]> git.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/iso15693.c
Update default_pwd.dic (#735)
[proxmark3-svn] / armsrc / iso15693.c
index 9b0ab29ecf4e93a43f9080a83bcc97047e8563f9..da2aab69bfa1d6971bc3c3a88edac8340e7f88f2 100644 (file)
@@ -2,33 +2,31 @@
 // 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, but at the moment I've implemented only the reader
-// stuff, and that barely.
-// Modified to perform modulation onboard in arm rather than on PC
-// Also added additional reader commands (SELECT, READ etc.)
+// the `fake tag' modes.
 //-----------------------------------------------------------------------------
-// The ISO 15693 describes two transmission modes from reader to tag, and 4 
-// transmission modes from tag to reader. As of Mar 2010 this code only 
-// supports one of each: "1of4" mode from reader to tag, and the highspeed 
-// 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. Further for 
-// the simulation to work, we will need to support all data rates.
+
+// 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) 
+//     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)
 //     high ASK: 26,48 kbit/s
 //     high FSK: 26,69 kbit/s
 //-----------------------------------------------------------------------------
-// added "1 out of 256" mode (for VCD->PICC) - atrox 20100911
 
 
 // Random Remarks:
 // *) UID is always used "transmission order" (LSB), which is reverse to display order
 
 // TODO / BUGS / ISSUES:
-// *) writing to tags takes longer: we miss the answer from the tag in most cases
-//    -> tweak the read-timeout times
-// *) signal decoding from the card is still a bit shaky. 
-// *) signal decoding is unable to detect collissions.
-// *) add anti-collission support for inventory-commands 
+// *) signal decoding is unable to detect collisions.
+// *) add anti-collision support for inventory-commands
 // *) read security status of a block
-// *) sniffing and simulation do only support one transmission mode. need to support 
-//             all 8 transmission combinations
-//     *) remove or refactor code under "depricated"
+// *) sniffing and simulation do not support two subcarrier modes.
+// *) remove or refactor code under "depricated"
 // *) document all the functions
 
 
@@ -63,6 +56,7 @@
 #include "apps.h"
 #include "string.h"
 #include "iso15693tools.h"
+#include "protocols.h"
 #include "cmd.h"
 
 #define arraylen(x) (sizeof(x)/sizeof((x)[0]))
@@ -83,18 +77,25 @@ static int DEBUG = 0;
 #define AddCrc(data,datalen)  Iso15693AddCrc(data,datalen)
 #define sprintUID(target,uid)  Iso15693sprintUID(target,uid)
 
-// approximate amplitude=sqrt(ci^2+cq^2) 
+// approximate amplitude=sqrt(ci^2+cq^2) by amplitude = max(|ci|,|cq|) + 1/2*min(|ci|,|cq|)
 #define AMPLITUDE(ci, cq) (MAX(ABS(ci), ABS(cq)) + MIN(ABS(ci), ABS(cq))/2)
 
-// DMA buffer
-#define ISO15693_DMA_BUFFER_SIZE 128
+// buffers
+#define ISO15693_DMA_BUFFER_SIZE     128
+#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.
+#define DELAY_READER_TO_ARM            8
+#define DELAY_ARM_TO_READER            1
+#define DELAY_ISO15693_VCD_TO_VICC   132 // 132/423.75kHz = 311.5us from end of EOF to start of tag response
 
 // ---------------------------
-// Signal Processing 
+// Signal Processing
 // ---------------------------
 
 // prepare data using "1 out of 4" code for later transmission
-// resulting data rate is 26,48 kbit/s (fc/512)
+// resulting data rate is 26.48 kbit/s (fc/512)
 // cmd ... data
 // n ... length of data
 static void CodeIso15693AsReader(uint8_t *cmd, int n)
@@ -179,7 +180,7 @@ static void CodeIso15693AsReader(uint8_t *cmd, int n)
 }
 
 // encode data using "1 out of 256" scheme
-// data rate is 1,66 kbit/s (fc/8192) 
+// 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)
 {
@@ -201,7 +202,7 @@ static void CodeIso15693AsReader256(uint8_t *cmd, int n)
        ToSendStuffBit(1);
        ToSendStuffBit(1);
        ToSendStuffBit(0);
-       
+
        for(i = 0; i < n; i++) {
                for (j = 0; j<=255; j++) {
                        if (cmd[i]==j) {
@@ -210,8 +211,8 @@ static void CodeIso15693AsReader256(uint8_t *cmd, int n)
                        } else {
                                ToSendStuffBit(1);
                                ToSendStuffBit(1);
-                       }                       
-               }       
+                       }
+               }
        }
        // EOF
        ToSendStuffBit(1);
@@ -219,10 +220,53 @@ static void CodeIso15693AsReader256(uint8_t *cmd, int n)
        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);
        }
+
+       ToSendMax++;
+}
+
+
+static void CodeIso15693AsTag(uint8_t *cmd, int n)
+{
+       ToSendReset();
+
+       // 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++;
 }
 
 
@@ -244,29 +288,50 @@ static void TransmitTo15693Tag(const uint8_t *cmd, int len)
 }
 
 //-----------------------------------------------------------------------------
-// Transmit the command (to the reader) that was placed in cmd[].
+// Transmit the tag response (to the reader) that was placed in cmd[].
 //-----------------------------------------------------------------------------
-static void TransmitTo15693Reader(const uint8_t *cmd, int len)
+static void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t start_time, bool slow)
 {
+       // 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);
 
+       uint8_t shift_delay = start_time & 0x00000007;
+       uint8_t bitmask = 0x00;
+       for (int i = 0; i < shift_delay; i++) {
+               bitmask |= (0x01 << i);
+       }
+
+       while (GetCountSspClk() < (start_time & 0xfffffff8)) ;
+       AT91C_BASE_SSC->SSC_THR = 0x00; // clear TXRDY
+
        LED_C_ON();
-    for(int c = 0; c < len; ) {
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-            AT91C_BASE_SSC->SSC_THR = cmd[c];
-            c++;
+       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();
+                       }
         }
-        WDT_HIT();
     }
        LED_C_OFF();
 }
 
