X-Git-Url: http://cvs.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/bce5d24494997238052d7f3fa7a3b89df43bce9f..a015ef37330ddd44c9a2d820e1def6545d4dea8d:/armsrc/iso15693.c?ds=sidebyside

diff --git a/armsrc/iso15693.c b/armsrc/iso15693.c
index ec8120b9..da2aab69 100644
--- a/armsrc/iso15693.c
+++ b/armsrc/iso15693.c
@@ -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)
@@ -39,22 +37,17 @@
 // 	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
 
 
@@ -63,10 +56,13 @@
 #include "apps.h"
 #include "string.h"
 #include "iso15693tools.h"
+#include "protocols.h"
 #include "cmd.h"
 
 #define arraylen(x) (sizeof(x)/sizeof((x)[0]))
 
+static int DEBUG = 0;
+
 ///////////////////////////////////////////////////////////////////////
 // ISO 15693 Part 2 - Air Interface
 // This section basicly contains transmission and receiving of bits
@@ -81,15 +77,25 @@
 #define AddCrc(data,datalen)  Iso15693AddCrc(data,datalen)
 #define sprintUID(target,uid)	Iso15693sprintUID(target,uid)
 
-int DEBUG=0;
+// 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)
 
+// 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)
@@ -165,14 +171,16 @@ static void CodeIso15693AsReader(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++;
 }
 
-// encode data using "1 out of 256" sheme
-// data rate is 1,66 kbit/s (fc/8192) 
+// 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)
 {
@@ -194,7 +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) {
@@ -203,8 +211,8 @@ static void CodeIso15693AsReader256(uint8_t *cmd, int n)
 			} else {
 				ToSendStuffBit(1);
 				ToSendStuffBit(1);
-			}			
-		}	
+			}
+		}
 	}
 	// EOF
 	ToSendStuffBit(1);
@@ -212,379 +220,722 @@ 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++;
 }
 
 
-// Transmit the command (to the tag) that was placed in ToSend[].
-static void TransmitTo15693Tag(const uint8_t *cmd, int len, int *samples, int *wait)
+static void CodeIso15693AsTag(uint8_t *cmd, int n)
 {
-    int c;
+	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);
+			}
+		}
+	}
 
-//    FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
+	// EOF
+	ToSendStuffBit(1);
+	ToSendStuffBit(0);
+	ToSendStuffBit(1);
+	ToSendStuffBit(1);
+	ToSendStuffBit(1);
+	ToSendStuffBit(0);
+	ToSendStuffBit(0);
+	ToSendStuffBit(0);
+
+	ToSendMax++;
+}
+
+
+// Transmit the command (to the tag) that was placed in cmd[].
+static void TransmitTo15693Tag(const uint8_t *cmd, int len)
+{
+	FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_TX);
 	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 uint32_t r = AT91C_BASE_SSC->SSC_RHR;
-//            (void)r;
-//        }
-//        WDT_HIT();
-//    }
-
-    c = 0;
-    for(;;) {
+
+	LED_B_ON();
+    for(int c = 0; c < len; ) {
         if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-            AT91C_BASE_SSC->SSC_THR = cmd[c];
+            AT91C_BASE_SSC->SSC_THR = ~cmd[c];
             c++;
-            if(c >= len) {
-                break;
-            }
-        }
-        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-            volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
-            (void)r;
         }
         WDT_HIT();
     }
-	*samples = (c + *wait) << 3;
+	LED_B_OFF();
 }
 
 //-----------------------------------------------------------------------------
-// Transmit the command (to the reader) that was placed in ToSend[].
+// Transmit the tag response (to the reader) that was placed in cmd[].
 //-----------------------------------------------------------------------------
-static void TransmitTo15693Reader(const uint8_t *cmd, int len, int *samples, int *wait)
+static void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t start_time, bool slow)
 {
-    int c = 0;
-	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR|FPGA_HF_SIMULATOR_MODULATE_424K);
-	if(*wait < 10) { *wait = 10; }
+	// 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);
 
-    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 uint32_t r = AT91C_BASE_SSC->SSC_RHR;
-            (void)r;
+	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();
+	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();
     }
-	*samples = (c + *wait) << 3;
+	LED_C_OFF();
 }
 
