X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/30f2a7d38fd35b2427a7eb42e1cd75fb1105f927..a88dc6ab3b734bc0c501c24cd26cc2142289c10a:/armsrc/iso14443.c

diff --git a/armsrc/iso14443.c b/armsrc/iso14443.c
index 2579b053..7a445bcb 100644
--- a/armsrc/iso14443.c
+++ b/armsrc/iso14443.c
@@ -1,988 +1,1239 @@
-//-----------------------------------------------------------------------------
-// Routines to support ISO 14443. This includes both the reader software and
-// the `fake tag' modes. At the moment only the Type B modulation is
-// supported.
-// Jonathan Westhues, split Nov 2006
-//-----------------------------------------------------------------------------
-#include <proxmark3.h>
-#include "apps.h"
-#include "../common/iso14443_crc.c"
-
-
-//static void GetSamplesFor14443(BOOL weTx, int n);
-
-#define DMA_BUFFER_SIZE 256
-
-//=============================================================================
-// An ISO 14443 Type B tag. We listen for commands from the reader, using
-// a UART kind of thing that's implemented in software. When we get a
-// frame (i.e., a group of bytes between SOF and EOF), we check the CRC.
-// If it's good, then we can do something appropriate with it, and send
-// a response.
-//=============================================================================
-
-//-----------------------------------------------------------------------------
-// Code up a string of octets at layer 2 (including CRC, we don't generate
-// that here) so that they can be transmitted to the reader. Doesn't transmit
-// them yet, just leaves them ready to send in ToSend[].
-//-----------------------------------------------------------------------------
-static void CodeIso14443bAsTag(const BYTE *cmd, int len)
-{
-    int i;
-
-    ToSendReset();
-
-    // Transmit a burst of ones, as the initial thing that lets the
-    // reader get phase sync. This (TR1) must be > 80/fs, per spec,
-    // but tag that I've tried (a Paypass) exceeds that by a fair bit,
-    // so I will too.
-    for(i = 0; i < 20; i++) {
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-    }
-
-    // Send SOF.
-    for(i = 0; i < 10; i++) {
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-    }
-    for(i = 0; i < 2; i++) {
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-    }
-
-    for(i = 0; i < len; i++) {
-        int j;
-        BYTE b = cmd[i];
-
-        // Start bit
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-
-        // Data bits
-        for(j = 0; j < 8; j++) {
-            if(b & 1) {
-                ToSendStuffBit(1);
-                ToSendStuffBit(1);
-                ToSendStuffBit(1);
-                ToSendStuffBit(1);
-            } else {
-                ToSendStuffBit(0);
-                ToSendStuffBit(0);
-                ToSendStuffBit(0);
-                ToSendStuffBit(0);
-            }
-            b >>= 1;
-        }
-
-        // Stop bit
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-    }
-
-    // Send SOF.
-    for(i = 0; i < 10; i++) {
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-        ToSendStuffBit(0);
-    }
-    for(i = 0; i < 10; i++) {
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-    }
-
-    // Convert from last byte pos to length
-    ToSendMax++;
-
-    // Add a few more for slop
-    ToSendMax += 2;
-}
-
-//-----------------------------------------------------------------------------
-// The software UART that receives commands from the reader, and its state
-// variables.
-//-----------------------------------------------------------------------------
-static struct {
-    enum {
-        STATE_UNSYNCD,
-        STATE_GOT_FALLING_EDGE_OF_SOF,
-        STATE_AWAITING_START_BIT,
-        STATE_RECEIVING_DATA,
-        STATE_ERROR_WAIT
-    }       state;
-    WORD    shiftReg;
-    int     bitCnt;
-    int     byteCnt;
-    int     byteCntMax;
-    int     posCnt;
-    BYTE   *output;
-} Uart;
-
-static BOOL Handle14443UartBit(int bit)
-{
-    switch(Uart.state) {
-        case STATE_UNSYNCD:
-            if(!bit) {
-                // we went low, so this could be the beginning
-                // of an SOF
-                Uart.state = STATE_GOT_FALLING_EDGE_OF_SOF;
-                Uart.posCnt = 0;
-                Uart.bitCnt = 0;
-            }
-            break;
-
-        case STATE_GOT_FALLING_EDGE_OF_SOF:
-            Uart.posCnt++;
-            if(Uart.posCnt == 2) {
-                if(bit) {
-                    if(Uart.bitCnt >= 10) {
-                        // we've seen enough consecutive
-                        // zeros that it's a valid SOF
-                        Uart.posCnt = 0;
-                        Uart.byteCnt = 0;
-                        Uart.state = STATE_AWAITING_START_BIT;
-                    } else {
-                        // didn't stay down long enough
-                        // before going high, error
-                        Uart.state = STATE_ERROR_WAIT;
-                    }
-                } else {
-                    // do nothing, keep waiting
-                }
-                Uart.bitCnt++;
-            }
-            if(Uart.posCnt >= 4) Uart.posCnt = 0;
-            if(Uart.bitCnt > 14) {
-                // Give up if we see too many zeros without
-                // a one, too.
-                Uart.state = STATE_ERROR_WAIT;
-            }
-            break;
-
-        case STATE_AWAITING_START_BIT:
-            Uart.posCnt++;
-            if(bit) {
-                if(Uart.posCnt > 25) {
-                    // stayed high for too long between
-                    // characters, error
-                    Uart.state = STATE_ERROR_WAIT;
-                }
-            } else {
-                // falling edge, this starts the data byte
-                Uart.posCnt = 0;
-                Uart.bitCnt = 0;
-                Uart.shiftReg = 0;
-                Uart.state = STATE_RECEIVING_DATA;
-            }
-            break;
-
-        case STATE_RECEIVING_DATA:
-            Uart.posCnt++;
-            if(Uart.posCnt == 2) {
-                // time to sample a bit
-                Uart.shiftReg >>= 1;
-                if(bit) {
-                    Uart.shiftReg |= 0x200;
-                }
-                Uart.bitCnt++;
-            }
-            if(Uart.posCnt >= 4) {
-                Uart.posCnt = 0;
-            }
-            if(Uart.bitCnt == 10) {
-                if((Uart.shiftReg & 0x200) && !(Uart.shiftReg & 0x001))
-                {
-                    // this is a data byte, with correct
-                    // start and stop bits
-                    Uart.output[Uart.byteCnt] = (Uart.shiftReg >> 1) & 0xff;
-                    Uart.byteCnt++;
-
-                    if(Uart.byteCnt >= Uart.byteCntMax) {
-                        // Buffer overflowed, give up
-                        Uart.posCnt = 0;
-                        Uart.state = STATE_ERROR_WAIT;
-                    } else {
-                        // so get the next byte now
-                        Uart.posCnt = 0;
-                        Uart.state = STATE_AWAITING_START_BIT;
-                    }
-                } else if(Uart.shiftReg == 0x000) {
-                    // this is an EOF byte
-                    return TRUE;
-                } else {
-                    // this is an error
-                    Uart.posCnt = 0;
-                    Uart.state = STATE_ERROR_WAIT;
-                }
-            }
-            break;
-
-        case STATE_ERROR_WAIT:
-            // We're all screwed up, so wait a little while
-            // for whatever went wrong to finish, and then
-            // start over.
-            Uart.posCnt++;
-            if(Uart.posCnt > 10) {
-                Uart.state = STATE_UNSYNCD;
-            }
-            break;
-
-        default:
-            Uart.state = STATE_UNSYNCD;
-            break;
-    }
-
-    return FALSE;
-}
-
-//-----------------------------------------------------------------------------
-// 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 BOOL GetIso14443CommandFromReader(BYTE *received, int *len, int maxLen)
-{
-    BYTE mask;
-    int i, bit;
-
-    // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
-    // only, since we are receiving, not transmitting).
-    FpgaWriteConfWord(
-    	FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
-
-
-    // Now run a `software UART' on the stream of incoming samples.
-    Uart.output = received;
-    Uart.byteCntMax = maxLen;
-    Uart.state = STATE_UNSYNCD;
-
-    for(;;) {
-        WDT_HIT();
-
-        if(BUTTON_PRESS()) return FALSE;
-
-        if(SSC_STATUS & (SSC_STATUS_TX_READY)) {
-            SSC_TRANSMIT_HOLDING = 0x00;
-        }
-        if(SSC_STATUS & (SSC_STATUS_RX_READY)) {
-            BYTE b = (BYTE)SSC_RECEIVE_HOLDING;
-
-            mask = 0x80;
-            for(i = 0; i < 8; i++, mask >>= 1) {
-                bit = (b & mask);
-                if(Handle14443UartBit(bit)) {
-                    *len = Uart.byteCnt;
-                    return TRUE;
-                }
-            }
-        }
-    }
-}
-
-//-----------------------------------------------------------------------------
-// Main loop of simulated tag: receive commands from reader, decide what
-// response to send, and send it.