 
 //=============================================================================
-// An ISO 15693 demodulator (one subcarrier only). Uses cross correlation to 
-// identify the SOF, each bit, and EOF.
+// An ISO 15693 decoder for tag responses (one subcarrier only).
+// Uses cross correlation to identify the SOF, 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, 
+// 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.
@@ -279,13 +344,13 @@ static void TransmitTo15693Reader(const uint8_t *cmd, int len)
 #define SUBCARRIER_DETECT_THRESHOLD    2
 #define SOF_CORRELATOR_LEN (1<<5)
 
-typedef struct Demod {
+typedef struct DecodeTag {
        enum {
-               DEMOD_UNSYNCD,
-               DEMOD_AWAIT_SOF_1,
-               DEMOD_AWAIT_SOF_2,
-               DEMOD_RECEIVING_DATA,
-               DEMOD_AWAIT_EOF
+               STATE_TAG_UNSYNCD,
+               STATE_TAG_AWAIT_SOF_1,
+               STATE_TAG_AWAIT_SOF_2,
+               STATE_TAG_RECEIVING_DATA,
+               STATE_TAG_AWAIT_EOF
        }         state;
        int       bitCount;
        int       posCount;
@@ -305,145 +370,145 @@ typedef struct Demod {
        int32_t   SOF_corr;
        int32_t   SOF_corr_prev;
        uint8_t   SOF_correlator[SOF_CORRELATOR_LEN];
-} Demod_t;
+} DecodeTag_t;
 
-static RAMFUNC int Handle15693SamplesDemod(int8_t ci, int8_t cq, Demod_t *Demod)
+static int Handle15693SamplesFromTag(int8_t ci, int8_t cq, DecodeTag_t *DecodeTag)
 {
-       switch(Demod->state) {
-               case DEMOD_UNSYNCD:
+       switch(DecodeTag->state) {
+               case STATE_TAG_UNSYNCD:
                        // initialize SOF correlator. We are looking for 12 samples low and 12 samples high.
-                       Demod->SOF_low = 0;
-                       Demod->SOF_high = 12;
-                       Demod->SOF_last = 23;
-                       memset(Demod->SOF_correlator, 0x00, Demod->SOF_last + 1);
-                       Demod->SOF_correlator[Demod->SOF_last] = AMPLITUDE(ci,cq);
-                       Demod->SOF_corr = Demod->SOF_correlator[Demod->SOF_last];
-                       Demod->SOF_corr_prev = Demod->SOF_corr;
-                       // initialize Demodulator
-                       Demod->posCount = 0;
-                       Demod->bitCount = 0;
-                       Demod->len = 0;
-                       Demod->state = DEMOD_AWAIT_SOF_1;
+                       DecodeTag->SOF_low = 0;
+                       DecodeTag->SOF_high = 12;
+                       DecodeTag->SOF_last = 23;
+                       memset(DecodeTag->SOF_correlator, 0x00, DecodeTag->SOF_last + 1);
+                       DecodeTag->SOF_correlator[DecodeTag->SOF_last] = AMPLITUDE(ci,cq);
+                       DecodeTag->SOF_corr = DecodeTag->SOF_correlator[DecodeTag->SOF_last];
+                       DecodeTag->SOF_corr_prev = DecodeTag->SOF_corr;
+                       // initialize Decoder
+                       DecodeTag->posCount = 0;
+                       DecodeTag->bitCount = 0;
+                       DecodeTag->len = 0;
+                       DecodeTag->state = STATE_TAG_AWAIT_SOF_1;
                        break;
-                       
-               case DEMOD_AWAIT_SOF_1:
+
+               case STATE_TAG_AWAIT_SOF_1:
                        // calculate the correlation in real time. Look at differences only.
-                       Demod->SOF_corr += Demod->SOF_correlator[Demod->SOF_low++];
-                       Demod->SOF_corr -= 2*Demod->SOF_correlator[Demod->SOF_high++];
-                       Demod->SOF_last++;
-                       Demod->SOF_low &= (SOF_CORRELATOR_LEN-1);
-                       Demod->SOF_high &= (SOF_CORRELATOR_LEN-1);
-                       Demod->SOF_last &= (SOF_CORRELATOR_LEN-1);
-                       Demod->SOF_correlator[Demod->SOF_last] = AMPLITUDE(ci,cq);
-                       Demod->SOF_corr += Demod->SOF_correlator[Demod->SOF_last];
+                       DecodeTag->SOF_corr += DecodeTag->SOF_correlator[DecodeTag->SOF_low++];
+                       DecodeTag->SOF_corr -= 2*DecodeTag->SOF_correlator[DecodeTag->SOF_high++];
+                       DecodeTag->SOF_last++;
+                       DecodeTag->SOF_low &= (SOF_CORRELATOR_LEN-1);
+                       DecodeTag->SOF_high &= (SOF_CORRELATOR_LEN-1);
+                       DecodeTag->SOF_last &= (SOF_CORRELATOR_LEN-1);
+                       DecodeTag->SOF_correlator[DecodeTag->SOF_last] = AMPLITUDE(ci,cq);
+                       DecodeTag->SOF_corr += DecodeTag->SOF_correlator[DecodeTag->SOF_last];
 
                        // if correlation increases for 10 consecutive samples, we are close to maximum correlation
-                       if (Demod->SOF_corr > Demod->SOF_corr_prev + SUBCARRIER_DETECT_THRESHOLD) {
-                               Demod->posCount++;
+                       if (DecodeTag->SOF_corr > DecodeTag->SOF_corr_prev + SUBCARRIER_DETECT_THRESHOLD) {
+                               DecodeTag->posCount++;
                        } else {
-                               Demod->posCount = 0;
+                               DecodeTag->posCount = 0;
                        }
 
-                       if (Demod->posCount == 10) {    // correlation increased 10 times
-                               Demod->state = DEMOD_AWAIT_SOF_2;
+                       if (DecodeTag->posCount == 10) {        // correlation increased 10 times
+                               DecodeTag->state = STATE_TAG_AWAIT_SOF_2;
                        }
-                               
-                       Demod->SOF_corr_prev = Demod->SOF_corr;
-                               
+
+                       DecodeTag->SOF_corr_prev = DecodeTag->SOF_corr;
+
                        break;
 
