X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/d1869c3336e82b7f2eb68b7fa9a5bdb865ff6b23..893534d3b5753b110b84144596da6c6d0815c1cc:/common/lfdemod.c diff --git a/common/lfdemod.c b/common/lfdemod.c index 5ed2d16c..fbed6a9a 100644 --- a/common/lfdemod.c +++ b/common/lfdemod.c @@ -62,28 +62,30 @@ uint8_t parityTest(uint32_t bits, uint8_t bitLen, uint8_t pType) for (uint8_t i = 0; i < bitLen; i++){ ans ^= ((bits >> i) & 1); } - //PrintAndLog("DEBUG: ans: %d, ptype: %d",ans,pType); + if (g_debugMode) prnt("DEBUG: ans: %d, ptype: %d, bits: %08X",ans,pType,bits); return (ans == pType); } // by marshmellow // takes a array of binary values, start position, length of bits per parity (includes parity bit), -// Parity Type (1 for odd; 0 for even; 2 Always 1's), and binary Length (length to run) +// Parity Type (1 for odd; 0 for even; 2 for Always 1's; 3 for Always 0's), and binary Length (length to run) size_t removeParity(uint8_t *BitStream, size_t startIdx, uint8_t pLen, uint8_t pType, size_t bLen) { uint32_t parityWd = 0; size_t j = 0, bitCnt = 0; - for (int word = 0; word < (bLen); word+=pLen){ - for (int bit=0; bit < pLen; bit++){ + for (int word = 0; word < (bLen); word+=pLen) { + for (int bit=0; bit < pLen; bit++) { parityWd = (parityWd << 1) | BitStream[startIdx+word+bit]; BitStream[j++] = (BitStream[startIdx+word+bit]); } + if (word+pLen >= bLen) break; + j--; // overwrite parity with next data // if parity fails then return 0 - if (pType == 2) { // then marker bit which should be a 1 - if (!BitStream[j]) return 0; - } else { - if (parityTest(parityWd, pLen, pType) == 0) return 0; + switch (pType) { + case 3: if (BitStream[j]==1) {return 0;} break; //should be 0 spacer bit + case 2: if (BitStream[j]==0) {return 0;} break; //should be 1 spacer bit + default: if (parityTest(parityWd, pLen, pType) == 0) {return 0;} break; //test parity } bitCnt+=(pLen-1); parityWd = 0; @@ -95,7 +97,8 @@ size_t removeParity(uint8_t *BitStream, size_t startIdx, uint8_t pLen, uint8_t p // by marshmellow // takes a array of binary values, length of bits per parity (includes parity bit), -// Parity Type (1 for odd; 0 for even; 2 Always 1's), and binary Length (length to run) +// Parity Type (1 for odd; 0 for even; 2 Always 1's; 3 Always 0's), and binary Length (length to run) +// Make sure *dest is long enough to store original sourceLen + #_of_parities_to_be_added size_t addParity(uint8_t *BitSource, uint8_t *dest, uint8_t sourceLen, uint8_t pLen, uint8_t pType) { uint32_t parityWd = 0; @@ -106,10 +109,12 @@ size_t addParity(uint8_t *BitSource, uint8_t *dest, uint8_t sourceLen, uint8_t p dest[j++] = (BitSource[word+bit]); } // if parity fails then return 0 - if (pType == 2) { // then marker bit which should be a 1 - dest[j++]=1; - } else { - dest[j++] = parityTest(parityWd, pLen-1, pType) ^ 1; + switch (pType) { + case 3: dest[j++]=0; break; // marker bit which should be a 0 + case 2: dest[j++]=1; break; // marker bit which should be a 1 + default: + dest[j++] = parityTest(parityWd, pLen-1, pType) ^ 1; + break; } bitCnt += pLen; parityWd = 0; @@ -145,6 +150,9 @@ uint32_t bytebits_to_byteLSBF(uint8_t *src, size_t numbits) //search for given preamble in given BitStream and return success=1 or fail=0 and startIndex and length uint8_t preambleSearch(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; + uint8_t foundCnt=0; for (int idx=0; idx < *size - pLen; idx++){ if (memcmp(BitStream+idx, preamble, pLen) == 0){ @@ -162,6 +170,23 @@ uint8_t preambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_ return 0; } +// search for given preamble in given BitStream and return success=1 or fail=0 and startIndex (where it was found) +// does not look for a repeating preamble +// em4x05/4x69 only sends preamble once, so look for it once in the first pLen bits +// leave it generic so it could be reused later... +bool onePreambleSearch(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 false; + for (size_t idx = 0; idx < size - pLen; idx++) { + if (memcmp(BitStream+idx, preamble, pLen) == 0) { + if (g_debugMode) prnt("DEBUG: preamble found at %u", idx); + *startIdx = idx; + return true; + } + } + return false; +} + //by marshmellow //takes 1s and 0s and searches for EM410x format - output EM ID uint8_t Em410xDecode(uint8_t *BitStream, size_t *size, size_t *startIdx, uint32_t *hi, uint64_t *lo) @@ -256,15 +281,18 @@ int cleanAskRawDemod(uint8_t *BinStream, size_t *size, int clk, int invert, int //by marshmellow void askAmp(uint8_t *BitStream, size_t size) { + uint8_t Last = 128; for(size_t i = 1; i<size; i++){ if (BitStream[i]-BitStream[i-1]>=30) //large jump up - BitStream[i]=127; - else if(BitStream[i]-BitStream[i-1]<=-20) //large jump down - BitStream[i]=-127; + Last = 255; + else if(BitStream[i-1]-BitStream[i]>=20) //large jump down + Last = 0; + + BitStream[i-1] = Last; } return; } - + //by marshmellow //attempts to demodulate ask modulations, askType == 0 for ask/raw, askType==1 for ask/manchester int askdemod(uint8_t *BinStream, size_t *size, int *clk, int *invert, int maxErr, uint8_t amp, uint8_t askType) @@ -274,7 +302,7 @@ int askdemod(uint8_t *BinStream, size_t *size, int *clk, int *invert, int maxErr if (*clk==0 || start < 0) return -3; if (*invert != 1) *invert = 0; if (amp==1) askAmp(BinStream, *size); - if (g_debugMode==2) prnt("DEBUG ASK: clk %d, beststart %d", *clk, start); + if (g_debugMode==2) prnt("DEBUG ASK: clk %d, beststart %d, amp %d", *clk, start, amp); uint8_t initLoopMax = 255; if (initLoopMax > *size) initLoopMax = *size; @@ -460,10 +488,10 @@ int gProxII_Demod(uint8_t BitStream[], size_t *size) //return start position return (int) startIdx; } - return -5; + return -5; //spacer bits not found - not a valid gproxII } -//translate wave to 11111100000 (1 for each short wave 0 for each long wave) +//translate wave to 11111100000 (1 for each short wave [higher freq] 0 for each long wave [lower freq]) size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow) { size_t last_transition = 0; @@ -476,41 +504,67 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow size_t preLastSample = 0; size_t LastSample = 0; size_t currSample = 0; - // sync to first lo-hi transition, and threshold + if ( size < 1024 ) return 0; // not enough samples + + // jump to modulating data by finding the first 4 threshold crossings (or first 2 waves) + // in case you have junk or noise at the beginning of the trace... + uint8_t thresholdCnt = 0; + size_t waveSizeCnt = 0; + bool isAboveThreshold = dest[idx++] >= threshold_value; + for (; idx < size-20; idx++ ) { + if(dest[idx] < threshold_value && isAboveThreshold) { + thresholdCnt++; + if (thresholdCnt > 2 && waveSizeCnt < fchigh+1) break; + isAboveThreshold = false; + waveSizeCnt = 0; + } else if (dest[idx] >= threshold_value && !isAboveThreshold) { + thresholdCnt++; + if (thresholdCnt > 2 && waveSizeCnt < fchigh+1) break; + isAboveThreshold = true; + waveSizeCnt = 0; + } else { + waveSizeCnt++; + } + if (thresholdCnt > 10) break; + } + if (g_debugMode == 2) prnt("threshold Count reached at %u",idx); // Need to