-//-----------------------------------------------------------------------------
-void SimulateIso14443Tag(void)
-{
-    static const BYTE cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
-    static const BYTE response1[] = {
-        0x50, 0x82, 0x0d, 0xe1, 0x74, 0x20, 0x38, 0x19, 0x22,
-        0x00, 0x21, 0x85, 0x5e, 0xd7
-    };
-
-    BYTE *resp;
-    int respLen;
-
-    BYTE *resp1 = (((BYTE *)BigBuf) + 800);
-    int resp1Len;
-
-    BYTE *receivedCmd = (BYTE *)BigBuf;
-    int len;
-
-    int i;
-
-    int cmdsRecvd = 0;
-
-    memset(receivedCmd, 0x44, 400);
-
-    CodeIso14443bAsTag(response1, sizeof(response1));
-    memcpy(resp1, ToSend, ToSendMax); resp1Len = ToSendMax;
-
-    // We need to listen to the high-frequency, peak-detected path.
-    SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
-    FpgaSetupSsc();
-
-    cmdsRecvd = 0;
-
-    for(;;) {
-        BYTE b1, b2;
-
-        if(!GetIso14443CommandFromReader(receivedCmd, &len, 100)) {
-            DbpIntegers(cmdsRecvd, 0, 0);
-            DbpString("button press");
-            break;
-        }
-
-        // Good, look at the command now.
-
-        if(len == sizeof(cmd1) && memcmp(receivedCmd, cmd1, len)==0) {
-            resp = resp1; respLen = resp1Len;
-        } else {
-            DbpString("new cmd from reader:");
-            DbpIntegers(len, 0x1234, cmdsRecvd);
-            // And print whether the CRC fails, just for good measure
-            ComputeCrc14443(CRC_14443_B, receivedCmd, len-2, &b1, &b2);
-            if(b1 != receivedCmd[len-2] || b2 != receivedCmd[len-1]) {
-                // Not so good, try again.
-                DbpString("+++CRC fail");
-            } else {
-                DbpString("CRC passes");
-            }
-            break;
-        }
-
-        memset(receivedCmd, 0x44, 32);
-
-        cmdsRecvd++;
-
-        if(cmdsRecvd > 0x30) {
-            DbpString("many commands later...");
-            break;
-        }
-
-        if(respLen <= 0) continue;
-
-        // Modulate BPSK
-        FpgaWriteConfWord(
-        	FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_BPSK);
-        SSC_TRANSMIT_HOLDING = 0xff;
-        FpgaSetupSsc();
-
-        // Transmit the response.
-        i = 0;
-        for(;;) {
-            if(SSC_STATUS & (SSC_STATUS_TX_READY)) {
-                BYTE b = resp[i];
-
-                SSC_TRANSMIT_HOLDING = b;
-
-                i++;
-                if(i > respLen) {
-                    break;
-                }
-            }
-            if(SSC_STATUS & (SSC_STATUS_RX_READY)) {
-                volatile BYTE b = (BYTE)SSC_RECEIVE_HOLDING;
-                (void)b;
-            }
-        }
-    }
-}
-
-//=============================================================================
-// An ISO 14443 Type B reader. We take layer two commands, code them
-// appropriately, and then send them to the tag. We then listen for the
-// tag's response, which we leave in the buffer to be demodulated on the
-// PC side.
-//=============================================================================
-
-static struct {
-    enum {
-        DEMOD_UNSYNCD,
-        DEMOD_PHASE_REF_TRAINING,
-        DEMOD_AWAITING_FALLING_EDGE_OF_SOF,
-        DEMOD_GOT_FALLING_EDGE_OF_SOF,
-        DEMOD_AWAITING_START_BIT,
-        DEMOD_RECEIVING_DATA,
-        DEMOD_ERROR_WAIT
-    }       state;
-    int     bitCount;
-    int     posCount;
-    int     thisBit;
-    int     metric;
-    int     metricN;
-    WORD    shiftReg;
-    BYTE   *output;
-    int     len;
-    int     sumI;
-    int     sumQ;
-} Demod;
-
-static BOOL Handle14443SamplesDemod(int ci, int cq)
-{
-    int v;
-
-    // The soft decision on the bit uses an estimate of just the
-    // quadrant of the reference angle, not the exact angle.
-#define MAKE_SOFT_DECISION() { \
-        if(Demod.sumI > 0) { \
-            v = ci; \
-        } else { \
-            v = -ci; \
-        } \
-        if(Demod.sumQ > 0) { \
-            v += cq; \
-        } else { \
-            v -= cq; \
-        } \
-    }
-
-    switch(Demod.state) {
-        case DEMOD_UNSYNCD:
-            v = ci;
-            if(v < 0) v = -v;
-            if(cq > 0) {
-                v += cq;
-            } else {
-                v -= cq;
-            }
-            if(v > 40) {
-                Demod.posCount = 0;
-                Demod.state = DEMOD_PHASE_REF_TRAINING;
-                Demod.sumI = 0;
-                Demod.sumQ = 0;
-            }
-            break;
-
-        case DEMOD_PHASE_REF_TRAINING:
-            if(Demod.posCount < 8) {
-                Demod.sumI += ci;
-                Demod.sumQ += cq;
-            } else if(Demod.posCount > 100) {
-                // error, waited too long
-                Demod.state = DEMOD_UNSYNCD;
-            } else {
-                MAKE_SOFT_DECISION();
-                if(v < 0) {
-                    Demod.state = DEMOD_AWAITING_FALLING_EDGE_OF_SOF;
-                    Demod.posCount = 0;
-                }
-            }
-            Demod.posCount++;
-            break;
-
-        case DEMOD_AWAITING_FALLING_EDGE_OF_SOF:
-            MAKE_SOFT_DECISION();
-            if(v < 0) {
-                Demod.state = DEMOD_GOT_FALLING_EDGE_OF_SOF;
-                Demod.posCount = 0;
-            } else {
-                if(Demod.posCount > 100) {
-                    Demod.state = DEMOD_UNSYNCD;
-                }
-            }
-            Demod.posCount++;
-            break;
-
-        case DEMOD_GOT_FALLING_EDGE_OF_SOF:
-            MAKE_SOFT_DECISION();
-            if(v > 0) {
-                if(Demod.posCount < 12) {
-                    Demod.state = DEMOD_UNSYNCD;
-                } else {
-                    Demod.state = DEMOD_AWAITING_START_BIT;
-                    Demod.posCount = 0;
-                    Demod.len = 0;
-                    Demod.metricN = 0;
-                    Demod.metric = 0;
-                }
-            } else {
-                if(Demod.posCount > 100) {
-                    Demod.state = DEMOD_UNSYNCD;
-                }
-            }
-            Demod.posCount++;
-            break;
-
-        case DEMOD_AWAITING_START_BIT:
-            MAKE_SOFT_DECISION();
-            if(v > 0) {
-                if(Demod.posCount > 10) {
-                    Demod.state = DEMOD_UNSYNCD;
-                }
-            } else {
-                Demod.bitCount = 0;
-                Demod.posCount = 1;
-                Demod.thisBit = v;
-                Demod.shiftReg = 0;
-                Demod.state = DEMOD_RECEIVING_DATA;
-            }
-            break;
-
-        case DEMOD_RECEIVING_DATA:
-            MAKE_SOFT_DECISION();
-            if(Demod.posCount == 0) {
-                Demod.thisBit = v;
-                Demod.posCount = 1;
-            } else {
-                Demod.thisBit += v;
-
-                if(Demod.thisBit > 0) {
-                    Demod.metric += Demod.thisBit;
-                } else {
-                    Demod.metric -= Demod.thisBit;
-                }
-                (Demod.metricN)++;
-
-                Demod.shiftReg >>= 1;
-                if(Demod.thisBit > 0) {
-                    Demod.shiftReg |= 0x200;
-                }
-
-                Demod.bitCount++;
-                if(Demod.bitCount == 10) {
-                    WORD s = Demod.shiftReg;
-                    if((s & 0x200) && !(s & 0x001)) {
-                        BYTE b = (s >> 1);
-                        Demod.output[Demod.len] = b;
-                        Demod.len++;
-                        Demod.state = DEMOD_AWAITING_START_BIT;
-                    } else if(s == 0x000) {
-                        // This is EOF
-                        return TRUE;
-                        Demod.state = DEMOD_UNSYNCD;
-                    } else {
-                        Demod.state = DEMOD_UNSYNCD;
-                    }
-                }
-                Demod.posCount = 0;
-            }
-            break;
-
-        default:
-            Demod.state = DEMOD_UNSYNCD;
-            break;
-    }
-
-    return FALSE;
-}
-
-static void GetSamplesFor14443Demod(BOOL weTx, int n)
-{
-    int max = 0;
-    BOOL gotFrame = FALSE;
-
-//#   define DMA_BUFFER_SIZE 8
-    SBYTE *dmaBuf;
-
-    int lastRxCounter;
-    SBYTE *upTo;
-
-    int ci, cq;
-
-    int samples = 0;
-
-    // Clear out the state of the "UART" that receives from the tag.
-    memset(BigBuf, 0x44, 400);
-    Demod.output = (BYTE *)BigBuf;
-    Demod.len = 0;
-    Demod.state = DEMOD_UNSYNCD;
-
-    // And the UART that receives from the reader
-    Uart.output = (((BYTE *)BigBuf) + 1024);
-    Uart.byteCntMax = 100;
-    Uart.state = STATE_UNSYNCD;
-
-    // Setup for the DMA.
