+
+
+int manchester_decode(const int * data, const size_t len, uint8_t * dataout){
+
+ int bitlength = 0;
+ int i, clock, high, low, startindex;
+ low = startindex = 0;
+ high = 1;
+ uint8_t bitStream[len];
+
+ memset(bitStream, 0x00, len);
+
+ /* Detect high and lows */
+ for (i = 0; i < len; i++) {
+ if (data[i] > high)
+ high = data[i];
+ else if (data[i] < low)
+ low = data[i];
+ }
+
+ /* get clock */
+ clock = GetT55x7Clock( data, len, high );
+ startindex = DetectFirstTransition(data, len, high, low);
+
+ PrintAndLog(" Clock : %d", clock);
+ PrintAndLog(" startindex : %d", startindex);
+
+ if (high != 1)
+ bitlength = ManchesterConvertFrom255(data, len, bitStream, high, low, clock, startindex);
+ else
+ bitlength= ManchesterConvertFrom1(data, len, bitStream, clock, startindex);
+
+ if ( bitlength > 0 ){
+ PrintPaddedManchester(bitStream, bitlength, clock);
+ }
+
+ memcpy(dataout, bitStream, bitlength);
+
+ free(bitStream);
+ return bitlength;
+}
+
+ int GetT55x7Clock( const int * data, const size_t len, int peak ){
+
+ int i,lastpeak,clock;
+ clock = 0xFFFF;
+ lastpeak = 0;
+
+ /* Detect peak if we don't have one */
+ if (!peak) {
+ for (i = 0; i < len; ++i) {
+ if (data[i] > peak) {
+ peak = data[i];
+ }
+ }
+ }
+
+ for (i = 1; i < len; ++i) {
+ /* if this is the beginning of a peak */
+ if ( data[i-1] != data[i] && data[i] == peak) {
+ /* find lowest difference between peaks */
+ if (lastpeak && i - lastpeak < clock)
+ clock = i - lastpeak;
+ lastpeak = i;
+ }
+ }
+ //return clock;
+ //defaults clock to precise values.
+ switch(clock){
+ case 8:
+ case 16:
+ case 32:
+ case 40:
+ case 50:
+ case 64:
+ case 100:
+ case 128:
+ return clock;
+ break;
+ default: break;
+ }
+ return 32;
+ }
+
+ int DetectFirstTransition(const int * data, const size_t len, int high, int low){
+
+ int i, retval;
+ retval = 0;
+ /*
+ Detect first transition Lo-Hi (arbitrary)
+ skip to the first high
+ */
+ for (i = 0; i < len; ++i)
+ if (data[i] == high)
+ break;
+
+ /* now look for the first low */
+ for (; i < len; ++i) {
+ if (data[i] == low) {
+ retval = i;
+ break;
+ }
+ }
+ return retval;
+ }
+
+ int ManchesterConvertFrom255(const int * data, const size_t len, uint8_t * dataout, int high, int low, int clock, int startIndex){
+
+ int i, j, hithigh, hitlow, first, bit, bitIndex;
+ i = startIndex;
+ bitIndex = 0;
+
+ /*
+ * We assume the 1st bit is zero, it may not be
+ * the case: this routine (I think) has an init problem.
+ * Ed.
+ */
+ bit = 0;
+
+ for (; i < (int)(len / clock); i++)
+ {
+ hithigh = 0;
+ hitlow = 0;
+ first = 1;
+
+ /* Find out if we hit both high and low peaks */
+ for (j = 0; j < clock; j++)
+ {
+ if (data[(i * clock) + j] == high)
+ hithigh = 1;
+ else if (data[(i * clock) + j] == low)
+ hitlow = 1;
+
+ /* it doesn't count if it's the first part of our read
+ because it's really just trailing from the last sequence */
+ if (first && (hithigh || hitlow))
+ hithigh = hitlow = 0;
+ else
+ first = 0;
+
+ if (hithigh && hitlow)
+ break;
+ }
+
+ /* If we didn't hit both high and low peaks, we had a bit transition */
+ if (!hithigh || !hitlow)
+ bit ^= 1;
+
+ dataout[bitIndex++] = bit;
+ }
+ return bitIndex;
+ }
+
+ int ManchesterConvertFrom1(const int * data, const size_t len, uint8_t * dataout, int clock, int startIndex){
+
+ int i,j, bitindex, lc, tolerance, warnings;
+ warnings = 0;
+ int upperlimit = len*2/clock+8;
+ i = startIndex;
+ j = 0;
+ tolerance = clock/4;
+ uint8_t decodedArr[len];
+
+ /* Then detect duration between 2 successive transitions */
+ for (bitindex = 1; i < len; i++) {
+
+ if (data[i-1] != data[i]) {
+ lc = i - startIndex;
+ startIndex = i;
+
+ // Error check: if bitindex becomes too large, we do not
+ // have a Manchester encoded bitstream or the clock is really wrong!