-               case DEMOD_AWAIT_SOF_2:
+               case STATE_TAG_AWAIT_SOF_2:
                        // calculate the correlation in real time. Look at differences only.
-                       Demod->SOF_corr += Demod->SOF_correlator[Demod->SOF_low++];
-                       Demod->SOF_corr -= 2*Demod->SOF_correlator[Demod->SOF_high++];
-                       Demod->SOF_last++;
-                       Demod->SOF_low &= (SOF_CORRELATOR_LEN-1);
-                       Demod->SOF_high &= (SOF_CORRELATOR_LEN-1);
-                       Demod->SOF_last &= (SOF_CORRELATOR_LEN-1);
-                       Demod->SOF_correlator[Demod->SOF_last] = AMPLITUDE(ci,cq);
-                       Demod->SOF_corr += Demod->SOF_correlator[Demod->SOF_last];
-
-                       if (Demod->SOF_corr >= Demod->SOF_corr_prev) { // we are looking for the maximum correlation
-                               Demod->SOF_corr_prev = Demod->SOF_corr;
+                       DecodeTag->SOF_corr += DecodeTag->SOF_correlator[DecodeTag->SOF_low++];
+                       DecodeTag->SOF_corr -= 2*DecodeTag->SOF_correlator[DecodeTag->SOF_high++];
+                       DecodeTag->SOF_last++;
+                       DecodeTag->SOF_low &= (SOF_CORRELATOR_LEN-1);
+                       DecodeTag->SOF_high &= (SOF_CORRELATOR_LEN-1);
+                       DecodeTag->SOF_last &= (SOF_CORRELATOR_LEN-1);
+                       DecodeTag->SOF_correlator[DecodeTag->SOF_last] = AMPLITUDE(ci,cq);
+                       DecodeTag->SOF_corr += DecodeTag->SOF_correlator[DecodeTag->SOF_last];
+
+                       if (DecodeTag->SOF_corr >= DecodeTag->SOF_corr_prev) { // we are looking for the maximum correlation
+                               DecodeTag->SOF_corr_prev = DecodeTag->SOF_corr;
                        } else {
-                               Demod->lastBit = SOF_PART1;  // detected 1st part of SOF
-                               Demod->sum1 = Demod->SOF_correlator[Demod->SOF_last];
-                               Demod->sum2 = 0;
-                               Demod->posCount = 2;
-                               Demod->state = DEMOD_RECEIVING_DATA;
+                               DecodeTag->lastBit = SOF_PART1;  // detected 1st part of SOF
+                               DecodeTag->sum1 = DecodeTag->SOF_correlator[DecodeTag->SOF_last];
+                               DecodeTag->sum2 = 0;
+                               DecodeTag->posCount = 2;
+                               DecodeTag->state = STATE_TAG_RECEIVING_DATA;
                                LED_C_ON();
                        }
-                       
+
                        break;
 
-               case DEMOD_RECEIVING_DATA:
-                       if (Demod->posCount == 1) {
-                               Demod->sum1 = 0;
-                               Demod->sum2 = 0;
+               case STATE_TAG_RECEIVING_DATA:
+                       if (DecodeTag->posCount == 1) {
+                               DecodeTag->sum1 = 0;
+                               DecodeTag->sum2 = 0;
                        }
 
-                       if (Demod->posCount <= 4) {
-                               Demod->sum1 += AMPLITUDE(ci, cq);
+                       if (DecodeTag->posCount <= 4) {
+                               DecodeTag->sum1 += AMPLITUDE(ci, cq);
                        } else {
-                               Demod->sum2 += AMPLITUDE(ci, cq);
+                               DecodeTag->sum2 += AMPLITUDE(ci, cq);
                        }
 
-                       if (Demod->posCount == 8) {
-                               int16_t corr_1 = (Demod->sum2 - Demod->sum1) / 4;
-                               int16_t corr_0 = (Demod->sum1 - Demod->sum2) / 4;
-                               int16_t corr_EOF = (Demod->sum1 + Demod->sum2) / 8;
+                       if (DecodeTag->posCount == 8) {
+                               int16_t corr_1 = (DecodeTag->sum2 - DecodeTag->sum1) / 4;
+                               int16_t corr_0 = (DecodeTag->sum1 - DecodeTag->sum2) / 4;
+                               int16_t corr_EOF = (DecodeTag->sum1 + DecodeTag->sum2) / 8;
                                if (corr_EOF > corr_0 && corr_EOF > corr_1) {
-                                       Demod->state = DEMOD_AWAIT_EOF;
+                                       DecodeTag->state = STATE_TAG_AWAIT_EOF;
                                } else if (corr_1 > corr_0) {
                                        // logic 1
-                                       if (Demod->lastBit == SOF_PART1) { // still part of SOF
-                                               Demod->lastBit = SOF_PART2;
+                                       if (DecodeTag->lastBit == SOF_PART1) { // still part of SOF
+                                               DecodeTag->lastBit = SOF_PART2;
                                        } else {
-                                               Demod->lastBit = LOGIC1;
-                                               Demod->shiftReg >>= 1;
-                                               Demod->shiftReg |= 0x80;
-                                               Demod->bitCount++;
-                                               if (Demod->bitCount == 8) {
-                                                       Demod->output[Demod->len] = Demod->shiftReg;
-                                                       Demod->len++;
-                                                       Demod->bitCount = 0;
-                                                       Demod->shiftReg = 0;
+                                               DecodeTag->lastBit = LOGIC1;
+                                               DecodeTag->shiftReg >>= 1;
+                                               DecodeTag->shiftReg |= 0x80;
+                                               DecodeTag->bitCount++;
+                                               if (DecodeTag->bitCount == 8) {
+                                                       DecodeTag->output[DecodeTag->len] = DecodeTag->shiftReg;
+                                                       DecodeTag->len++;
+                                                       DecodeTag->bitCount = 0;
+                                                       DecodeTag->shiftReg = 0;
                                                }
                                        }
                                } else {
                                        // logic 0
-                                       if (Demod->lastBit == SOF_PART1) { // incomplete SOF
-                                               Demod->state = DEMOD_UNSYNCD;
+                                       if (DecodeTag->lastBit == SOF_PART1) { // incomplete SOF
+                                               DecodeTag->state = STATE_TAG_UNSYNCD;
                                                LED_C_OFF();
                                        } else {
-                                               Demod->lastBit = LOGIC0;
-                                               Demod->shiftReg >>= 1;
-                                               Demod->bitCount++;
-                                               if (Demod->bitCount == 8) {
-                                                       Demod->output[Demod->len] = Demod->shiftReg;
-                                                       Demod->len++;
-                                                       Demod->bitCount = 0;
-                                                       Demod->shiftReg = 0;
+                                               DecodeTag->lastBit = LOGIC0;
+                                               DecodeTag->shiftReg >>= 1;
+                                               DecodeTag->bitCount++;
+                                               if (DecodeTag->bitCount == 8) {
+                                                       DecodeTag->output[DecodeTag->len] = DecodeTag->shiftReg;
+                                                       DecodeTag->len++;
+                                                       DecodeTag->bitCount = 0;
+                                                       DecodeTag->shiftReg = 0;
                                                }
                                        }
                                }
-                               Demod->posCount = 0;
+                               DecodeTag->posCount = 0;
                        }
-                       Demod->posCount++;
+                       DecodeTag->posCount++;
                        break;
-               
-               case DEMOD_AWAIT_EOF:
-                       if (Demod->lastBit == LOGIC0) {  // this was already part of EOF 
+
+               case STATE_TAG_AWAIT_EOF:
+                       if (DecodeTag->lastBit == LOGIC0) {  // this was already part of EOF
                                LED_C_OFF();
                                return true;
                        } else {
-                               Demod->state = DEMOD_UNSYNCD;
+                               DecodeTag->state = STATE_TAG_UNSYNCD;
                                LED_C_OFF();
                        }
                        break;
 
