Improved askdemod to detect transitions from peak to peak, instead of zero-crossings, works much better for more tag types (all tags in the traces directory at least).

Now just use "askdemod 1" or "askdemod 0" and do not give the clock rate as argument (not necessary anymore)

winsrc/command.cpp

@@ -211,10 +211,10 @@ int CmdClearGraph(int redraw)
 {
 	int gtl = GraphTraceLen;
 	GraphTraceLen = 0;
-	
+
 	if (redraw)
 		RepaintGraphWindow();
-	
+
 	return gtl;
 }
 
@@ -225,8 +225,8 @@ static void CmdAppendGraph(int redraw, int clock, int bit)
 
 	for (i = 0; i < (int)(clock/2); i++)
 		GraphBuffer[GraphTraceLen++] = bit ^ 1;
-	
+
-	for (i = (int)(clock/2); i < clock; i++)	
+	for (i = (int)(clock/2); i < clock; i++)
 		GraphBuffer[GraphTraceLen++] = bit;
 
 	if (redraw)
@@ -240,7 +240,7 @@ static void CmdEM410xwatch(char *str)
 	char *zero = "";
 	char *twok = "2000";
 	go = 1;
-	
+
 	do
 	{
 		CmdLoread(zero);
@@ -264,7 +264,7 @@ static void CmdEM410xread(char *str)
 	char id[11];
 	int BitStream[MAX_GRAPH_TRACE_LEN];
 	high = low = 0;
-	
+
 	/* Detect high and lows and clock */
 	for (i = 0; i < GraphTraceLen; i++)
 	{
@@ -272,15 +272,15 @@ static void CmdEM410xread(char *str)
 			high = GraphBuffer[i];
 		else if (GraphBuffer[i] < low)
 			low = GraphBuffer[i];
-	}	
+	}
-	
+
 	/* get clock */
 	clock = GetClock(str, high);
-	
+
 	/* parity for our 4 columns */
 	parity[0] = parity[1] = parity[2] = parity[3] = 0;
 	header = rows = 0;
-	
+
 	/* manchester demodulate */
 	bit = bit2idx = 0;
 	for (i = 0; i < (int)(GraphTraceLen / clock); i++)
@@ -288,7 +288,7 @@ static void CmdEM410xread(char *str)
 		hithigh = 0;
 		hitlow = 0;
 		first = 1;
-		
+
 		/* Find out if we hit both high and low peaks */
 		for (j = 0; j < clock; j++)
 		{
@@ -296,25 +296,25 @@ static void CmdEM410xread(char *str)
 				hithigh = 1;
 			else if (GraphBuffer[(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;
-		
+
 		BitStream[bit2idx++] = bit;
 	}
-	
+
 	/* We go till 5 before the graph ends because we'll get that far below */
 	for (i = 1; i < bit2idx - 5; i++)
 	{
@@ -327,29 +327,29 @@ static void CmdEM410xread(char *str)
 				/* Read another byte! */
 				sprintf(id+rows, "%x", (8 * BitStream[i]) + (4 * BitStream[i+1]) + (2 * BitStream[i+2]) + (1 * BitStream[i+3]));
 				rows++;
-				
+
 				/* Keep parity info */
 				parity[0] ^= BitStream[i];
 				parity[1] ^= BitStream[i+1];
 				parity[2] ^= BitStream[i+2];
 				parity[3] ^= BitStream[i+3];
-				
+
 				/* Move 4 bits ahead */
 				i += 4;
 			}
-			
+
 			/* Damn, something wrong! reset */
 			else
 			{
 				PrintToScrollback("Thought we had a valid tag but failed at word %d (i=%d)", rows + 1, i);
-				
+
 				/* Start back rows * 5 + 9 header bits, -1 to not start at same place */
 				i -= 9 + (5 * rows) - 5;
 
