[proxmark3-svn] / client / cmdlfem4x.c

//-----------------------------------------------------------------------------
// Copyright (C) 2010 iZsh <izsh at fail0verflow.com>
//
// 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.
//-----------------------------------------------------------------------------
// Low frequency EM4x commands
//-----------------------------------------------------------------------------

#include "cmdlfem4x.h"

uint64_t g_em410xid = 0;

static int CmdHelp(const char *Cmd);

int CmdEMdemodASK(const char *Cmd)
{
        char cmdp = param_getchar(Cmd, 0);
        uint8_t findone = (cmdp == '1') ? 1 : 0;
        UsbCommand c = {CMD_EM410X_DEMOD, {findone, 0, 0}};
        SendCommand(&c);
        return 0;
}

/* Read the ID of an EM410x tag.
 * Format:
 *   1111 1111 1           <-- standard non-repeatable header
 *   XXXX [row parity bit] <-- 10 rows of 5 bits for our 40 bit tag ID
 *   ....
 *   CCCC                  <-- each bit here is parity for the 10 bits above in corresponding column
 *   0                     <-- stop bit, end of tag
 */
int CmdEM410xRead(const char *Cmd)
{
        uint32_t hi=0;
        uint64_t lo=0;

        if(!AskEm410xDemod("", &hi, &lo, false)) return 0;
        PrintAndLog("EM410x pattern found: ");
        printEM410x(hi, lo);
        if (hi){
                PrintAndLog ("EM410x XL pattern found");
                return 0;
        }
        g_em410xid = lo;
        return 1;
}


int usage_lf_em410x_sim(void) {
        PrintAndLog("Simulating EM410x tag");
        PrintAndLog("");
        PrintAndLog("Usage:  lf em4x em410xsim [h] <uid> <clock>");
        PrintAndLog("Options:");
        PrintAndLog("       h         - this help");
        PrintAndLog("       uid       - uid (10 HEX symbols)");
        PrintAndLog("       clock     - clock (32|64) (optional)");
        PrintAndLog("samples:");
        PrintAndLog("      lf em4x em410xsim 0F0368568B");
        PrintAndLog("      lf em4x em410xsim 0F0368568B 32");
        return 0;
}

// emulate an EM410X tag
int CmdEM410xSim(const char *Cmd)
{
        int i, n, j, binary[4], parity[4];
        uint8_t uid[5] = {0x00};

        char cmdp = param_getchar(Cmd, 0);
        if (cmdp == 'h' || cmdp == 'H') return usage_lf_em410x_sim();

        /* clock is 64 in EM410x tags */
        uint8_t clock = 64;

        if (param_gethex(Cmd, 0, uid, 10)) {
                PrintAndLog("UID must include 10 HEX symbols");
                return 0;
        }
        
        param_getdec(Cmd, 1, &clock);
        
        PrintAndLog("Starting simulating UID %02X%02X%02X%02X%02X  clock: %d", uid[0],uid[1],uid[2],uid[3],uid[4],clock);
        PrintAndLog("Press pm3-button to about simulation");

        /* clear our graph */
        ClearGraph(0);

        /* write 9 start bits */
        for (i = 0; i < 9; i++)
                AppendGraph(0, clock, 1);

        /* for each hex char */
        parity[0] = parity[1] = parity[2] = parity[3] = 0;
        for (i = 0; i < 10; i++)
        {
                /* read each hex char */
                sscanf(&Cmd[i], "%1x", &n);
                for (j = 3; j >= 0; j--, n/= 2)
                        binary[j] = n % 2;

                /* append each bit */
                AppendGraph(0, clock, binary[0]);
                AppendGraph(0, clock, binary[1]);
                AppendGraph(0, clock, binary[2]);
                AppendGraph(0, clock, binary[3]);

                /* append parity bit */
                AppendGraph(0, clock, binary[0] ^ binary[1] ^ binary[2] ^ binary[3]);

                /* keep track of column parity */
                parity[0] ^= binary[0];
                parity[1] ^= binary[1];
                parity[2] ^= binary[2];
                parity[3] ^= binary[3];
        }

        /* parity columns */
        AppendGraph(0, clock, parity[0]);
        AppendGraph(0, clock, parity[1]);
        AppendGraph(0, clock, parity[2]);
        AppendGraph(0, clock, parity[3]);

