X-Git-Url: http://cvs.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/6ff6ade2f5f24ffb52a9f90238ee7b8c77edc89c..225ccb910e9de6c38b6d1c81d4fc025d05c13570:/common/lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index d30262f3..eb5a4d95 100644
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -8,389 +8,418 @@
 // Low frequency commands
 //-----------------------------------------------------------------------------
 
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include "lfdemod.h"
 
 //by marshmellow
 //takes 1s and 0s and searches for EM410x format - output EM ID
-uint64_t Em410xDecode(uint8_t *BitStream,uint32_t BitLen)
+uint64_t Em410xDecode(uint8_t *BitStream, uint32_t BitLen)
 {
-  //no arguments needed - built this way in case we want this to be a direct call from "data " cmds in the future
-  //  otherwise could be a void with no arguments
-  //set defaults
-  int high=0, low=128;
-  uint64_t lo=0; //hi=0,
+	//no arguments needed - built this way in case we want this to be a direct call from "data " cmds in the future
+	//  otherwise could be a void with no arguments
+	//set defaults
+	int high = 0, low = 128;
+	uint64_t lo = 0; 
+	uint32_t i = 0;
+	uint32_t initLoopMax = 65;
+
+	if (initLoopMax > BitLen) 
+		initLoopMax = BitLen;
+
+	for (; i < initLoopMax; ++i) //65 samples should be plenty to find high and low values
+	{
+		if (BitStream[i] > high)
+			high = BitStream[i];
+		else if (BitStream[i] < low)
+			low = BitStream[i];
+	}
 
-  uint32_t i = 0;
-  uint32_t initLoopMax = 65;
-  if (initLoopMax>BitLen) initLoopMax=BitLen;
+	if (((high !=1)||(low !=0))){  //allow only 1s and 0s 
+		return 0;
+	}
+
+	uint8_t parityTest = 0;
+	// 111111111 bit pattern represent start of frame
+	uint8_t frame_marker_mask[] = {1,1,1,1,1,1,1,1,1};
+	uint32_t idx = 0;
+	uint32_t j = 0;
+	uint8_t resetCnt = 0;
+	while( (idx + 64) < BitLen) {
+
+	restart:
 
-  for (;i < initLoopMax; ++i) //65 samples should be plenty to find high and low values
-  {
-    if (BitStream[i] > high)
-      high = BitStream[i];
-    else if (BitStream[i] < low)
-      low = BitStream[i];
-  }
-  if (((high !=1)||(low !=0))){  //allow only 1s and 0s 
-   // PrintAndLog("no data found"); 
-    return 0;
-  }
-  uint8_t parityTest=0;
-   // 111111111 bit pattern represent start of frame
-  uint8_t frame_marker_mask[] = {1,1,1,1,1,1,1,1,1};
-  uint32_t idx = 0;
-  uint32_t ii=0;
-  uint8_t resetCnt = 0;
-  while( (idx + 64) < BitLen) {
- restart:
     // search for a start of frame marker
-    if ( memcmp(BitStream+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0)
-    { // frame marker found
-      idx+=9;//sizeof(frame_marker_mask);
-      for (i=0; i<10;i++){
-        for(ii=0; ii<5; ++ii){
-          parityTest += BitStream[(i*5)+ii+idx];        
-        }
-        if (parityTest== ((parityTest>>1)<<1)){
-          parityTest=0;
-          for (ii=0; ii<4;++ii){
-            //hi = (hi<<1)|(lo>>31);
-            lo=(lo<<1LL)|(BitStream[(i*5)+ii+idx]);
-          }
-          //PrintAndLog("DEBUG: EM parity passed parity val: %d, i:%d, ii:%d,idx:%d, Buffer: %d%d%d%d%d,lo: %d",parityTest,i,ii,idx,BitStream[idx+ii+(i*5)-5],BitStream[idx+ii+(i*5)-4],BitStream[idx+ii+(i*5)-3],BitStream[idx+ii+(i*5)-2],BitStream[idx+ii+(i*5)-1],lo);          
-        }else {//parity failed
-          //PrintAndLog("DEBUG: EM parity failed parity val: %d, i:%d, ii:%d,idx:%d, Buffer: %d%d%d%d%d",parityTest,i,ii,idx,BitStream[idx+ii+(i*5)-5],BitStream[idx+ii+(i*5)-4],BitStream[idx+ii+(i*5)-3],BitStream[idx+ii+(i*5)-2],BitStream[idx+ii+(i*5)-1]);
-          parityTest=0;
-          idx-=8;
-          if (resetCnt>5)return 0;
-          resetCnt++;
-          goto restart;//continue;
-        }
-      }
-      //skip last 5 bit parity test for simplicity.
-      return lo;
-    }else{
-      idx++;
-    }
-  }
-  return 0;
+    if ( memcmp(BitStream+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0) {
+		// frame marker found
+		idx += 9;//sizeof(frame_marker_mask);
+		for ( i = 0; i < 10; ++i){
+			for( j = 0; j < 5; ++j){
+				parityTest += BitStream[(i*5) + j + idx];        
+			}
+			if (parityTest == ( (parityTest >> 1) << 1)){
+				parityTest = 0;
+				for (j = 0; j < 4; ++j){
+					lo = ( lo << 1LL)|( BitStream[( i * 5 ) + j + idx]);
+				}
+			} else {
+				//parity failed
+				parityTest = 0;
+				idx -= 8;
+				if (resetCnt > 5) return 0;
+				resetCnt++;
+				goto restart;//continue;
+			}
+		}
+		//skip last 5 bit parity test for simplicity.
+		return lo;
+		} else {
+			idx++;
+		}
+	}	
+	return 0;
 }
 