                default:
-                       Demod->state = DEMOD_UNSYNCD;
+                       DecodeTag->state = STATE_TAG_UNSYNCD;
                        LED_C_OFF();
                        break;
        }
@@ -452,15 +517,14 @@ static RAMFUNC int Handle15693SamplesDemod(int8_t ci, int8_t cq, Demod_t *Demod)
 }
 
 
-static void DemodInit(Demod_t* Demod, uint8_t* data)
+static void DecodeTagInit(DecodeTag_t *DecodeTag, uint8_t *data)
 {
-       Demod->output = data;
-       Demod->state = DEMOD_UNSYNCD;
+       DecodeTag->output = data;
+       DecodeTag->state = STATE_TAG_UNSYNCD;
 }
 
-
 /*
- *  Demodulate the samples we received from the tag, also log to tracebuffer
+ *  Receive and decode the tag response, also log to tracebuffer
  */
 static int GetIso15693AnswerFromTag(uint8_t* response, int timeout)
 {
@@ -468,19 +532,12 @@ static int GetIso15693AnswerFromTag(uint8_t* response, int timeout)
        int lastRxCounter, samples = 0;
        int8_t ci, cq;
        bool gotFrame = false;
-       
-       // Allocate memory from BigBuf for some buffers
-       // free all previous allocations first
-       BigBuf_free();
 
-       // 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 dmaBuf[ISO15693_DMA_BUFFER_SIZE];
 
-       // the Demodulatur data structure
-       Demod_t* Demod = (Demod_t*) BigBuf_malloc(sizeof(Demod_t));
-       
-       // Set up the demodulator for tag -> reader responses.
-       DemodInit(Demod, response);
+       // the Decoder data structure
+       DecodeTag_t DecodeTag;
+       DecodeTagInit(&DecodeTag, response);
 
        // wait for last transfer to complete
        while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
@@ -491,7 +548,6 @@ static int GetIso15693AnswerFromTag(uint8_t* response, int timeout)
        // Setup and start DMA.
        FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
        FpgaSetupSscDma((uint8_t*) dmaBuf, ISO15693_DMA_BUFFER_SIZE);
-
        uint16_t *upTo = dmaBuf;
        lastRxCounter = ISO15693_DMA_BUFFER_SIZE;
 
@@ -502,7 +558,7 @@ static int GetIso15693AnswerFromTag(uint8_t* response, int timeout)
                }
 
                if (behindBy < 1) continue;
-               
+
                ci = (int8_t)(*upTo >> 8);
                cq = (int8_t)(*upTo & 0xff);
 
@@ -518,156 +574,368 @@ static int GetIso15693AnswerFromTag(uint8_t* response, int timeout)
                }
                samples++;
 
-               if (Handle15693SamplesDemod(ci, cq, Demod)) {
+               if (Handle15693SamplesFromTag(ci, cq, &DecodeTag)) {
                        gotFrame = true;
                        break;
                }
 
-               if(samples > timeout && Demod->state < DEMOD_RECEIVING_DATA) {
-                       Demod->len = 0;
+               if(samples > timeout && DecodeTag.state < STATE_TAG_RECEIVING_DATA) {
+                       DecodeTag.len = 0;
                        break;
                }
+
        }
 
        FpgaDisableSscDma();
 
-       if (DEBUG) Dbprintf("max behindby = %d, samples = %d, gotFrame = %d, Demod.state = %d, Demod.len = %d, Demod.bitCount = %d, Demod.posCount = %d", 
-                           maxBehindBy, samples, gotFrame, Demod->state, Demod->len, Demod->bitCount, Demod->posCount);
+       if (DEBUG) Dbprintf("max behindby = %d, samples = %d, gotFrame = %d, Decoder: state = %d, len = %d, bitCount = %d, posCount = %d",
+                           maxBehindBy, samples, gotFrame, DecodeTag.state, DecodeTag.len, DecodeTag.bitCount, DecodeTag.posCount);
 
-       if (tracing && Demod->len > 0) {
-               uint8_t parity[MAX_PARITY_SIZE];
-               LogTrace(Demod->output, Demod->len, 0, 0, parity, false);
+       if (tracing && DecodeTag.len > 0) {
+               LogTrace(DecodeTag.output, DecodeTag.len, 0, 0, NULL, false);
        }
 