        /* stop bit */
        AppendGraph(1, clock, 0);
 
        CmdLFSim("0"); //240 start_gap.
        return 0;
}

/* Function is equivalent of lf read + data samples + em410xread
 * looped until an EM410x tag is detected 
 * 
 * Why is CmdSamples("16000")?
 *  TBD: Auto-grow sample size based on detected sample rate.  IE: If the
 *       rate gets lower, then grow the number of samples
 *  Changed by martin, 4000 x 4 = 16000, 
 *  see http://www.proxmark.org/forum/viewtopic.php?pid=7235#p7235
*/
int CmdEM410xWatch(const char *Cmd)
{
        do {
                if (ukbhit()) {
                        printf("\naborted via keyboard!\n");
                        break;
                }
                
                CmdLFRead("s");
                getSamples("8201",true); //capture enough to get 2 complete preambles (4096*2+9)        
        } while (!CmdEM410xRead(""));

        return 0;
}

//currently only supports manchester modulations
// todo: helptext
int CmdEM410xWatchnSpoof(const char *Cmd)
{
        // loops if the captured ID was in XL-format.
        CmdEM410xWatch(Cmd);
        PrintAndLog("# Replaying captured ID: %llu", g_em410xid);
        CmdLFaskSim("");
        return 0;
}

int CmdEM410xWrite(const char *Cmd)
{
        uint64_t id = 0xFFFFFFFFFFFFFFFF; // invalid id value
        int card = 0xFF; // invalid card value
        uint32_t clock = 0; // invalid clock value

        sscanf(Cmd, "%" PRIx64 " %d %d", &id, &card, &clock);

        // Check ID
        if (id == 0xFFFFFFFFFFFFFFFF) {
                PrintAndLog("Error! ID is required.\n");
                return 0;
        }
        if (id >= 0x10000000000) {
                PrintAndLog("Error! Given EM410x ID is longer than 40 bits.\n");
                return 0;
        }

        // Check Card
        if (card == 0xFF) {
                PrintAndLog("Error! Card type required.\n");
                return 0;
        }
        if (card < 0) {
                PrintAndLog("Error! Bad card type selected.\n");
                return 0;
        }

        // Check Clock
                // Default: 64
        if (clock == 0)
                clock = 64;

        // Allowed clock rates: 16, 32, 40 and 64
        if ((clock != 16) && (clock != 32) && (clock != 64) && (clock != 40)) {
                PrintAndLog("Error! Clock rate %d not valid. Supported clock rates are 16, 32, 40 and 64.\n", clock);
                return 0;
        }

        if (card == 1) {
                PrintAndLog("Writing %s tag with UID 0x%010" PRIx64 " (clock rate: %d)", "T55x7", id, clock);
                // NOTE: We really should pass the clock in as a separate argument, but to
                //   provide for backwards-compatibility for older firmware, and to avoid
                //   having to add another argument to CMD_EM410X_WRITE_TAG, we just store
                //   the clock rate in bits 8-15 of the card value
                card = (card & 0xFF) | ((clock << 8) & 0xFF00);
        }       else if (card == 0) {
                PrintAndLog("Writing %s tag with UID 0x%010" PRIx64, "T5555", id, clock);
                card = (card & 0xFF) | ((clock << 8) & 0xFF00);
        } else {
                PrintAndLog("Error! Bad card type selected.\n");
                return 0;
        }

        UsbCommand c = {CMD_EM410X_WRITE_TAG, {card, (uint32_t)(id >> 32), (uint32_t)id}};
        SendCommand(&c);
        return 0;
}

bool EM_EndParityTest(uint8_t *BitStream, size_t size, uint8_t rows, uint8_t cols, uint8_t pType)
{
        if (rows*cols>size) return false;
        uint8_t colP=0;
        //assume last col is a parity and do not test
        for (uint8_t colNum = 0; colNum < cols-1; colNum++) {
                for (uint8_t rowNum = 0; rowNum < rows; rowNum++) {
                        colP ^= BitStream[(rowNum*cols)+colNum];
                }
                if (colP != pType) return false;
        }
        return true;
}

