- if ( firstST == 4)
- break;
- }
- return bitIndex;
- }
-
- int ManchesterConvertFrom1(const int * data, const size_t len, uint8_t * dataout, int clock, int startIndex){
-
- PrintAndLog(" Path B");
-
- 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];
-
- /* 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));
+ // remove DC offset and mix to complex baseband
+ x = (sample - 127.5f) * cexpf( _Complex_I * 2 * M_PI * fc * i );
+
+ // apply low-pass filter, removing spectral image (IIR using direct-form II)
+ iir_buf[2] = iir_buf[1];
+ iir_buf[1] = iir_buf[0];
+ iir_buf[0] = x - a[1]*iir_buf[1] - a[2]*iir_buf[2];
+ x = b[0]*iir_buf[0] +
+ b[1]*iir_buf[1] +
+ b[2]*iir_buf[2];
+
+ // compute instantaneous frequency by looking at phase difference
+ // between adjacent samples
+ float freq = cargf(x*conjf(x_prime));
+ x_prime = x; // retain this sample for next iteration
+
+ output[i] =(freq > 0)? 10 : -10;
+ }
+
+ // show data
+ for (j=0; j<adjustedLen; ++j)
+ data[j] = output[j];
+
+ free(output);