-       return Demod->len;
+       return DecodeTag.len;
 }
 
 
-// Now the GetISO15693 message from sniffing command
-// TODO: fix it. This cannot work for several reasons: 
-//   1. Carrier is switched on during sniffing?
-//   2. We most probable miss the next reader command when demodulating
-static int GetIso15693AnswerFromSniff(uint8_t *receivedResponse, int maxLen, int *samples, int *elapsed)
+//=============================================================================
+// 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 int Handle15693SampleFromReader(uint8_t bit, DecodeReader_t* DecodeReader)
 {
-       uint8_t *dest = BigBuf_get_addr();
+       switch(DecodeReader->state) {
+               case STATE_READER_UNSYNCD:
+                       if(!bit) {
+                               // we went low, so this could be the beginning of a SOF
+                               DecodeReader->state = STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF;
+                               DecodeReader->posCount = 1;
+                       }
+                       break;
 
-// NOW READ RESPONSE
-       LED_D_ON();
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
-       //spindelay(60);        // greg - experiment to get rid of some of the 0 byte/failed reads
-       for(int c = 0; c < BIGBUF_SIZE; ) {
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-                       uint16_t iq = AT91C_BASE_SSC->SSC_RHR;
-                       // The samples are correlations against I and Q versions of the
-                       // tone that the tag AM-modulates. We just want power, 
-                       // so abs(I) + abs(Q) is close to what we want.
-                       int8_t i = (int8_t)(iq >> 8);
-                       int8_t q = (int8_t)(iq & 0xff);
-                       uint8_t r = AMPLITUDE(i, q);
-                       dest[c++] = r;
-               }
+               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)
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                               } else { // SOF
+                                       DecodeReader->state = STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF;
+                               }
+                       } else {
+                               if(DecodeReader->posCount > 5) { // stayed low for too long
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                               } else {
+                                       // 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)
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                               } 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)
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                               } 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;
+                               }
+                       } else {
+                               if(DecodeReader->posCount > 29) { // stayed high for too long
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                               } else {
+                                       // do nothing, keep waiting
+                               }
+                       }
+                       break;
+
+               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)
+                                               DecodeReader->state = STATE_READER_UNSYNCD;
+                                       } 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)
+                                               DecodeReader->state = STATE_READER_UNSYNCD;
+                                       } 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
+                                               DecodeReader->state = STATE_READER_UNSYNCD;
+                                       } else {
+                                               // do nothing, keep waiting
+                                       }
+                               } else { // CODING_1_OUT_OF_4
+                                       if (DecodeReader->posCount > 26) { // signal stayed low for too long
+                                               DecodeReader->state = STATE_READER_UNSYNCD;
+                                       } else {
+                                               // do nothing, keep waiting
+                                       }
+                               }
+                       }
+                       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
+                               DecodeReader->state = STATE_READER_UNSYNCD;
+                       }
+                       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 {
+                               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
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                                       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();
+                                               DecodeReader->state = STATE_READER_UNSYNCD;
+                                       }
+                                       DecodeReader->bitCount = 0;
+                               } else {
+                                       DecodeReader->bitCount++;
+                               }
+                       }
+                       break;
+
+               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
+                                       DecodeReader->state = STATE_READER_UNSYNCD;
+                                       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();
+                                               DecodeReader->state = STATE_READER_UNSYNCD;
+                                       }
+                               }
+                               DecodeReader->bitCount++;
+                       }
+                       break;
+
+               default:
+                       LED_B_OFF();
+                       DecodeReader->state = STATE_READER_UNSYNCD;
+                       break;
        }
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+
+       return false;
+}
+
+
+static void DecodeReaderInit(uint8_t *data, uint16_t max_len, DecodeReader_t* DecodeReader)
+{
+       DecodeReader->output = data;
+       DecodeReader->byteCountMax = max_len;
+       DecodeReader->state = STATE_READER_UNSYNCD;
+       DecodeReader->byteCount = 0;
+       DecodeReader->bitCount = 0;
+       DecodeReader->posCount = 0;
+       DecodeReader->shiftReg = 0;
+}
+
+
+//-----------------------------------------------------------------------------
+// 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.
+//-----------------------------------------------------------------------------
+
+static int GetIso15693CommandFromReader(uint8_t *received, size_t max_len, uint32_t *eof_time)
+{
+       int maxBehindBy = 0;
+       int lastRxCounter, samples = 0;
+       bool gotFrame = false;
+       uint8_t b;
+
+       uint8_t dmaBuf[ISO15693_DMA_BUFFER_SIZE];
+
+       // the decoder data structure
+       DecodeReader_t DecodeReader = {0};
+       DecodeReaderInit(received, max_len, &DecodeReader);
+
+       // 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);
 
-       //////////////////////////////////////////
-       /////////// DEMODULATE ///////////////////
-       //////////////////////////////////////////
+       // 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)) ;
 
-       int i, j;
-       int max = 0, maxPos=0;
+       uint32_t bit_time = GetCountSspClk() & 0xfffffff8;
 
-       int skip = 2;
+       // Setup and start DMA.
+       FpgaSetupSscDma(dmaBuf, ISO15693_DMA_BUFFER_SIZE);
+       uint8_t *upTo = dmaBuf;
+       lastRxCounter = ISO15693_DMA_BUFFER_SIZE;
 
-       // First, correlate for SOF
-       for(i = 0; i < 38000; 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;
+       for(;;) {
+               int behindBy = (lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR) & (ISO15693_DMA_BUFFER_SIZE-1);
+               if(behindBy > maxBehindBy) {
+                       maxBehindBy = behindBy;
                }
-       }
 
-       if (DEBUG) Dbprintf("SOF at %d, correlation %d", maxPos,max/(arraylen(FrameSOF)/skip));
+               if (behindBy < 1) continue;
 
-       int k = 0; // this will be our return value
+               b = *upTo++;
+               lastRxCounter--;
+               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
+                       lastRxCounter += ISO15693_DMA_BUFFER_SIZE;
+               }
+               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
+               }
 