bool EM_ByteParityTest(uint8_t *BitStream, size_t size, uint8_t rows, uint8_t cols, uint8_t pType)
{
        if (rows*cols>size) return false;
        uint8_t rowP=0;
        //assume last row is a parity row and do not test
        for (uint8_t rowNum = 0; rowNum < rows-1; rowNum++) {
                for (uint8_t colNum = 0; colNum < cols; colNum++) {
                        rowP ^= BitStream[(rowNum*cols)+colNum];
                }
                if (rowP != pType) return false;
        }
        return true;
}

uint32_t OutputEM4x50_Block(uint8_t *BitStream, size_t size, bool verbose, bool pTest)
{
        if (size<45) return 0;
        
        uint32_t code = bytebits_to_byte(BitStream,8);
        code = code<<8 | bytebits_to_byte(BitStream+9,8);
        code = code<<8 | bytebits_to_byte(BitStream+18,8);
        code = code<<8 | bytebits_to_byte(BitStream+27,8);
        
        if (verbose || g_debugMode){
                for (uint8_t i = 0; i<5; i++){
                        if (i == 4) PrintAndLog(""); //parity byte spacer
                        PrintAndLog("%d%d%d%d%d%d%d%d %d -> 0x%02x",
                            BitStream[i*9],
                            BitStream[i*9+1],
                            BitStream[i*9+2],
                            BitStream[i*9+3],
                            BitStream[i*9+4],
                            BitStream[i*9+5],
                            BitStream[i*9+6],
                            BitStream[i*9+7],
                            BitStream[i*9+8],
                            bytebits_to_byte(BitStream+i*9,8)
                        );
                }
                if (pTest)
                        PrintAndLog("Parity Passed");
                else
                        PrintAndLog("Parity Failed");
        }
        return code;
}
/* Read the transmitted data of an EM4x50 tag from the graphbuffer
 * Format:
 *
 *  XXXXXXXX [row parity bit (even)] <- 8 bits plus parity
 *  XXXXXXXX [row parity bit (even)] <- 8 bits plus parity
 *  XXXXXXXX [row parity bit (even)] <- 8 bits plus parity
 *  XXXXXXXX [row parity bit (even)] <- 8 bits plus parity
 *  CCCCCCCC                         <- column parity bits
 *  0                                <- stop bit
 *  LW                               <- Listen Window
 *
 * This pattern repeats for every block of data being transmitted.
 * Transmission starts with two Listen Windows (LW - a modulated
 * pattern of 320 cycles each (32/32/128/64/64)).
 *
 * Note that this data may or may not be the UID. It is whatever data
 * is stored in the blocks defined in the control word First and Last
 * Word Read values. UID is stored in block 32.
 */
 //completed by Marshmellow
int EM4x50Read(const char *Cmd, bool verbose)
{

        uint8_t fndClk[] = {8,16,32,40,50,64,128};
        int clk = 0; 
        int invert = 0;
        int tol = 0;
        int i, j, startblock, skip, block, start, end, low, high, minClk;
        bool complete = false;
        int tmpbuff[MAX_GRAPH_TRACE_LEN / 64];
        uint32_t Code[6];
        char tmp[6];
        char tmp2[20];
        int phaseoff;
        high = low = 0;
        memset(tmpbuff, 0, MAX_GRAPH_TRACE_LEN / 64);

        // get user entry if any
        sscanf(Cmd, "%i %i", &clk, &invert);
        
        // save GraphBuffer - to restore it later       
        save_restoreGB(1);

        // first get high and low values
        for (i = 0; i < GraphTraceLen; i++) {
                if (GraphBuffer[i] > high)
                        high = GraphBuffer[i];
                else if (GraphBuffer[i] < low)
                        low = GraphBuffer[i];
        }

        i = 0;
        j = 0;
        minClk = 255;
        // get to first full low to prime loop and skip incomplete first pulse
        while ((GraphBuffer[i] < high) && (i < GraphTraceLen))
                ++i;
        while ((GraphBuffer[i] > low) && (i < GraphTraceLen))
                ++i;
        skip = i;