 //by marshmellow
 //takes 2 arguments - clock and invert both as integers
 //attempts to demodulate ask while decoding manchester 
 //prints binary found and saves in graphbuffer for further commands
-int askmandemod(uint8_t * BinStream,uint32_t *BitLen,int *clk, int *invert)
+int askmandemod(uint8_t *BinStream, uint32_t *BitLen, int *clk, int *invert)
 {
-  int i;
-  int high = 0, low = 128;
-  *clk=DetectASKClock(BinStream,(size_t)*BitLen,*clk); //clock default
-
-  if (*clk<8) *clk =64;
-  if (*clk<32) *clk=32;
-  if (*invert != 1) *invert=0;
+	int i;
+	int high = 0, low = 128;
+	*clk = DetectASKClock(BinStream, (size_t)*BitLen, *clk); //clock default
+	
+	if (*clk < 8 )    *clk = 64;
+	if (*clk < 32 )	  *clk = 32;
+	if (*invert != 1) *invert = 0;
+	
+	uint32_t initLoopMax = 200;
+	if (initLoopMax > *BitLen) 
+		initLoopMax = *BitLen;
   
-  uint32_t initLoopMax = 200;
-  if (initLoopMax>*BitLen) initLoopMax=*BitLen;
+	// Detect high and lows 
+	// 200 samples should be enough to find high and low values
+	for (i = 0; i < initLoopMax; ++i) {
+		if (BinStream[i] > high)
+			high = BinStream[i];
+		else if (BinStream[i] < low)
+			low = BinStream[i];
+	}
   
-  // Detect high and lows 
-  for (i = 0; i < initLoopMax; ++i) //200 samples should be enough to find high and low values
-  {
-    if (BinStream[i] > high)
-      high = BinStream[i];
-    else if (BinStream[i] < low)
-      low = BinStream[i];
-  }
-  if ((high < 158) ){  //throw away static 
-    return -2;
-  }
-  //25% fuzz in case highs and lows aren't clipped [marshmellow]
-  high=(int)((high-128)*.75)+128;
-  low= (int)((low-128)*.75)+128;
+	//throw away static 
+	if ((high < 158) )
+		return -2;
+
+	//25% fuzz in case highs and lows aren't clipped [marshmellow]
+	high = (int)(high * .75);
+	low  = (int)(low+128 * .25);
  
-  //PrintAndLog("DEBUG - valid high: %d - valid low: %d",high,low);
-  int lastBit = 0;  //set first clock check
-  uint32_t bitnum = 0;     //output counter
-  int tol = 0;  //clock tolerance adjust - waves will be accepted as within the clock if they fall + or - this value + clock from last valid wave
-  if (*clk==32)tol=1;    //clock tolerance may not be needed anymore currently set to + or - 1 but could be increased for poor waves or removed entirely 
-  int iii = 0;
-  uint32_t gLen = *BitLen;
-  if (gLen > 3000) gLen=3000;
-  uint8_t errCnt =0;
-  uint32_t bestStart = *BitLen;
-  uint32_t bestErrCnt = (*BitLen/1000);
-  uint32_t maxErr = (*BitLen/1000);
+	int lastBit = 0;      // set first clock check
+	uint32_t bitnum = 0;  // output counter
+
+	// clock tolerance adjust - waves will be accepted as within the clock if they fall + or - this value + clock from last valid wave
+	//clock tolerance may not be needed anymore currently set to + or - 1 but could be increased for poor waves or removed entirely 
+	int tol = ( *clk == 32 ) ? 1 : 0;  
+
+	int j = 0;
+	uint32_t gLen = *BitLen;
+
+	if (gLen > 3000) gLen = 3000;
+
+	uint8_t errCnt = 0;
+	uint32_t bestStart = *BitLen;
+	uint32_t bestErrCnt = (*BitLen/1000);
+	uint32_t maxErr = bestErrCnt;
 
   //loop to find first wave that works
-  for (iii=0; iii < gLen; ++iii){
-    if ((BinStream[iii]>=high)||(BinStream[iii]<=low)){
-      lastBit=iii-*clk;    
-      errCnt=0;
+	for (j=0; j < gLen; ++j){
+  
+		if ((BinStream[j] >= high)||(BinStream[j] <= low)){
+		  lastBit = j - *clk;    
+		  errCnt = 0;
+	  
       //loop through to see if this start location works
-      for (i = iii; i < *BitLen; ++i) {   
+      for (i = j; i < *BitLen; ++i) {   
         if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
-          lastBit+=*clk;
+          lastBit += *clk;
         } else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
           //low found and we are expecting a bar
-          lastBit+=*clk;
+          lastBit += *clk;
         } else {
           //mid value found or no bar supposed to be here
-          if ((i-lastBit)>(*clk+tol)){
+          if ((i-lastBit) > (*clk + tol)){
             //should have hit a high or low based on clock!!
            
