 0x32;
-       cmd[3]= 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05;
-       cmd[9]= 0xe0; // always e0 (not exactly unique)
-       // Parameter
-       cmd[10] = 0x00;
-       cmd[11] = 0x0a;
+       // Setup and start DMA.
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
+       FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+       uint16_t *upTo = dmaBuf;
 
 
-//     cmd[12] = 0x00;
-//     cmd[13] = 0x00; //Now the CRC
-       crc = Crc(cmd, 12); // the crc needs to be calculated over 2 bytes
-       cmd[12] = crc & 0xff;
-       cmd[13] = crc >> 8;
+       for(;;) {
+               uint16_t behindBy = ((uint16_t*)AT91C_BASE_PDC_SSC->PDC_RPR - upTo) & (ISO15693_DMA_BUFFER_SIZE-1);
 
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
+               if (behindBy == 0) continue;
+
+               uint16_t tagdata = *upTo++;
+
+               if(upTo >= dmaBuf + ISO15693_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*ISO15693_DMA_BUFFER_SIZE/10)) {
+                               Dbprintf("About to blow circular buffer - aborted! behindBy=%d", behindBy);
+                               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 = ISO15693_DMA_BUFFER_SIZE;   // DMA Next Counter registers
+               }
+
+               samples++;
+
+               if (Handle15693SamplesFromTag(tagdata, &DecodeTag)) {
+                       gotFrame = true;
+                       break;
+               }
+
+               if (samples > timeout && DecodeTag.state < STATE_TAG_RECEIVING_DATA) {
+                       DecodeTag.len = 0;
+                       break;
+               }
+
+       }
+
+       FpgaDisableSscDma();
+       BigBuf_free();
+       
+       if (DEBUG) Dbprintf("samples = %d, gotFrame = %d, Decoder: state = %d, len = %d, bitCount = %d, posCount = %d",
+                           samples, gotFrame, DecodeTag.state, DecodeTag.len, DecodeTag.bitCount, DecodeTag.posCount);
+
+       if (DecodeTag.len > 0) {
+               LogTrace(DecodeTag.output, DecodeTag.len, 0, 0, NULL, false);
+       }
+
+       return DecodeTag.len;
 }
 
 }
 
-static void __attribute__((unused)) BuildArbitraryCustomRequest(BYTE uid[], BYTE CmdCode)
+
+//=============================================================================
+// An ISO15693 decoder for reader commands.
+//
+// This function is called 4 times per bit (every 2 subcarrier cycles).
+// Subcarrier frequency fs is 848kHz, 1/fs = 1,18us, i.e. function is called every 2,36us
+// LED handling:
+//    LED B -> ON once we have received the SOF and are expecting the rest.
+//    LED B -> OFF once we have received EOF or are in error state or unsynced
+//
+// Returns: true  if we received a EOF
+//          false if we are still waiting for some more
+//=============================================================================
+
+typedef struct DecodeReader {
+       enum {
+               STATE_READER_UNSYNCD,
+               STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF,
+               STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF,
+               STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF,
+               STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4,
+               STATE_READER_RECEIVE_DATA_1_OUT_OF_4,
+               STATE_READER_RECEIVE_DATA_1_OUT_OF_256
+       }           state;
+       enum {
+               CODING_1_OUT_OF_4,
+               CODING_1_OUT_OF_256
+       }           Coding;
+       uint8_t     shiftReg;
+       uint8_t     bitCount;
+       int         byteCount;
+       int         byteCountMax;
+       int         posCount;
+       int                     sum1, sum2;
+       uint8_t     *output;
+} DecodeReader_t;
+
+
+static void DecodeReaderInit(DecodeReader_t* DecodeReader, uint8_t *data, uint16_t max_len)
 {
 {
-       BYTE cmd[14];
+       DecodeReader->output = data;
+       DecodeReader->byteCountMax = max_len;
+       DecodeReader->state = STATE_READER_UNSYNCD;
+       DecodeReader->byteCount = 0;
+       DecodeReader->bitCount = 0;
+       DecodeReader->posCount = 1;
+       DecodeReader->shiftReg = 0;
+}
 
 
-       WORD crc;
-       // If we set the Option_Flag in this request, the VICC will respond with the secuirty status of the block
-       // followed by teh block data
-       // one sub-carrier, inventory, 1 slot, fast rate
-       cmd[0] =   (1 << 5) | (1 << 1); // no SELECT bit
-       // READ BLOCK command code
-       cmd[1] = CmdCode;
-       // UID may be optionally specified here
-       // 64-bit UID
-       cmd[2] = 0x32;
-       cmd[3]= 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05;
-       cmd[9]= 0xe0; // always e0 (not exactly unique)
-       // Parameter
-       cmd[10] = 0x05; // for custom codes this must be manufcturer code
-       cmd[11] = 0x00;
-
-//     cmd[12] = 0x00;
-//     cmd[13] = 0x00; //Now the CRC
-       crc = Crc(cmd, 12); // the crc needs to be calculated over 2 bytes
-       cmd[12] = crc & 0xff;
-       cmd[13] = crc >> 8;
-
-       CodeIso15693AsReader(cmd, sizeof(cmd));
-}
-
-/////////////////////////////////////////////////////////////////////////
-// Now the VICC>VCD responses when we are simulating a tag
-////////////////////////////////////////////////////////////////////
-
- static void BuildInventoryResponse(void)
-{
-       BYTE cmd[12];
-
-       WORD crc;
-       // one sub-carrier, inventory, 1 slot, fast rate
-       // AFI is at bit 5 (1<<4) when doing an INVENTORY
-       cmd[0] = 0; //(1 << 2) | (1 << 5) | (1 << 1);
-       cmd[1] = 0;
-       // 64-bit UID
-       cmd[2] = 0x32;
-       cmd[3]= 0x4b;
-       cmd[4] = 0x03;
-       cmd[5] = 0x01;
-       cmd[6] = 0x00;
-       cmd[7] = 0x10;
-       cmd[8] = 0x05;
-       cmd[9]= 0xe0;
-       //Now the CRC
-       crc = Crc(cmd, 10);
-       cmd[10] = crc & 0xff;
-       cmd[11] = crc >> 8;
 
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
-}
-
-//-----------------------------------------------------------------------------
-// Transmit the command (to the tag) that was placed in ToSend[].
-//-----------------------------------------------------------------------------
-static void TransmitTo15693Tag(const BYTE *cmd, int len, int *samples, int *wait)
+static void DecodeReaderReset(DecodeReader_t* DecodeReader)
 {
 {
-    int c;
-
-//    FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
-       if(*wait < 10) { *wait = 10; }
-
-//    for(c = 0; c < *wait;) {
-//        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-//            AT91C_BASE_SSC->SSC_THR = 0x00;          // For exact timing!
-//            c++;
-//        }
-//        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-//            volatile DWORD r = AT91C_BASE_SSC->SSC_RHR;
-//            (void)r;
-//        }
-//        WDT_HIT();
-//    }
-
-    c = 0;
-    for(;;) {
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-            AT91C_BASE_SSC->SSC_THR = cmd[c];
-            c++;
-            if(c >= len) {
-                break;
-            }
-        }
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-            volatile DWORD r = AT91C_BASE_SSC->SSC_RHR;
-            (void)r;
-        }
-        WDT_HIT();
-    }
-       *samples = (c + *wait) << 3;
+       DecodeReader->state = STATE_READER_UNSYNCD;
 }
 
 }
 
-//-----------------------------------------------------------------------------
-// Transmit the command (to the reader) that was placed in ToSend[].
-//-----------------------------------------------------------------------------
-static void TransmitTo15693Reader(const BYTE *cmd, int len, int *samples, int *wait)
-{
-    int c;
-
-//     FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR);        // No requirement to energise my coils
-       if(*wait < 10) { *wait = 10; }
-
-    c = 0;
-    for(;;) {
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-            AT91C_BASE_SSC->SSC_THR = cmd[c];
-            c++;
-            if(c >= len) {
-                break;
-            }
-        }
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-            volatile DWORD r = AT91C_BASE_SSC->SSC_RHR;
-            (void)r;
-        }
-        WDT_HIT();
-    }
-       *samples = (c + *wait) << 3;
-}
 