        // populate tmpbuff buffer with pulse lengths
        while (i < GraphTraceLen) {
                // measure from low to low
                while ((GraphBuffer[i] > low) && (i < GraphTraceLen))
                        ++i;
                start= i;
                while ((GraphBuffer[i] < high) && (i < GraphTraceLen))
                        ++i;
                while ((GraphBuffer[i] > low) && (i < GraphTraceLen))
                        ++i;
                if (j>=(MAX_GRAPH_TRACE_LEN/64)) {
                        break;
                }
                tmpbuff[j++]= i - start;
                if (i-start < minClk && i < GraphTraceLen) {
                        minClk = i - start;
                }
        }
        // set clock
        if (!clk) {
                for (uint8_t clkCnt = 0; clkCnt<7; clkCnt++) {
                        tol = fndClk[clkCnt]/8;
                        if (minClk >= fndClk[clkCnt]-tol && minClk <= fndClk[clkCnt]+1) { 
                                clk=fndClk[clkCnt];
                                break;
                        }
                }
                if (!clk) {
                        PrintAndLog("ERROR: EM4x50 - didn't find a clock");
                        return 0;
                }
        } else tol = clk/8;

        // look for data start - should be 2 pairs of LW (pulses of clk*3,clk*2)
        start = -1;
        for (i= 0; i < j - 4 ; ++i) {
                skip += tmpbuff[i];
                if (tmpbuff[i] >= clk*3-tol && tmpbuff[i] <= clk*3+tol)  //3 clocks
                        if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol)  //2 clocks
                                if (tmpbuff[i+2] >= clk*3-tol && tmpbuff[i+2] <= clk*3+tol) //3 clocks
                                        if (tmpbuff[i+3] >= clk-tol)  //1.5 to 2 clocks - depends on bit following
                                        {
                                                start= i + 4;
                                                break;
                                        }
        }
        startblock = i + 4;

        // skip over the remainder of LW
        skip += tmpbuff[i+1] + tmpbuff[i+2] + clk;
        if (tmpbuff[i+3]>clk) 
                phaseoff = tmpbuff[i+3]-clk;
        else
                phaseoff = 0;
        // now do it again to find the end
        end = skip;
        for (i += 3; i < j - 4 ; ++i) {
                end += tmpbuff[i];
                if (tmpbuff[i] >= clk*3-tol && tmpbuff[i] <= clk*3+tol)  //3 clocks
                        if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol)  //2 clocks
                                if (tmpbuff[i+2] >= clk*3-tol && tmpbuff[i+2] <= clk*3+tol) //3 clocks
                                        if (tmpbuff[i+3] >= clk-tol)  //1.5 to 2 clocks - depends on bit following
                                        {
                                                complete= true;
                                                break;
                                        }
        }
        end = i;
        // report back
        if (verbose || g_debugMode) {
                if (start >= 0) {
                        PrintAndLog("\nNote: one block = 50 bits (32 data, 12 parity, 6 marker)");
                }       else {
                        PrintAndLog("No data found!, clock tried:%d",clk);
                        PrintAndLog("Try again with more samples.");
                        PrintAndLog("  or after a 'data askedge' command to clean up the read");
                        return 0;
                }
        } else if (start < 0) return 0;
        start = skip;
        snprintf(tmp2, sizeof(tmp2),"%d %d 1000 %d", clk, invert, clk*47);
        // get rid of leading crap 
        snprintf(tmp, sizeof(tmp), "%i", skip);
        CmdLtrim(tmp);
        bool pTest;
        bool AllPTest = true;
        // now work through remaining buffer printing out data blocks
        block = 0;
        i = startblock;
        while (block < 6) {
                if (verbose || g_debugMode) PrintAndLog("\nBlock %i:", block);
                skip = phaseoff;
                