             errCnt++;
-            lastBit+=*clk;//skip over until hit too many errors
-            if (errCnt>(maxErr)) break;  //allow 1 error for every 1000 samples else start over
+            lastBit += *clk;//skip over until hit too many errors
+            if (errCnt > maxErr) break;  //allow 1 error for every 1000 samples else start over
           }
         }
-        if ((i-iii) >(400 * *clk)) break; //got plenty of bits
+        if ((i-j) >(400 * *clk)) break; //got plenty of bits
       }
       //we got more than 64 good bits and not all errors
-      if ((((i-iii)/ *clk) > (64+errCnt)) && (errCnt<maxErr)) {
+      if ((((i-j)/ *clk) > (64 + errCnt)) && (errCnt < maxErr)) {
         //possible good read
-        if (errCnt==0){
-			bestStart=iii;
-			bestErrCnt=errCnt;
+        if (errCnt == 0){
+			bestStart = j;
+			bestErrCnt = errCnt;
 			break;  //great read - finish
         } 
-        if (errCnt<bestErrCnt){  //set this as new best run
-          bestErrCnt=errCnt;
-          bestStart = iii;
+        if (errCnt < bestErrCnt){  //set this as new best run
+          bestErrCnt = errCnt;
+          bestStart = j;
         }
       }
     }
   }
-  if (bestErrCnt<maxErr){
+  if (bestErrCnt < maxErr){
   	//best run is good enough set to best run and set overwrite BinStream
-  	iii=bestStart;
-  	lastBit=bestStart-*clk;
-  	bitnum=0;
-    for (i = iii; i < *BitLen; ++i) {   
-      if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
-        lastBit+=*clk;
-        BinStream[bitnum] =  *invert;
-        bitnum++;
-      } else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
-        //low found and we are expecting a bar
-        lastBit+=*clk;
-        BinStream[bitnum] = 1-*invert; 
-        bitnum++;
-      } else {
-        //mid value found or no bar supposed to be here
-        if ((i-lastBit)>(*clk+tol)){
-          //should have hit a high or low based on clock!!
-
-          if (bitnum > 0){
-            BinStream[bitnum]=77;
-            bitnum++;
-          }
-          
-          lastBit+=*clk;//skip over error
-        }
-      }
-      if (bitnum >=400) break;
-    }
-    *BitLen=bitnum;
-	} else{
-  	*invert=bestStart;
-  	*clk=iii;
-  	return -1; 
-  }	
+  	j = bestStart;
+  	lastBit = bestStart - *clk;
+  	bitnum = 0;
+    for (i = j; i < *BitLen; ++i) {   
+		if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
+			lastBit += *clk;
+			BinStream[bitnum] = *invert;
+			bitnum++;
+		} else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
+			//low found and we are expecting a bar
+			lastBit += *clk;
+			BinStream[bitnum] = 1 - *invert; 
+			bitnum++;
+		} else {
+			//mid value found or no bar supposed to be here
+			if ((i-lastBit) > (*clk+tol)){
+				//should have hit a high or low based on clock!!
+				if (bitnum > 0){
+					BinStream[bitnum] = 77;
+					bitnum++;
+				}
+				lastBit += *clk;//skip over error
+			}
+		}
+		if (bitnum >= 400) break;
+		}
+		*BitLen = bitnum;
+	} else {
+		*invert = bestStart;
+		*clk = j;
+		return -1; 
+	}	
   return bestErrCnt;
 }
 
 //by marshmellow
 //take 10 and 01 and manchester decode
 //run through 2 times and take least errCnt
-int manrawdecode(uint8_t * BitStream, int *bitLen)
+int manrawdecode(uint8_t * bits, int *bitlen)
 {
-  int bitnum=0;
-  int errCnt =0;
-  int i=1;
+  int bitnum = 0;
+  int errCnt = 0;
   int bestErr = 1000;
   int bestRun = 0;
-  int ii=1;
-  for (ii=1;ii<3;++ii){
-  	i=1;
-		for (i=i+ii;i<*bitLen-2;i+=2){
-		  if(BitStream[i]==1 && (BitStream[i+1]==0)){
-		  } else if((BitStream[i]==0)&& BitStream[i+1]==1){
-	    } else {
-		      errCnt++;
-	    }
-	    if(bitnum>300) break;
+  int i = 1;
+  int j = 1;
+
+	for (; j < 3; ++j){
+		i = 1;
+		for ( i = i + j; i < *bitlen-2; i += 2){
+			if ( bits[i]==1 && (bits[i+1]==0)){
+			} else if ((bits[i]==0)&& bits[i+1]==1){
+			} else {
+				errCnt++;
+			}
+			if(bitnum > 300) break;
 		}
-		if (bestErr>errCnt){
-		  bestErr=errCnt;
-		  bestRun=ii;
+		if (bestErr > errCnt){
+			bestErr = errCnt;
+			bestRun = j;
 		}	
-		errCnt=0;
-  }
-  errCnt=bestErr;
-  if (errCnt<20){
-  	ii=bestRun;
-  	i=1;
-		for (i=i+ii;i<*bitLen-2;i+=2){
-		  if(BitStream[i]==1 && (BitStream[i+1]==0)){
-		    BitStream[bitnum++]=0;
-		  } else if((BitStream[i]==0)&& BitStream[i+1]==1){
-		    BitStream[bitnum++]=1;
-	    } else {
-	      BitStream[bitnum++]=77;
-		      //errCnt++;
-	    }
-	    if(bitnum>300) break;
+		errCnt = 0;
+	}
+	errCnt = bestErr;
+	if (errCnt < 20){
+		j = bestRun;
+		i = 1;
+		for ( i = i+j; i < *bitlen-2; i += 2){
+			if ( bits[i] == 1 && bits[i + 1] == 0 ){
+					bits[bitnum++] = 0;
+			} else if ( bits[i] == 0 && bits[i + 1] == 1 ){
+					bits[bitnum++] = 1;
+			} else {
+				bits[bitnum++] = 77;
+			}
+			if ( bitnum > 300 ) break;
 		}
-  	*bitLen=bitnum;
+		*bitlen = bitnum;
 	}   
-  return errCnt;
+	return errCnt;
 }
 