 
-// Read from Tag
-// Parameters:
-//		receivedResponse
-//		maxLen
-//		samples
-//		elapsed
-// returns: 
-//		number of decoded bytes
-static int GetIso15693AnswerFromTag(uint8_t *receivedResponse, int maxLen, int *samples, int *elapsed)
+//=============================================================================
+// 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,
+// 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 SUBCARRIER_DETECT_THRESHOLD	2
+#define SOF_CORRELATOR_LEN (1<<5)
+
+typedef struct DecodeTag {
+	enum {
+		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;
+	enum {
+		LOGIC0,
+		LOGIC1,
+		SOF_PART1,
+		SOF_PART2
+	}         lastBit;
+	uint16_t  shiftReg;
+	uint8_t   *output;
+	int       len;
+	int       sum1, sum2;
+	uint8_t   SOF_low;
+	uint8_t   SOF_high;
+	uint8_t   SOF_last;
+	int32_t   SOF_corr;
+	int32_t   SOF_corr_prev;
+	uint8_t   SOF_correlator[SOF_CORRELATOR_LEN];
+} DecodeTag_t;
+
+static int Handle15693SamplesFromTag(int8_t ci, int8_t cq, DecodeTag_t *DecodeTag)
 {
-	int c = 0;
-	uint8_t *dest = (uint8_t *)BigBuf;
-	int getNext = 0;
+	switch(DecodeTag->state) {
+		case STATE_TAG_UNSYNCD:
+			// initialize SOF correlator. We are looking for 12 samples low and 12 samples high.
+			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 STATE_TAG_AWAIT_SOF_1:
+			// calculate the correlation in real time. Look at differences only.
+			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 (DecodeTag->SOF_corr > DecodeTag->SOF_corr_prev + SUBCARRIER_DETECT_THRESHOLD) {
+				DecodeTag->posCount++;
+			} else {
+				DecodeTag->posCount = 0;
+			}
 
-	int8_t prev = 0;
+			if (DecodeTag->posCount == 10) {	// correlation increased 10 times
+				DecodeTag->state = STATE_TAG_AWAIT_SOF_2;
+			}
 
-// 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)) {
-			int8_t b;
-			b = (int8_t)AT91C_BASE_SSC->SSC_RHR;
+			DecodeTag->SOF_corr_prev = DecodeTag->SOF_corr;
 
-			// 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) {
-				int8_t r;
-
-				if(b < 0) {
-					r = -b;
-				} else {
-					r = b;
-				}
-				if(prev < 0) {
-					r -= prev;
-				} else {
-					r += prev;
-				}
+			break;
 
-				dest[c++] = (uint8_t)r;
+		case STATE_TAG_AWAIT_SOF_2:
+			// calculate the correlation in real time. Look at differences only.
+			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(c >= 2000) {
-					break;
+			if (DecodeTag->SOF_corr >= DecodeTag->SOF_corr_prev) { // we are looking for the maximum correlation
+				DecodeTag->SOF_corr_prev = DecodeTag->SOF_corr;
+			} else {
+				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 STATE_TAG_RECEIVING_DATA:
+			if (DecodeTag->posCount == 1) {
+				DecodeTag->sum1 = 0;
+				DecodeTag->sum2 = 0;
+			}
+
+			if (DecodeTag->posCount <= 4) {
+				DecodeTag->sum1 += AMPLITUDE(ci, cq);
+			} else {
+				DecodeTag->sum2 += AMPLITUDE(ci, cq);
+			}
+
+			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) {
+					DecodeTag->state = STATE_TAG_AWAIT_EOF;
+				} else if (corr_1 > corr_0) {
+					// logic 1
+					if (DecodeTag->lastBit == SOF_PART1) { // still part of SOF
+						DecodeTag->lastBit = SOF_PART2;
+					} else {
+						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 (DecodeTag->lastBit == SOF_PART1) { // incomplete SOF
+						DecodeTag->state = STATE_TAG_UNSYNCD;
+						LED_C_OFF();
+					} else {
+						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;
+						}
+					}
 				}
+				DecodeTag->posCount = 0;
+			}
+			DecodeTag->posCount++;
+			break;
+
+		case STATE_TAG_AWAIT_EOF:
+			if (DecodeTag->lastBit == LOGIC0) {  // this was already part of EOF
+				LED_C_OFF();
+				return true;
 			} else {
-				prev = b;
+				DecodeTag->state = STATE_TAG_UNSYNCD;
+				LED_C_OFF();
 			}
+			break;
 