                // look for LW before start of next block
                for ( ; i < j - 4 ; ++i) {
                        skip += tmpbuff[i];
                        if (tmpbuff[i] >= clk*3-tol && tmpbuff[i] <= clk*3+tol)
                                if (tmpbuff[i+1] >= clk-tol)
                                        break;
                }
                if (i >= j-4) break; //next LW not found
                skip += clk;
                if (tmpbuff[i+1]>clk)
                        phaseoff = tmpbuff[i+1]-clk;
                else
                        phaseoff = 0;
                i += 2;
                if (ASKDemod(tmp2, false, false, 1) < 1) {
                        save_restoreGB(0);
                        return 0;
                }
                //set DemodBufferLen to just one block
                DemodBufferLen = skip/clk;
                //test parities
                pTest = EM_ByteParityTest(DemodBuffer,DemodBufferLen,5,9,0);    
                pTest &= EM_EndParityTest(DemodBuffer,DemodBufferLen,5,9,0);
                AllPTest &= pTest;
                //get output
                Code[block] = OutputEM4x50_Block(DemodBuffer,DemodBufferLen,verbose, pTest);
                if (g_debugMode) PrintAndLog("\nskipping %d samples, bits:%d", skip, skip/clk);
                //skip to start of next block
                snprintf(tmp,sizeof(tmp),"%i",skip);
                CmdLtrim(tmp);
                block++;
                if (i >= end) break; //in case chip doesn't output 6 blocks
        }
        //print full code:
        if (verbose || g_debugMode || AllPTest){
                if (!complete) {
                        PrintAndLog("*** Warning!");
                        PrintAndLog("Partial data - no end found!");
                        PrintAndLog("Try again with more samples.");
                }
                PrintAndLog("Found data at sample: %i - using clock: %i", start, clk);    
                end = block;
                for (block=0; block < end; block++){
                        PrintAndLog("Block %d: %08x",block,Code[block]);
                }
                if (AllPTest) {
                        PrintAndLog("Parities Passed");
                } else {
                        PrintAndLog("Parities Failed");
                        PrintAndLog("Try cleaning the read samples with 'data askedge'");
                }
        }

        //restore GraphBuffer
        save_restoreGB(0);
        return (int)AllPTest;
}

int CmdEM4x50Read(const char *Cmd) {
        return EM4x50Read(Cmd, true);
}

int usage_lf_em_read(void) {
        PrintAndLog("Read EM4x05/EM4x69.  Tag must be on antenna. ");
        PrintAndLog("");
        PrintAndLog("Usage:  lf em readword [h] <address> <pwd>");
        PrintAndLog("Options:");
        PrintAndLog("       h         - this help");
        PrintAndLog("       address   - memory address to read. (0-15)");
        PrintAndLog("       pwd       - password (hex) (optional)");
        PrintAndLog("samples:");
        PrintAndLog("      lf em readword 1");
        PrintAndLog("      lf em readword 1 11223344");
        return 0;
}

//search for given preamble in given BitStream and return success=1 or fail=0 and startIndex
uint8_t EMpreambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_t size, size_t *startIdx) {
        // Sanity check.  If preamble length is bigger than bitstream length.
        if ( size <= pLen ) return 0;
        
        // em only sends preamble once, so look for it once in the first x bits
        uint8_t foundCnt = 0;
        for (int idx = 0; idx < size - pLen; idx++){
                if (memcmp(BitStream+idx, preamble, pLen) == 0){
                        //first index found
                        foundCnt++;
                        if (foundCnt == 1) {
                                *startIdx = idx;
                                return 1;
                        }
                }
        }
        return 0;
}

#define EM_PREAMBLE_LEN 6
bool detectFSK(){
        // detect fsk clock
        if (!GetFskClock("", FALSE, FALSE)) {
                if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305: FSK clock failed");
                return FALSE;
        }
        // demod
        int ans = FSKrawDemod("0 0", FALSE);
        if (!ans) {
                if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305: FSK Demod failed");
                return FALSE;
        }
        return TRUE;
}
// PSK clocks should be easy to detect ( but difficult to demod a non-repeating pattern... )
bool detectPSK(){       
        int     ans = GetPskClock("", FALSE, FALSE);
        if (!ans) {
                if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305: PSK clock failed");                
                return FALSE;
        }
        PrintAndLog("PSK response possibly found, run `data rawd p1` to attempt to demod");
        return TRUE;
}
// try manchester - NOTE: ST only applies to T55x7 tags.
bool detectASK_MAN(){
        bool stcheck = FALSE;
        int ans = ASKDemod_ext("0 0 0", TRUE, FALSE, 1, &stcheck);
        if (!ans) {
                if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305: ASK/Manchester Demod failed");
                return FALSE;
        } 
        return TRUE;
}
bool detectASK_BI(){
        int ans = ASKbiphaseDemod("0 0 1", FALSE);
        if (!ans) { 
                if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305: ASK/biphase normal demod failed");
                
                ans = ASKbiphaseDemod("0 1 1", FALSE);
                if (!ans) {
                        if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305: ASK/biphase inverted demod failed");
                        return FALSE;
                }
        }
        return TRUE;
}
bool doPreambleSearch(size_t *startIdx){