 
 //by marshmellow
 //take 01 or 10 = 0 and 11 or 00 = 1
-int BiphaseRawDecode(uint8_t * BitStream, int *bitLen, int offset)
+int BiphaseRawDecode(uint8_t * bits, int *bitlen, int offset)
 {
-  uint8_t bitnum = 0;
-  uint32_t errCnt = 0;
-  uint32_t i = 1;
-  i=offset;
-	for (;i<*bitLen-2;i+=2){
-	  if((BitStream[i]==1 && BitStream[i+1]==0)||(BitStream[i]==0 && BitStream[i+1]==1)){
-	    BitStream[bitnum++]=1;
-	  } else if((BitStream[i]==0 && BitStream[i+1]==0)||(BitStream[i]==1 && BitStream[i+1]==1)){
-	    BitStream[bitnum++]=0;
-    } else {
-	    BitStream[bitnum++]=77;
-      errCnt++;
-    }
-    if(bitnum>250) break;
+	uint8_t bitnum = 0;
+	uint32_t errCnt = 0;
+	uint32_t i = offset;
+	
+	for (; i < *bitlen-2; i += 2 ){
+		if ( (bits[i]==1 && bits[i+1]==0)||
+			 (bits[i]==0 && bits[i+1]==1)){
+			bits[bitnum++] = 1;
+		} else if ( (bits[i]==0 && bits[i+1]==0)||
+					(bits[i]==1 && bits[i+1]==1)){
+			bits[bitnum++] = 0;
+		} else {
+			bits[bitnum++] = 77;
+			errCnt++;
+		}
+		if ( bitnum > 250) break;
 	}  
-  *bitLen=bitnum;
-  return errCnt;
+	*bitlen = bitnum;
+	return errCnt;
 }
 
 //by marshmellow
 //takes 2 arguments - clock and invert both as integers
 //attempts to demodulate ask only
 //prints binary found and saves in graphbuffer for further commands
-int askrawdemod(uint8_t *BinStream, int *bitLen,int *clk, int *invert)
+int askrawdemod(uint8_t *BinStream, int *bitLen, int *clk, int *invert)
 {
   uint32_t i;
- // int invert=0;  //invert default
+  uint32_t initLoopMax = 200;
   int high = 0, low = 128;
-  *clk=DetectASKClock(BinStream,*bitLen,*clk); //clock default
-  uint8_t BitStream[502] = {0};
-
-  if (*clk<8) *clk =64;
-  if (*clk<32) *clk=32;
+  uint8_t BitStream[502] = {0x00};
+  
+  *clk = DetectASKClock(BinStream, *bitLen, *clk); //clock default
+  
+  if (*clk < 8)		*clk = 64;	
+  if (*clk < 32)	*clk = 32;	
   if (*invert != 1) *invert = 0;
+
+  if (initLoopMax > *bitLen) 
+	initLoopMax = *bitLen;
   
-  uint32_t initLoopMax = 200;
-  if (initLoopMax>*bitLen) initLoopMax=*bitLen;
   // Detect high and lows 
   for (i = 0; i < initLoopMax; ++i) //200 samples should be plenty to find high and low values
   {
     if (BinStream[i] > high)
-      high = BinStream[i];
+		high = BinStream[i];
     else if (BinStream[i] < low)
-      low = BinStream[i];
-  }
-  if ((high < 158)){  //throw away static
-    return -2;
+		low = BinStream[i];
   }
-  //25% fuzz in case highs and lows aren't clipped [marshmellow]
-  high=(int)((high-128)*.75)+128;
-  low= (int)((low-128)*.75)+128;
-
-  int lastBit = 0;  //set first clock check
-  uint32_t bitnum = 0;     //output counter
-  uint8_t tol = 0;  //clock tolerance adjust - waves will be accepted as within the clock if they fall + or - this value + clock from last valid wave
-  if (*clk==32) tol=1;    //clock tolerance may not be needed anymore currently set to + or - 1 but could be increased for poor waves or removed entirely 
-  uint32_t iii = 0;
+  
+  //throw away static
+	if ((high < 158)){  
+		return -2;
+	}
+  
+	//25% fuzz in case highs and lows aren't clipped [marshmellow]
+	high = (int)(high * .75);
+	low  = (int)(low+128 * .25);
+
+  int lastBit = 0;			//set first clock check
+  uint32_t bitnum = 0;		//output counter
+  
+  uint8_t tol = 0;			//clock tolerance adjust - waves will be accepted as within the clock if they fall + or - this value + clock from last valid wave
+  if (*clk==32) tol = 1;	//clock tolerance may not be needed anymore currently set to + or - 1 but could be increased for poor waves or removed entirely 
+
   uint32_t gLen = *bitLen;
-  if (gLen > 500) gLen=500;
-  uint8_t errCnt =0;
-  uint32_t bestStart = *bitLen;
-  uint32_t bestErrCnt = (*bitLen/1000);
-  uint8_t midBit=0;
+  if (gLen > 500) gLen = 500;
 
