-
-
-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;
- }