+ if (bitindex > upperlimit ) {
+ PrintAndLog("Error: the clock you gave is probably wrong, aborting.");
+ return 0;
+ }
+ // Then switch depending on lc length:
+ // Tolerance is 1/4 of clock rate (arbitrary)
+ if (abs((lc-clock)/2) < tolerance) {
+ // Short pulse : either "1" or "0"
+ decodedArr[bitindex++] = data[i-1];
+ } else if (abs(lc-clock) < tolerance) {
+ // Long pulse: either "11" or "00"
+ decodedArr[bitindex++] = data[i-1];
+ decodedArr[bitindex++] = data[i-1];
+ } else {
+ ++warnings;
+ PrintAndLog("Warning: Manchester decode error for pulse width detection.");
+ if (warnings > 10) {
+ PrintAndLog("Error: too many detection errors, aborting.");
+ return 0;
+ }
+ }
+ }
+ }
+
+ /*
+ * We have a decodedArr of "01" ("1") or "10" ("0")
+ * parse it into final decoded dataout
+ */
+ for (i = 0; i < bitindex; i += 2) {
+
+ if ((decodedArr[i] == 0) && (decodedArr[i+1] == 1)) {
+ dataout[j++] = 1;
+ } else if ((decodedArr[i] == 1) && (decodedArr[i+1] == 0)) {
+ dataout[j++] = 0;
+ } else {
+ i++;
+ warnings++;
+ PrintAndLog("Unsynchronized, resync...");
+ PrintAndLog("(too many of those messages mean the stream is not Manchester encoded)");
+
+ if (warnings > 10) {
+ PrintAndLog("Error: too many decode errors, aborting.");
+ return 0;
+ }
+ }
+ }
+
+ PrintAndLog("%s", sprint_hex(dataout, j));
+ return j;
+ }
+
+ void ManchesterDiffDecodedString(const uint8_t* bitstream, size_t len, uint8_t invert){
+ /*
+ * We have a bitstream of "01" ("1") or "10" ("0")
+ * parse it into final decoded bitstream
+ */
+ int i, j, warnings;
+ uint8_t decodedArr[(len/2)+1];
+
+ j = warnings = 0;
+
+ uint8_t lastbit = 0;
+
+ for (i = 0; i < len; i += 2) {
+
+ uint8_t first = bitstream[i];
+ uint8_t second = bitstream[i+1];
+
+ if ( first == second ) {
+ ++i;
+ ++warnings;
+ if (warnings > 10) {
+ PrintAndLog("Error: too many decode errors, aborting.");
+ return;
+ }
+ }
+ else if ( lastbit != first ) {
+ decodedArr[j++] = 0 ^ invert;
+ }
+ else {
+ decodedArr[j++] = 1 ^ invert;
+ }
+ lastbit = second;
+ }
+
+ PrintAndLog("%s", sprint_hex(decodedArr, j));
+}
+
+
+void PrintPaddedManchester( uint8_t* bitStream, size_t len, size_t blocksize){
+
+ PrintAndLog(" Manchester decoded bitstream : %d bits", len);
+
+ uint8_t mod = len % blocksize;
+ uint8_t div = len / blocksize;
+ int i;
+ // Now output the bitstream to the scrollback by line of 16 bits
+ for (i = 0; i < div*blocksize; i+=blocksize) {
+ PrintAndLog(" %s", sprint_bin(bitStream+i,blocksize) );
+ }
+ if ( mod > 0 ){
+ PrintAndLog(" %s", sprint_bin(bitStream+i, mod) );
+ }
+}
projects / proxmark3-svn / blobdiff