 
-static int GetIso15693AnswerFromTag(BYTE *receivedResponse, int maxLen, int *samples, int *elapsed)
+static int inline __attribute__((always_inline)) Handle15693SampleFromReader(uint8_t bit, DecodeReader_t *restrict DecodeReader)
 {
 {
-       int c = 0;
-       BYTE *dest = (BYTE *)BigBuf;
-       int getNext = 0;
-
-       SBYTE prev = 0;
+       switch(DecodeReader->state) {
+               case STATE_READER_UNSYNCD:
+                       if(!bit) {
+                               // we went low, so this could be the beginning of a SOF
+                               DecodeReader->posCount = 1;
+                               DecodeReader->state = STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF;
+                       }
+                       break;
 
 
-// NOW READ RESPONSE
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
-       //spindelay(60);        // greg - experiment to get rid of some of the 0 byte/failed reads
-       c = 0;
-       getNext = FALSE;
-       for(;;) {
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       AT91C_BASE_SSC->SSC_THR = 0x43;
-               }
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-                       SBYTE b;
-                       b = (SBYTE)AT91C_BASE_SSC->SSC_RHR;
-
-                       // The samples are correlations against I and Q versions of the
-                       // tone that the tag AM-modulates, so every other sample is I,
-                       // every other is Q. We just want power, so abs(I) + abs(Q) is
-                       // close to what we want.
-                       if(getNext) {
-                               SBYTE r;
-
-                               if(b < 0) {
-                                       r = -b;
+               case STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF:
+                       DecodeReader->posCount++;
+                       if(bit) { // detected rising edge
+                               if(DecodeReader->posCount < 4) { // rising edge too early (nominally expected at 5)
+                                       DecodeReaderReset(DecodeReader);
+                               } else { // SOF
+                                       DecodeReader->state = STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF;
+                               }
+                       } else {
+                               if(DecodeReader->posCount > 5) { // stayed low for too long
+                                       DecodeReaderReset(DecodeReader);
                                } else {
                                } else {
-                                       r = b;
+                                       // do nothing, keep waiting
+                               }
+                       }
+                       break;
+
+               case STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF:
+                       DecodeReader->posCount++;
+                       if(!bit) { // detected a falling edge
+                               if (DecodeReader->posCount < 20) {         // falling edge too early (nominally expected at 21 earliest)
+                                       DecodeReaderReset(DecodeReader);
+                               } else if (DecodeReader->posCount < 23) {  // SOF for 1 out of 4 coding
+                                       DecodeReader->Coding = CODING_1_OUT_OF_4;
+                                       DecodeReader->state = STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF;
+                               } else if (DecodeReader->posCount < 28) {  // falling edge too early (nominally expected at 29 latest)
+                                       DecodeReaderReset(DecodeReader);
+                               } else {                                 // SOF for 1 out of 4 coding
+                                       DecodeReader->Coding = CODING_1_OUT_OF_256;
+                                       DecodeReader->state = STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF;
                                }
                                }
-                               if(prev < 0) {
-                                       r -= prev;
+                       } else {
+                               if(DecodeReader->posCount > 29) { // stayed high for too long
+                                       DecodeReaderReset(DecodeReader);
                                } else {
                                } else {
-                                       r += prev;
+                                       // do nothing, keep waiting
                                }
                                }
+                       }
+                       break;
 
 
-                               dest[c++] = (BYTE)r;
+               case STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF:
+                       DecodeReader->posCount++;
+                       if (bit) { // detected rising edge
+                               if (DecodeReader->Coding == CODING_1_OUT_OF_256) {
+                                       if (DecodeReader->posCount < 32) { // rising edge too early (nominally expected at 33)
+                                       DecodeReaderReset(DecodeReader);
+                                       } else {
+                                               DecodeReader->posCount = 1;
+                                               DecodeReader->bitCount = 0;
+                                               DecodeReader->byteCount = 0;
+                                               DecodeReader->sum1 = 1;
+                                               DecodeReader->state = STATE_READER_RECEIVE_DATA_1_OUT_OF_256;
+                                               LED_B_ON();
+                                       }
+                               } else { // CODING_1_OUT_OF_4
+                                       if (DecodeReader->posCount < 24) { // rising edge too early (nominally expected at 25)
+                                       DecodeReaderReset(DecodeReader);
+                                       } else {
+                                               DecodeReader->state = STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4;
+                                       }
+                               }
+                       } else {
+                               if (DecodeReader->Coding == CODING_1_OUT_OF_256) {
+                                       if (DecodeReader->posCount > 34) { // signal stayed low for too long
+                                       DecodeReaderReset(DecodeReader);
+                                       } else {
+                                               // do nothing, keep waiting
+                                       }
+                               } else { // CODING_1_OUT_OF_4
+                                       if (DecodeReader->posCount > 26) { // signal stayed low for too long
+                                       DecodeReaderReset(DecodeReader);
+                                       } else {
+                                               // do nothing, keep waiting
+                                       }
+                               }
+                       }
+                       break;
 
 
-                               if(c >= 2000) {
-                                       break;
+               case STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4:
+                       DecodeReader->posCount++;
+                       if (bit) {
+                               if (DecodeReader->posCount == 33) {
+                                       DecodeReader->posCount = 1;
+                                       DecodeReader->bitCount = 0;
+                                       DecodeReader->byteCount = 0;
+                                       DecodeReader->sum1 = 1;
+                                       DecodeReader->state = STATE_READER_RECEIVE_DATA_1_OUT_OF_4;
+                                       LED_B_ON();
+                               } else {
+                                       // do nothing, keep waiting
                                }
                                }
+                       } else { // unexpected falling edge
+                                       DecodeReaderReset(DecodeReader);
+                       }
+                       break;
+
+               case STATE_READER_RECEIVE_DATA_1_OUT_OF_4:
+                       DecodeReader->posCount++;
+                       if (DecodeReader->posCount == 1) {
+                               DecodeReader->sum1 = bit;
+                       } else if (DecodeReader->posCount <= 4) {
+                               DecodeReader->sum1 += bit;
+                       } else if (DecodeReader->posCount == 5) {
+                               DecodeReader->sum2 = bit;
                        } else {
                        } else {
-                               prev = b;
+                               DecodeReader->sum2 += bit;
                        }
                        }
+                       if (DecodeReader->posCount == 8) {
+                               DecodeReader->posCount = 0;
+                               int corr10 = DecodeReader->sum1 - DecodeReader->sum2;
+                               int corr01 = DecodeReader->sum2 - DecodeReader->sum1;
+                               int corr11 = (DecodeReader->sum1 + DecodeReader->sum2) / 2;
+                               if (corr01 > corr11 && corr01 > corr10) { // EOF
+                                       LED_B_OFF(); // Finished receiving
+                                       DecodeReaderReset(DecodeReader);
+                                       if (DecodeReader->byteCount != 0) {
+                                               return true;
+                                       }
+                               }
+                               if (corr10 > corr11) { // detected a 2bit position
+                                       DecodeReader->shiftReg >>= 2;
+                                       DecodeReader->shiftReg |= (DecodeReader->bitCount << 6);
+                               }
+                               if (DecodeReader->bitCount == 15) { // we have a full byte
+                                       DecodeReader->output[DecodeReader->byteCount++] = DecodeReader->shiftReg;
+                                       if (DecodeReader->byteCount > DecodeReader->byteCountMax) {
+                                               // buffer overflow, give up
+                                               LED_B_OFF();
+                                               DecodeReaderReset(DecodeReader);
+                                       }
+                                       DecodeReader->bitCount = 0;
+                                       DecodeReader->shiftReg = 0;
+                               } else {
+                                       DecodeReader->bitCount++;
+                               }
+                       }
+                       break;
 
 
-                       getNext = !getNext;
-               }
+               case STATE_READER_RECEIVE_DATA_1_OUT_OF_256:
+                       DecodeReader->posCount++;
+                       if (DecodeReader->posCount == 1) {
+                               DecodeReader->sum1 = bit;
+                       } else if (DecodeReader->posCount <= 4) {
+                               DecodeReader->sum1 += bit;
+                       } else if (DecodeReader->posCount == 5) {
+                               DecodeReader->sum2 = bit;
+                       } else {
+                               DecodeReader->sum2 += bit;
+                       }
+                       if (DecodeReader->posCount == 8) {
+                               DecodeReader->posCount = 0;
+                               int corr10 = DecodeReader->sum1 - DecodeReader->sum2;
+                               int corr01 = DecodeReader->sum2 - DecodeReader->sum1;
+                               int corr11 = (DecodeReader->sum1 + DecodeReader->sum2) / 2;
+                               if (corr01 > corr11 && corr01 > corr10) { // EOF
+                                       LED_B_OFF(); // Finished receiving
+                                       DecodeReaderReset(DecodeReader);
+                                       if (DecodeReader->byteCount != 0) {
+                                               return true;
+                                       }
+                               }
+                               if (corr10 > corr11) { // detected the bit position
+                                       DecodeReader->shiftReg = DecodeReader->bitCount;
+                               }
+                               if (DecodeReader->bitCount == 255) { // we have a full byte
+                                       DecodeReader->output[DecodeReader->byteCount++] = DecodeReader->shiftReg;
+                                       if (DecodeReader->byteCount > DecodeReader->byteCountMax) {
+                                               // buffer overflow, give up
+                                               LED_B_OFF();
+                                               DecodeReaderReset(DecodeReader);
+                                       }
+                               }
+                               DecodeReader->bitCount++;
+                       }
+                       break;
+
+               default:
+                       LED_B_OFF();
+                       DecodeReaderReset(DecodeReader);
+                       break;
        }
 
