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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).

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Now just use "askdemod 1" or "askdemod 0" and do not give the clock rate as argument (not necessary anymore)
This commit is contained in:
edouard@lafargue.name 2009-07-02 22:54:44 +00:00
parent ababf78201
commit 15db5fb71a
1 changed files with 89 additions and 92 deletions
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69
winsrc/command.cpp
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@ -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) * or high mod means one)
* *
* Updates the Graph trace with 0/1 values * Updates the Graph trace with 0/1 values
* *
* Arguments: * Arguments:
* sl : bit length in terms of number of samples per bit
* (use yellow/purple markers to compute).
* c : 0 or 1 * c : 0 or 1
*/ */
static void Cmdaskdemod(char *str) { static void Cmdaskdemod(char *str) {
int i; int i;
int sign = 1;
int n = 0; int n = 0;
int c = 0; int c,high,low = 0;
int t1 = 0;
// TODO: complain if we do not give 2 arguments here ! // 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 { } else {
GraphBuffer[0] = 0; GraphBuffer[0] = c;
} }
for(i=1;i<GraphTraceLen;i++) { 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 { } else {
/* No transition */
GraphBuffer[i] = GraphBuffer[i-1]; GraphBuffer[i] = GraphBuffer[i-1];
} }
} }
@ -2101,8 +2095,11 @@ static void Cmdmanchesterdemod(char *str) {
/* If we're not working with 1/0s, demod based off clock */ /* If we're not working with 1/0s, demod based off clock */
if (high != 1) 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; hithigh = 0;
hitlow = 0; hitlow = 0;