+  uint32_t j = 0;
+  uint8_t errCnt = 0;
+  uint32_t bestStart = *bitLen;
+  uint32_t bestErrCnt = (*bitLen / 1000);
+  uint32_t errCntLimit = bestErrCnt;
+  uint8_t midBit = 0;
+  
   //loop to find first wave that works
-  for (iii=0; iii < gLen; ++iii){
-    if ((BinStream[iii]>=high)||(BinStream[iii]<=low)){
-      lastBit=iii-*clk;    
+  for (j = 0; j < gLen; ++j){
+  
+    if ((BinStream[j] >= high)||(BinStream[j] <= low)){
+      lastBit = j - *clk;    
       //loop through to see if this start location works
-      for (i = iii; i < *bitLen; ++i) {  
+      for (i = j; i < *bitLen; ++i) {  
         if ((BinStream[i] >= high) && ((i-lastBit)>(*clk-tol))){
-          lastBit+=*clk;
+          lastBit += *clk;
           BitStream[bitnum] =  *invert;
           bitnum++;
-          midBit=0;
+          midBit = 0;
         } else if ((BinStream[i] <= low) && ((i-lastBit)>(*clk-tol))){
           //low found and we are expecting a bar
-          lastBit+=*clk;
+          lastBit += *clk;
           BitStream[bitnum] = 1-*invert; 
           bitnum++;
           midBit=0;
         } else if ((BinStream[i]<=low) && (midBit==0) && ((i-lastBit)>((*clk/2)-tol))){
           //mid bar?
-          midBit=1;
-          BitStream[bitnum]= 1-*invert;
+          midBit = 1;
+          BitStream[bitnum] = 1 - *invert;
           bitnum++;
         } else if ((BinStream[i]>=high)&&(midBit==0) && ((i-lastBit)>((*clk/2)-tol))){
           //mid bar?
-          midBit=1;
-          BitStream[bitnum]= *invert;
+          midBit = 1;
+          BitStream[bitnum] = *invert;
           bitnum++;
         } else if ((i-lastBit)>((*clk/2)+tol)&&(midBit==0)){
           //no mid bar found
-          midBit=1;
-          BitStream[bitnum]= BitStream[bitnum-1];
+          midBit = 1;
+          BitStream[bitnum] = BitStream[bitnum-1];
           bitnum++;
         } else {
           //mid value found or no bar supposed to be here
 
-          if ((i-lastBit)>(*clk+tol)){
+          if (( i - lastBit) > ( *clk + tol)){
             //should have hit a high or low based on clock!!
 
             if (bitnum > 0){
-              BitStream[bitnum]=77;
+              BitStream[bitnum] = 77;
               bitnum++;
             }
 
             errCnt++;
-            lastBit+=*clk;//skip over until hit too many errors
-            if (errCnt>((*bitLen/1000))){  //allow 1 error for every 1000 samples else start over
-              errCnt=0;
-              bitnum=0;//start over
+            lastBit += *clk;//skip over until hit too many errors
+            if (errCnt > errCntLimit){  //allow 1 error for every 1000 samples else start over
+              errCnt = 0;
+              bitnum = 0;//start over
               break;
             }
           }          
         }
-        if (bitnum>500) break;
+        if (bitnum > 500) break;
       }
       //we got more than 64 good bits and not all errors
-      if ((bitnum > (64+errCnt)) && (errCnt<(*bitLen/1000))) {
-        //possible good read
-        if (errCnt==0) break;  //great read - finish
-        if (bestStart == iii) break;  //if current run == bestErrCnt run (after exhausted testing) then finish 
-        if (errCnt<bestErrCnt){  //set this as new best run
-          bestErrCnt=errCnt;
-          bestStart = iii;
+	  //possible good read
+      if ((bitnum > (64 + errCnt)) && (errCnt < errCntLimit)) {
+
+		//great read - finish
+        if (errCnt == 0) break;  
+		
+		//if current run == bestErrCnt run (after exhausted testing) then finish 
+        if (bestStart == j) break;  
+        
+		//set this as new best run
+		if (errCnt < bestErrCnt){
+          bestErrCnt = errCnt;
+          bestStart = j;
         }
       }
     }
-    if (iii>=gLen){ //exhausted test
+    if (j >= gLen){ //exhausted test
       //if there was a ok test go back to that one and re-run the best run (then dump after that run)
-      if (bestErrCnt < (*bitLen/1000)) iii=bestStart;
+      if (bestErrCnt < errCntLimit) 
+		j = bestStart;
     }
   }
-	if (bitnum>16){
+	if (bitnum > 16){
 
-		for (i=0; i < bitnum; ++i){
-			BinStream[i]=BitStream[i];
+		for (i = 0; i < bitnum; ++i){
+			BinStream[i] = BitStream[i];
 		}
 		*bitLen = bitnum;
 	} else {
@@ -403,43 +432,49 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow
 {
 	uint32_t last_transition = 0;
 	uint32_t idx = 1;
-	uint32_t maxVal=0;
-	if (fchigh==0) fchigh=10;
-	if (fclow==0) fclow=8;
+	uint32_t maxVal = 0;
+	
+	if (fchigh == 0) fchigh = 10;
+	if (fclow == 0) fclow = 8;
+	
 	// we do care about the actual theshold value as sometimes near the center of the
 	// wave we may get static that changes direction of wave for one value
 	// if our value is too low it might affect the read.  and if our tag or
 	// antenna is weak a setting too high might not see anything. [marshmellow]
-	if (size<100) return 0;
-	for(idx=1; idx<100; idx++){
-    if(maxVal<dest[idx]) maxVal = dest[idx];
-  }
+	if ( size < 100)
+		return 0;
+	
+	// Find high from first 100 samples
+	for ( idx = 1; idx < 100; idx++ ){
+		if ( maxVal < dest[idx]) 
+			maxVal = dest[idx];
+	}
+	
     // set close to the top of the wave threshold with 25% margin for error
     // less likely to get a false transition up there. 
     // (but have to be careful not to go too high and miss some short waves)
-	uint8_t threshold_value = (uint8_t)(((maxVal-128)*.75)+128); 
+	uint8_t threshold_value = (uint8_t)(maxVal * .75);
 	
 	// sync to first lo-hi transition, and threshold
 	// Need to threshold first sample
 	