threshold first sample - // skip 160 samples to allow antenna/samples to settle - if(dest[160] < threshold_value) dest[0] = 0; + if(dest[idx] < threshold_value) dest[0] = 0; else dest[0] = 1; - + idx++; + size_t numBits = 0; // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8) - // or 10 (fc/10) cycles but in practice due to noise etc we may end up with with anywhere + // or 10 (fc/10) cycles but in practice due to noise etc we may end up with anywhere // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10 - for(idx = 161; idx < size-20; idx++) { + // (could also be fc/5 && fc/7 for fsk1 = 4-9) + for(; idx < size-20; idx++) { // threshold current value if (dest[idx] < threshold_value) dest[idx] = 0; else dest[idx] = 1; // Check for 0->1 transition - if (dest[idx-1] < dest[idx]) { // 0 -> 1 transition + if (dest[idx-1] < dest[idx]) { preLastSample = LastSample; LastSample = currSample; currSample = idx-last_transition; - if (currSample < (fclow-2)){ //0-5 = garbage noise (or 0-3) + if (currSample < (fclow-2)) { //0-5 = garbage noise (or 0-3) //do nothing with extra garbage - } else if (currSample < (fchigh-1)) { //6-8 = 8 sample waves or 3-6 = 5 - if (LastSample > (fchigh-2) && (preLastSample < (fchigh-1) || preLastSample == 0 )){ - dest[numBits-1]=1; //correct previous 9 wave surrounded by 8 waves + } else if (currSample < (fchigh-1)) { //6-8 = 8 sample waves (or 3-6 = 5) + //correct previous 9 wave surrounded by 8 waves (or 6 surrounded by 5) + if (LastSample > (fchigh-2) && (preLastSample < (fchigh-1))){ + dest[numBits-1]=1; } dest[numBits++]=1; - } else if (currSample > (fchigh) && !numBits) { //12 + and first bit = garbage - //do nothing with beginning garbage - } else if (currSample == (fclow+1) && LastSample == (fclow-1)) { // had a 7 then a 9 should be two 8's + } else if (currSample > (fchigh+1) && numBits < 3) { //12 + and first two bit = unusable garbage + //do nothing with beginning garbage and reset.. should be rare.. + numBits = 0; + } else if (currSample == (fclow+1) && LastSample == (fclow-1)) { // had a 7 then a 9 should be two 8's (or 4 then a 6 should be two 5's) dest[numBits++]=1; - } else { //9+ = 10 sample waves + } else { //9+ = 10 sample waves (or 6+ = 7) dest[numBits++]=0; } last_transition = idx; @@ -520,6 +574,7 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow } //translate 11111100000 to 10 +//rfLen = clock, fchigh = larger field clock, fclow = smaller field clock size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t invert, uint8_t fchigh, uint8_t fclow) { @@ -529,8 +584,9 @@ size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t rfLen, uint32_t n=1; for( idx=1; idx < size; idx++) { n++; - if (dest[idx]==lastval) continue; + if (dest[idx]==lastval) continue; //skip until we hit a transition + //find out how many bits (n) we collected //if lastval was 1, we have a 1->0 crossing if (dest[idx-1]==1) { n = (n * fclow + rfLen/2) / rfLen; @@ -539,6 +595,7 @@ size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t rfLen, } if (n == 0) n = 1; + //add to our destination the bits we collected memset(dest+numBits, dest[idx-1]^invert , n); numBits += n; n=0; @@ -680,6 +737,19 @@ int VikingDemod_AM(uint8_t *dest, size_t *size) { return (int) startIdx; } +// find presco preamble 0x10D in already demoded data +int PrescoDemod(uint8_t *dest, size_t *size) { + //make sure buffer has data + if (*size < 64*2) return -2; + + size_t startIdx = 0; + uint8_t preamble[] = {1,0,0,0,0,1,1,0,1,0,0,0,0,0,0,0,0,0,0,0}; + uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx); + if (errChk == 0) return -4; //preamble not found + //return start position + return (int) startIdx; +} + // Ask/Biphase Demod then try to locate an ISO 11784/85 ID // BitStream must contain previously askrawdemod and biphasedemoded data int FDXBdemodBI(uint8_t *dest, size_t *size) @@ -1348,10 +1418,10 @@ uint16_t countFC(uint8_t *BitStream, size_t size, uint8_t fskAdj) uint8_t fcLens[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; uint16_t fcCnts[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; uint8_t fcLensFnd = 0; - uint8_t lastFCcnt=0; + uint8_t lastFCcnt = 0; uint8_t fcCounter = 0; size_t i; - if (size == 0) return 0; + if (size < 180) return 0; // prime i to first up transition for (i = 160; i < size-20; i++) @@ -1438,7 +1508,7 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert) size_t numBits=0; uint8_t curPhase = *invert; - size_t i, waveStart=1, waveEnd=0, firstFullWave=0, lastClkBit=0; + size_t i=0, waveStart=1, waveEnd=0, firstFullWave=0, lastClkBit=0; uint8_t fc=0, fullWaveLen=0, tol=1; uint16_t errCnt=0, waveLenCnt=0; fc = countFC(dest, *size, 0); @@ -1446,19 +1516,45 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert) //PrintAndLog("DEBUG: FC: %d",fc); *clock = DetectPSKClock(dest, *size, *clock); if (*clock == 0) return -1; + // jump to modulating data by finding the first 2 threshold crossings (or first 1 waves) + // in case you have junk or noise at the beginning of the trace... + uint8_t thresholdCnt = 0; + size_t waveSizeCnt = 0; + uint8_t threshold_value = 123; //-5 + bool isAboveThreshold = dest[i++] >= threshold_value; + for (; i < *size-20; i++ ) { + if(dest[i] < threshold_value && isAboveThreshold) { + thresholdCnt++; + if (thresholdCnt > 2 && waveSizeCnt < fc+1) break; + isAboveThreshold = false; + waveSizeCnt = 0; + } else if (dest[i] >= threshold_value && !isAboveThreshold) { + thresholdCnt++; + if (thresholdCnt > 2 && waveSizeCnt < fc+1) break; + isAboveThreshold = true; + waveSizeCnt = 0; + } else { + waveSizeCnt++; + } + if (thresholdCnt > 10) break; + } + if (g_debugMode == 2) prnt("DEBUG PSK: threshold Count reached at %u, count: %u",i, thresholdCnt); + + int avgWaveVal=0, lastAvgWaveVal=0; + waveStart = i+1; //find first phase shift - for (i=0; i<loopCnt; i++){ + for (; i<loopCnt; i++){ if (dest[i]+fc < dest[i+1] && dest[i+1] >= dest[i+2]){ waveEnd = i+1; - //PrintAndLog("DEBUG: waveEnd: %d",waveEnd); + if (g_debugMode == 2) prnt("DEBUG PSK: waveEnd: %u, waveStart: %u",waveEnd, waveStart); waveLenCnt = waveEnd-waveStart; - if (waveLenCnt > fc && waveStart > fc && !(waveLenCnt > fc+2)){ //not first peak and is a large wave but not out of whack + if (waveLenCnt > fc && waveStart > fc && !(waveLenCnt > fc+3)){ //not first peak and is a large wave but not out of whack lastAvgWaveVal = avgWaveVal/(waveLenCnt); firstFullWave = waveStart; fullWaveLen=waveLenCnt; //if average wave value is > graph 0 then it is an up wave or a 1 - if (lastAvgWaveVal > 123) curPhase ^= 1; //fudge graph 0 a little 123 vs 128 + if (lastAvgWaveVal > threshold_value) curPhase ^= 1; //fudge graph 0 a little 123 vs 128 break; } waveStart = i+1; @@ -1478,8 +1574,8 @@ int pskRawDemod(uint8_t dest[], size_t *size, int *clock, int *invert) numBits += (firstFullWave / *clock); //set start of wave as clock align lastClkBit = firstFullWave; - //PrintAndLog("DEBUG: firstFullWave: %d, waveLen: %d",firstFullWave,fullWaveLen); - //PrintAndLog("DEBUG: clk: %d, lastClkBit: %d", *clock, lastClkBit); + if (g_debugMode==2) prnt("DEBUG