-			getNext = !getNext;
-		}
+		default:
+			DecodeTag->state = STATE_TAG_UNSYNCD;
+			LED_C_OFF();
+			break;
 	}
 
-	//////////////////////////////////////////
-	/////////// DEMODULATE ///////////////////
-	//////////////////////////////////////////
+	return false;
+}
 
-	int i, j;
-	int max = 0, maxPos=0;
 
-	int skip = 4;
+static void DecodeTagInit(DecodeTag_t *DecodeTag, uint8_t *data)
+{
+	DecodeTag->output = data;
+	DecodeTag->state = STATE_TAG_UNSYNCD;
+}
+
+/*
+ *  Receive and decode the tag response, also log to tracebuffer
+ */
+static int GetIso15693AnswerFromTag(uint8_t* response, int timeout)
+{
+	int maxBehindBy = 0;
+	int lastRxCounter, samples = 0;
+	int8_t ci, cq;
+	bool gotFrame = false;
+
+	uint16_t dmaBuf[ISO15693_DMA_BUFFER_SIZE];
+
+	// 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));
 
-	//	if(GraphTraceLen < 1000) return;	// THIS CHECKS FOR A BUFFER TO SMALL
+	// And put the FPGA in the appropriate mode
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
+
+	// 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;
 
-	// 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)];
+	for(;;) {
+		int behindBy = (lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR) & (ISO15693_DMA_BUFFER_SIZE-1);
+		if(behindBy > maxBehindBy) {
+			maxBehindBy = behindBy;
 		}
-		if(corr > max) {
-			max = corr;
-			maxPos = i;
+
+		if (behindBy < 1) continue;
+
+		ci = (int8_t)(*upTo >> 8);
+		cq = (int8_t)(*upTo & 0xff);
+
+		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
+		}
+		samples++;
+
+		if (Handle15693SamplesFromTag(ci, cq, &DecodeTag)) {
+			gotFrame = true;
+			break;
+		}
+
+		if(samples > timeout && DecodeTag.state < STATE_TAG_RECEIVING_DATA) {
+			DecodeTag.len = 0;
+			break;
+		}
+
 	}
-	//	DbpString("SOF at %d, correlation %d", maxPos,max/(arraylen(FrameSOF)/skip));
 
-	int k = 0; // this will be our return value
+	FpgaDisableSscDma();
 
-	// greg - If correlation is less than 1 then there's little point in continuing
-	if ((max/(arraylen(FrameSOF)/skip)) >= 1)
-	{
+	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);
 
-		i = maxPos + arraylen(FrameSOF)/skip;
-	
-		uint8_t outBuf[20];
-		memset(outBuf, 0, sizeof(outBuf));
-		uint8_t mask = 0x01;
-		for(;;) {
-			int corr0 = 0, corr1 = 0, corrEOF = 0;
-			for(j = 0; j < arraylen(Logic0); j += skip) {
-				corr0 += Logic0[j]*dest[i+(j/skip)];
+	if (tracing && DecodeTag.len > 0) {
+		LogTrace(DecodeTag.output, DecodeTag.len, 0, 0, NULL, false);
+	}
+
+	return DecodeTag.len;
+}
+
+
+//=============================================================================
+// 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)
+{
+	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;
 			}
-			for(j = 0; j < arraylen(Logic1); j += skip) {
-				corr1 += Logic1[j]*dest[i+(j/skip)];
+			break;
+
+		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
+				}
 			}
-			for(j = 0; j < arraylen(FrameEOF); j += skip) {
-				corrEOF += FrameEOF[j]*dest[i+(j/skip)];
+			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
+				}
 			}
-			// Even things out by the length of the target waveform.
-			corr0 *= 4;
-			corr1 *= 4;
-	
-			if(corrEOF > corr1 && corrEOF > corr0) {
-	//			DbpString("EOF at %d", i);
-				break;
-			} else if(corr1 > corr0) {
-				i += arraylen(Logic1)/skip;
-				outBuf[k] |= mask;
+			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 {
-				i += arraylen(Logic0)/skip;
+				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
+					}
+				}
 			}
-			mask <<= 1;
-			if(mask == 0) {
-				k++;
-				mask = 0x01;
+			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;
 			}
-			if((i+(int)arraylen(FrameEOF)) >= 2000) {
-				DbpString("ran off end!");
-				break;
+			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(mask != 0x01) { // this happens, when we miss the EOF
-			// TODO: for some reason this happens quite often
-			if (DEBUG) Dbprintf("error, uneven octet! (extra bits!) mask=%02x", mask);
-			if (mask<0x08) k--; // discard the last uneven octet;
-			// 0x08 is an assumption - but works quite often
-		}
-	//	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];
-		}
-	} // "end if correlation > 0" 	(max/(arraylen(FrameSOF)/skip))
-	return k; // return the number of bytes demodulated
+			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;
 
