add bitswap option for lf em 4x05write (#236)

default read mode of this chip outputs in reverse order...  so offer the
option to program in reverse order

diff --git a/client/cmdlfem4x.c b/client/cmdlfem4x.c
index d2ccfae8ef05768320979b3ea0e4730d1f51f73a..6a076e3386a26cd29cefa43c35b0e7e921c4ff76 100644 (file)
--- a/client/cmdlfem4x.c
+++ b/client/cmdlfem4x.c
@@ -763,9 +763,10 @@ int CmdEM4x05dump(const char *Cmd) {
 int usage_lf_em_write(void) {
        PrintAndLog("Write EM4x05/EM4x69.  Tag must be on antenna. ");
        PrintAndLog("");
-       PrintAndLog("Usage:  lf em 4x05writeword [h] <address> <data> <pwd>");
+       PrintAndLog("Usage:  lf em 4x05writeword [h] [s] <address> <data> <pwd>");
        PrintAndLog("Options:");
        PrintAndLog("       h         - this help");
+       PrintAndLog("       s         - swap data bit order before write");
        PrintAndLog("       address   - memory address to write to. (0-15)");
        PrintAndLog("       data      - data to write (hex)");  
        PrintAndLog("       pwd       - password (hex) (optional)");
@@ -778,18 +779,23 @@ int usage_lf_em_write(void) {
 int CmdEM4x05WriteWord(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;
-               
+
        uint8_t addr = 16; // default to invalid address
        uint32_t data = 0xFFFFFFFF; // default to blank data
        uint32_t pwd = 0xFFFFFFFF; // default to blank password
-       
-       addr = param_get8ex(Cmd, 0, 16, 10);
-       data = param_get32ex(Cmd, 1, 0, 16);
-       pwd =  param_get32ex(Cmd, 2, 1, 16);
-       
-       
+       char swap = 0;
+
+       int p = 0;
+       swap = param_getchar(Cmd, 0);
+       if (swap == 's' || swap=='S') p++;
+       addr = param_get8ex(Cmd, p++, 16, 10);
+       data = param_get32ex(Cmd, p++, 0, 16);
+       pwd  = param_get32ex(Cmd, p++, 1, 16);
+
+       if (swap == 's' || swap=='S') data = SwapBits(data, 32);
+
        if ( (addr > 15) ) {
                PrintAndLog("Address must be between 0 and 15");
                return 1;
@@ -798,15 +804,15 @@ int CmdEM4x05WriteWord(const char *Cmd) {
                PrintAndLog("Writing address %d data %08X", addr, data);        
        else {
                usePwd = true;
-               PrintAndLog("Writing address %d data %08X using password %08X", addr, data, pwd);               
+               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;        
+       UsbCommand resp;
        if (!WaitForResponseTimeout(CMD_ACK, &resp, 2000)){
                PrintAndLog("Error occurred, device did not respond during write operation.");
                return -1;
@@ -814,7 +820,7 @@ int CmdEM4x05WriteWord(const char *Cmd) {
        if ( !downloadSamplesEM() ) {
                return -1;
        }
-       //check response for 00001010 for write confirmation!   
+       //check response for 00001010 for write confirmation!
        //attempt demod:
        uint32_t dummy = 0;
        int result = demodEM4x05resp(&dummy,false);

diff --git a/client/util.c b/client/util.c
index 81b2d844f4376bdda269f6e3850a5c9925915216..7c70d55d5c98bb16d7b6472da681611e4e290d97 100644 (file)
--- a/client/util.c
+++ b/client/util.c
@@ -257,6 +257,15 @@ void num_to_bytebitsLSBF(uint64_t n, size_t len, uint8_t *dest) {
        }
 }
 
+// Swap bit order on a uint32_t value.  Can be limited by nrbits just use say 8bits reversal
+// And clears the rest of the bits.
+uint32_t SwapBits(uint32_t value, int nrbits) {
+       uint32_t newvalue = 0;
+       for(int i = 0; i < nrbits; i++) {
+               newvalue ^= ((value >> i) & 1) << (nrbits - 1 - i);
+       }
+       return newvalue;
+}
 
 // aa,bb,cc,dd,ee,ff,gg,hh, ii,jj,kk,ll,mm,nn,oo,pp
 // to

diff --git a/client/util.h b/client/util.h
index 1739498eeaf8d4ab4844951ecb332d64f90f10a9..27f9348e64132089f096a36606f8de9416e5359d 100644 (file)
--- a/client/util.h
+++ b/client/util.h
@@ -47,6 +47,7 @@ extern uint64_t bytes_to_num(uint8_t* src, size_t len);
 extern void num_to_bytebits(uint64_t   n, size_t len, uint8_t *dest);
 extern void num_to_bytebitsLSBF(uint64_t n, size_t len, uint8_t *dest);
 extern char *printBits(size_t const size, void const * const ptr);
+extern uint32_t SwapBits(uint32_t value, int nrbits);
 extern uint8_t *SwapEndian64(const uint8_t *src, const size_t len, const uint8_t blockSize);
 extern void SwapEndian64ex(const uint8_t *src, const size_t len, const uint8_t blockSize, uint8_t *dest);