        }
 
-//////////////////////////////////////////
-/////////// DEMODULATE ///////////////////
-//////////////////////////////////////////
+       return false;
+}
 
 
-       int i, j;
-       int max = 0, maxPos=0;
 
 
-       int skip = 4;
+//-----------------------------------------------------------------------------
+// Receive a command (from the reader to us, where we are the simulated tag),
+// and store it in the given buffer, up to the given maximum length. Keeps
+// spinning, waiting for a well-framed command, until either we get one
+// (returns true) or someone presses the pushbutton on the board (false).
+//
+// Assume that we're called with the SSC (to the FPGA) and ADC path set
+// correctly.
+//-----------------------------------------------------------------------------
 
 
-//     if(GraphTraceLen < 1000) return;        // THIS CHECKS FOR A BUFFER TO SMALL
+static int GetIso15693CommandFromReader(uint8_t *received, size_t max_len, uint32_t *eof_time)
+{
+       int samples = 0;
+       bool gotFrame = false;
+       uint8_t b;
 
 
-       // First, correlate for SOF
-       for(i = 0; i < 100; i++) {
-               int corr = 0;
-               for(j = 0; j < arraylen(FrameSOF); j += skip) {
-                       corr += FrameSOF[j]*dest[i+(j/skip)];
-               }
-               if(corr > max) {
-                       max = corr;
-                       maxPos = i;
-               }
-       }
-//     DbpString("SOF at %d, correlation %d", maxPos,max/(arraylen(FrameSOF)/skip));
+       uint8_t *dmaBuf = BigBuf_malloc(ISO15693_DMA_BUFFER_SIZE);
 
 
-       int k = 0; // this will be our return value
+       // the decoder data structure
+       DecodeReader_t DecodeReader = {0};
+       DecodeReaderInit(&DecodeReader, received, max_len);
 
 
-       // greg - If correlation is less than 1 then there's little point in continuing
-       if ((max/(arraylen(FrameSOF)/skip)) >= 1)
-       {
+       // wait for last transfer to complete
+       while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
+
+       LED_D_OFF();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
+
+       // clear receive register and wait for next transfer
+       uint32_t temp = AT91C_BASE_SSC->SSC_RHR;
+       (void) temp;
+       while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY)) ;
 
 
-       i = maxPos + arraylen(FrameSOF)/skip;
+       uint32_t bit_time = GetCountSspClk() & 0xfffffff8;
+
+       // Setup and start DMA.
+       FpgaSetupSscDma(dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+       uint8_t *upTo = dmaBuf;
 
 
-       BYTE outBuf[20];
-       memset(outBuf, 0, sizeof(outBuf));
-       BYTE mask = 0x01;
        for(;;) {
        for(;;) {
-               int corr0 = 0, corr1 = 0, corrEOF = 0;
-               for(j = 0; j < arraylen(Logic0); j += skip) {
-                       corr0 += Logic0[j]*dest[i+(j/skip)];
+               uint16_t behindBy = ((uint8_t*)AT91C_BASE_PDC_SSC->PDC_RPR - upTo) & (ISO15693_DMA_BUFFER_SIZE-1);
+
+               if (behindBy == 0) continue;
+
+               b = *upTo++;
+               if(upTo >= dmaBuf + ISO15693_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*ISO15693_DMA_BUFFER_SIZE/10)) {
+                               Dbprintf("About to blow circular buffer - aborted! behindBy=%d", behindBy);
+                               break;
+                       }
                }
                }
-               for(j = 0; j < arraylen(Logic1); j += skip) {
-                       corr1 += Logic1[j]*dest[i+(j/skip)];
+               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 = ISO15693_DMA_BUFFER_SIZE;   // DMA Next Counter registers
                }
                }
-               for(j = 0; j < arraylen(FrameEOF); j += skip) {
-                       corrEOF += FrameEOF[j]*dest[i+(j/skip)];
+
+               for (int i = 7; i >= 0; i--) {
+                       if (Handle15693SampleFromReader((b >> i) & 0x01, &DecodeReader)) {
+                               *eof_time = bit_time + samples - DELAY_READER_TO_ARM_SIM; // end of EOF
+                               gotFrame = true;
+                               break;
+                       }
+                       samples++;
                }
                }
-               // Even things out by the length of the target waveform.
-               corr0 *= 4;
-               corr1 *= 4;
 
 
-               if(corrEOF > corr1 && corrEOF > corr0) {
-//                     DbpString("EOF at %d", i);
+               if (gotFrame) {
                        break;
                        break;
-               } else if(corr1 > corr0) {
-                       i += arraylen(Logic1)/skip;
-                       outBuf[k] |= mask;
-               } else {
-                       i += arraylen(Logic0)/skip;
-               }
-               mask <<= 1;
-               if(mask == 0) {
-                       k++;
-                       mask = 0x01;
                }
                }
-               if((i+(int)arraylen(FrameEOF)) >= 2000) {
-                       DbpString("ran off end!");
+
+               if (BUTTON_PRESS()) {
+                       DecodeReader.byteCount = 0;
                        break;
                }
                        break;
                }
+
+               WDT_HIT();
        }
        }
-       if(mask != 0x01) {
-               DbpString("error, uneven octet! (discard extra bits!)");
-///            DbpString("   mask=%02x", mask);
-       }
-//     BYTE str1 [8];
-//     itoa(k,str1);
-//     strcat(str1," octets read");
 
 
-//     DbpString(  str1);    // DbpString("%d octets", k);
 
 
-//     for(i = 0; i < k; i+=3) {
-//             //DbpString("# %2d: %02x ", i, outBuf[i]);
-//             DbpIntegers(outBuf[i],outBuf[i+1],outBuf[i+2]);
-//     }
+       FpgaDisableSscDma();
+       BigBuf_free_keep_EM();
+       
+       if (DEBUG) Dbprintf("samples = %d, gotFrame = %d, Decoder: state = %d, len = %d, bitCount = %d, posCount = %d",
+                           samples, gotFrame, DecodeReader.state, DecodeReader.byteCount, DecodeReader.bitCount, DecodeReader.posCount);
 
 
-       for(i = 0; i < k; i++) {
-               receivedResponse[i] = outBuf[i];
+       if (DecodeReader.byteCount > 0) {
+               LogTrace(DecodeReader.output, DecodeReader.byteCount, 0, *eof_time, NULL, true);
        }
        }
-       } // "end if correlation > 0"   (max/(arraylen(FrameSOF)/skip))
-       return k; // return the number of bytes demodulated
 
 
-///    DbpString("CRC=%04x", Iso15693Crc(outBuf, k-2));
+       return DecodeReader.byteCount;
+}
+
+
+// Encode (into the ToSend buffers) an identify request, which is the first
+// thing that you must send to a tag to get a response.
+static void BuildIdentifyRequest(void)
+{
+       uint8_t cmd[5];
+
+       uint16_t crc;
+       // one sub-carrier, inventory, 1 slot, fast rate
+       // AFI is at bit 5 (1<<4) when doing an INVENTORY
+       cmd[0] = (1 << 2) | (1 << 5) | (1 << 1);
+       // inventory command code
+       cmd[1] = 0x01;
+       // no mask
+       cmd[2] = 0x00;
+       //Now the CRC
+       crc = Crc(cmd, 3);
+       cmd[3] = crc & 0xff;
+       cmd[4] = crc >> 8;
 