-    dmaBuf = (SBYTE *)(BigBuf + 32);
-    upTo = dmaBuf;
-    lastRxCounter = DMA_BUFFER_SIZE;
-    FpgaSetupSscDma((BYTE *)dmaBuf, DMA_BUFFER_SIZE);
-
-    // And put the FPGA in the appropriate mode
-    FpgaWriteConfWord(
-    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
-    	(weTx ? 0 : FPGA_HF_READER_RX_XCORR_SNOOP));
-
-    for(;;) {
-        int behindBy = lastRxCounter - PDC_RX_COUNTER(SSC_BASE);
-        if(behindBy > max) max = behindBy;
-
-        LED_D_ON();
-        while(((lastRxCounter-PDC_RX_COUNTER(SSC_BASE)) & (DMA_BUFFER_SIZE-1))
-                    > 2)
-        {
-            ci = upTo[0];
-            cq = upTo[1];
-            upTo += 2;
-            if(upTo - dmaBuf > DMA_BUFFER_SIZE) {
-                upTo -= DMA_BUFFER_SIZE;
-                PDC_RX_NEXT_POINTER(SSC_BASE) = (DWORD)upTo;
-                PDC_RX_NEXT_COUNTER(SSC_BASE) = DMA_BUFFER_SIZE;
-            }
-            lastRxCounter -= 2;
-            if(lastRxCounter <= 0) {
-                lastRxCounter += DMA_BUFFER_SIZE;
-            }
-
-            samples += 2;
-
-            Handle14443UartBit(1);
-            Handle14443UartBit(1);
-
-            if(Handle14443SamplesDemod(ci, cq)) {
-                gotFrame = 1;
-            }
-        }
-        LED_D_OFF();
-
-        if(samples > 2000) {
-            break;
-        }
-    }
-    PDC_CONTROL(SSC_BASE) = PDC_RX_DISABLE;
-    DbpIntegers(max, gotFrame, -1);
-}
-
-//-----------------------------------------------------------------------------
-// Read the tag's response. We just receive a stream of slightly-processed
-// samples from the FPGA, which we will later do some signal processing on,
-// to get the bits.
-//-----------------------------------------------------------------------------
-/*static void GetSamplesFor14443(BOOL weTx, int n)
-{
-    BYTE *dest = (BYTE *)BigBuf;
-    int c;
-
-    FpgaWriteConfWord(
-    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
-    	(weTx ? 0 : FPGA_HF_READER_RX_XCORR_SNOOP));
-
-    c = 0;
-    for(;;) {
-        if(SSC_STATUS & (SSC_STATUS_TX_READY)) {
-            SSC_TRANSMIT_HOLDING = 0x43;
-        }
-        if(SSC_STATUS & (SSC_STATUS_RX_READY)) {
-            SBYTE b;
-            b = (SBYTE)SSC_RECEIVE_HOLDING;
-
-            dest[c++] = (BYTE)b;
-
-            if(c >= n) {
-                break;
-            }
-        }
-    }
-}*/
-
-//-----------------------------------------------------------------------------
-// Transmit the command (to the tag) that was placed in ToSend[].
-//-----------------------------------------------------------------------------
-static void TransmitFor14443(void)
-{
-    int c;
-
-    FpgaSetupSsc();
-
-    while(SSC_STATUS & (SSC_STATUS_TX_READY)) {
-        SSC_TRANSMIT_HOLDING = 0xff;
-    }
-
-    FpgaWriteConfWord(
-    	FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
-
-    for(c = 0; c < 10;) {
-        if(SSC_STATUS & (SSC_STATUS_TX_READY)) {
-            SSC_TRANSMIT_HOLDING = 0xff;
-            c++;
-        }
-        if(SSC_STATUS & (SSC_STATUS_RX_READY)) {
-            volatile DWORD r = SSC_RECEIVE_HOLDING;
-            (void)r;
-        }
-        WDT_HIT();
-    }
-
-    c = 0;
-    for(;;) {
-        if(SSC_STATUS & (SSC_STATUS_TX_READY)) {
-            SSC_TRANSMIT_HOLDING = ToSend[c];
-            c++;
-            if(c >= ToSendMax) {
-                break;
-            }
-        }
-        if(SSC_STATUS & (SSC_STATUS_RX_READY)) {
-            volatile DWORD r = SSC_RECEIVE_HOLDING;
-            (void)r;
-        }
-        WDT_HIT();
-    }
-}
-
-//-----------------------------------------------------------------------------
-// Code a layer 2 command (string of octets, including CRC) into ToSend[],
-// so that it is ready to transmit to the tag using TransmitFor14443().
-//-----------------------------------------------------------------------------
-void CodeIso14443bAsReader(const BYTE *cmd, int len)
-{
-    int i, j;
-    BYTE b;
-
-    ToSendReset();
-
-    // Establish initial reference level
-    for(i = 0; i < 40; i++) {
-        ToSendStuffBit(1);
-    }
-    // Send SOF
-    for(i = 0; i < 10; i++) {
-        ToSendStuffBit(0);
-    }
-
-    for(i = 0; i < len; i++) {
-        // Stop bits/EGT
-        ToSendStuffBit(1);
-        ToSendStuffBit(1);
-        // Start bit
-        ToSendStuffBit(0);
-        // Data bits
-        b = cmd[i];
-        for(j = 0; j < 8; j++) {
-            if(b & 1) {
-                ToSendStuffBit(1);
-            } else {
-                ToSendStuffBit(0);
-            }
-            b >>= 1;
-        }
-    }
-    // Send EOF
-    ToSendStuffBit(1);
-    for(i = 0; i < 10; i++) {
-        ToSendStuffBit(0);
-    }
-    for(i = 0; i < 8; i++) {
-        ToSendStuffBit(1);
-    }
-
-    // And then a little more, to make sure that the last character makes
-    // it out before we switch to rx mode.
-    for(i = 0; i < 24; i++) {
-        ToSendStuffBit(1);
-    }
-
-    // Convert from last character reference to length
-    ToSendMax++;
-}
-
-//-----------------------------------------------------------------------------
-// Read an ISO 14443 tag. We send it some set of commands, and record the
-// responses.
-//-----------------------------------------------------------------------------
-void AcquireRawAdcSamplesIso14443(DWORD parameter)
-{
-//    BYTE cmd1[] = { 0x05, 0x00, 0x00, 0x71, 0xff };
-    BYTE cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
-
-    // Make sure that we start from off, since the tags are stateful;
-    // confusing things will happen if we don't reset them between reads.
-    LED_D_OFF();
-    FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-    SpinDelay(200);
-
-    SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
-    FpgaSetupSsc();
-
-    // Now give it time to spin up.
-    FpgaWriteConfWord(
-    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
-    SpinDelay(200);
-
-    CodeIso14443bAsReader(cmd1, sizeof(cmd1));
-    TransmitFor14443();
-    LED_A_ON();
-    GetSamplesFor14443Demod(TRUE, 2000);
-    LED_A_OFF();
-}
-
-//=============================================================================
-// Finally, the `sniffer' combines elements from both the reader and
-// simulated tag, to show both sides of the conversation.
-//=============================================================================
-
-//-----------------------------------------------------------------------------
-// Record the sequence of commands sent by the reader to the tag, with
-// triggering so that we start recording at the point that the tag is moved
-// near the reader.
-//-----------------------------------------------------------------------------
-void SnoopIso14443(void)
-{
-    // We won't start recording the frames that we acquire until we trigger;
-    // a good trigger condition to get started is probably when we see a
-    // response from the tag.
-    BOOL triggered = FALSE;
-
-    // The command (reader -> tag) that we're working on receiving.
-    BYTE *receivedCmd = (((BYTE *)BigBuf) + 1024);
-    // The response (tag -> reader) that we're working on receiving.
-    BYTE *receivedResponse = (((BYTE *)BigBuf) + 1536);
-
-    // As we receive stuff, we copy it from receivedCmd or receivedResponse
-    // into trace, along with its length and other annotations.
-    BYTE *trace = (BYTE *)BigBuf;
-    int traceLen = 0;
-
-    // The DMA buffer, used to stream samples from the FPGA.
-//#   define DMA_BUFFER_SIZE 256
-    SBYTE *dmaBuf = ((SBYTE *)BigBuf) + 2048;
-    int lastRxCounter;
-    SBYTE *upTo;
-    int ci, cq;
-    int maxBehindBy = 0;
-
-    // Count of samples received so far, so that we can include timing
-    // information in the trace buffer.
-    int samples = 0;
-
-    memset(trace, 0x44, 1000);
-
-    // Set up the demodulator for tag -> reader responses.
-    Demod.output = receivedResponse;
-    Demod.len = 0;
-    Demod.state = DEMOD_UNSYNCD;
-
-    // And the reader -> tag commands
-    memset(&Uart, 0, sizeof(Uart));
-    Uart.output = receivedCmd;
-    Uart.byteCntMax = 100;
-    Uart.state = STATE_UNSYNCD;
-
-    // And put the FPGA in the appropriate mode
-    FpgaWriteConfWord(
-    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
-    	FPGA_HF_READER_RX_XCORR_SNOOP);
-    SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
-
-    // Setup for the DMA.
-    FpgaSetupSsc();
-    upTo = dmaBuf;
-    lastRxCounter = DMA_BUFFER_SIZE;
-    FpgaSetupSscDma((BYTE *)dmaBuf, DMA_BUFFER_SIZE);
-
-    LED_A_ON();
-
-    // And now we loop, receiving samples.