-       // greg - If correlation is less than 1 then there's little point in continuing
-       if ((max/(arraylen(FrameSOF)/skip)) >= 1)       // THIS SHOULD BE 1
-       {
-       
-               i = maxPos + arraylen(FrameSOF)/skip;
-       
-               uint8_t outBuf[20];
-               memset(outBuf, 0, sizeof(outBuf));
-               uint8_t mask = 0x01;
-               for(;;) {
-                       int corr0 = 0, corr00 = 0, corr01 = 0, corr1 = 0, corrEOF = 0;
-                       for(j = 0; j < arraylen(Logic0); j += skip) {
-                               corr0 += Logic0[j]*dest[i+(j/skip)];
-                       }
-                       corr01 = corr00 = corr0;
-                       for(j = 0; j < arraylen(Logic0); j += skip) {
-                               corr00 += Logic0[j]*dest[i+arraylen(Logic0)/skip+(j/skip)];
-                               corr01 += Logic1[j]*dest[i+arraylen(Logic0)/skip+(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.
-                       corr00 *= 2;
-                       corr01 *= 2;
-                       corr0 *= 4;
-                       corr1 *= 4;
-       
-                       if(corrEOF > corr1 && corrEOF > corr00 && corrEOF > corr01) {
-                               if (DEBUG) Dbprintf("EOF at %d, correlation %d (corr01: %d, corr00: %d, corr1: %d, corr0: %d)", 
-                                        i, corrEOF, corr01, corr00, corr1, corr0);
-                               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)/skip) >= BIGBUF_SIZE) {
-                               DbpString("ran off end!");
+               for (int i = 7; i >= 0; i--) {
+                       if (Handle15693SampleFromReader((b >> i) & 0x01, &DecodeReader)) {
+                               *eof_time = bit_time + samples - DELAY_READER_TO_ARM; // end of EOF
+                               gotFrame = true;
                                break;
                        }
+                       samples++;
                }
-               if(mask != 0x01) {
-                       DbpString("sniff: error, uneven octet! (discard extra bits!)");
-       ///             DbpString("   mask=%02x", mask);
+
+               if (gotFrame) {
+                       break;
                }
-       //      uint8_t str1 [8];
-       //      itoa(k,str1);
-       //      strncat(str1," octets read",8);
-       
-       //      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]);
-       //      }
-       
-               for(i = 0; i < k; i++) {
-                       receivedResponse[i] = outBuf[i];
+
+               if (BUTTON_PRESS()) {
+                       DecodeReader.byteCount = 0;
+                       break;
                }
-       } // "end if correlation > 0"   (max/(arraylen(FrameSOF)/skip))
-       return k; // return the number of bytes demodulated
 
-///    DbpString("CRC=%04x", Iso15693Crc(outBuf, k-2));
+               WDT_HIT();
+       }
+
+
+       FpgaDisableSscDma();
+
+       if (DEBUG) Dbprintf("max behindby = %d, samples = %d, gotFrame = %d, Decoder: state = %d, len = %d, bitCount = %d, posCount = %d",
+                           maxBehindBy, samples, gotFrame, DecodeReader.state, DecodeReader.byteCount, DecodeReader.bitCount, DecodeReader.posCount);
+
+       if (tracing && DecodeReader.byteCount > 0) {
+               LogTrace(DecodeReader.output, DecodeReader.byteCount, 0, 0, NULL, true);
+       }
+
+       return DecodeReader.byteCount;
 }
 
 
@@ -681,7 +949,7 @@ void AcquireRawAdcSamplesIso15693(void)
 {
        LEDsoff();
        LED_A_ON();
-       
+
        uint8_t *dest = BigBuf_get_addr();
 
        FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
@@ -718,7 +986,7 @@ void AcquireRawAdcSamplesIso15693(void)
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
                        uint16_t iq = AT91C_BASE_SSC->SSC_RHR;
                        // The samples are correlations against I and Q versions of the
-                       // tone that the tag AM-modulates. We just want power, 
+                       // tone that the tag AM-modulates. We just want power,
                        // so abs(I) + abs(Q) is close to what we want.
                        int8_t i = (int8_t)(iq >> 8);
                        int8_t q = (int8_t)(iq & 0xff);
@@ -732,7 +1000,7 @@ void AcquireRawAdcSamplesIso15693(void)
 }
 
 
-// TODO: there is no trigger condition. The 14000 samples represent a time frame of 66ms. 
+// TODO: there is no trigger condition. The 14000 samples represent a time frame of 66ms.
 // It is unlikely that we get something meaningful.
 // TODO: Currently we only record tag answers. Add tracing of reader commands.
 // TODO: would we get something at all? The carrier is switched on...
@@ -740,7 +1008,7 @@ void RecordRawAdcSamplesIso15693(void)
 {
        LEDsoff();
        LED_A_ON();
-       
+
        uint8_t *dest = BigBuf_get_addr();
 
        FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
@@ -762,7 +1030,7 @@ void RecordRawAdcSamplesIso15693(void)
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
                        uint16_t iq = AT91C_BASE_SSC->SSC_RHR;
                        // The samples are correlations against I and Q versions of the
-                       // tone that the tag AM-modulates. We just want power, 
+                       // tone that the tag AM-modulates. We just want power,
                        // so abs(I) + abs(Q) is close to what we want.
                        int8_t i = (int8_t)(iq >> 8);
                        int8_t q = (int8_t)(iq & 0xff);
@@ -778,7 +1046,7 @@ void RecordRawAdcSamplesIso15693(void)
 }
 
 
-// Initialize the proxmark as iso15k reader 
+// Initialize the proxmark as iso15k reader
 // (this might produces glitches that confuse some tags
 static void Iso15693InitReader() {
        FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
@@ -851,7 +1119,7 @@ static void BuildReadBlockRequest(uint8_t *uid, uint8_t blockNumber )
        // Block number to read
        cmd[10] = blockNumber;//0x00;
        //Now the CRC
-       crc = Crc(cmd, 11); // the crc needs to be calculated over 12 bytes
+       crc = Crc(cmd, 11); // the crc needs to be calculated over 11 bytes
        cmd[11] = crc & 0xff;
        cmd[12] = crc >> 8;
 
@@ -860,15 +1128,13 @@ static void BuildReadBlockRequest(uint8_t *uid, uint8_t blockNumber )
 