 				rows = header = 0;
 			}
 		}
-		
+
 		/* Step 3: Got our 40 bits! confirm column parity */
 		else if (rows == 10)
 		{
@@ -360,29 +360,29 @@ static void CmdEM410xread(char *str)
 			{
 				/* Sweet! */
 				PrintToScrollback("EM410x Tag ID: %s", id);
-				
+
 				/* Stop any loops */
 				go = 0;
 				break;
 			}
-			
+
 			/* Crap! Incorrect parity or no stop bit, start all over */
 			else
 			{
 				rows = header = 0;
-				
+
 				/* Go back 59 bits (9 header bits + 10 rows at 4+1 parity) */
 				i -= 59;
 			}
 		}
-				
+
 		/* Step 1: get our header */
 		else if (header < 9)
 		{
 			/* Need 9 consecutive 1's */
 			if (BitStream[i] == 1)
 				header++;
-			
+
 			/* We don't have a header, not enough consecutive 1 bits */
 			else
 				header = 0;
@@ -402,20 +402,20 @@ static void CmdEM410xsim(char *str)
 {
 	int i, n, j, h, binary[4], parity[4];
 	char *s = "0";
-	
+
 	/* clock is 64 in EM410x tags */
 	int clock = 64;
-	
+
 	/* clear our graph */
 	CmdClearGraph(0);
-	
+
 	/* write it out a few times */
 	for (h = 0; h < 4; h++)
 	{
 		/* write 9 start bits */
 		for (i = 0; i < 9; i++)
 			CmdAppendGraph(0, clock, 1);
-		
+
 		/* for each hex char */
 		parity[0] = parity[1] = parity[2] = parity[3] = 0;
 		for (i = 0; i < 10; i++)
@@ -424,36 +424,36 @@ static void CmdEM410xsim(char *str)
 			sscanf(&str[i], "%1x", &n);
 			for (j = 3; j >= 0; j--, n/= 2)
 				binary[j] = n % 2;
-			
+
 			/* append each bit */
 			CmdAppendGraph(0, clock, binary[0]);
 			CmdAppendGraph(0, clock, binary[1]);
 			CmdAppendGraph(0, clock, binary[2]);
 			CmdAppendGraph(0, clock, binary[3]);
-			
+
 			/* append parity bit */
 			CmdAppendGraph(0, clock, binary[0] ^ binary[1] ^ binary[2] ^ binary[3]);
-			
+
 			/* keep track of column parity */
 			parity[0] ^= binary[0];
 			parity[1] ^= binary[1];
 			parity[2] ^= binary[2];
 			parity[3] ^= binary[3];
 		}
-		
+
 		/* parity columns */
 		CmdAppendGraph(0, clock, parity[0]);
 		CmdAppendGraph(0, clock, parity[1]);
 		CmdAppendGraph(0, clock, parity[2]);
 		CmdAppendGraph(0, clock, parity[3]);
-		
+
 		/* stop bit */
 		CmdAppendGraph(0, clock, 0);
 	}
-	
+
 	/* modulate that biatch */
 	Cmdmanchestermod(s);
-	
+
 	/* booyah! */
 	RepaintGraphWindow();
 
@@ -463,7 +463,7 @@ static void CmdEM410xsim(char *str)
 static void ChkBitstream(char *str)
 {
 	int i;
-	
+
 	/* convert to bitstream if necessary */
 	for (i = 0; i < (int)(GraphTraceLen / 2); i++)
 	{
@@ -479,10 +479,10 @@ static void CmdLosim(char *str)
 {
 	int i;
 	char *zero = "0";
-	
+
 	/* convert to bitstream if necessary */
 	ChkBitstream(str);
-	
+
 	for (i = 0; i < GraphTraceLen; i += 48) {
 		UsbCommand c;
 		int j;
@@ -1822,60 +1822,54 @@ static void CmdFlexdemod(char *str)
 }
 
 /*
- * Generic command to demodulate ASK. bit length in argument.
+ * Generic command to demodulate ASK.
- * Giving the bit length helps discriminate ripple effects
- * upon zero crossing for noisy traces.
  *
- * Second is convention: positive or negative (High mod means zero
+ * Argument is convention: positive or negative (High mod means zero
  * or high mod means one)
  *
  * Updates the Graph trace with 0/1 values
  *
  * Arguments:
- * sl : bit length in terms of number of samples per bit
- *      (use yellow/purple markers to compute).
  * c : 0 or 1
  */
 
 static void Cmdaskdemod(char *str) {
 	int i;
-	int sign = 1;
 	int n = 0;
-	int c = 0;
+	int c,high,low = 0;
-	int t1 = 0;
 
 	// TODO: complain if we do not give 2 arguments here !
-	sscanf(str, "%i %i", &n, &c);
+	sscanf(str, "%i", &c);
-	if (c == 0) {
+
-		c = 1 ;
+	/* Detect high and lows and clock */
-	} else {
+	for (i = 0; i < GraphTraceLen; i++)
-		c = -1;
+	{
+		if (GraphBuffer[i] > high)
+			high = GraphBuffer[i];
+		else if (GraphBuffer[i] < low)
+			low = GraphBuffer[i];
 	}
 