-	if(dest[0] < threshold_value) dest[0] = 0;
-	else dest[0] = 1;
+	dest[0] = (dest[0] < threshold_value) ? 0 : 1;
 
 	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
 	// between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
 	for(idx = 1; idx < size; idx++) {
-		// threshold current value
 
-		if (dest[idx] < threshold_value) dest[idx] = 0;
-		else dest[idx] = 1;
+		// threshold current value
+		dest[idx] = (dest[idx] < threshold_value) ? 0 : 1;
 
 		// Check for 0->1 transition
 		if (dest[idx-1] < dest[idx]) { // 0 -> 1 transition
-			if ((idx-last_transition)<(fclow-2)){            //0-5 = garbage noise
+			if ( ( idx - last_transition ) <( fclow - 2 ) ) {      //0-5 = garbage noise
 				//do nothing with extra garbage
-			} else if ((idx-last_transition) < (fchigh-1)) { //6-8 = 8 waves
+			} else if ((idx - last_transition) < ( fchigh - 1 )) { //6-8 = 8 waves
 				dest[numBits]=1;
 			} else {							//9+ = 10 waves
 				dest[numBits]=0;
@@ -448,7 +483,8 @@ size_t fsk_wave_demod(uint8_t * dest, size_t size, uint8_t fchigh, uint8_t fclow
 			numBits++;
 		}
 	}
-	return numBits; //Actually, it returns the number of bytes, but each byte represents a bit: 1 or 0
+	//it returns the number of bytes, but each byte represents a bit: 1 or 0
+	return numBits; 
 }
 
 uint32_t myround2(float f)
@@ -458,87 +494,90 @@ uint32_t myround2(float f)
 }
 
 //translate 11111100000 to 10 
-size_t aggregate_bits(uint8_t *dest,size_t size,  uint8_t rfLen, uint8_t maxConsequtiveBits, uint8_t invert,uint8_t fchigh,uint8_t fclow )// uint8_t h2l_crossing_value,uint8_t l2h_crossing_value, 
+size_t aggregate_bits(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t maxConsequtiveBits, uint8_t invert, uint8_t fchigh, uint8_t fclow )
 {
-	uint8_t lastval=dest[0];
-	uint32_t idx=0;
-	size_t numBits=0;
-	uint32_t n=1;
+	uint8_t lastval = dest[0];
+	uint32_t idx = 0;
+	uint32_t n = 1;
+	size_t numBits = 0;
 
-	for( idx=1; idx < size; idx++) {
+	for( idx = 1; idx < size; idx++) {
 
-		if (dest[idx]==lastval) {
+		if (dest[idx] == lastval) {
 			n++;
 			continue;
 		}
 		//if lastval was 1, we have a 1->0 crossing
-		if ( dest[idx-1]==1 ) {
-			n=myround2((float)(n+1)/((float)(rfLen)/(float)fclow));
-			//n=(n+1) / h2l_crossing_value;
-		} else {// 0->1 crossing
-			n=myround2((float)(n+1)/((float)(rfLen-2)/(float)fchigh));  //-2 for fudge factor
-			//n=(n+1) / l2h_crossing_value;
+		if ( dest[idx-1] == 1 ) {
+			n = myround2( (float)( n + 1 ) / ((float)(rfLen)/(float)fclow));
+		} else { // 0->1 crossing
+			n = myround2( (float)( n + 1 ) / ((float)(rfLen-2)/(float)fchigh));  //-2 for fudge factor
 		}
 		if (n == 0) n = 1;
 
 		if(n < maxConsequtiveBits) //Consecutive 
 		{
-			if(invert==0){ //invert bits 
+			if(invert == 0){ //invert bits 
 				memset(dest+numBits, dest[idx-1] , n);
 			}else{
 				memset(dest+numBits, dest[idx-1]^1 , n);	
 			}			
 			numBits += n;
 		}
-		n=0;
-		lastval=dest[idx];
+		n = 0;
+		lastval = dest[idx];
 	}//end for
 	return numBits;
 }
+
 //by marshmellow  (from holiman's base)
 // full fsk demod from GraphBuffer wave to decoded 1s and 0s (no mandemod)
 int fskdemod(uint8_t *dest, size_t size, uint8_t rfLen, uint8_t invert, uint8_t fchigh, uint8_t fclow)
 {
-  // FSK demodulator
-  size = fsk_wave_demod(dest, size, fchigh, fclow);
-  size = aggregate_bits(dest, size,rfLen,192,invert,fchigh,fclow);
-  return size;
+	// FSK demodulator
+	size = fsk_wave_demod(dest, size, fchigh, fclow);
+	if ( size > 0 )
+		size = aggregate_bits(dest, size, rfLen, 192, invert, fchigh, fclow);
+	return size;
 }
+
 // loop to get raw HID waveform then FSK demodulate the TAG ID from it
 int HIDdemodFSK(uint8_t *dest, size_t size, uint32_t *hi2, uint32_t *hi, uint32_t *lo)
 {
-	
-	size_t idx=0; //, found=0; //size=0,
+	size_t idx = 0;
+	int numshifts = 0;
+
 	// FSK demodulator
-	size = fskdemod(dest, size,50,0,10,8);
+	size = fskdemod(dest, size, 50, 0, 10, 8);
 