PSK: firstFullWave: %u, waveLen: %u",firstFullWave,fullWaveLen); + if (g_debugMode==2) prnt("DEBUG: clk: %d, lastClkBit: %u, fc: %u", *clock, lastClkBit,(unsigned int) fc); waveStart = 0; dest[numBits++] = curPhase; //set first read bit for (i = firstFullWave + fullWaveLen - 1; i < *size-3; i++){ @@ -1529,11 +1625,12 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { uint8_t fndClk[] = {8,16,32,40,50,64,128}; int clk = 0; int tol = 0; - int i, j, skip, start, end, low, high, minClk; + int i, j, skip, start, end, low, high, minClk, waveStart; bool complete = false; - int tmpbuff[bufsize / 64]; + int tmpbuff[bufsize / 32]; //guess rf/32 clock, if click is smaller we will only have room for a fraction of the samples captured + int waveLen[bufsize / 32]; // if clock is larger then we waste memory in array size that is not needed... size_t testsize = (bufsize < 512) ? bufsize : 512; - //int phaseoff = 0; + int phaseoff = 0; high = low = 128; memset(tmpbuff, 0, sizeof(tmpbuff)); @@ -1541,7 +1638,6 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { if (g_debugMode==2) prnt("DEBUG STT: just noise detected - quitting"); return false; //just noise } - i = 0; j = 0; minClk = 255; @@ -1560,11 +1656,14 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { start= i; while ((buffer[i] < high) && (i < bufsize)) ++i; + //first high point for this wave + waveStart = i; while ((buffer[i] > low) && (i < bufsize)) ++i; - if (j >= (bufsize/64)) { + if (j >= (bufsize/32)) { break; } + waveLen[j] = i - waveStart; //first high to first low tmpbuff[j++] = i - start; if (i-start < minClk && i < bufsize) { minClk = i - start; @@ -1592,10 +1691,10 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { start = -1; for (i = 0; i < j - 4; ++i) { skip += tmpbuff[i]; - if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol) { //1 to 2 clocks depending on 2 bits prior - if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol) { //2 clocks - if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol) { //1 1/2 to 2 clocks - if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= (clk*3)/2+tol) { //1 to 1 1/2 clocks for end of ST + first bit + if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) { //1 to 2 clocks depending on 2 bits prior + if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol && waveLen[i+1] > clk*3/2-tol) { //2 clocks and wave size is 1 1/2 + if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol && waveLen[i+2] > clk-tol) { //1 1/2 to 2 clocks and at least one full clock wave + if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit start = i + 3; break; } @@ -1607,8 +1706,14 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { if (start < 0) { if (g_debugMode==2) prnt("DEBUG STT: first STT not found - quitting"); return false; + } else { + if (g_debugMode==2) prnt("DEBUG STT: first STT found at: %d, j=%d",start, j); } - + if (waveLen[i+2] > clk*1+tol) + phaseoff = 0; + else + phaseoff = clk/2; + // skip over the remainder of ST skip += clk*7/2; //3.5 clocks from tmpbuff[i] = end of st - also aligns for ending point @@ -1616,10 +1721,10 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { end = skip; for (i += 3; i < j - 4; ++i) { end += tmpbuff[i]; - if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol) { //1 to 2 clocks depending on 2 bits prior - if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol) { //2 clocks - if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol) { //1 1/2 to 2 clocks - if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= (clk*3)/2+tol) { //1 