-    for(;;) {
-        int behindBy = (lastRxCounter - PDC_RX_COUNTER(SSC_BASE)) &
-                                (DMA_BUFFER_SIZE-1);
-        if(behindBy > maxBehindBy) {
-            maxBehindBy = behindBy;
-            if(behindBy > 100) {
-                DbpString("blew circular buffer!");
-                goto done;
-            }
-        }
-        if(behindBy < 2) continue;
-
-        ci = upTo[0];
-        cq = upTo[1];
-        upTo += 2;
-        lastRxCounter -= 2;
-        if(upTo - dmaBuf > DMA_BUFFER_SIZE) {
-            upTo -= DMA_BUFFER_SIZE;
-            lastRxCounter += DMA_BUFFER_SIZE;
-            PDC_RX_NEXT_POINTER(SSC_BASE) = (DWORD)upTo;
-            PDC_RX_NEXT_COUNTER(SSC_BASE) = DMA_BUFFER_SIZE;
-        }
-
-        samples += 2;
-
-#define HANDLE_BIT_IF_BODY \
-            if(triggered) { \
-                trace[traceLen++] = ((samples >>  0) & 0xff); \
-                trace[traceLen++] = ((samples >>  8) & 0xff); \
-                trace[traceLen++] = ((samples >> 16) & 0xff); \
-                trace[traceLen++] = ((samples >> 24) & 0xff); \
-                trace[traceLen++] = 0; \
-                trace[traceLen++] = 0; \
-                trace[traceLen++] = 0; \
-                trace[traceLen++] = 0; \
-                trace[traceLen++] = Uart.byteCnt; \
-                memcpy(trace+traceLen, receivedCmd, Uart.byteCnt); \
-                traceLen += Uart.byteCnt; \
-                if(traceLen > 1000) break; \
-            } \
-            /* And ready to receive another command. */ \
-            memset(&Uart, 0, sizeof(Uart)); \
-            Uart.output = receivedCmd; \
-            Uart.byteCntMax = 100; \
-            Uart.state = STATE_UNSYNCD; \
-            /* And also reset the demod code, which might have been */ \
-            /* false-triggered by the commands from the reader. */ \
-            memset(&Demod, 0, sizeof(Demod)); \
-            Demod.output = receivedResponse; \
-            Demod.state = DEMOD_UNSYNCD; \
-
-        if(Handle14443UartBit(ci & 1)) {
-            HANDLE_BIT_IF_BODY
-        }
-        if(Handle14443UartBit(cq & 1)) {
-            HANDLE_BIT_IF_BODY
-        }
-
-        if(Handle14443SamplesDemod(ci, cq)) {
-            // timestamp, as a count of samples
-            trace[traceLen++] = ((samples >>  0) & 0xff);
-            trace[traceLen++] = ((samples >>  8) & 0xff);
-            trace[traceLen++] = ((samples >> 16) & 0xff);
-            trace[traceLen++] = 0x80 | ((samples >> 24) & 0xff);
-            // correlation metric (~signal strength estimate)
-            if(Demod.metricN != 0) {
-                Demod.metric /= Demod.metricN;
-            }
-            trace[traceLen++] = ((Demod.metric >>  0) & 0xff);
-            trace[traceLen++] = ((Demod.metric >>  8) & 0xff);
-            trace[traceLen++] = ((Demod.metric >> 16) & 0xff);
-            trace[traceLen++] = ((Demod.metric >> 24) & 0xff);
-            // length
-            trace[traceLen++] = Demod.len;
-            memcpy(trace+traceLen, receivedResponse, Demod.len);
-            traceLen += Demod.len;
-            if(traceLen > 1000) break;
-
-            triggered = TRUE;
-            LED_A_OFF();
-            LED_B_ON();
-
-            // And ready to receive another response.
-            memset(&Demod, 0, sizeof(Demod));
-            Demod.output = receivedResponse;
-            Demod.state = DEMOD_UNSYNCD;
-        }
-
-        if(BUTTON_PRESS()) {
-            DbpString("cancelled");
-            goto done;
-        }
-    }
-
-    DbpString("in done pt");
-
-    DbpIntegers(maxBehindBy, Uart.state, Uart.byteCnt);
-    DbpIntegers(Uart.byteCntMax, traceLen, 0x23);
-
-done:
-    PDC_CONTROL(SSC_BASE) = PDC_RX_DISABLE;
-    LED_A_OFF();
-    LED_B_OFF();
-}
+//-----------------------------------------------------------------------------
+// Jonathan Westhues, split Nov 2006
+//
+// 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 14443. This includes both the reader software and
+// the `fake tag' modes. At the moment only the Type B modulation is
+// supported.
+//-----------------------------------------------------------------------------
+
+#include "proxmark3.h"
+#include "apps.h"
+#include "util.h"
+#include "string.h"
+
+#include "iso14443crc.h"
+
+//static void GetSamplesFor14443(int weTx, int n);
+
+#define DEMOD_TRACE_SIZE 4096
+#define READER_TAG_BUFFER_SIZE 2048
+#define TAG_READER_BUFFER_SIZE 2048
+#define DEMOD_DMA_BUFFER_SIZE 1024
+
+//=============================================================================
+// An ISO 14443 Type B tag. We listen for commands from the reader, using
+// a UART kind of thing that's implemented in software. When we get a
+// frame (i.e., a group of bytes between SOF and EOF), we check the CRC.
+// If it's good, then we can do something appropriate with it, and send
+// a response.
+//=============================================================================
+
+//-----------------------------------------------------------------------------
+// Code up a string of octets at layer 2 (including CRC, we don't generate
+// that here) so that they can be transmitted to the reader. Doesn't transmit
+// them yet, just leaves them ready to send in ToSend[].
+//-----------------------------------------------------------------------------
+static void CodeIso14443bAsTag(const uint8_t *cmd, int len)
+{
+    int i;
+
+    ToSendReset();
+
+    // Transmit a burst of ones, as the initial thing that lets the
+    // reader get phase sync. This (TR1) must be > 80/fs, per spec,
+    // but tag that I've tried (a Paypass) exceeds that by a fair bit,
+    // so I will too.
+    for(i = 0; i < 20; i++) {
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+    }
+
+    // Send SOF.
+    for(i = 0; i < 10; i++) {
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+    }
+    for(i = 0; i < 2; i++) {
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+    }
+
+    for(i = 0; i < len; i++) {
+        int j;
+        uint8_t b = cmd[i];
+
+        // Start bit
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+
+        // Data bits
+        for(j = 0; j < 8; j++) {
+            if(b & 1) {
+                ToSendStuffBit(1);
+                ToSendStuffBit(1);
+                ToSendStuffBit(1);
+                ToSendStuffBit(1);
+            } else {
+                ToSendStuffBit(0);
+                ToSendStuffBit(0);
+                ToSendStuffBit(0);
+                ToSendStuffBit(0);
+            }
+            b >>= 1;
+        }
+
+        // Stop bit
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+    }
+
+    // Send SOF.
+    for(i = 0; i < 10; i++) {
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+        ToSendStuffBit(0);
+    }
+    for(i = 0; i < 10; i++) {
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+    }
+
+    // Convert from last byte pos to length
+    ToSendMax++;
+
+    // Add a few more for slop
+    ToSendMax += 2;
+}
+
+//-----------------------------------------------------------------------------
+// The software UART that receives commands from the reader, and its state
+// variables.
+//-----------------------------------------------------------------------------
+static struct {
+    enum {
+        STATE_UNSYNCD,
+        STATE_GOT_FALLING_EDGE_OF_SOF,
+        STATE_AWAITING_START_BIT,
+        STATE_RECEIVING_DATA,
+        STATE_ERROR_WAIT
+    }       state;
+    uint16_t    shiftReg;
+    int     bitCnt;
+    int     byteCnt;
+    int     byteCntMax;
+    int     posCnt;
+    uint8_t   *output;
+} Uart;
+
+/* Receive & handle a bit coming from the reader.
+ *
+ * LED handling:
+ * LED A -> ON once we have received the SOF and are expecting the rest.
+ * LED A -> OFF once we have received EOF or are in error state or unsynced
+ *
+ * Returns: true if we received a EOF
+ *          false if we are still waiting for some more
+ */
+static int Handle14443UartBit(int bit)
+{
+    switch(Uart.state) {
+        case STATE_UNSYNCD:
+        	LED_A_OFF();
+            if(!bit) {
+                // we went low, so this could be the beginning
+                // of an SOF
+                Uart.state = STATE_GOT_FALLING_EDGE_OF_SOF;
+                Uart.posCnt = 0;
+                Uart.bitCnt = 0;
+            }
+            break;
+
+        case STATE_GOT_FALLING_EDGE_OF_SOF:
+            Uart.posCnt++;
+            if(Uart.posCnt == 2) {
+                if(bit) {
+                    if(Uart.bitCnt >= 10) {
+                        // we've seen enough consecutive
+                        // zeros that it's a valid SOF
+                        Uart.posCnt = 0;
+                        Uart.byteCnt = 0;
+                        Uart.state = STATE_AWAITING_START_BIT;
+                        LED_A_ON(); // Indicate we got a valid SOF
+                    } else {
+                        // didn't stay down long enough
+                        // before going high, error
+                        Uart.state = STATE_ERROR_WAIT;
+                    }
+                } else {
+                    // do nothing, keep waiting
+                }
+                Uart.bitCnt++;
+            }
+            if(Uart.posCnt >= 4) Uart.posCnt = 0;
+            if(Uart.bitCnt > 14) {
+                // Give up if we see too many zeros without
+                // a one, too.