-///	DbpString("CRC=%04x", Iso15693Crc(outBuf, k-2));
+		default:
+			LED_B_OFF();
+			DecodeReader->state = STATE_READER_UNSYNCD;
+			break;
+	}
 
+	return false;
 }
 
 
-// Now the GetISO15693 message from sniffing command
-static int GetIso15693AnswerFromSniff(uint8_t *receivedResponse, int maxLen, int *samples, int *elapsed)
+static void DecodeReaderInit(uint8_t *data, uint16_t max_len, DecodeReader_t* DecodeReader)
 {
-	int c = 0;
-	uint8_t *dest = (uint8_t *)BigBuf;
-	int getNext = 0;
+	DecodeReader->output = data;
+	DecodeReader->byteCountMax = max_len;
+	DecodeReader->state = STATE_READER_UNSYNCD;
+	DecodeReader->byteCount = 0;
+	DecodeReader->bitCount = 0;
+	DecodeReader->posCount = 0;
+	DecodeReader->shiftReg = 0;
+}
 
-	int8_t prev = 0;
 
-// 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)) {
-			int8_t b = (int8_t)AT91C_BASE_SSC->SSC_RHR;
+//-----------------------------------------------------------------------------
+// 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.
+//-----------------------------------------------------------------------------
 
-			// 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) {
-				int8_t r;
-
-				if(b < 0) {
-					r = -b;
-				} else {
-					r = b;
-				}
-				if(prev < 0) {
-					r -= prev;
-				} else {
-					r += prev;
-				}
+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;
 
-				dest[c++] = (uint8_t)r;
+	uint8_t dmaBuf[ISO15693_DMA_BUFFER_SIZE];
 
-				if(c >= 20000) {
-					break;
-				}
-			} else {
-				prev = b;
-			}
+	// the decoder data structure
+	DecodeReader_t DecodeReader = {0};
+	DecodeReaderInit(received, max_len, &DecodeReader);
 
-			getNext = !getNext;
-		}
-	}
+	// wait for last transfer to complete
+	while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
 
-	//////////////////////////////////////////
-	/////////// DEMODULATE ///////////////////
-	//////////////////////////////////////////
+	LED_D_OFF();
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
 
-	int i, j;
-	int max = 0, maxPos=0;
+	// 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 skip = 4;
+	uint32_t bit_time = GetCountSspClk() & 0xfffffff8;
 
-//	if(GraphTraceLen < 1000) return;	// THIS CHECKS FOR A BUFFER TO SMALL
+	// 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 < 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;
+	for(;;) {
+		int behindBy = (lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR) & (ISO15693_DMA_BUFFER_SIZE-1);
+		if(behindBy > maxBehindBy) {
+			maxBehindBy = behindBy;
 		}
-	}
-//	DbpString("SOF at %d, correlation %d", maxPos,max/(arraylen(FrameSOF)/skip));
 
-	int k = 0; // this will be our return value
+		if (behindBy < 1) continue;
 
-	// 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, 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;
-	
-			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;
-			}
-			mask <<= 1;
-			if(mask == 0) {
-				k++;
-				mask = 0x01;
-			}
-			if((i+(int)arraylen(FrameEOF)) >= 2000) {
-				DbpString("ran off end!");
+		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
+		}
+
+		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;
 }
 
 
@@ -596,11 +947,10 @@ static void BuildIdentifyRequest(void);
 //-----------------------------------------------------------------------------
 void AcquireRawAdcSamplesIso15693(void)
 {
-	uint8_t *dest = (uint8_t *)BigBuf;
+	LEDsoff();
+	LED_A_ON();
 