to 1 1/2 clocks for end of ST + first bit + if (tmpbuff[i] >= clk*1-tol && tmpbuff[i] <= (clk*2)+tol && waveLen[i] < clk+tol) { //1 to 2 clocks depending on 2 bits prior + if (tmpbuff[i+1] >= clk*2-tol && tmpbuff[i+1] <= clk*2+tol && waveLen[i+1] > clk*3/2-tol) { //2 clocks and wave size is 1 1/2 + if (tmpbuff[i+2] >= (clk*3)/2-tol && tmpbuff[i+2] <= clk*2+tol && waveLen[i+2] > clk-tol) { //1 1/2 to 2 clocks and at least one full clock wave + if (tmpbuff[i+3] >= clk*1-tol && tmpbuff[i+3] <= clk*2+tol) { //1 to 2 clocks for end of ST + first bit complete = true; break; } @@ -1627,22 +1732,26 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { } } } + end -= phaseoff; //didn't find second ST - ERROR if (!complete) { if (g_debugMode==2) prnt("DEBUG STT: second STT not found - quitting"); return false; } - if (g_debugMode==2) prnt("DEBUG STT: start of data: %d end of data: %d, datalen: %d, clk: %d, bits: %d", skip, end, end-skip, clk, (end-skip)/clk); + if (g_debugMode==2) prnt("DEBUG STT: start of data: %d end of data: %d, datalen: %d, clk: %d, bits: %d, phaseoff: %d", skip, end, end-skip, clk, (end-skip)/clk, phaseoff); //now begin to trim out ST so we can use normal demod cmds start = skip; size_t datalen = end - start; // check validity of datalen (should be even clock increments) - use a tolerance of up to 1/8th a clock - if (datalen % clk > clk/8) { + if ( clk - (datalen % clk) <= clk/8) { + // padd the amount off - could be problematic... but shouldn't happen often + datalen += clk - (datalen % clk); + } else if ( (datalen % clk) <= clk/8 ) { + // padd the amount off - could be problematic... but shouldn't happen often + datalen -= datalen % clk; + } else { if (g_debugMode==2) prnt("DEBUG STT: datalen not divisible by clk: %u %% %d = %d - quitting", datalen, clk, datalen % clk); return false; - } else { - // padd the amount off - could be problematic... but shouldn't happen often - datalen += datalen % clk; } // if datalen is less than one t55xx block - ERROR if (datalen/clk < 8*4) { @@ -1650,11 +1759,23 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { return false; } size_t dataloc = start; + if (buffer[dataloc-(clk*4)-(clk/8)] <= low && buffer[dataloc] <= low && buffer[dataloc-(clk*4)] >= high) { + //we have low drift (and a low just before the ST and a low just after the ST) - compensate by backing up the start + for ( i=0; i <= (clk/8); ++i ) { + if ( buffer[dataloc - (clk*4) - i] <= low ) { + dataloc -= i; + break; + } + } + } + size_t newloc = 0; i=0; + if (g_debugMode==2) prnt("DEBUG STT: Starting STT trim - start: %d, datalen: %d ",dataloc, datalen); + // warning - overwriting buffer given with raw wave data with ST removed... while ( dataloc < bufsize-(clk/2) ) { - //compensate for long high at end of ST not being high... (we cut out the high part) + //compensate for long high at end of ST not being high due to signal loss... (and we cut out the start of wave high part) if (buffer[dataloc]<high && buffer[dataloc]>low && buffer[dataloc+3]<high && buffer[dataloc+3]>low) { for(i=0; i < clk/2-tol; ++i) { buffer[dataloc+i] = high+5; @@ -1665,11 +1786,12 @@ bool DetectST(uint8_t buffer[], size_t *size, int *foundclock) { if (i+newloc < dataloc) buffer[i+newloc] = buffer[dataloc]; - dataloc++; + dataloc++; } } newloc += i; - //skip next ST + //skip next ST - we just assume it will be there from now on... + if (g_debugMode==2) prnt("DEBUG STT: skipping STT at %d to %d", dataloc, dataloc+(clk*4)); dataloc += clk*4; } *size = newloc;