        // skip first two 0 bits as they might have been missed in the demod 
        uint8_t preamble[EM_PREAMBLE_LEN] = {0,0,1,0,1,0};
        
        // set size to 10 to only test first 4 positions for the preamble
        size_t size = (10 > DemodBufferLen) ? DemodBufferLen : 10;
        *startIdx = 0; 

        if (g_debugMode) PrintAndLog("Before:: startindex: %u | size: %u", *startIdx, size);

        uint8_t errChk = !EMpreambleSearch(DemodBuffer, preamble, EM_PREAMBLE_LEN, size, startIdx);
        if ( errChk == 0) {
                if (g_debugMode) PrintAndLog("DEBUG: Error - EM4305 preamble not found :: %d", *startIdx);
                return FALSE;
        } 
        if (g_debugMode) PrintAndLog("After:: startindex: %u | size: %u", *startIdx, size);     
        return TRUE;
}

// FSK, PSK, ASK/MANCHESTER, ASK/BIPHASE, ASK/DIPHASE 
// should cover 90% of known used configs
// the rest will need to be manually demoded for now...
int demodEM4x05resp(uint8_t bitsNeeded) {

        size_t startIdx = 0;    
        
        if (detectASK_MAN() && doPreambleSearch( &startIdx ))
                goto EXIT_SET;
        
        if (detectASK_BI() && doPreambleSearch( &startIdx ))
                goto EXIT_SET;
        
        if (detectFSK() && doPreambleSearch( &startIdx ))
                goto EXIT_SET;
        

        if (detectPSK() && doPreambleSearch( &startIdx ))
                goto EXIT_SET;
        
        return -1;

EXIT_SET:       
        if ( bitsNeeded < DemodBufferLen) {
                setDemodBuf(DemodBuffer + startIdx + EM_PREAMBLE_LEN, bitsNeeded, 0);
                CmdPrintDemodBuff("x");
                return 1;
        }
        return -1;
}

int CmdReadWord(const char *Cmd) {
        int addr, pwd;
        bool usePwd = false;
        uint8_t ctmp = param_getchar(Cmd, 0);
        if ( strlen(Cmd) == 0 || ctmp == 'H' || ctmp == 'h' ) return usage_lf_em_read();

        addr = param_get8ex(Cmd, 0, -1, 10);
        pwd =  param_get32ex(Cmd, 1, -1, 16);
        
        if ( (addr > 15) || (addr < 0 ) || ( addr == -1) ) {
                PrintAndLog("Address must be between 0 and 15");
                return 1;
        }
        if ( pwd == -1 )
                PrintAndLog("Reading address %d", addr);
        else {
                usePwd = true;
                PrintAndLog("Reading address %d | password %08X", addr, pwd);
        }
        
        UsbCommand c = {CMD_EM4X_READ_WORD, {addr, pwd, usePwd}};
        clearCommandBuffer();
        SendCommand(&c);
        UsbCommand resp;        
        if (!WaitForResponseTimeout(CMD_ACK, &resp, 2500)){
                PrintAndLog("Command timed out");
                return -1;
        }
        
        uint8_t got[6000];
        GetFromBigBuf(got, sizeof(got), 0);
        if ( !WaitForResponseTimeout(CMD_ACK, NULL, 2500) ) {
                PrintAndLog("command execution time out");
                return -1;
        }
        setGraphBuf(got, sizeof(got));
        int testLen = (GraphTraceLen < 1000) ? GraphTraceLen : 1000;
        if (graphJustNoise(GraphBuffer, testLen)) {
                PrintAndLog("no tag not found");
                return -1;
        }