 
+       CodeIso15693AsReader(cmd, sizeof(cmd));
 }
 
 }
 
-// Now the GetISO15693 message from sniffing command
-static int GetIso15693AnswerFromSniff(BYTE *receivedResponse, int maxLen, int *samples, int *elapsed)
+
+//-----------------------------------------------------------------------------
+// Start to read an ISO 15693 tag. We send an identify request, then wait
+// for the response. The response is not demodulated, just left in the buffer
+// so that it can be downloaded to a PC and processed there.
+//-----------------------------------------------------------------------------
+void AcquireRawAdcSamplesIso15693(void)
 {
 {
-       int c = 0;
-       BYTE *dest = (BYTE *)BigBuf;
-       int getNext = 0;
+       LEDsoff();
+       LED_A_ON();
 
 
-       SBYTE prev = 0;
+       uint8_t *dest = BigBuf_get_addr();
 
 
-// NOW READ RESPONSE
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
-       //spindelay(60);        // greg - experiment to get rid of some of the 0 byte/failed reads
-       c = 0;
-       getNext = FALSE;
-       for(;;) {
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       AT91C_BASE_SSC->SSC_THR = 0x43;
-               }
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-                       SBYTE b;
-                       b = (SBYTE)AT91C_BASE_SSC->SSC_RHR;
-
-                       // The samples are correlations against I and Q versions of the
-                       // tone that the tag AM-modulates, so every other sample is I,
-                       // every other is Q. We just want power, so abs(I) + abs(Q) is
-                       // close to what we want.
-                       if(getNext) {
-                               SBYTE r;
-
-                               if(b < 0) {
-                                       r = -b;
-                               } else {
-                                       r = b;
-                               }
-                               if(prev < 0) {
-                                       r -= prev;
-                               } else {
-                                       r += prev;
-                               }
+       FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER);
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
+       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
 
-                               dest[c++] = (BYTE)r;
+       BuildIdentifyRequest();
 
 
-                               if(c >= 20000) {
-                                       break;
-                               }
-                       } else {
-                               prev = b;
-                       }
+       // Give the tags time to energize
+       LED_D_ON();
+       SpinDelay(100);
+
+       // Now send the command
+       TransmitTo15693Tag(ToSend, ToSendMax, 0);
+
+       // wait for last transfer to complete
+       while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY)) ;
 
 
-                       getNext = !getNext;
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_SUBCARRIER_424_KHZ | FPGA_HF_READER_MODE_RECEIVE_AMPLITUDE);
+
+       for(int c = 0; c < 4000; ) {
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+                       uint16_t r = AT91C_BASE_SSC->SSC_RHR;
+                       dest[c++] = r >> 5;
                }
        }
 
                }
        }
 
-//////////////////////////////////////////
-/////////// DEMODULATE ///////////////////
-//////////////////////////////////////////
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       LEDsoff();
+}
 
 
-       int i, j;
-       int max = 0, maxPos=0;
 
 
-       int skip = 4;
+void SnoopIso15693(void)
+{
+       LED_A_ON();
+       FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+       BigBuf_free();
 
 
-//     if(GraphTraceLen < 1000) return;        // THIS CHECKS FOR A BUFFER TO SMALL
+       clear_trace();
+       set_tracing(true);
 
 
-       // First, correlate for SOF
-       for(i = 0; i < 19000; i++) {
-               int corr = 0;
-               for(j = 0; j < arraylen(FrameSOF); j += skip) {
-                       corr += FrameSOF[j]*dest[i+(j/skip)];
-               }
-               if(corr > max) {
-                       max = corr;
-                       maxPos = i;
-               }
-       }
-//     DbpString("SOF at %d, correlation %d", maxPos,max/(arraylen(FrameSOF)/skip));
+       // The DMA buffer, used to stream samples from the FPGA
+       uint16_t* dmaBuf = (uint16_t*)BigBuf_malloc(ISO15693_DMA_BUFFER_SIZE*sizeof(uint16_t));
+       uint16_t *upTo;
 
 
-       int k = 0; // this will be our return value
+       // Count of samples received so far, so that we can include timing
+       // information in the trace buffer.
+       int samples = 0;
 
 
-       // greg - If correlation is less than 1 then there's little point in continuing
-       if ((max/(arraylen(FrameSOF)/skip)) >= 1)       // THIS SHOULD BE 1
-       {
+       DecodeTag_t DecodeTag = {0};
+       uint8_t response[ISO15693_MAX_RESPONSE_LENGTH];
+       DecodeTagInit(&DecodeTag, response, sizeof(response));
+
+       DecodeReader_t DecodeReader = {0};;
+       uint8_t cmd[ISO15693_MAX_COMMAND_LENGTH];
+       DecodeReaderInit(&DecodeReader, cmd, sizeof(cmd));
+
+       // Print some debug information about the buffer sizes
+       if (DEBUG) {
+               Dbprintf("Snooping buffers initialized:");
+               Dbprintf("  Trace:         %i bytes", BigBuf_max_traceLen());
+               Dbprintf("  Reader -> tag: %i bytes", ISO15693_MAX_COMMAND_LENGTH);
+               Dbprintf("  tag -> Reader: %i bytes", ISO15693_MAX_RESPONSE_LENGTH);
+               Dbprintf("  DMA:           %i bytes", ISO15693_DMA_BUFFER_SIZE * sizeof(uint16_t));
+       }
+       Dbprintf("Snoop started. Press PM3 Button to stop.");
+       
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_MODE_SNOOP_AMPLITUDE);
+       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
 
-       i = maxPos + arraylen(FrameSOF)/skip;
+       // Setup for the DMA.
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
+       upTo = dmaBuf;
+       FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
 
 
-       BYTE outBuf[20];
-       memset(outBuf, 0, sizeof(outBuf));
-       BYTE mask = 0x01;
+       bool TagIsActive = false;
+       bool ReaderIsActive = false;
+       bool ExpectTagAnswer = false;
+
+       // And now we loop, receiving samples.
        for(;;) {
        for(;;) {
-               int corr0 = 0, corr1 = 0, corrEOF = 0;
-               for(j = 0; j < arraylen(Logic0); j += skip) {
-                       corr0 += Logic0[j]*dest[i+(j/skip)];
-               }
-               for(j = 0; j < arraylen(Logic1); j += skip) {
-                       corr1 += Logic1[j]*dest[i+(j/skip)];
-               }
-               for(j = 0; j < arraylen(FrameEOF); j += skip) {
-                       corrEOF += FrameEOF[j]*dest[i+(j/skip)];
-               }
-               // Even things out by the length of the target waveform.
-               corr0 *= 4;
-               corr1 *= 4;
+               uint16_t behindBy = ((uint16_t*)AT91C_BASE_PDC_SSC->PDC_RPR - upTo) & (ISO15693_DMA_BUFFER_SIZE-1);
 
 
-               if(corrEOF > corr1 && corrEOF > corr0) {
-//                     DbpString("EOF at %d", i);
-                       break;
-               } else if(corr1 > corr0) {
-                       i += arraylen(Logic1)/skip;
-                       outBuf[k] |= mask;
-               } else {
-                       i += arraylen(Logic0)/skip;
+               if (behindBy == 0) continue;
+
+               uint16_t snoopdata = *upTo++;
+
+               if(upTo >= dmaBuf + ISO15693_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*ISO15693_DMA_BUFFER_SIZE/10)) {
+                               Dbprintf("About to blow circular buffer - aborted! behindBy=%d, samples=%d", behindBy, samples);
+                               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 = ISO15693_DMA_BUFFER_SIZE;   // DMA Next Counter registers
+                               WDT_HIT();
+                               if(BUTTON_PRESS()) {
+                                       DbpString("Snoop stopped.");
+                                       break;
+                               }
+                       }
                }
                }
-               mask <<= 1;
-               if(mask == 0) {
-                       k++;
-                       mask = 0x01;
+               samples++;
+               
+               if (!TagIsActive) {                                            // no need to try decoding reader data if the tag is sending
+                       if (Handle15693SampleFromReader(snoopdata & 0x02, &DecodeReader)) {
+                               FpgaDisableSscDma();
+                               ExpectTagAnswer = true;
+                               LogTrace(DecodeReader.output, DecodeReader.byteCount, samples, samples, NULL, true);
+                               /* And ready to receive another command. */
+                               DecodeReaderReset(&DecodeReader);
+                               /* And also reset the demod code, which might have been */
+                               /* false-triggered by the commands from the reader. */
+                               DecodeTagReset(&DecodeTag);
+                               upTo = dmaBuf;
+                               FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+                       }
+                       if (Handle15693SampleFromReader(snoopdata & 0x01, &DecodeReader)) {
+                               FpgaDisableSscDma();
+                               ExpectTagAnswer = true;
+                               LogTrace(DecodeReader.output, DecodeReader.byteCount, samples, samples, NULL, true);
+                               /* And ready to receive another command. */
+                               DecodeReaderReset(&DecodeReader);
+                               /* And also reset the demod code, which might have been */
+                               /* false-triggered by the commands from the reader. */
+                               DecodeTagReset(&DecodeTag);
+                               upTo = dmaBuf;
+                               FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+                       }
+                       ReaderIsActive = (DecodeReader.state >= STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF);
                }
                }
-               if((i+(int)arraylen(FrameEOF)) >= 2000) {
-                       DbpString("ran off end!");
-                       break;
+
+               if (!ReaderIsActive && ExpectTagAnswer) {                                               // no need to try decoding tag data if the reader is currently sending or no answer expected yet
+                       if (Handle15693SamplesFromTag(snoopdata >> 2, &DecodeTag)) {
+                               FpgaDisableSscDma();
+                               //Use samples as a time measurement
+                               LogTrace(DecodeTag.output, DecodeTag.len, samples, samples, NULL, false);
+                               // And ready to receive another response.
+                               DecodeTagReset(&DecodeTag);
+                               DecodeReaderReset(&DecodeReader);
+                               ExpectTagAnswer = false;
+                               upTo = dmaBuf;
+                               FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+                       }
+                       TagIsActive = (DecodeTag.state >= STATE_TAG_RECEIVING_DATA);
                }
                }
+
        }
        }
-       if(mask != 0x01) {
-               DbpString("error, uneven octet! (discard extra bits!)");
-///            DbpString("   mask=%02x", mask);
-       }
-//     BYTE str1 [8];
-//     itoa(k,str1);
-//     strcat(str1," octets read");
 