-	int c = 0;
-	int getNext = 0;
-	int8_t prev = 0;
+	uint8_t *dest = BigBuf_get_addr();
 
 	FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
 	BuildIdentifyRequest();
@@ -608,173 +958,118 @@ void AcquireRawAdcSamplesIso15693(void)
 	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
 	// Give the tags time to energize
+	LED_D_ON();
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 	SpinDelay(100);
 
 	// Now send the command
-	FpgaSetupSsc();
+	FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_TX);
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
 
-	c = 0;
-	for(;;) {
+	LED_B_ON();
+	for(int c = 0; c < ToSendMax; ) {
 		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-			AT91C_BASE_SSC->SSC_THR = ToSend[c];
+			AT91C_BASE_SSC->SSC_THR = ~ToSend[c];
 			c++;
-			if(c == ToSendMax+3) {
-				break;
-			}
-		}
-		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-			volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
-			(void)r;
 		}
 		WDT_HIT();
 	}
+	LED_B_OFF();
+
+	// wait for last transfer to complete
+	while (!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXEMPTY));
 
+	FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 
-	c = 0;
-	getNext = FALSE;
-	for(;;) {
-		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-			AT91C_BASE_SSC->SSC_THR = 0x43;
-		}
+	for(int c = 0; c < 4000; ) {
 		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-			int8_t b;
-			b = (int8_t)AT91C_BASE_SSC->SSC_RHR;
-
+			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, 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) {
-				int8_t r;
-
-				if(b < 0) {
-					r = -b;
-				} else {
-					r = b;
-				}
-				if(prev < 0) {
-					r -= prev;
-				} else {
-					r += prev;
-				}
-
-				dest[c++] = (uint8_t)r;
-
-				if(c >= 2000) {
-					break;
-				}
-			} else {
-				prev = b;
-			}
-
-			getNext = !getNext;
+			// 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;
 		}
 	}
+
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+	LEDsoff();
 }
 
 
+// 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...
 void RecordRawAdcSamplesIso15693(void)
 {
-	uint8_t *dest =  (uint8_t *)BigBuf;
+	LEDsoff();
+	LED_A_ON();
 
-	int c = 0;
-	int getNext = 0;
-	int8_t prev = 0;
+	uint8_t *dest = BigBuf_get_addr();
 
 	FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
 	// Setup SSC
-	FpgaSetupSsc();
+	FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 
 	// Start from off (no field generated)
-    	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-    	SpinDelay(200);
+   	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+   	SpinDelay(200);
 
 	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
 	SpinDelay(100);
 
+	LED_D_ON();
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 
-	c = 0;
-	getNext = FALSE;
-	for(;;) {
-		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-			AT91C_BASE_SSC->SSC_THR = 0x43;
-		}
+	for(int c = 0; c < 14000;) {
 		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-			int8_t b;
-			b = (int8_t)AT91C_BASE_SSC->SSC_RHR;
-
+			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, 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) {
-				int8_t r;
-
-				if(b < 0) {
-					r = -b;
-				} else {
-					r = b;
-				}
-				if(prev < 0) {
-					r -= prev;
-				} else {
-					r += prev;
-				}
-
-				dest[c++] = (uint8_t)r;
-
-				if(c >= 7000) {
-					break;
-				}
-			} else {
-				prev = b;
-			}
-
-			getNext = !getNext;
-			WDT_HIT();
+			// 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;
 		}
 	}
-	Dbprintf("fin record");
+
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+	LED_D_OFF();
+	Dbprintf("finished recording");
+	LED_A_OFF();
 }
 
 
-// Initialize the proxmark as iso15k reader 
+// Initialize the proxmark as iso15k reader
 // (this might produces glitches that confuse some tags
-void Iso15693InitReader() {
-	LED_A_ON();
-	LED_B_ON();
-	LED_C_OFF();
-	LED_D_OFF();
-	
+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();
+	FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 
 	// Give the tags time to energize
+	LED_D_ON();
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 	SpinDelay(250);
-
-	LED_A_ON();
-	LED_B_OFF();
-	LED_C_OFF();
-	LED_D_OFF();
 }
 