        //attempt demod:
        //need 32 bits from a read word
        return demodEM4x05resp(32);
}

int usage_lf_em_write(void) {
        PrintAndLog("Write EM4x05/EM4x69.  Tag must be on antenna. ");
        PrintAndLog("");
        PrintAndLog("Usage:  lf em writeword [h] <address> <data> <pwd>");
        PrintAndLog("Options:");
        PrintAndLog("       h         - this help");
        PrintAndLog("       address   - memory address to write to. (0-15)");
        PrintAndLog("       data      - data to write (hex)");  
        PrintAndLog("       pwd       - password (hex) (optional)");
        PrintAndLog("samples:");
        PrintAndLog("      lf em writeword 1");
        PrintAndLog("      lf em writeword 1 deadc0de 11223344");
        return 0;
}
int CmdWriteWord(const char *Cmd) {
        uint8_t ctmp = param_getchar(Cmd, 0);
        if ( strlen(Cmd) == 0 || ctmp == 'H' || ctmp == 'h' ) return usage_lf_em_write();
        
        bool usePwd = false;
                
        int addr = 16; // default to invalid address
        int data = 0xFFFFFFFF; // default to blank data
        int pwd = 0xFFFFFFFF; // default to blank password
        
        addr = param_get8ex(Cmd, 0, -1, 10);
        data = param_get32ex(Cmd, 1, -1, 16);
        pwd =  param_get32ex(Cmd, 2, -1, 16);
        
        if ( (addr > 15) || (addr < 0 ) || ( addr == -1) ) {
                PrintAndLog("Address must be between 0 and 15");
                return 1;
        }
        if ( pwd == -1 )
                PrintAndLog("Writing address %d data %08X", addr, data);        
        else {
                usePwd = true;
                PrintAndLog("Writing address %d data %08X using password %08X", addr, data, pwd);               
        }
        
        uint16_t flag = (addr << 8 ) | usePwd;
        
        UsbCommand c = {CMD_EM4X_WRITE_WORD, {flag, data, pwd}};
        clearCommandBuffer();
        SendCommand(&c);
        UsbCommand resp;        
        if (!WaitForResponseTimeout(CMD_ACK, &resp, 1000)){
                PrintAndLog("Error occurred, device did not respond during write operation.");
                return -1;
        }
        
        //get response if there is one
        uint8_t got[6000]; // 8 bit preamble + 32 bit word response (max clock (128) * 40bits = 5120 samples)
        GetFromBigBuf(got, sizeof(got), 0);
        if ( !WaitForResponseTimeout(CMD_ACK, NULL, 2500) ) {
                PrintAndLog("command execution time out");
                return -2;
        }
        setGraphBuf(got, sizeof(got));
        
        //todo: check response for 00001010 then write data for write confirmation!
        
        //attempt demod:
        //need 0 bits demoded (after preamble) to verify write cmd
        int result = demodEM4x05resp(0);
        if (result == 1) {
                PrintAndLog("Write Verified");
        }
        return result;
}

static command_t CommandTable[] = {
        {"help",                CmdHelp,                        1, "This help"},
        {"em410xdemod", CmdEMdemodASK,          0, "[findone] -- Extract ID from EM410x tag (option 0 for continuous loop, 1 for only 1 tag)"},  
        {"em410xread",  CmdEM410xRead,          1, "[clock rate] -- Extract ID from EM410x tag in GraphBuffer"},
        {"em410xsim",   CmdEM410xSim,           0, "<UID> -- Simulate EM410x tag"},
        {"em410xwatch", CmdEM410xWatch,         0, "['h'] -- Watches for EM410x 125/134 kHz tags (option 'h' for 134)"},
        {"em410xspoof", CmdEM410xWatchnSpoof, 0, "['h'] --- Watches for EM410x 125/134 kHz tags, and replays them. (option 'h' for 134)" },
        {"em410xwrite", CmdEM410xWrite,         0, "<UID> <'0' T5555> <'1' T55x7> [clock rate] -- Write EM410x UID to T5555(Q5) or T55x7 tag, optionally setting clock rate"},
        {"em4x50read",  CmdEM4x50Read,          1, "demod data from EM4x50 tag from the graphbuffer"},
        {"readword",    CmdReadWord,            1, "read EM4x05/4x69 data"},
        {"writeword",   CmdWriteWord,           1, "write EM405/4x69 data"},
        {NULL, NULL, 0, NULL}
};

int CmdLFEM4X(const char *Cmd) {
        clearCommandBuffer();
        CmdsParse(CommandTable, Cmd);
        return 0;
}

int CmdHelp(const char *Cmd) {
        CmdsHelp(CommandTable);
        return 0;
}