 
-//     DbpString(  str1);    // DbpString("%d octets", k);
+       FpgaDisableSscDma();
+       BigBuf_free();
+       
+       LEDsoff();
+
+       DbpString("Snoop statistics:");
+       Dbprintf("  ExpectTagAnswer: %d", ExpectTagAnswer);
+       Dbprintf("  DecodeTag State: %d", DecodeTag.state);
+       Dbprintf("  DecodeTag byteCnt: %d", DecodeTag.len);
+       Dbprintf("  DecodeReader State: %d", DecodeReader.state);
+       Dbprintf("  DecodeReader byteCnt: %d", DecodeReader.byteCount);
+       Dbprintf("  Trace length: %d", BigBuf_get_traceLen());
+}
 
 
-//     for(i = 0; i < k; i+=3) {
-//             //DbpString("# %2d: %02x ", i, outBuf[i]);
-//             DbpIntegers(outBuf[i],outBuf[i+1],outBuf[i+2]);
-//     }
 
 
-       for(i = 0; i < k; i++) {
-               receivedResponse[i] = outBuf[i];
-       }
-       } // "end if correlation > 0"   (max/(arraylen(FrameSOF)/skip))
-       return k; // return the number of bytes demodulated
+// Initialize the proxmark as iso15k reader
+static void Iso15693InitReader() {
+       FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+       // Setup SSC
+       // FpgaSetupSsc();
+
+       // Start from off (no field generated)
+       LED_D_OFF();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       SpinDelay(10);
+
+       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
 
 
-///    DbpString("CRC=%04x", Iso15693Crc(outBuf, k-2));
+       // Give the tags time to energize
+       LED_D_ON();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER);
+       SpinDelay(250);
 }
 
 }
 
-//-----------------------------------------------------------------------------
-// Start to read an ISO 15693 tag. We send an identify request, then wait
-// for the response. The response is not demodulated, just left in the buffer
-// so that it can be downloaded to a PC and processed there.
-//-----------------------------------------------------------------------------
-void AcquireRawAdcSamplesIso15693(void)
+///////////////////////////////////////////////////////////////////////
+// ISO 15693 Part 3 - Air Interface
+// This section basically contains transmission and receiving of bits
+///////////////////////////////////////////////////////////////////////
+
+
+// uid is in transmission order (which is reverse of display order)
+static void BuildReadBlockRequest(uint8_t *uid, uint8_t blockNumber )
 {
 {
-       int c = 0;
-       BYTE *dest = (BYTE *)BigBuf;
-       int getNext = 0;
+       uint8_t cmd[13];
 
 
-       SBYTE prev = 0;
+       uint16_t crc;
+       // If we set the Option_Flag in this request, the VICC will respond with the security status of the block
+       // followed by the block data
+       cmd[0] = ISO15693_REQ_OPTION | ISO15693_REQ_ADDRESS | ISO15693_REQ_DATARATE_HIGH; 
+       // READ BLOCK command code
+       cmd[1] = ISO15693_READBLOCK;
+       // UID may be optionally specified here
+       // 64-bit UID
+       cmd[2] = uid[0];
+       cmd[3] = uid[1];
+       cmd[4] = uid[2];
+       cmd[5] = uid[3];
+       cmd[6] = uid[4];
+       cmd[7] = uid[5];
+       cmd[8] = uid[6];
+       cmd[9] = uid[7]; // 0xe0; // always e0 (not exactly unique)
+       // Block number to read
+       cmd[10] = blockNumber;
+       //Now the CRC
+       crc = Crc(cmd, 11); // the crc needs to be calculated over 11 bytes
+       cmd[11] = crc & 0xff;
+       cmd[12] = crc >> 8;
 
 
-       BuildIdentifyRequest();
+       CodeIso15693AsReader(cmd, sizeof(cmd));
+}
 
 
-       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
 
-       // Give the tags time to energize
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
-       SpinDelay(100);
+// Now the VICC>VCD responses when we are simulating a tag
+static void BuildInventoryResponse(uint8_t *uid)
+{
+       uint8_t cmd[12];
 
 
-       // Now send the command
-       FpgaSetupSsc();
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
+       uint16_t crc;
 
 
-       c = 0;
-       for(;;) {
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       AT91C_BASE_SSC->SSC_THR = ToSend[c];
-                       c++;
-                       if(c == ToSendMax+3) {
-                               break;
-                       }
-               }
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-                       volatile DWORD r = AT91C_BASE_SSC->SSC_RHR;
-                       (void)r;
-               }
-               WDT_HIT();
+       cmd[0] = 0; // No error, no protocol format extension
+       cmd[1] = 0; // DSFID (data storage format identifier).  0x00 = not supported
+       // 64-bit UID
+       cmd[2] = uid[7]; //0x32;
+       cmd[3] = uid[6]; //0x4b;
+       cmd[4] = uid[5]; //0x03;
+       cmd[5] = uid[4]; //0x01;
+       cmd[6] = uid[3]; //0x00;
+       cmd[7] = uid[2]; //0x10;
+       cmd[8] = uid[1]; //0x05;
+       cmd[9] = uid[0]; //0xe0;
+       //Now the CRC
+       crc = Crc(cmd, 10);
+       cmd[10] = crc & 0xff;
+       cmd[11] = crc >> 8;
+
+       CodeIso15693AsTag(cmd, sizeof(cmd));
+}
+
+// Universal Method for sending to and recv bytes from a tag
+//     init ... should we initialize the reader?
+//     speed ... 0 low speed, 1 hi speed
+//     *recv will contain the tag's answer
+//     return: lenght of received data
+int SendDataTag(uint8_t *send, int sendlen, bool init, int speed, uint8_t *recv, uint16_t max_recv_len, uint32_t start_time) {
+
+       LED_A_ON();
+       LED_B_OFF();
+       LED_C_OFF();
+
+       if (init) Iso15693InitReader();
+
+       int answerLen=0;
+
+       if (!speed) {
+               // low speed (1 out of 256)
+               CodeIso15693AsReader256(send, sendlen);
+       } else {
+               // high speed (1 out of 4)
+               CodeIso15693AsReader(send, sendlen);
        }
 
        }
 
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
+       TransmitTo15693Tag(ToSend, ToSendMax, start_time);
 
 
-       c = 0;
-       getNext = FALSE;
-       for(;;) {
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       AT91C_BASE_SSC->SSC_THR = 0x43;
-               }
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-                       SBYTE b;
-                       b = (SBYTE)AT91C_BASE_SSC->SSC_RHR;
-
-                       // The samples are correlations against I and Q versions of the
-                       // tone that the tag AM-modulates, so every other sample is I,
-                       // every other is Q. We just want power, so abs(I) + abs(Q) is
-                       // close to what we want.
-                       if(getNext) {
-                               SBYTE r;
-
-                               if(b < 0) {
-                                       r = -b;
-                               } else {
-                                       r = b;
-                               }
-                               if(prev < 0) {
-                                       r -= prev;
-                               } else {
-                                       r += prev;
-                               }
+       // Now wait for a response
+       if (recv != NULL) {
+               answerLen = GetIso15693AnswerFromTag(recv, max_recv_len, DELAY_ISO15693_VCD_TO_VICC_READER * 2);
+       }
+
+       LED_A_OFF();
+
+       return answerLen;
+}
 