 ///////////////////////////////////////////////////////////////////////
 // ISO 15693 Part 3 - Air Interface
-// This section basicly contains transmission and receiving of bits
+// This section basically contains transmission and receiving of bits
 ///////////////////////////////////////////////////////////////////////
 
 // Encode (into the ToSend buffers) an identify request, which is the first
@@ -824,23 +1119,22 @@ 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;
 
 	CodeIso15693AsReader(cmd, sizeof(cmd));
 }
 
+
 // 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;
@@ -856,33 +1150,27 @@ static void BuildReadBlockRequest(uint8_t *uid, uint8_t blockNumber )
 	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, int init, int speed, uint8_t **recv) {
+int SendDataTag(uint8_t *send, int sendlen, bool init, int speed, uint8_t **recv) {
 
-	int samples = 0;
-	int tsamples = 0;
-	int wait = 0;
-	int elapsed = 0;
-	
 	LED_A_ON();
-	LED_B_ON();
+	LED_B_OFF();
 	LED_C_OFF();
-	LED_D_OFF();
-	
-	int answerLen=0;
-	uint8_t *answer = (((uint8_t *)BigBuf) + 3660);
-	if (recv!=NULL) memset(BigBuf + 3660, 0, 100);
 
 	if (init) Iso15693InitReader();
-	
+
+	int answerLen=0;
+	uint8_t *answer = BigBuf_get_addr() + 4000;
+	if (recv != NULL) memset(answer, 0, 100);
+
 	if (!speed) {
 		// low speed (1 out of 256)
 		CodeIso15693AsReader256(send, sendlen);
@@ -890,30 +1178,22 @@ int SendDataTag(uint8_t *send, int sendlen, int init, int speed, uint8_t **recv)
 		// high speed (1 out of 4)
 		CodeIso15693AsReader(send, sendlen);
 	}
-	
-	LED_A_ON();
-	LED_B_OFF();
-	
-	TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);	
+
+	TransmitTo15693Tag(ToSend,ToSendMax);
 	// Now wait for a response
 	if (recv!=NULL) {
-		LED_A_OFF();
-		LED_B_ON();
-		answerLen = GetIso15693AnswerFromTag(answer, 100, &samples, &elapsed) ;	
+		answerLen = GetIso15693AnswerFromTag(answer, 100);
 		*recv=answer;
 	}
 
 	LED_A_OFF();
-	LED_B_OFF();
-	LED_C_OFF();
-	LED_D_OFF();
-	
+
 	return answerLen;
 }
 
 
 // --------------------------------------------------------------------
-// Debug Functions 
+// Debug Functions
 // --------------------------------------------------------------------
 
 // Decodes a message from a tag and displays its metadata and content
@@ -923,37 +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:
@@ -963,12 +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);
 	}
@@ -986,66 +1266,46 @@ void SetDebugIso15693(uint32_t debug) {
 	return;
 }
 
-
-
 //-----------------------------------------------------------------------------
 // Simulate an ISO15693 reader, perform anti-collision and then attempt to read a sector
 // all demodulation performed in arm rather than host. - greg
 //-----------------------------------------------------------------------------
 void ReaderIso15693(uint32_t parameter)
 {
+	LEDsoff();
 	LED_A_ON();
-	LED_B_ON();
-	LED_C_OFF();
-	LED_D_OFF();
-
-	uint8_t *answer1 = (((uint8_t *)BigBuf) + 3660); //
-	uint8_t *answer2 = (((uint8_t *)BigBuf) + 3760);
-	uint8_t *answer3 = (((uint8_t *)BigBuf) + 3860);
 
 	int answerLen1 = 0;
-	int answerLen2 = 0;
-	int answerLen3 = 0;
-	int i = 0;
-	int samples = 0;
-	int tsamples = 0;
-	int wait = 0;
-	int elapsed = 0;
 	uint8_t TagUID[8] = {0x00};
 
-
-	// Blank arrays
-	memset(BigBuf + 3660, 0x00, 300);
-
 	FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
 
+	uint8_t *answer1 = BigBuf_get_addr() + 4000;
+	memset(answer1, 0x00, 200);
+
 	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 	// Setup SSC
-	FpgaSetupSsc();
+	FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 
 	// Start from off (no field generated)
-    	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-    	SpinDelay(200);
+   	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+   	SpinDelay(200);
 