+                Uart.state = STATE_ERROR_WAIT;
+            }
+            break;
+
+        case STATE_AWAITING_START_BIT:
+            Uart.posCnt++;
+            if(bit) {
+                if(Uart.posCnt > 25) {
+                    // stayed high for too long between
+                    // characters, error
+                    Uart.state = STATE_ERROR_WAIT;
+                }
+            } else {
+                // falling edge, this starts the data byte
+                Uart.posCnt = 0;
+                Uart.bitCnt = 0;
+                Uart.shiftReg = 0;
+                Uart.state = STATE_RECEIVING_DATA;
+                LED_A_ON(); // Indicate we're receiving
+            }
+            break;
+
+        case STATE_RECEIVING_DATA:
+            Uart.posCnt++;
+            if(Uart.posCnt == 2) {
+                // time to sample a bit
+                Uart.shiftReg >>= 1;
+                if(bit) {
+                    Uart.shiftReg |= 0x200;
+                }
+                Uart.bitCnt++;
+            }
+            if(Uart.posCnt >= 4) {
+                Uart.posCnt = 0;
+            }
+            if(Uart.bitCnt == 10) {
+                if((Uart.shiftReg & 0x200) && !(Uart.shiftReg & 0x001))
+                {
+                    // this is a data byte, with correct
+                    // start and stop bits
+                    Uart.output[Uart.byteCnt] = (Uart.shiftReg >> 1) & 0xff;
+                    Uart.byteCnt++;
+
+                    if(Uart.byteCnt >= Uart.byteCntMax) {
+                        // Buffer overflowed, give up
+                        Uart.posCnt = 0;
+                        Uart.state = STATE_ERROR_WAIT;
+                    } else {
+                        // so get the next byte now
+                        Uart.posCnt = 0;
+                        Uart.state = STATE_AWAITING_START_BIT;
+                    }
+                } else if(Uart.shiftReg == 0x000) {
+                    // this is an EOF byte
+                	LED_A_OFF(); // Finished receiving
+                    return TRUE;
+                } else {
+                    // this is an error
+                    Uart.posCnt = 0;
+                    Uart.state = STATE_ERROR_WAIT;
+                }
+            }
+            break;
+
+        case STATE_ERROR_WAIT:
+            // We're all screwed up, so wait a little while
+            // for whatever went wrong to finish, and then
+            // start over.
+            Uart.posCnt++;
+            if(Uart.posCnt > 10) {
+                Uart.state = STATE_UNSYNCD;
+            }
+            break;
+
+        default:
+            Uart.state = STATE_UNSYNCD;
+            break;
+    }
+
+    // This row make the error blew circular buffer in hf 14b snoop
+    //if (Uart.state == STATE_ERROR_WAIT) LED_A_OFF(); // Error
+
+    return FALSE;
+}
+
+//-----------------------------------------------------------------------------
+// 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 GetIso14443CommandFromReader(uint8_t *received, int *len, int maxLen)
+{
+    uint8_t mask;
+    int i, bit;
+
+    // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
+    // only, since we are receiving, not transmitting).
+    // Signal field is off with the appropriate LED
+    LED_D_OFF();
+    FpgaWriteConfWord(
+    	FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_NO_MODULATION);
+
+
+    // Now run a `software UART' on the stream of incoming samples.
+    Uart.output = received;
+    Uart.byteCntMax = maxLen;
+    Uart.state = STATE_UNSYNCD;
+
+    for(;;) {
+        WDT_HIT();
+
+        if(BUTTON_PRESS()) return FALSE;
+
+        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+            AT91C_BASE_SSC->SSC_THR = 0x00;
+        }
+        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+            uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+
+            mask = 0x80;
+            for(i = 0; i < 8; i++, mask >>= 1) {
+                bit = (b & mask);
+                if(Handle14443UartBit(bit)) {
+                    *len = Uart.byteCnt;
+                    return TRUE;
+                }
+            }
+        }
+    }
+}
+
+//-----------------------------------------------------------------------------
+// Main loop of simulated tag: receive commands from reader, decide what
+// response to send, and send it.
+//-----------------------------------------------------------------------------
+void SimulateIso14443Tag(void)
+{
+    static const uint8_t cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
+    static const uint8_t response1[] = {
+        0x50, 0x82, 0x0d, 0xe1, 0x74, 0x20, 0x38, 0x19, 0x22,
+        0x00, 0x21, 0x85, 0x5e, 0xd7
+    };
+
+    uint8_t *resp;
+    int respLen;
+
+    uint8_t *resp1 = (((uint8_t *)BigBuf) + 800);
+    int resp1Len;
+
+    uint8_t *receivedCmd = (uint8_t *)BigBuf;
+    int len;
+
+    int i;
+
+    int cmdsRecvd = 0;
+
+    FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+    memset(receivedCmd, 0x44, 400);
+
+    CodeIso14443bAsTag(response1, sizeof(response1));
+    memcpy(resp1, ToSend, ToSendMax); resp1Len = ToSendMax;
+
+    // We need to listen to the high-frequency, peak-detected path.
+    SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+    FpgaSetupSsc();
+
+    cmdsRecvd = 0;
+
+    for(;;) {
+        uint8_t b1, b2;
+
+        if(!GetIso14443CommandFromReader(receivedCmd, &len, 100)) {
+		Dbprintf("button pressed, received %d commands", cmdsRecvd);
+		break;
+        }
+
+        // Good, look at the command now.
+
+        if(len == sizeof(cmd1) && memcmp(receivedCmd, cmd1, len)==0) {
+            resp = resp1; respLen = resp1Len;
+        } else {
+            Dbprintf("new cmd from reader: len=%d, cmdsRecvd=%d", len, cmdsRecvd);
+            // And print whether the CRC fails, just for good measure
+            ComputeCrc14443(CRC_14443_B, receivedCmd, len-2, &b1, &b2);
+            if(b1 != receivedCmd[len-2] || b2 != receivedCmd[len-1]) {
+                // Not so good, try again.
+                DbpString("+++CRC fail");
+            } else {
+                DbpString("CRC passes");
+            }
+            break;
+        }
+
+        memset(receivedCmd, 0x44, 32);
+
+        cmdsRecvd++;
+
+        if(cmdsRecvd > 0x30) {
+            DbpString("many commands later...");
+            break;
+        }
+
+        if(respLen <= 0) continue;
+
+        // Modulate BPSK
+        // Signal field is off with the appropriate LED
+        LED_D_OFF();
+        FpgaWriteConfWord(
+        	FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_BPSK);
+        AT91C_BASE_SSC->SSC_THR = 0xff;
+        FpgaSetupSsc();
+
+        // Transmit the response.
+        i = 0;
+        for(;;) {
+            if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                uint8_t b = resp[i];
+
+                AT91C_BASE_SSC->SSC_THR = b;
+
+                i++;
+                if(i > respLen) {
+                    break;
+                }
+            }
+            if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+                volatile uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+                (void)b;
+            }
+        }
+    }
+}
+
+//=============================================================================
+// An ISO 14443 Type B reader. We take layer two commands, code them
+// appropriately, and then send them to the tag. We then listen for the
+// tag's response, which we leave in the buffer to be demodulated on the
+// PC side.
+//=============================================================================
+
+static struct {
+    enum {
+        DEMOD_UNSYNCD,
+        DEMOD_PHASE_REF_TRAINING,
+        DEMOD_AWAITING_FALLING_EDGE_OF_SOF,
+        DEMOD_GOT_FALLING_EDGE_OF_SOF,
+        DEMOD_AWAITING_START_BIT,
+        DEMOD_RECEIVING_DATA,
+        DEMOD_ERROR_WAIT
+    }       state;
+    int     bitCount;
+    int     posCount;
+    int     thisBit;
+    int     metric;
+    int     metricN;
+    uint16_t    shiftReg;
+    uint8_t   *output;
+    int     len;
+    int     sumI;
+    int     sumQ;
+} Demod;
+
+/*
+ * Handles reception of a bit from the tag
+ *
+ * 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
+ *
+ */
+static RAMFUNC int Handle14443SamplesDemod(int ci, int cq)
+{
+    int v;
+
+    // The soft decision on the bit uses an estimate of just the
+    // quadrant of the reference angle, not the exact angle.