 
 // Now the VICC>VCD responses when we are simulating a tag
-static void BuildInventoryResponse( uint8_t *uid)
+static void BuildInventoryResponse(uint8_t *uid)
 {
        uint8_t cmd[12];
 
        uint16_t crc;
-       // one sub-carrier, inventory, 1 slot, fast rate
-       // AFI is at bit 5 (1<<4) when doing an INVENTORY
-    //(1 << 2) | (1 << 5) | (1 << 1);
-       cmd[0] = 0; // 
+
+       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;
@@ -884,21 +1150,21 @@ static void BuildInventoryResponse( uint8_t *uid)
        cmd[10] = crc & 0xff;
        cmd[11] = crc >> 8;
 
-       CodeIso15693AsReader(cmd, sizeof(cmd));
+       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 
+//     speed ... 0 low speed, 1 hi speed
 //     **recv will return you a pointer to the received data
-//     If you do not need the answer use NULL for *recv[] 
+//     If you do not need the answer use NULL for *recv[]
 //     return: lenght of received data
 int SendDataTag(uint8_t *send, int sendlen, bool init, int speed, uint8_t **recv) {
 
        LED_A_ON();
        LED_B_OFF();
        LED_C_OFF();
-       
+
        if (init) Iso15693InitReader();
 
        int answerLen=0;
@@ -912,22 +1178,22 @@ int SendDataTag(uint8_t *send, int sendlen, bool init, int speed, uint8_t **recv
                // high speed (1 out of 4)
                CodeIso15693AsReader(send, sendlen);
        }
-       
-       TransmitTo15693Tag(ToSend,ToSendMax);   
+
+       TransmitTo15693Tag(ToSend,ToSendMax);
        // Now wait for a response
        if (recv!=NULL) {
-               answerLen = GetIso15693AnswerFromTag(answer, 100);      
+               answerLen = GetIso15693AnswerFromTag(answer, 100);
                *recv=answer;
        }
 
        LED_A_OFF();
-       
+
        return answerLen;
 }
 
 
 // --------------------------------------------------------------------
-// Debug Functions 
+// Debug Functions
 // --------------------------------------------------------------------
 
 // Decodes a message from a tag and displays its metadata and content
@@ -937,37 +1203,37 @@ void DbdecodeIso15693Answer(int len, uint8_t *d) {
        uint16_t crc;
 
        if (len>3) {
-               if (d[0]&(1<<3)) 
+               if (d[0]&(1<<3))
                        strncat(status,"ProtExt ",DBD15STATLEN);
-               if (d[0]&1) { 
+               if (d[0]&1) {
                        // error
                        strncat(status,"Error ",DBD15STATLEN);
                        switch (d[1]) {
-                               case 0x01: 
+                               case 0x01:
                                        strncat(status,"01:notSupp",DBD15STATLEN);
                                        break;
-                               case 0x02: 
+                               case 0x02:
                                        strncat(status,"02:notRecog",DBD15STATLEN);
                                        break;
-                               case 0x03: 
+                               case 0x03:
                                        strncat(status,"03:optNotSupp",DBD15STATLEN);
                                        break;
-                               case 0x0f: 
+                               case 0x0f:
                                        strncat(status,"0f:noInfo",DBD15STATLEN);
                                        break;
-                               case 0x10: 
+                               case 0x10:
                                        strncat(status,"10:dontExist",DBD15STATLEN);
                                        break;
-                               case 0x11: 
+                               case 0x11:
                                        strncat(status,"11:lockAgain",DBD15STATLEN);
                                        break;
-                               case 0x12: 
+                               case 0x12:
                                        strncat(status,"12:locked",DBD15STATLEN);
                                        break;
-                               case 0x13: 
+                               case 0x13:
                                        strncat(status,"13:progErr",DBD15STATLEN);
                                        break;
-                               case 0x14: 
+                               case 0x14:
                                        strncat(status,"14:lockErr",DBD15STATLEN);
                                        break;
                                default:
@@ -977,12 +1243,12 @@ void DbdecodeIso15693Answer(int len, uint8_t *d) {
                } else {
                        strncat(status,"NoErr ",DBD15STATLEN);
                }
-                       
+
                crc=Crc(d,len-2);
-               if ( (( crc & 0xff ) == d[len-2]) && (( crc >> 8 ) == d[len-1]) ) 
+               if ( (( crc & 0xff ) == d[len-2]) && (( crc >> 8 ) == d[len-1]) )
                        strncat(status,"CrcOK",DBD15STATLEN);
                else
-                       strncat(status,"CrcFail!",DBD15STATLEN); 
+                       strncat(status,"CrcFail!",DBD15STATLEN);
 
                Dbprintf("%s",status);
        }
@@ -1035,9 +1301,9 @@ void ReaderIso15693(uint32_t parameter)
 
        // Now send the IDENTIFY command
        BuildIdentifyRequest();
-       
+
        TransmitTo15693Tag(ToSend,ToSendMax);
-       
+
        // Now wait for a response
        answerLen1 = GetIso15693AnswerFromTag(answer1, 100) ;
 
@@ -1055,11 +1321,11 @@ void ReaderIso15693(uint32_t parameter)
        }
 
        Dbprintf("%d octets read from IDENTIFY request:", answerLen1);
-       DbdecodeIso15693Answer(answerLen1,answer1);
-       Dbhexdump(answerLen1,answer1,true);
+       DbdecodeIso15693Answer(answerLen1, answer1);
+       Dbhexdump(answerLen1, answer1, false);
 
        // UID is reverse
-       if (answerLen1 >= 12) 
+       if (answerLen1 >= 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]);
@@ -1076,72 +1342,64 @@ void ReaderIso15693(uint32_t parameter)
        // read all pages
        if (answerLen1 >= 12 && DEBUG) {
                uint8_t *answer2 = BigBuf_get_addr() + 4100;
-               int i=0;                        
-               while (i<32) {  // sanity check, assume max 32 pages
-                       BuildReadBlockRequest(TagUID,i);
-                       TransmitTo15693Tag(ToSend,ToSendMax);  
+               int i = 0;
+               while (i < 32) {  // sanity check, assume max 32 pages
+                       BuildReadBlockRequest(TagUID, i);
+                       TransmitTo15693Tag(ToSend, ToSendMax);
                        int answerLen2 = GetIso15693AnswerFromTag(answer2, 100);
-                       if (answerLen2>0) {
-                               Dbprintf("READ SINGLE BLOCK %d returned %d octets:",i,answerLen2);
-                               DbdecodeIso15693Answer(answerLen2,answer2);
-                               Dbhexdump(answerLen2,answer2,true);
-                               if ( *((uint32_t*) answer2) == 0x07160101 ) break; // exit on NoPageErr 
-                       } 
+                       if (answerLen2 > 0) {
+                               Dbprintf("READ SINGLE BLOCK %d returned %d octets:", i, answerLen2);
+                               DbdecodeIso15693Answer(answerLen2, answer2);
+                               Dbhexdump(answerLen2, answer2, false);
+                               if ( *((uint32_t*) answer2) == 0x07160101 ) break; // exit on NoPageErr
+                       }
                        i++;
-               } 
+               }
        }
 