 	// Give the tags time to energize
+	LED_D_ON();
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
 	SpinDelay(200);
 
-	LED_A_ON();
-	LED_B_OFF();
-	LED_C_OFF();
-	LED_D_OFF();
-
 	// FIRST WE RUN AN INVENTORY TO GET THE TAG UID
 	// THIS MEANS WE CAN PRE-BUILD REQUESTS TO SAVE CPU TIME
 
 	// Now send the IDENTIFY command
 	BuildIdentifyRequest();
-	
-	TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);
-	
+
+	TransmitTo15693Tag(ToSend,ToSendMax);
+
 	// Now wait for a response
-	answerLen1 = GetIso15693AnswerFromTag(answer1, 100, &samples, &elapsed) ;
+	answerLen1 = GetIso15693AnswerFromTag(answer1, 100) ;
 
 	if (answerLen1 >=12) // we should do a better check than this
 	{
@@ -1061,180 +1321,169 @@ 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]);
 
 
-	Dbprintf("%d octets read from SELECT request:", answerLen2);
-	DbdecodeIso15693Answer(answerLen2,answer2);
-	Dbhexdump(answerLen2,answer2,true);
+	// 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);
+	// Dbprintf("%d octets read from XXX request:", answerLen3);
+	// DbdecodeIso15693Answer(answerLen3,answer3);
+	// Dbhexdump(answerLen3,answer3,true);
 
 	// read all pages
-	if (answerLen1>=12 && DEBUG) {
-		i=0;			
-		while (i<32) {  // sanity check, assume max 32 pages
-			BuildReadBlockRequest(TagUID,i);
-	      TransmitTo15693Tag(ToSend,ToSendMax,&tsamples, &wait);  
-         answerLen2 = GetIso15693AnswerFromTag(answer2, 100, &samples, &elapsed);
-			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 (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 answerLen2 = GetIso15693AnswerFromTag(answer2, 100);
+			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++;
-		} 
+		}
 	}
 
-	LED_A_OFF();
-	LED_B_OFF();
-	LED_C_OFF();
+	// 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();
-	LED_B_ON();
-	LED_C_OFF();
-	LED_D_OFF();
-
-	uint8_t *buf = (((uint8_t *)BigBuf) + 3660); //
-	
-	int answerLen1 = 0;
-	int samples = 0;
-	int tsamples = 0;
-	int wait = 0;
-	int elapsed = 0;
-
-	memset(buf, 0x00, 100);
 
 	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);
 
-	FpgaSetupSsc();
+	StartCountSspClk();
 
-	// Start from off (no field generated)
-    	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-	SpinDelay(200);
+	uint8_t cmd[ISO15693_MAX_COMMAND_LENGTH];
 
-	LED_A_OFF();
-	LED_B_OFF();
-	LED_C_ON();
-	LED_D_OFF();
+	// Build a suitable response to the reader INVENTORY command
+	BuildInventoryResponse(uid);
 
 	// Listen to reader
-	answerLen1 = GetIso15693AnswerFromSniff(buf, 100, &samples, &elapsed) ;
+	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);
+		}
 
-	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, &tsamples, &wait);
+		Dbprintf("%d bytes read from reader:", cmd_len);
+		Dbhexdump(cmd_len, cmd, false);
 	}
 
-	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]);
-
-	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]);
-
-	LED_A_OFF();
-	LED_B_OFF();
-	LED_C_OFF();
-	LED_D_OFF();
+	LEDsoff();
 }
 
 
 // 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,0,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,0,speed,&recv);
+		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();
 }
 
 // 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[]) {
+void DirectTag15693Command(uint32_t datalen, uint32_t speed, uint32_t recv, uint8_t data[]) {
 
 	int recvlen=0;
-	uint8_t *recvbuf=(uint8_t *)BigBuf;
-//	UsbCommand n;
-	
+	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,1,speed,(recv?&recvbuf:NULL));
 
-	if (recv) { 
-		LED_B_ON();
-    cmd_send(CMD_ACK,recvlen>48?48:recvlen,0,0,recvbuf,48);
-		LED_B_OFF();	
-		
+	recvlen = SendDataTag(data, datalen, true, speed, (recv?&recvbuf:NULL));
+
+	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
+	// 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();
 }