 	// final loop, go over previously decoded manchester data and decode into usable tag ID
 	// 111000 bit pattern represent start of frame, 01 pattern represents a 1 and 10 represents a 0
 	uint8_t frame_marker_mask[] = {1,1,1,0,0,0};
-	int numshifts = 0;
-	idx = 0;
+
+	uint8_t mask_len =  sizeof frame_marker_mask /  sizeof frame_marker_mask[0];
+	
 	//one scan
-	while( idx + sizeof(frame_marker_mask) < size) {
+	while( idx + mask_len < size) {
 	// search for a start of frame marker
 		if ( memcmp(dest+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0)
 		{ // frame marker found
-			idx+=sizeof(frame_marker_mask);
+			idx += mask_len;
 			while(dest[idx] != dest[idx+1] && idx < size-2)
 			{	
 				// Keep going until next frame marker (or error)
 				// Shift in a bit. Start by shifting high registers
-				*hi2 = (*hi2<<1)|(*hi>>31);
-				*hi = (*hi<<1)|(*lo>>31);
+				*hi2 = ( *hi2 << 1 ) | ( *hi >> 31 );
+				*hi = ( *hi << 1 ) | ( *lo >> 31 );
 				//Then, shift in a 0 or one into low
 				if (dest[idx] && !dest[idx+1])	// 1 0
-					*lo=(*lo<<1)|0;
+					*lo = ( *lo << 1 ) | 0;
 				else // 0 1
-					*lo=(*lo<<1)|1;
+					*lo = ( *lo << 1 ) | 1;
 				numshifts++;
 				idx += 2;
 			}
 			// Hopefully, we read a tag and	 hit upon the next frame marker
-			if(idx + sizeof(frame_marker_mask) < size)
+			if(idx + mask_len < size)
 			{
 				if ( memcmp(dest+idx, frame_marker_mask, sizeof(frame_marker_mask)) == 0)
 				{
@@ -556,10 +595,12 @@ int HIDdemodFSK(uint8_t *dest, size_t size, uint32_t *hi2, uint32_t *hi, uint32_
 	return -1;
 }
 
-uint32_t bytebits_to_byte(uint8_t* src, int numbits)
+uint32_t bytebits_to_byte(uint8_t *src, int numbits)
 {
+	//HACK:  potential overflow in numbits is larger then uint32 bits.
+	
 	uint32_t num = 0;
-	for(int i = 0 ; i < numbits ; i++)	{
+	for(int i = 0 ; i < numbits ; ++i)	{
 		num = (num << 1) | (*src);
 		src++;
 	}
@@ -568,41 +609,54 @@ uint32_t bytebits_to_byte(uint8_t* src, int numbits)
 
 int IOdemodFSK(uint8_t *dest, size_t size)
 {
-  uint32_t idx=0;
 	//make sure buffer has data
-	if (size < 66) return -1;
+	if (size < 100) return -1;
+	
+	uint32_t idx = 0;
+	uint8_t testMax = 0;
+	
 	//test samples are not just noise
-	uint8_t testMax=0;
-	for(idx=0;idx<65;idx++){
-		if (testMax<dest[idx]) testMax=dest[idx];
+	for (; idx < 65; ++idx ){
+		if (testMax < dest[idx])
+			testMax = dest[idx];
+	}
+
+	//if not, just noise
+	if (testMax < 20) return -2;
+		
+	// FSK demodulator
+	size = fskdemod(dest, size, 64, 1, 10, 8);  //  RF/64 and invert
+	
+	//did we get a good demod?
+	if (size < 65) return -3;
+	
+	//Index map
+	//0           10          20          30          40          50          60
+	//|           |           |           |           |           |           |
+	//01234567 8 90123456 7 89012345 6 78901234 5 67890123 4 56789012 3 45678901 23
+	//-----------------------------------------------------------------------------
+	//00000000 0 11110000 1 facility 1 version* 1 code*one 1 code*two 1 ???????? 11
+	//
+	//XSF(version)facility:codeone+codetwo
+	//Handle the data
+	
+	uint8_t mask[] = {0,0,0,0,0,0,0,0,0,1};
+	
+	for( idx = 0; idx < (size - 65); ++idx) {
+	if ( memcmp(dest + idx, mask, sizeof(mask))==0) {
+		//frame marker found
+		if (!dest[idx+8] && 
+			dest[idx+17] == 1 &&
+			dest[idx+26] == 1 &&
+			dest[idx+35] == 1 &&
+			dest[idx+44] == 1 &&
+			dest[idx+53] == 1){
+				//confirmed proper separator bits found
+				//return start position
+				return (int) idx;
+			}
+		}		
 	}
-	idx=0;
-	//if not just noise
-	if (testMax>170){
-		// FSK demodulator
-		size = fskdemod(dest, size,64,1,10,8);  //  RF/64 and invert
-		if (size < 65) return -1;  //did we get a good demod?
-		//Index map
-		//0           10          20          30          40          50          60
-		//|           |           |           |           |           |           |
-		//01234567 8 90123456 7 89012345 6 78901234 5 67890123 4 56789012 3 45678901 23
-		//-----------------------------------------------------------------------------
-		//00000000 0 11110000 1 facility 1 version* 1 code*one 1 code*two 1 ???????? 11
-		//
-		//XSF(version)facility:codeone+codetwo
-		//Handle the data
- 	  uint8_t mask[] = {0,0,0,0,0,0,0,0,0,1};
-		for( idx=0; idx < (size - 65); idx++) {
-    	if ( memcmp(dest + idx, mask, sizeof(mask))==0) {
-    		//frame marker found
-    		if (!dest[idx+8] && dest[idx+17]==1 && dest[idx+26]==1 && dest[idx+35]==1 && dest[idx+44]==1 && dest[idx+53]==1){
-    			//confirmed proper separator bits found
-    			//return start position
-					return (int) idx;
-				}
-			}		
-		}
-	}	
 	return 0;
 }
 