-	if (GraphBuffer[0]*c > 0) {
+	if (GraphBuffer[0] > 0) {
-		GraphBuffer[0] = 1;
+		GraphBuffer[0] = 1-c;
 	} else {
-		GraphBuffer[0] = 0;
+		GraphBuffer[0] = c;
 	}
 	for(i=1;i<GraphTraceLen;i++) {
-		/* Analyse signal within the symbol length */
+		/* Transitions are detected at each peak
-		/* Decide if we crossed a zero */
+		 * Transitions are either:
-		if (GraphBuffer[i]*sign < 0) {
+		 * - we're low: transition if we hit a high
-			 /* Crossed a zero, check if this is a ripple or not */
+		 * - we're high: transition if we hit a low
-			if ( (i-t1) > n/4 ) {
+		 * (we need to do it this way because some tags keep high or
-				sign = -sign;
+		 * low for long periods, others just reach the peak and go
-				t1=i;
+		 * down)
-				if (GraphBuffer[i]*c > 0){
+		 */
-					GraphBuffer[i]=1;
+		if ((GraphBuffer[i]==high) && (GraphBuffer[i-1] == c)) {
-				} else {
+					GraphBuffer[i]=1-c;
-					GraphBuffer[i]=0;
+		} else if ((GraphBuffer[i]==low) && (GraphBuffer[i-1] == (1-c))){
-				}
+			GraphBuffer[i] = c;
-			} else {
-			/* This is a ripple, set the current sample value
-			   to the same as previous */
-				GraphBuffer[i] = GraphBuffer[i-1];
-			}
 		} else {
+			/* No transition */
 			GraphBuffer[i] = GraphBuffer[i-1];
 		}
 	}
@@ -1917,7 +1911,7 @@ int detectclock(int peak)
 			lastpeak = i;
 		}
 	}
-	
+
 	return clock;
 }
 
@@ -1925,7 +1919,7 @@ int detectclock(int peak)
 int GetClock(char *str, int peak)
 {
 	int clock;
-	
+
 	sscanf(str, "%i", &clock);
 	if (!strcmp(str, ""))
 		clock = 0;
@@ -1934,12 +1928,12 @@ int GetClock(char *str, int peak)
 	if (!clock)
 	{
 		clock = detectclock(peak);
-		
+
 		/* Only print this message if we're not looping something */
 		if (!go)
 			PrintToScrollback("Auto-detected clock rate: %d", clock);
 	}
-	
+
 	return clock;
 }
 
@@ -1966,16 +1960,16 @@ static void Cmdbitstream(char *str) {
 
 	/* Get our clock */
 	clock = GetClock(str, high);
-	
+
 	gtl = CmdClearGraph(0);
-	
+
 	bit = 0;
 	for (i = 0; i < (int)(gtl / clock); i++)
 	{
 		hithigh = 0;
 		hitlow = 0;
 		first = 1;
-		
+
 		/* Find out if we hit both high and low peaks */
 		for (j = 0; j < clock; j++)
 		{
@@ -1983,18 +1977,18 @@ static void Cmdbitstream(char *str) {
 				hithigh = 1;
 			else if (GraphBuffer[(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;
@@ -2015,7 +2009,7 @@ static void Cmdmanchestermod(char *str)
 	int i, j;
 	int clock;
 	int bit, lastbit, wave;
-	
+
 	/* Get our clock */
 	clock = GetClock(str, 0);
 
@@ -2024,17 +2018,17 @@ static void Cmdmanchestermod(char *str)
 	for (i = 0; i < (int)(GraphTraceLen / clock); i++)
 	{
 		bit = GraphBuffer[i * clock] ^ 1;
-		
+
 		for (j = 0; j < (int)(clock/2); j++)
 			GraphBuffer[(i * clock) + j] = bit ^ lastbit ^ wave;
 		for (j = (int)(clock/2); j < clock; j++)
 			GraphBuffer[(i * clock) + j] = bit ^ lastbit ^ wave ^ 1;
-		
+
 		/* Keep track of how we start our wave and if we changed or not this time */
 		wave ^= bit ^ lastbit;
 		lastbit = bit;
 	}
-	
+
 	RepaintGraphWindow();
 }
 
@@ -2084,9 +2078,9 @@ static void Cmdmanchesterdemod(char *str) {
 
 	/* Get our clock */
 	clock = GetClock(str, high);
-	
+
 	int tolerance = clock/4;
-	
+
 	/* Detect first transition */
 	/* Lo-Hi (arbitrary)       */
 	for (i = 0; i < GraphTraceLen; i++)
@@ -2101,8 +2095,11 @@ static void Cmdmanchesterdemod(char *str) {
 	/* If we're not working with 1/0s, demod based off clock */
 	if (high != 1)
 	{
-		bit = 0;
+		bit = 0; /* We assume the 1st bit is zero, it may not be
-		for (i = 0; i < (int)(GraphTraceLen / clock); i++)
+		          * the case: this routine (I think) has an init problem.
+		          * Ed.
+		          */
+		for (; i < (int)(GraphTraceLen / clock); i++)
 		{
 			hithigh = 0;
 			hitlow = 0;