 
-                               dest[c++] = (BYTE)r;
 
 
-                               if(c >= 2000) {
+// --------------------------------------------------------------------
+// Debug Functions
+// --------------------------------------------------------------------
+
+// Decodes a message from a tag and displays its metadata and content
+#define DBD15STATLEN 48
+void DbdecodeIso15693Answer(int len, uint8_t *d) {
+       char status[DBD15STATLEN+1]={0};
+       uint16_t crc;
+
+       if (len > 3) {
+               if (d[0] & ISO15693_RES_EXT)
+                       strncat(status,"ProtExt ", DBD15STATLEN);
+               if (d[0] & ISO15693_RES_ERROR) {
+                       // error
+                       strncat(status,"Error ", DBD15STATLEN);
+                       switch (d[1]) {
+                               case 0x01:
+                                       strncat(status,"01:notSupp", DBD15STATLEN);
                                        break;
                                        break;
-                               }
-                       } else {
-                               prev = b;
+                               case 0x02:
+                                       strncat(status,"02:notRecog", DBD15STATLEN);
+                                       break;
+                               case 0x03:
+                                       strncat(status,"03:optNotSupp", DBD15STATLEN);
+                                       break;
+                               case 0x0f:
+                                       strncat(status,"0f:noInfo", DBD15STATLEN);
+                                       break;
+                               case 0x10:
+                                       strncat(status,"10:doesn'tExist", DBD15STATLEN);
+                                       break;
+                               case 0x11:
+                                       strncat(status,"11:lockAgain", DBD15STATLEN);
+                                       break;
+                               case 0x12:
+                                       strncat(status,"12:locked", DBD15STATLEN);
+                                       break;
+                               case 0x13:
+                                       strncat(status,"13:progErr", DBD15STATLEN);
+                                       break;
+                               case 0x14:
+                                       strncat(status,"14:lockErr", DBD15STATLEN);
+                                       break;
+                               default:
+                                       strncat(status,"unknownErr", DBD15STATLEN);
                        }
                        }
-
-                       getNext = !getNext;
+                       strncat(status," ", DBD15STATLEN);
+               } else {
+                       strncat(status,"NoErr ", DBD15STATLEN);
                }
                }
+
+               crc=Crc(d,len-2);
+               if ( (( crc & 0xff ) == d[len-2]) && (( crc >> 8 ) == d[len-1]) )
+                       strncat(status,"CrcOK",DBD15STATLEN);
+               else
+                       strncat(status,"CrcFail!",DBD15STATLEN);
+
+               Dbprintf("%s",status);
        }
 }
 
        }
 }
 
-//-----------------------------------------------------------------------------
-// Simulate an ISO15693 reader, perform anti-collision and then attempt to read a sector
+
+
+///////////////////////////////////////////////////////////////////////
+// Functions called via USB/Client
+///////////////////////////////////////////////////////////////////////
+
+void SetDebugIso15693(uint32_t debug) {
+       DEBUG=debug;
+       Dbprintf("Iso15693 Debug is now %s",DEBUG?"on":"off");
+       return;
+}
+
+
+//---------------------------------------------------------------------------------------
+// Simulate an ISO15693 reader, perform anti-collision and then attempt to read a sector.
 // all demodulation performed in arm rather than host. - greg
 // all demodulation performed in arm rather than host. - greg
-//-----------------------------------------------------------------------------
-void ReaderIso15693(DWORD parameter)
+//---------------------------------------------------------------------------------------
+void ReaderIso15693(uint32_t parameter)
 {
 {
+       LEDsoff();
        LED_A_ON();
        LED_A_ON();
-       LED_B_ON();
-       LED_C_OFF();
-       LED_D_OFF();
 
 
-//DbpString(parameter);
+       set_tracing(true);
+       
+       int answerLen = 0;
+       uint8_t TagUID[8] = {0x00};
 
 
-       //BYTE *answer0 = (((BYTE *)BigBuf) + 3560); // allow 100 bytes per reponse (way too much)
-       BYTE *answer1 = (((BYTE *)BigBuf) + 3660); //
-       BYTE *answer2 = (((BYTE *)BigBuf) + 3760);
-       BYTE *answer3 = (((BYTE *)BigBuf) + 3860);
-       //BYTE *TagUID= (((BYTE *)BigBuf) + 3960);              // where we hold the uid for hi15reader
-//     int answerLen0 = 0;
-       int answerLen1 = 0;
-       int answerLen2 = 0;
-       int answerLen3 = 0;
+       FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
 
 
-       // Blank arrays
-       memset(BigBuf + 3660, 0, 300);
+       uint8_t answer[ISO15693_MAX_RESPONSE_LENGTH];
 
 
+       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
        // Setup SSC
        // Setup SSC
-       FpgaSetupSsc();
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
 
        // Start from off (no field generated)
 
        // Start from off (no field generated)
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-       SpinDelay(200);
-
-       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
-       FpgaSetupSsc();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       SpinDelay(200);
 
        // Give the tags time to energize
 
        // Give the tags time to energize
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
+       LED_D_ON();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER);
        SpinDelay(200);
        SpinDelay(200);
+       StartCountSspClk();
 
 
-       LED_A_ON();
-       LED_B_OFF();
-       LED_C_OFF();
-       LED_D_OFF();
-
-       int samples = 0;
-       int tsamples = 0;
-       int wait = 0;
-       int elapsed = 0;
 
        // FIRST WE RUN AN INVENTORY TO GET THE TAG UID
        // THIS MEANS WE CAN PRE-BUILD REQUESTS TO SAVE CPU TIME
 
        // FIRST WE RUN AN INVENTORY TO GET THE TAG UID
        // THIS MEANS WE CAN PRE-BUILD REQUESTS TO SAVE CPU TIME
- BYTE TagUID[7];               // where we hold the uid for hi15reader
-
-//     BuildIdentifyRequest();
-//     //TransmitTo15693Tag(ToSend,ToSendMax+3,&tsamples, &wait);
-//     TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);  // No longer ToSendMax+3
-//     // Now wait for a response
-//     responseLen0 = GetIso15693AnswerFromTag(receivedAnswer0, 100, &samples, &elapsed) ;
-//     if (responseLen0 >=12) // we should do a better check than this
-//     {
-//             // really we should check it is a valid mesg
-//             // but for now just grab what we think is the uid
-//             TagUID[0] = receivedAnswer0[2];
-//             TagUID[1] = receivedAnswer0[3];
-//             TagUID[2] = receivedAnswer0[4];
-//             TagUID[3] = receivedAnswer0[5];
-//             TagUID[4] = receivedAnswer0[6];
-//             TagUID[5] = receivedAnswer0[7];
-//             TagUID[6] = receivedAnswer0[8]; // IC Manufacturer code
-//     DbpIntegers(TagUID[6],TagUID[5],TagUID[4]);
-//}
 
        // Now send the IDENTIFY command
        BuildIdentifyRequest();
 
        // Now send the IDENTIFY command
        BuildIdentifyRequest();
-       //TransmitTo15693Tag(ToSend,ToSendMax+3,&tsamples, &wait);
-       TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);  // No longer ToSendMax+3
+       TransmitTo15693Tag(ToSend, ToSendMax, 0);
+       
        // Now wait for a response
        // Now wait for a response
-       answerLen1 = GetIso15693AnswerFromTag(answer1, 100, &samples, &elapsed) ;
+       answerLen = GetIso15693AnswerFromTag(answer, sizeof(answer), DELAY_ISO15693_VCD_TO_VICC_READER * 2) ;
+       uint32_t start_time = GetCountSspClk() + DELAY_ISO15693_VICC_TO_VCD_READER;
 
 
-       if (answerLen1 >=12) // we should do a better check than this
+       if (answerLen >=12) // we should do a better check than this
        {
        {
+               TagUID[0] = answer[2];
+               TagUID[1] = answer[3];
+               TagUID[2] = answer[4];
+               TagUID[3] = answer[5];
+               TagUID[4] = answer[6];
+               TagUID[5] = answer[7];
+               TagUID[6] = answer[8]; // IC Manufacturer code
+               TagUID[7] = answer[9]; // always E0
 