@@ -611,67 +665,86 @@ int IOdemodFSK(uint8_t *dest, size_t size)
 // maybe somehow adjust peak trimming value based on samples to fix?
 int DetectASKClock(uint8_t dest[], size_t size, int clock)
 {
-  int i=0;
-  int peak=0;
-  int low=128;
-  int clk[]={16,32,40,50,64,100,128,256};
-  int loopCnt = 256;  //don't need to loop through entire array...
-  if (size<loopCnt) loopCnt = size;
-
-  //if we already have a valid clock quit
-  for (;i<8;++i)
-  	if (clk[i]==clock) return clock;
-
-  //get high and low peak
-  for (i=0;i<loopCnt;++i){
-    if(dest[i]>peak){
-      peak = dest[i]; 
-    }
-    if(dest[i]<low){
-      low = dest[i];
-    }
-  }
-  peak=(int)((peak-128)*.75)+128;
-  low= (int)((low-128)*.75)+128;
-  int ii;
-  int clkCnt;
-  int tol = 0;
-  int bestErr=1000;
-  int errCnt[]={0,0,0,0,0,0,0,0};
-  //test each valid clock from smallest to greatest to see which lines up
-  for(clkCnt=0; clkCnt<6;++clkCnt){
-    if (clk[clkCnt]==32){
-      tol=1;
-    }else{
-      tol=0;
-    }
-    bestErr=1000;
-    //try lining up the peaks by moving starting point (try first 256) 
-    for (ii=0; ii<loopCnt; ++ii){
-      if ((dest[ii]>=peak) || (dest[ii]<=low)){
-        errCnt[clkCnt]=0;
-        // now that we have the first one lined up test rest of wave array
-        for (i=0; i<((int)(size/clk[clkCnt])-1); ++i){
-          if (dest[ii+(i*clk[clkCnt])]>=peak || dest[ii+(i*clk[clkCnt])]<=low){
-          }else if(dest[ii+(i*clk[clkCnt])-tol]>=peak || dest[ii+(i*clk[clkCnt])-tol]<=low){
-          }else if(dest[ii+(i*clk[clkCnt])+tol]>=peak || dest[ii+(i*clk[clkCnt])+tol]<=low){
-          }else{  //error no peak detected
-            errCnt[clkCnt]++;
-          }    
-        }
-        //if we found no errors this is correct one - return this clock
-        if(errCnt[clkCnt]==0) return clk[clkCnt];
-        //if we found errors see if it is lowest so far and save it as best run
-        if(errCnt[clkCnt]<bestErr) bestErr=errCnt[clkCnt];
-      }
-    } 
-  }
-  int iii=0;
-  int best=0;
-  for (iii=0; iii<6;++iii){
-    if (errCnt[iii]<errCnt[best]){
-      best = iii;
-    }
-  }
-  return clk[best];
+	int i = 0;
+	int clk[] = {16,32,40,50,64,100,128,256};
+	uint8_t clkLen = sizeof clk / sizeof clk[0];
+	
+	//if we already have a valid clock quit
+	for (; i < clkLen; ++i)
+		if (clk[i] == clock) 
+			return clock;
+			
+	int peak = 0;
+	int low = 128;	
+	int loopCnt = 256;
+	if (size < loopCnt) 
+		loopCnt = size;
+	
+	//get high and low peak
+	for ( i = 0; i < loopCnt; ++i ){
+		if(dest[i] > peak) 
+			peak = dest[i]; 
+		if(dest[i] < low) 
+			low = dest[i];
+	}
+
+	peak = (int)(peak * .75);
+	low  = (int)(low+128 * .25);
+ 
+	int ii, cnt, bestErr, tol = 0;
+	int errCnt[clkLen];
+	memset(errCnt, 0x00, clkLen);
+	
+	int tmpIndex, tmphigh, tmplow;
+	
+	//test each valid clock from smallest to greatest to see which lines up
+	for( cnt = 0; cnt < clkLen; ++cnt ){
+
+		tol = (clk[cnt] == 32) ? 1 : 0;
+		bestErr = 1000;
+		tmpIndex = tmphigh = tmplow = 0;
+
+		//try lining up the peaks by moving starting point (try first 256) 
+		for (ii=0; ii < loopCnt; ++ii){
+		
+			// not a peak? continue
+			if ( (dest[ii] < peak) && (dest[ii] > low)) 
+				continue;
+
+			errCnt[cnt] = 0;
+			
+			// now that we have the first one lined up test rest of wave array
+			for ( i = 0; i < ((int)(size / clk[cnt]) - 1); ++i){
+			  
+				tmpIndex = ii + (i * clk[cnt] );
+				tmplow  = dest[ tmpIndex - tol];
+				tmphigh = dest[ tmpIndex + tol];
+				
+				if ( dest[tmpIndex] >= peak || dest[tmpIndex] <= low ) {
+				}
+				else if ( tmplow >= peak || tmplow <= low){
+				}					
+				else if ( tmphigh >= peak || tmphigh <= low){
+				}
+				else 
+					errCnt[cnt]++; //error no peak detected
+			}
+
+			//if we found no errors this is correct one - return this clock
+			if ( errCnt[cnt] == 0 )
+				return clk[cnt];
+
+			if ( errCnt[cnt] < bestErr) 
+				bestErr = errCnt[cnt];
+		}
+		// save the least error.
+		errCnt[cnt] = bestErr;
+	}
+	// find best clock which has lowest number of errors
+	int j = 0, bestIndex = 0;
+	for (; j < clkLen; ++j){
+		if ( errCnt[j] < errCnt[bestIndex] )
+			bestIndex = j;
+	}
+	return clk[bestIndex];
 }