+#define MAKE_SOFT_DECISION() { \
+        if(Demod.sumI > 0) { \
+            v = ci; \
+        } else { \
+            v = -ci; \
+        } \
+        if(Demod.sumQ > 0) { \
+            v += cq; \
+        } else { \
+            v -= cq; \
+        } \
+    }
+
+    switch(Demod.state) {
+        case DEMOD_UNSYNCD:
+            v = ci;
+            if(v < 0) v = -v;
+            if(cq > 0) {
+                v += cq;
+            } else {
+                v -= cq;
+            }
+            if(v > 40) {
+                Demod.posCount = 0;
+                Demod.state = DEMOD_PHASE_REF_TRAINING;
+                Demod.sumI = 0;
+                Demod.sumQ = 0;
+            }
+            break;
+
+        case DEMOD_PHASE_REF_TRAINING:
+            if(Demod.posCount < 8) {
+                Demod.sumI += ci;
+                Demod.sumQ += cq;
+            } else if(Demod.posCount > 100) {
+                // error, waited too long
+                Demod.state = DEMOD_UNSYNCD;
+            } else {
+                MAKE_SOFT_DECISION();
+                if(v < 0) {
+                    Demod.state = DEMOD_AWAITING_FALLING_EDGE_OF_SOF;
+                    Demod.posCount = 0;
+                }
+            }
+            Demod.posCount++;
+            break;
+
+        case DEMOD_AWAITING_FALLING_EDGE_OF_SOF:
+            MAKE_SOFT_DECISION();
+            if(v < 0) {
+                Demod.state = DEMOD_GOT_FALLING_EDGE_OF_SOF;
+                Demod.posCount = 0;
+            } else {
+                if(Demod.posCount > 100) {
+                    Demod.state = DEMOD_UNSYNCD;
+                }
+            }
+            Demod.posCount++;
+            break;
+
+        case DEMOD_GOT_FALLING_EDGE_OF_SOF:
+            MAKE_SOFT_DECISION();
+            if(v > 0) {
+                if(Demod.posCount < 12) {
+                    Demod.state = DEMOD_UNSYNCD;
+                } else {
+                    LED_C_ON(); // Got SOF
+                    Demod.state = DEMOD_AWAITING_START_BIT;
+                    Demod.posCount = 0;
+                    Demod.len = 0;
+                    Demod.metricN = 0;
+                    Demod.metric = 0;
+                }
+            } else {
+                if(Demod.posCount > 100) {
+                    Demod.state = DEMOD_UNSYNCD;
+                }
+            }
+            Demod.posCount++;
+            break;
+
+        case DEMOD_AWAITING_START_BIT:
+            MAKE_SOFT_DECISION();
+            if(v > 0) {
+                if(Demod.posCount > 10) {
+                    Demod.state = DEMOD_UNSYNCD;
+                }
+            } else {
+                Demod.bitCount = 0;
+                Demod.posCount = 1;
+                Demod.thisBit = v;
+                Demod.shiftReg = 0;
+                Demod.state = DEMOD_RECEIVING_DATA;
+            }
+            break;
+
+        case DEMOD_RECEIVING_DATA:
+            MAKE_SOFT_DECISION();
+            if(Demod.posCount == 0) {
+                Demod.thisBit = v;
+                Demod.posCount = 1;
+            } else {
+                Demod.thisBit += v;
+
+                if(Demod.thisBit > 0) {
+                    Demod.metric += Demod.thisBit;
+                } else {
+                    Demod.metric -= Demod.thisBit;
+                }
+                (Demod.metricN)++;
+
+                Demod.shiftReg >>= 1;
+                if(Demod.thisBit > 0) {
+                    Demod.shiftReg |= 0x200;
+                }
+
+                Demod.bitCount++;
+                if(Demod.bitCount == 10) {
+                    uint16_t s = Demod.shiftReg;
+                    if((s & 0x200) && !(s & 0x001)) {
+                        uint8_t b = (s >> 1);
+                        Demod.output[Demod.len] = b;
+                        Demod.len++;
+                        Demod.state = DEMOD_AWAITING_START_BIT;
+                    } else if(s == 0x000) {
+                        // This is EOF
+                    	LED_C_OFF();
+                        Demod.state = DEMOD_UNSYNCD;
+                        return TRUE;
+                    } else {
+                        Demod.state = DEMOD_UNSYNCD;
+                    }
+                }
+                Demod.posCount = 0;
+            }
+            break;
+
+        default:
+            Demod.state = DEMOD_UNSYNCD;
+            break;
+    }
+
+    if (Demod.state == DEMOD_UNSYNCD) LED_C_OFF(); // Not synchronized...
+    return FALSE;
+}
+
+/*
+ *  Demodulate the samples we received from the tag
+ *  weTx: set to 'TRUE' if we behave like a reader
+ *        set to 'FALSE' if we behave like a snooper
+ *  quiet: set to 'TRUE' to disable debug output
+ */
+static void GetSamplesFor14443Demod(int weTx, int n, int quiet)
+{
+    int max = 0;
+    int gotFrame = FALSE;
+
+//#   define DMA_BUFFER_SIZE 8
+    int8_t *dmaBuf;
+
+    int lastRxCounter;
+    int8_t *upTo;
+
+    int ci, cq;
+
+    int samples = 0;
+
+    // Clear out the state of the "UART" that receives from the tag.
+    memset(BigBuf, 0x00, 400);
+    Demod.output = (uint8_t *)BigBuf;
+    Demod.len = 0;
+    Demod.state = DEMOD_UNSYNCD;
+
+    // And the UART that receives from the reader
+    Uart.output = (((uint8_t *)BigBuf) + 1024);
+    Uart.byteCntMax = 100;
+    Uart.state = STATE_UNSYNCD;
+
+    // Setup for the DMA.
+    dmaBuf = (int8_t *)(BigBuf + 32);
+    upTo = dmaBuf;
+    lastRxCounter = DEMOD_DMA_BUFFER_SIZE;
+    FpgaSetupSscDma((uint8_t *)dmaBuf, DEMOD_DMA_BUFFER_SIZE);
+
+    // Signal field is ON with the appropriate LED:
+    if (weTx) LED_D_ON(); else LED_D_OFF();
+    // And put the FPGA in the appropriate mode
+    FpgaWriteConfWord(
+    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
+    	(weTx ? 0 : FPGA_HF_READER_RX_XCORR_SNOOP));
+
+    for(;;) {
+        int behindBy = lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR;
+        if(behindBy > max) max = behindBy;
+
+        while(((lastRxCounter-AT91C_BASE_PDC_SSC->PDC_RCR) & (DEMOD_DMA_BUFFER_SIZE-1))
+                    > 2)
+        {
+            ci = upTo[0];
+            cq = upTo[1];
+            upTo += 2;
+            if(upTo - dmaBuf > DEMOD_DMA_BUFFER_SIZE) {
+                upTo -= DEMOD_DMA_BUFFER_SIZE;
+                AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) upTo;
+                AT91C_BASE_PDC_SSC->PDC_RNCR = DEMOD_DMA_BUFFER_SIZE;
+            }
+            lastRxCounter -= 2;
+            if(lastRxCounter <= 0) {
+                lastRxCounter += DEMOD_DMA_BUFFER_SIZE;
+            }
+
+            samples += 2;
+
+            Handle14443UartBit(1);
+            Handle14443UartBit(1);
+
+            if(Handle14443SamplesDemod(ci, cq)) {
+                gotFrame = 1;
+            }
+        }
+
+        if(samples > 2000) {
+            break;
+        }
+    }
+    AT91C_BASE_PDC_SSC->PDC_PTCR = AT91C_PDC_RXTDIS;
+    if (!quiet) Dbprintf("%x %x %x", max, gotFrame, Demod.len);
+}
+
+//-----------------------------------------------------------------------------
+// Read the tag's response. We just receive a stream of slightly-processed
+// samples from the FPGA, which we will later do some signal processing on,
+// to get the bits.
+//-----------------------------------------------------------------------------
+/*static void GetSamplesFor14443(int weTx, int n)
+{
+    uint8_t *dest = (uint8_t *)BigBuf;
+    int c;
+
+    FpgaWriteConfWord(
+    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
+    	(weTx ? 0 : FPGA_HF_READER_RX_XCORR_SNOOP));
+
+    c = 0;
+    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;
+
+            dest[c++] = (uint8_t)b;
+
+            if(c >= n) {
+                break;
+            }
+        }
+    }
+}*/
+
+//-----------------------------------------------------------------------------
+// Transmit the command (to the tag) that was placed in ToSend[].
+//-----------------------------------------------------------------------------
+static void TransmitFor14443(void)
+{
+    int c;
+
+    FpgaSetupSsc();
+
+    while(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+        AT91C_BASE_SSC->SSC_THR = 0xff;
+    }
+
+    // Signal field is ON with the appropriate Red LED
+	LED_D_ON();
+	// Signal we are transmitting with the Green LED
+	LED_B_ON();
+	FpgaWriteConfWord(
+    	FPGA_MAJOR_MODE_HF_READER_TX | FPGA_HF_READER_TX_SHALLOW_MOD);
+
+    for(c = 0; c < 10;) {
+        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+            AT91C_BASE_SSC->SSC_THR = 0xff;
+            c++;
+        }
+        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+            volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
+            (void)r;
+        }
+        WDT_HIT();
+    }
+
+    c = 0;
+    for(;;) {
+        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+            AT91C_BASE_SSC->SSC_THR = ToSend[c];
+            c++;
+            if(c >= ToSendMax) {
+                break;
+            }
+        }
+        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+            volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
+            (void)r;
+        }
+        WDT_HIT();
+    }
+    LED_B_OFF(); // Finished sending
+}
+
+//-----------------------------------------------------------------------------
+// Code a layer 2 command (string of octets, including CRC) into ToSend[],
+// so that it is ready to transmit to the tag using TransmitFor14443().