 
-               TagUID[0] = answer1[2];
-               TagUID[1] = answer1[3];
-               TagUID[2] = answer1[4];
-               TagUID[3] = answer1[5];
-               TagUID[4] = answer1[6];
-               TagUID[5] = answer1[7];
-               TagUID[6] = answer1[8]; // IC Manufacturer code
-
-               // Now send the SELECT command
-               BuildSelectRequest(TagUID);
-               TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);  // No longer ToSendMax+3
-               // Now wait for a response
-               answerLen2 = GetIso15693AnswerFromTag(answer2, 100, &samples, &elapsed);
-
-               // Now send the MULTI READ command
-//             BuildArbitraryRequest(*TagUID,parameter);
-               BuildArbitraryCustomRequest(TagUID,parameter);
-//             BuildReadBlockRequest(*TagUID,parameter);
-//             BuildSysInfoRequest(*TagUID);
-               //TransmitTo15693Tag(ToSend,ToSendMax+3,&tsamples, &wait);
-               TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);  // No longer ToSendMax+3
-               // Now wait for a response
-               answerLen3 = GetIso15693AnswerFromTag(answer3, 100, &samples, &elapsed) ;
+       }
 
 
+       Dbprintf("%d octets read from IDENTIFY request:", answerLen);
+       DbdecodeIso15693Answer(answerLen, answer);
+       Dbhexdump(answerLen, answer, false);
+
+       // UID is reverse
+       if (answerLen >= 12)
+               Dbprintf("UID = %02hX%02hX%02hX%02hX%02hX%02hX%02hX%02hX",
+                       TagUID[7],TagUID[6],TagUID[5],TagUID[4],
+                       TagUID[3],TagUID[2],TagUID[1],TagUID[0]);
+
+
+       // Dbprintf("%d octets read from SELECT request:", answerLen2);
+       // DbdecodeIso15693Answer(answerLen2,answer2);
+       // Dbhexdump(answerLen2,answer2,true);
+
+       // Dbprintf("%d octets read from XXX request:", answerLen3);
+       // DbdecodeIso15693Answer(answerLen3,answer3);
+       // Dbhexdump(answerLen3,answer3,true);
+
+       // read all pages
+       if (answerLen >= 12 && DEBUG) {
+               for (int i = 0; i < 32; i++) {  // sanity check, assume max 32 pages
+                       BuildReadBlockRequest(TagUID, i);
+                       TransmitTo15693Tag(ToSend, ToSendMax, start_time);
+                       int answerLen = GetIso15693AnswerFromTag(answer, sizeof(answer), DELAY_ISO15693_VCD_TO_VICC_READER * 2);
+                       start_time = GetCountSspClk() + DELAY_ISO15693_VICC_TO_VCD_READER;
+                       if (answerLen > 0) {
+                               Dbprintf("READ SINGLE BLOCK %d returned %d octets:", i, answerLen);
+                               DbdecodeIso15693Answer(answerLen, answer);
+                               Dbhexdump(answerLen, answer, false);
+                               if ( *((uint32_t*) answer) == 0x07160101 ) break; // exit on NoPageErr
+                       }
+               }
        }
 
        }
 
-       Dbprintf("%d octets read from IDENTIFY request: %x %x %x %x %x %x %x %x %x", answerLen1,
-               answer1[0], answer1[1], answer1[2],
-               answer1[3], answer1[4], answer1[5],
-               answer1[6], answer1[7], answer1[8]);
+       // for the time being, switch field off to protect rdv4.0
+       // note: this prevents using hf 15 cmd with s option - which isn't implemented yet anyway
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       LED_D_OFF();
 
 
-       Dbprintf("%d octets read from SELECT request: %x %x %x %x %x %x %x %x %x", answerLen2,
-               answer2[0], answer2[1], answer2[2],
-               answer2[3], answer2[4], answer2[5],
-               answer2[6], answer2[7], answer2[8]);
+       LED_A_OFF();
+}
 
 
-       Dbprintf("%d octets read from XXX request: %x %x %x %x %x %x %x %x %x", answerLen3,
-               answer3[0], answer3[1], answer3[2],
-               answer3[3], answer3[4], answer3[5],
-               answer3[6], answer3[7], answer3[8]);
 
 
+// Simulate an ISO15693 TAG.
+// For Inventory command: print command and send Inventory Response with given UID
+// TODO: interpret other reader commands and send appropriate response
+void SimTagIso15693(uint32_t parameter, uint8_t *uid)
+{
+       LEDsoff();
+       LED_A_ON();
 
 
-//     str2[0]=0;
-//     for(i = 0; i < responseLen3; i++) {
-//             itoa(str1,receivedAnswer3[i]);
-//             strcat(str2,str1);
-//     }
-//     DbpString(str2);
+       FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_SIMULATOR);
 
 
-       LED_A_OFF();
-       LED_B_OFF();
-       LED_C_OFF();
-       LED_D_OFF();
+       StartCountSspClk();
+
+       uint8_t cmd[ISO15693_MAX_COMMAND_LENGTH];
+
+       // Build a suitable response to the reader INVENTORY command
+       BuildInventoryResponse(uid);
+
+       // Listen to reader
+       while (!BUTTON_PRESS()) {
+               uint32_t eof_time = 0, start_time = 0;
+               int cmd_len = GetIso15693CommandFromReader(cmd, sizeof(cmd), &eof_time);
+
+               if ((cmd_len >= 5) && (cmd[0] & ISO15693_REQ_INVENTORY) && (cmd[1] == ISO15693_INVENTORY)) { // TODO: check more flags
+                       bool slow = !(cmd[0] & ISO15693_REQ_DATARATE_HIGH);
+                       start_time = eof_time + DELAY_ISO15693_VCD_TO_VICC_SIM - DELAY_ARM_TO_READER_SIM;
+                       TransmitTo15693Reader(ToSend, ToSendMax, start_time, slow);
+               }
+
+               Dbprintf("%d bytes read from reader:", cmd_len);
+               Dbhexdump(cmd_len, cmd, false);
+       }
+
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       LEDsoff();
 }
 
 }
 
-//-----------------------------------------------------------------------------
-// Simulate an ISO15693 TAG, perform anti-collision and then print any reader commands
-// all demodulation performed in arm rather than host. - greg
-//-----------------------------------------------------------------------------
-void SimTagIso15693(DWORD parameter)
+
+// Since there is no standardized way of reading the AFI out of a tag, we will brute force it
+// (some manufactures offer a way to read the AFI, though)
+void BruteforceIso15693Afi(uint32_t speed)
 {
 {
+       LEDsoff();
        LED_A_ON();
        LED_A_ON();
-       LED_B_ON();
-       LED_C_OFF();
-       LED_D_OFF();
 
 
-       BYTE *answer1 = (((BYTE *)BigBuf) + 3660); //
-       int answerLen1 = 0;
+       uint8_t data[6];
+       uint8_t recv[ISO15693_MAX_RESPONSE_LENGTH];
+       
+       int datalen=0, recvlen=0;
+
+       Iso15693InitReader();
+       StartCountSspClk();
+       
+       // first without AFI
+       // Tags should respond without AFI and with AFI=0 even when AFI is active
+
+       data[0] = ISO15693_REQ_DATARATE_HIGH | ISO15693_REQ_INVENTORY | ISO15693_REQINV_SLOT1;
+       data[1] = ISO15693_INVENTORY;
+       data[2] = 0; // mask length
+       datalen = AddCrc(data,3);
+       recvlen = SendDataTag(data, datalen, false, speed, recv, sizeof(recv), 0);
+       uint32_t start_time = GetCountSspClk() + DELAY_ISO15693_VICC_TO_VCD_READER;
+       WDT_HIT();
+       if (recvlen>=12) {
+               Dbprintf("NoAFI UID=%s", sprintUID(NULL, &recv[2]));
+       }
 
 
-       // Blank arrays
-       memset(answer1, 0, 100);
+       // now with AFI
 
 
-       // Setup SSC
-       FpgaSetupSsc();
+       data[0] = ISO15693_REQ_DATARATE_HIGH | ISO15693_REQ_INVENTORY | ISO15693_REQINV_AFI | ISO15693_REQINV_SLOT1;
+       data[1] = ISO15693_INVENTORY;
+       data[2] = 0; // AFI
+       data[3] = 0; // mask length
 