-       // for the time being, switch field off to protect rdv4.0 
+       // 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();
 }
 
-// Simulate an ISO15693 TAG, perform anti-collision and then print any reader commands
-// all demodulation performed in arm rather than host. - greg
+
+// 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();
 
-       int answerLen1 = 0;
-       int samples = 0;
-       int elapsed = 0;
-
        FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
-
-       uint8_t *buf = BigBuf_get_addr() + 4000;
-       memset(buf, 0x00, 100);
-       
        SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
-       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
+       FpgaSetupSsc(FPGA_MAJOR_MODE_HF_SIMULATOR);
 
-       // Start from off (no field generated)
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-       SpinDelay(200);
+       StartCountSspClk();
 
-       // Listen to reader
-       answerLen1 = GetIso15693AnswerFromSniff(buf, 100, &samples, &elapsed) ;
+       uint8_t cmd[ISO15693_MAX_COMMAND_LENGTH];
 
-       if (answerLen1 >=1) // we should do a better check than this
-       {
-               // Build a suitable reponse to the reader INVENTORY cocmmand
-               // not so obsvious, but in the call to BuildInventoryResponse,  the command is copied to the global ToSend buffer used below.
-               
-               BuildInventoryResponse(uid);
-       
-               TransmitTo15693Reader(ToSend,ToSendMax);
-       }
+       // Build a suitable response to the reader INVENTORY command
+       BuildInventoryResponse(uid);
 
-       Dbprintf("%d octets read from reader command: %x %x %x %x %x %x %x %x %x", answerLen1,
-               buf[0], buf[1], buf[2], buf[3],
-               buf[4], buf[5], buf[6], buf[7], buf[8]);
+       // 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 - DELAY_ARM_TO_READER;
+                       TransmitTo15693Reader(ToSend, ToSendMax, start_time, slow);
+               }
 
-       Dbprintf("Simulationg uid: %x %x %x %x %x %x %x %x",
-               uid[0], uid[1], uid[2], uid[3],
-               uid[4], uid[5], uid[6], uid[7]);
+               Dbprintf("%d bytes read from reader:", cmd_len);
+               Dbhexdump(cmd_len, cmd, false);
+       }
 
        LEDsoff();
 }
@@ -1149,50 +1407,48 @@ void SimTagIso15693(uint32_t parameter, uint8_t *uid)
 
 // 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) 
-{      
+void BruteforceIso15693Afi(uint32_t speed)
+{
        LEDsoff();
        LED_A_ON();
-       
+
        uint8_t data[20];
        uint8_t *recv=data;
        int datalen=0, recvlen=0;
-               
+
        Iso15693InitReader();
-       
+
        // first without AFI
-       // Tags should respond wihtout AFI and with AFI=0 even when AFI is active
-       
-       data[0]=ISO15_REQ_SUBCARRIER_SINGLE | ISO15_REQ_DATARATE_HIGH | 
-               ISO15_REQ_INVENTORY | ISO15_REQINV_SLOT1;
-       data[1]=ISO15_CMD_INVENTORY;
-       data[2]=0; // mask length
-       datalen=AddCrc(data,3);
-       recvlen=SendDataTag(data, datalen, false, speed, &recv);
+       // 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);
        WDT_HIT();
        if (recvlen>=12) {
                Dbprintf("NoAFI UID=%s",sprintUID(NULL,&recv[2]));
        }
-       
+
        // now with AFI
-       
-       data[0]=ISO15_REQ_SUBCARRIER_SINGLE | ISO15_REQ_DATARATE_HIGH | 
-               ISO15_REQ_INVENTORY | ISO15_REQINV_AFI | ISO15_REQINV_SLOT1;
-       data[1]=ISO15_CMD_INVENTORY;
-       data[2]=0; // AFI
-       data[3]=0; // mask length
-       
+
+       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
+
        for (int i=0;i<256;i++) {
                data[2]=i & 0xFF;
                datalen=AddCrc(data,4);
                recvlen=SendDataTag(data, datalen, false, speed, &recv);
                WDT_HIT();
                if (recvlen>=12) {
-                       Dbprintf("AFI=%i UID=%s",i,sprintUID(NULL,&recv[2]));
+                       Dbprintf("AFI=%i UID=%s", i, sprintUID(NULL,&recv[2]));
                }
-       }       
+       }
        Dbprintf("AFI Bruteforcing done.");
-       
+
        FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
        LEDsoff();
 }
@@ -1202,31 +1458,31 @@ void DirectTag15693Command(uint32_t datalen, uint32_t speed, uint32_t recv, uint
 
        int recvlen=0;
        uint8_t *recvbuf = BigBuf_get_addr();
-       
+
        LED_A_ON();
-       
+
        if (DEBUG) {
                Dbprintf("SEND");
-               Dbhexdump(datalen,data,true);
+               Dbhexdump(datalen, data, false);
        }
-       
+
        recvlen = SendDataTag(data, datalen, true, speed, (recv?&recvbuf:NULL));
 
-       if (recv) { 
+       if (recv) {
                cmd_send(CMD_ACK, recvlen>48?48:recvlen, 0, 0, recvbuf, 48);
-               
+
                if (DEBUG) {
                        Dbprintf("RECV");
-                       DbdecodeIso15693Answer(recvlen,recvbuf); 
-                       Dbhexdump(recvlen,recvbuf,true);
+                       DbdecodeIso15693Answer(recvlen,recvbuf);
+                       Dbhexdump(recvlen, recvbuf, false);
                }
        }
 
-       // for the time being, switch field off to protect rdv4.0 
+       // 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();
 }
 
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