+//-----------------------------------------------------------------------------
+static void CodeIso14443bAsReader(const uint8_t *cmd, int len)
+{
+    int i, j;
+    uint8_t b;
+
+    ToSendReset();
+
+    // Establish initial reference level
+    for(i = 0; i < 40; i++) {
+        ToSendStuffBit(1);
+    }
+    // Send SOF
+    for(i = 0; i < 10; i++) {
+        ToSendStuffBit(0);
+    }
+
+    for(i = 0; i < len; i++) {
+        // Stop bits/EGT
+        ToSendStuffBit(1);
+        ToSendStuffBit(1);
+        // Start bit
+        ToSendStuffBit(0);
+        // Data bits
+        b = cmd[i];
+        for(j = 0; j < 8; j++) {
+            if(b & 1) {
+                ToSendStuffBit(1);
+            } else {
+                ToSendStuffBit(0);
+            }
+            b >>= 1;
+        }
+    }
+    // Send EOF
+    ToSendStuffBit(1);
+    for(i = 0; i < 10; i++) {
+        ToSendStuffBit(0);
+    }
+    for(i = 0; i < 8; i++) {
+        ToSendStuffBit(1);
+    }
+
+    // And then a little more, to make sure that the last character makes
+    // it out before we switch to rx mode.
+    for(i = 0; i < 24; i++) {
+        ToSendStuffBit(1);
+    }
+
+    // Convert from last character reference to length
+    ToSendMax++;
+}
+
+//-----------------------------------------------------------------------------
+// Read an ISO 14443 tag. We send it some set of commands, and record the
+// responses.
+// The command name is misleading, it actually decodes the reponse in HEX
+// into the output buffer (read the result using hexsamples, not hisamples)
+//
+// obsolete function only for test
+//-----------------------------------------------------------------------------
+void AcquireRawAdcSamplesIso14443(uint32_t parameter)
+{
+    uint8_t cmd1[] = { 0x05, 0x00, 0x08, 0x39, 0x73 };
+
+    SendRawCommand14443B(sizeof(cmd1),1,1,cmd1);
+}
+
+//-----------------------------------------------------------------------------
+// Read a SRI512 ISO 14443 tag.
+//
+// SRI512 tags are just simple memory tags, here we're looking at making a dump
+// of the contents of the memory. No anticollision algorithm is done, we assume
+// we have a single tag in the field.
+//
+// I tried to be systematic and check every answer of the tag, every CRC, etc...
+//-----------------------------------------------------------------------------
+void ReadSTMemoryIso14443(uint32_t dwLast)
+{
+    uint8_t i = 0x00;
+
+    FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+    // Make sure that we start from off, since the tags are stateful;
+    // confusing things will happen if we don't reset them between reads.
+    LED_D_OFF();
+    FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+    SpinDelay(200);
+
+    SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+    FpgaSetupSsc();
+
+    // Now give it time to spin up.
+    // Signal field is on with the appropriate LED
+    LED_D_ON();
+    FpgaWriteConfWord(
+    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
+    SpinDelay(200);
+
+    // First command: wake up the tag using the INITIATE command
+    uint8_t cmd1[] = { 0x06, 0x00, 0x97, 0x5b};
+    CodeIso14443bAsReader(cmd1, sizeof(cmd1));
+    TransmitFor14443();
+//    LED_A_ON();
+    GetSamplesFor14443Demod(TRUE, 2000,TRUE);
+//    LED_A_OFF();
+
+    if (Demod.len == 0) {
+	DbpString("No response from tag");
+	return;
+    } else {
+	Dbprintf("Randomly generated UID from tag (+ 2 byte CRC): %x %x %x",
+		Demod.output[0], Demod.output[1],Demod.output[2]);
+    }
+    // There is a response, SELECT the uid
+    DbpString("Now SELECT tag:");
+    cmd1[0] = 0x0E; // 0x0E is SELECT
+    cmd1[1] = Demod.output[0];
+    ComputeCrc14443(CRC_14443_B, cmd1, 2, &cmd1[2], &cmd1[3]);
+    CodeIso14443bAsReader(cmd1, sizeof(cmd1));
+    TransmitFor14443();
+//    LED_A_ON();
+    GetSamplesFor14443Demod(TRUE, 2000,TRUE);
+//    LED_A_OFF();
+    if (Demod.len != 3) {
+	Dbprintf("Expected 3 bytes from tag, got %d", Demod.len);
+	return;
+    }
+    // Check the CRC of the answer:
+    ComputeCrc14443(CRC_14443_B, Demod.output, 1 , &cmd1[2], &cmd1[3]);
+    if(cmd1[2] != Demod.output[1] || cmd1[3] != Demod.output[2]) {
+	DbpString("CRC Error reading select response.");
+	return;
+    }
+    // Check response from the tag: should be the same UID as the command we just sent:
+    if (cmd1[1] != Demod.output[0]) {
+	Dbprintf("Bad response to SELECT from Tag, aborting: %x %x", cmd1[1], Demod.output[0]);
+	return;
+    }
+    // Tag is now selected,
+    // First get the tag's UID:
+    cmd1[0] = 0x0B;
+    ComputeCrc14443(CRC_14443_B, cmd1, 1 , &cmd1[1], &cmd1[2]);
+    CodeIso14443bAsReader(cmd1, 3); // Only first three bytes for this one
+    TransmitFor14443();
+//    LED_A_ON();
+    GetSamplesFor14443Demod(TRUE, 2000,TRUE);
+//    LED_A_OFF();
+    if (Demod.len != 10) {
+	Dbprintf("Expected 10 bytes from tag, got %d", Demod.len);
+	return;
+    }
+    // The check the CRC of the answer (use cmd1 as temporary variable):
+    ComputeCrc14443(CRC_14443_B, Demod.output, 8, &cmd1[2], &cmd1[3]);
+           if(cmd1[2] != Demod.output[8] || cmd1[3] != Demod.output[9]) {
+	Dbprintf("CRC Error reading block! - Below: expected, got %x %x",
+		(cmd1[2]<<8)+cmd1[3], (Demod.output[8]<<8)+Demod.output[9]);
+	// Do not return;, let's go on... (we should retry, maybe ?)
+    }
+    Dbprintf("Tag UID (64 bits): %08x %08x",
+	(Demod.output[7]<<24) + (Demod.output[6]<<16) + (Demod.output[5]<<8) + Demod.output[4],
+	(Demod.output[3]<<24) + (Demod.output[2]<<16) + (Demod.output[1]<<8) + Demod.output[0]);
+
+    // Now loop to read all 16 blocks, address from 0 to last block
+    Dbprintf("Tag memory dump, block 0 to %d",dwLast);
+    cmd1[0] = 0x08;
+    i = 0x00;
+    dwLast++;
+    for (;;) {
+           if (i == dwLast) {
+		    DbpString("System area block (0xff):");
+		    i = 0xff;
+	    }
+	    cmd1[1] = i;
+	    ComputeCrc14443(CRC_14443_B, cmd1, 2, &cmd1[2], &cmd1[3]);
+	    CodeIso14443bAsReader(cmd1, sizeof(cmd1));
+	    TransmitFor14443();
+//	    LED_A_ON();
+	    GetSamplesFor14443Demod(TRUE, 2000,TRUE);
+//	    LED_A_OFF();
+	    if (Demod.len != 6) { // Check if we got an answer from the tag
+		DbpString("Expected 6 bytes from tag, got less...");
+		return;
+	    }
+	    // The check the CRC of the answer (use cmd1 as temporary variable):
+	    ComputeCrc14443(CRC_14443_B, Demod.output, 4, &cmd1[2], &cmd1[3]);
+            if(cmd1[2] != Demod.output[4] || cmd1[3] != Demod.output[5]) {
+		Dbprintf("CRC Error reading block! - Below: expected, got %x %x",
+			(cmd1[2]<<8)+cmd1[3], (Demod.output[4]<<8)+Demod.output[5]);
+		// Do not return;, let's go on... (we should retry, maybe ?)
+	    }
+	    // Now print out the memory location:
+	    Dbprintf("Address=%x, Contents=%x, CRC=%x", i,
+		(Demod.output[3]<<24) + (Demod.output[2]<<16) + (Demod.output[1]<<8) + Demod.output[0],
+		(Demod.output[4]<<8)+Demod.output[5]);
+	    if (i == 0xff) {
+		break;
+	    }
+	    i++;
+    }
+}
+
+
+//=============================================================================
+// Finally, the `sniffer' combines elements from both the reader and
+// simulated tag, to show both sides of the conversation.
+//=============================================================================
+
+//-----------------------------------------------------------------------------
+// Record the sequence of commands sent by the reader to the tag, with
+// triggering so that we start recording at the point that the tag is moved
+// near the reader.
+//-----------------------------------------------------------------------------
+/*
+ * Memory usage for this function, (within BigBuf)
+ * 0-4095 : Demodulated samples receive (4096 bytes) - DEMOD_TRACE_SIZE
+ * 4096-6143 : Last Received command, 2048 bytes (reader->tag) - READER_TAG_BUFFER_SIZE
+ * 6144-8191 : Last Received command, 2048 bytes(tag->reader) - TAG_READER_BUFFER_SIZE
+ * 8192-9215 : DMA Buffer, 1024 bytes (samples) - DEMOD_DMA_BUFFER_SIZE
+ */
+void RAMFUNC SnoopIso14443(void)
+{
+    // We won't start recording the frames that we acquire until we trigger;
+    // a good trigger condition to get started is probably when we see a
+    // response from the tag.
+    int triggered = TRUE;
+
+    FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+    // The command (reader -> tag) that we're working on receiving.
