X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/1888664863b3f2d3b185fd1c724a6dcf4f4cb15a..c85858f5247daf444cf2db070ba54df4f646d9f8:/common/lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index 8324c440..a32d3b85 100644
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -62,7 +62,7 @@ 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);
 }
 
@@ -73,11 +73,13 @@ size_t removeParity(uint8_t *BitStream, size_t startIdx, uint8_t pLen, uint8_t p
 {
 	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
 		switch (pType) {
@@ -148,6 +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){
@@ -482,19 +487,42 @@ 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 > 4 && waveSizeCnt < fchigh+1) break;			
+			isAboveThreshold = false;
+			waveSizeCnt = 0;
+		} else if (dest[idx] >= threshold_value && !isAboveThreshold) {
+			thresholdCnt++;
+			if (thresholdCnt > 4 && 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 anywhere
 	// between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
 	//  (could also be fc/5 && fc/7 for fsk1 = 4-9)
-	for(idx = 161; idx < size-20; idx++) {
+	for(; idx < size-20; idx++) {
 		// threshold current value
 
 		if (dest[idx] < threshold_value) dest[idx] = 0;
@@ -509,13 +537,14 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow
 				//do nothing with extra garbage
 			} 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) || preLastSample	== 0 )){
+				if (LastSample > (fchigh-2) && (preLastSample < (fchigh-1))){
 					dest[numBits-1]=1;
 				}
 				dest[numBits++]=1;
 
-			} else if (currSample > (fchigh) && !numBits) { //12 + and first bit = unusable garbage 
-				//do nothing with beginning garbage
+			} 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 (or 6+ = 7)
@@ -1372,10 +1401,10 @@ 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++)