 
-       // Start from off (no field generated)
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-       SpinDelay(200);
+       for (int i = 0; i < 256; i++) {
+               data[2] = i & 0xFF;
+               datalen = AddCrc(data,4);
+               recvlen = SendDataTag(data, datalen, false, speed, recv, sizeof(recv), start_time);
+               start_time = GetCountSspClk() + DELAY_ISO15693_VICC_TO_VCD_READER;
+               WDT_HIT();
+               if (recvlen >= 12) {
+                       Dbprintf("AFI=%i UID=%s", i, sprintUID(NULL, &recv[2]));
+               }
+       }
+       Dbprintf("AFI Bruteforcing done.");
 
 
-       SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
-       FpgaSetupSsc();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       LEDsoff();
+}
 
 
-       // Give the tags time to energize
-//     FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);  // NO GOOD FOR SIM TAG!!!!
-       SpinDelay(200);
+// Allows to directly send commands to the tag via the client
+void DirectTag15693Command(uint32_t datalen, uint32_t speed, uint32_t recv, uint8_t data[]) {
 
 
-       LED_A_OFF();
-       LED_B_OFF();
-       LED_C_ON();
-       LED_D_OFF();
+       int recvlen = 0;
+       uint8_t recvbuf[ISO15693_MAX_RESPONSE_LENGTH];
 
 
-       int samples = 0;
-       int tsamples = 0;
-       int wait = 0;
-       int elapsed = 0;
+       LED_A_ON();
+
+       if (DEBUG) {
+               Dbprintf("SEND:");
+               Dbhexdump(datalen, data, false);
+       }
 
 
-       answerLen1 = GetIso15693AnswerFromSniff(answer1, 100, &samples, &elapsed) ;
+       recvlen = SendDataTag(data, datalen, true, speed, (recv?recvbuf:NULL), sizeof(recvbuf), 0);
+
+       if (recv) {
+               if (DEBUG) {
+                       Dbprintf("RECV:");
+                       Dbhexdump(recvlen, recvbuf, false);
+                       DbdecodeIso15693Answer(recvlen, recvbuf);
+               }
+
+               cmd_send(CMD_ACK, recvlen>ISO15693_MAX_RESPONSE_LENGTH?ISO15693_MAX_RESPONSE_LENGTH:recvlen, 0, 0, recvbuf, ISO15693_MAX_RESPONSE_LENGTH);
 
 
-       if (answerLen1 >=1) // we should do a better check than this
-       {
-               // Build a suitable reponse to the reader INVENTORY cocmmand
-               BuildInventoryResponse();
-               TransmitTo15693Reader(ToSend,ToSendMax, &tsamples, &wait);
        }
 
        }
 
-       Dbprintf("%d octets read from reader command: %x %x %x %x %x %x %x %x %x", answerLen1,
-               answer1[0], answer1[1], answer1[2],
-               answer1[3], answer1[4], answer1[5],
-               answer1[6], answer1[7], answer1[8]);
+       // for the time being, switch field off to protect rdv4.0
+       // note: this prevents using hf 15 cmd with s option - which isn't implemented yet anyway
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       LED_D_OFF();
 
        LED_A_OFF();
 
        LED_A_OFF();
-       LED_B_OFF();
-       LED_C_OFF();
-       LED_D_OFF();
 }
 }
+
+
+
+
+// --------------------------------------------------------------------
+// -- Misc & deprecated functions
+// --------------------------------------------------------------------
+
+/*
+
+// do not use; has a fix UID
+static void __attribute__((unused)) BuildSysInfoRequest(uint8_t *uid)
+{
+       uint8_t cmd[12];
+
+       uint16_t crc;
+       // If we set the Option_Flag in this request, the VICC will respond with the security status of the block
+       // followed by the block data
+       // one sub-carrier, inventory, 1 slot, fast rate
+       cmd[0] =  (1 << 5) | (1 << 1); // no SELECT bit
+       // System Information command code
+       cmd[1] = 0x2B;
+       // UID may be optionally specified here
+       // 64-bit UID
+       cmd[2] = 0x32;
+       cmd[3]= 0x4b;
+       cmd[4] = 0x03;
+       cmd[5] = 0x01;
+       cmd[6] = 0x00;
+       cmd[7] = 0x10;
+       cmd[8] = 0x05;
+       cmd[9]= 0xe0; // always e0 (not exactly unique)
+       //Now the CRC
+       crc = Crc(cmd, 10); // the crc needs to be calculated over 2 bytes
+       cmd[10] = crc & 0xff;
+       cmd[11] = crc >> 8;
+
+       CodeIso15693AsReader(cmd, sizeof(cmd));
+}
+
+
+// do not use; has a fix UID
+static void __attribute__((unused)) BuildReadMultiBlockRequest(uint8_t *uid)
+{
+       uint8_t cmd[14];
+
+       uint16_t crc;
+       // If we set the Option_Flag in this request, the VICC will respond with the security status of the block
+       // followed by the block data
+       // one sub-carrier, inventory, 1 slot, fast rate
+       cmd[0] =  (1 << 5) | (1 << 1); // no SELECT bit
+       // READ Multi BLOCK command code
+       cmd[1] = 0x23;
+       // UID may be optionally specified here
+       // 64-bit UID
+       cmd[2] = 0x32;
+       cmd[3]= 0x4b;
+       cmd[4] = 0x03;
+       cmd[5] = 0x01;
+       cmd[6] = 0x00;
+       cmd[7] = 0x10;
+       cmd[8] = 0x05;
+       cmd[9]= 0xe0; // always e0 (not exactly unique)
+       // First Block number to read
+       cmd[10] = 0x00;
+       // Number of Blocks to read
+       cmd[11] = 0x2f; // read quite a few
+       //Now the CRC
+       crc = Crc(cmd, 12); // the crc needs to be calculated over 2 bytes
+       cmd[12] = crc & 0xff;
+       cmd[13] = crc >> 8;
+
+       CodeIso15693AsReader(cmd, sizeof(cmd));
+}
+
+// do not use; has a fix UID
+static void __attribute__((unused)) BuildArbitraryRequest(uint8_t *uid,uint8_t CmdCode)
+{
+       uint8_t cmd[14];
+
+       uint16_t crc;
+       // If we set the Option_Flag in this request, the VICC will respond with the security status of the block
+       // followed by the block data
+       // one sub-carrier, inventory, 1 slot, fast rate
+       cmd[0] =   (1 << 5) | (1 << 1); // no SELECT bit
+       // READ BLOCK command code
+       cmd[1] = CmdCode;
+       // UID may be optionally specified here
+       // 64-bit UID
+       cmd[2] = 0x32;
+       cmd[3]= 0x4b;
+       cmd[4] = 0x03;
+       cmd[5] = 0x01;
+       cmd[6] = 0x00;
+       cmd[7] = 0x10;
+       cmd[8] = 0x05;
+       cmd[9]= 0xe0; // always e0 (not exactly unique)
+       // Parameter
+       cmd[10] = 0x00;
+       cmd[11] = 0x0a;
+
+//     cmd[12] = 0x00;
+//     cmd[13] = 0x00; //Now the CRC
+       crc = Crc(cmd, 12); // the crc needs to be calculated over 2 bytes
+       cmd[12] = crc & 0xff;
+       cmd[13] = crc >> 8;
+
+       CodeIso15693AsReader(cmd, sizeof(cmd));
+}
+
+// do not use; has a fix UID
+static void __attribute__((unused)) BuildArbitraryCustomRequest(uint8_t uid[], uint8_t CmdCode)
+{
+       uint8_t cmd[14];
+
+       uint16_t crc;
+       // If we set the Option_Flag in this request, the VICC will respond with the security status of the block
+       // followed by the block data
+       // one sub-carrier, inventory, 1 slot, fast rate
+       cmd[0] =   (1 << 5) | (1 << 1); // no SELECT bit
+       // READ BLOCK command code
+       cmd[1] = CmdCode;
+       // UID may be optionally specified here
+       // 64-bit UID
+       cmd[2] = 0x32;
+       cmd[3]= 0x4b;
+       cmd[4] = 0x03;
+       cmd[5] = 0x01;
+       cmd[6] = 0x00;
+       cmd[7] = 0x10;
+       cmd[8] = 0x05;
+       cmd[9]= 0xe0; // always e0 (not exactly unique)
+       // Parameter
+       cmd[10] = 0x05; // for custom codes this must be manufacturer code
+       cmd[11] = 0x00;
+
+//     cmd[12] = 0x00;
+//     cmd[13] = 0x00; //Now the CRC
+       crc = Crc(cmd, 12); // the crc needs to be calculated over 2 bytes
+       cmd[12] = crc & 0xff;
+       cmd[13] = crc >> 8;
+
+       CodeIso15693AsReader(cmd, sizeof(cmd));
+}
+
+
+
+
+*/
+
+
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