+    uint8_t *receivedCmd = (uint8_t *)(BigBuf) + DEMOD_TRACE_SIZE;
+    // The response (tag -> reader) that we're working on receiving.
+    uint8_t *receivedResponse = (uint8_t *)(BigBuf) + DEMOD_TRACE_SIZE + READER_TAG_BUFFER_SIZE;
+
+    // As we receive stuff, we copy it from receivedCmd or receivedResponse
+    // into trace, along with its length and other annotations.
+    uint8_t *trace = (uint8_t *)BigBuf;
+    int traceLen = 0;
+
+    // The DMA buffer, used to stream samples from the FPGA.
+    int8_t *dmaBuf = (int8_t *)(BigBuf) + DEMOD_TRACE_SIZE + READER_TAG_BUFFER_SIZE + TAG_READER_BUFFER_SIZE;
+    int lastRxCounter;
+    int8_t *upTo;
+    int ci, cq;
+    int maxBehindBy = 0;
+
+    // Count of samples received so far, so that we can include timing
+    // information in the trace buffer.
+    int samples = 0;
+
+    // Initialize the trace buffer
+    memset(trace, 0x44, DEMOD_TRACE_SIZE);
+
+    // Set up the demodulator for tag -> reader responses.
+    Demod.output = receivedResponse;
+    Demod.len = 0;
+    Demod.state = DEMOD_UNSYNCD;
+
+    // And the reader -> tag commands
+    memset(&Uart, 0, sizeof(Uart));
+    Uart.output = receivedCmd;
+    Uart.byteCntMax = 100;
+    Uart.state = STATE_UNSYNCD;
+
+    // Print some debug information about the buffer sizes
+    Dbprintf("Snooping buffers initialized:");
+    Dbprintf("  Trace: %i bytes", DEMOD_TRACE_SIZE);
+    Dbprintf("  Reader -> tag: %i bytes", READER_TAG_BUFFER_SIZE);
+    Dbprintf("  tag -> Reader: %i bytes", TAG_READER_BUFFER_SIZE);
+    Dbprintf("  DMA: %i bytes", DEMOD_DMA_BUFFER_SIZE);
+
+    // And put the FPGA in the appropriate mode
+    // Signal field is off with the appropriate LED
+    LED_D_OFF();
+    FpgaWriteConfWord(
+    	FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ |
+    	FPGA_HF_READER_RX_XCORR_SNOOP);
+    SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+
+    // Setup for the DMA.
+    FpgaSetupSsc();
+    upTo = dmaBuf;
+    lastRxCounter = DEMOD_DMA_BUFFER_SIZE;
+    FpgaSetupSscDma((uint8_t *)dmaBuf, DEMOD_DMA_BUFFER_SIZE);
+		
+    LED_A_ON();
+		
+    // And now we loop, receiving samples.
+    for(;;) {
+    	int behindBy = (lastRxCounter - AT91C_BASE_PDC_SSC->PDC_RCR) &
+                                (DEMOD_DMA_BUFFER_SIZE-1);
+        if(behindBy > maxBehindBy) {
+            maxBehindBy = behindBy;
+            if(behindBy > (DEMOD_DMA_BUFFER_SIZE-2)) { // TODO: understand whether we can increase/decrease as we want or not?
+                Dbprintf("blew circular buffer! behindBy=0x%x", behindBy);
+                goto done;
+            }
+        }
+        if(behindBy < 2) continue;
+
+        ci = upTo[0];
+        cq = upTo[1];
+        upTo += 2;
+        lastRxCounter -= 2;
+        if(upTo - dmaBuf > DEMOD_DMA_BUFFER_SIZE) {
+            upTo -= DEMOD_DMA_BUFFER_SIZE;
+            lastRxCounter += DEMOD_DMA_BUFFER_SIZE;
+            AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) upTo;
+            AT91C_BASE_PDC_SSC->PDC_RNCR = DEMOD_DMA_BUFFER_SIZE;
+        }
+
+        samples += 2;
+
+#define HANDLE_BIT_IF_BODY \
+            if(triggered) { \
+                trace[traceLen++] = ((samples >>  0) & 0xff); \
+                trace[traceLen++] = ((samples >>  8) & 0xff); \
+                trace[traceLen++] = ((samples >> 16) & 0xff); \
+                trace[traceLen++] = ((samples >> 24) & 0xff); \
+                trace[traceLen++] = 0; \
+                trace[traceLen++] = 0; \
+                trace[traceLen++] = 0; \
+                trace[traceLen++] = 0; \
+                trace[traceLen++] = Uart.byteCnt; \
+                memcpy(trace+traceLen, receivedCmd, Uart.byteCnt); \
+                traceLen += Uart.byteCnt; \
+                if(traceLen > 1000) break; \
+            } \
+            /* And ready to receive another command. */ \
+            memset(&Uart, 0, sizeof(Uart)); \
+            Uart.output = receivedCmd; \
+            Uart.byteCntMax = 100; \
+            Uart.state = STATE_UNSYNCD; \
+            /* And also reset the demod code, which might have been */ \
+            /* false-triggered by the commands from the reader. */ \
+            memset(&Demod, 0, sizeof(Demod)); \
+            Demod.output = receivedResponse; \
+            Demod.state = DEMOD_UNSYNCD; \
+
+        if(Handle14443UartBit(ci & 1)) {
+            HANDLE_BIT_IF_BODY
+        }
+        if(Handle14443UartBit(cq & 1)) {
+            HANDLE_BIT_IF_BODY
+        }
+
+        if(Handle14443SamplesDemod(ci, cq)) {
+            // timestamp, as a count of samples
+            trace[traceLen++] = ((samples >>  0) & 0xff);
+            trace[traceLen++] = ((samples >>  8) & 0xff);
+            trace[traceLen++] = ((samples >> 16) & 0xff);
+            trace[traceLen++] = 0x80 | ((samples >> 24) & 0xff);
+            // correlation metric (~signal strength estimate)
+            if(Demod.metricN != 0) {
+                Demod.metric /= Demod.metricN;
+            }
+            trace[traceLen++] = ((Demod.metric >>  0) & 0xff);
+            trace[traceLen++] = ((Demod.metric >>  8) & 0xff);
+            trace[traceLen++] = ((Demod.metric >> 16) & 0xff);
+            trace[traceLen++] = ((Demod.metric >> 24) & 0xff);
+            // length
+            trace[traceLen++] = Demod.len;
+            memcpy(trace+traceLen, receivedResponse, Demod.len);
+            traceLen += Demod.len;
+            if(traceLen > DEMOD_TRACE_SIZE) {
+				DbpString("Reached trace limit");
+				goto done;
+			}
+
+            triggered = TRUE;
+            LED_A_OFF();
+            LED_B_ON();
+
+            // And ready to receive another response.
+            memset(&Demod, 0, sizeof(Demod));
+            Demod.output = receivedResponse;
+            Demod.state = DEMOD_UNSYNCD;
+        }
+	WDT_HIT();
+
+        if(BUTTON_PRESS()) {
+            DbpString("cancelled");
+            goto done;
+        }
+    }
+
+done:
+	LED_A_OFF();
+	LED_B_OFF();
+	LED_C_OFF();
+  AT91C_BASE_PDC_SSC->PDC_PTCR = AT91C_PDC_RXTDIS;
+	DbpString("Snoop statistics:");
+  Dbprintf("  Max behind by: %i", maxBehindBy);
+	Dbprintf("  Uart State: %x", Uart.state);
+	Dbprintf("  Uart ByteCnt: %i", Uart.byteCnt);
+	Dbprintf("  Uart ByteCntMax: %i", Uart.byteCntMax);
+	Dbprintf("  Trace length: %i", traceLen);
+}
+
+/*
+ * Send raw command to tag ISO14443B
+ * @Input
+ * datalen     len of buffer data
+ * recv        bool when true wait for data from tag and send to client
+ * powerfield  bool leave the field on when true
+ * data        buffer with byte to send
+ *
+ * @Output
+ * none
+ *
+ */
+
+void SendRawCommand14443B(uint32_t datalen, uint32_t recv,uint8_t powerfield, uint8_t data[])
+{
+    FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+    if(!powerfield)
+    {
+        // Make sure that we start from off, since the tags are stateful;
+        // confusing things will happen if we don't reset them between reads.
+        FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+        LED_D_OFF();
+        SpinDelay(200);
+    }
+
+    if(!GETBIT(GPIO_LED_D))
+    {
+        SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+        FpgaSetupSsc();
+
+        // Now give it time to spin up.
+        // Signal field is on with the appropriate LED
+        LED_D_ON();
+        FpgaWriteConfWord(
+            FPGA_MAJOR_MODE_HF_READER_RX_XCORR | FPGA_HF_READER_RX_XCORR_848_KHZ);
+        SpinDelay(200);
+    }
+
+    CodeIso14443bAsReader(data, datalen);
+    TransmitFor14443();
+    if(recv)
+    {
+        uint16_t iLen = MIN(Demod.len,USB_CMD_DATA_SIZE);
+        GetSamplesFor14443Demod(TRUE, 2000, TRUE);
+        cmd_send(CMD_ACK,iLen,0,0,Demod.output,iLen);
+    }
+    if(!powerfield)
+    {
+        FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+        LED_D_OFF();
+    }
+}
+