add lf PAC/Stanley tag read (#354)

[proxmark3-svn] / common / lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index d2e0fca42b4cab88ae4995575a482a5afe3ca021..880e2c2b04ebfe20cd6d212f82d20837db9e5eb4 100644 (file)
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -505,13 +505,14 @@ int DetectASKClock(uint8_t dest[], size_t size, int *clock, int maxErr) {
        return bestStart[best];
 }
 
-int DetectStrongNRZClk(uint8_t *dest, size_t size, int peak, int low){
+int DetectStrongNRZClk(uint8_t *dest, size_t size, int peak, int low, bool *strong) {
        //find shortest transition from high to low
+       *strong = false;
        size_t i = 0;
        size_t transition1 = 0;
        int lowestTransition = 255;
        bool lastWasHigh = false;
-
+       size_t transitionSampleCount = 0;
        //find first valid beginning of a high or low wave
        while ((dest[i] >= peak || dest[i] <= low) && (i < size))
                ++i;
@@ -527,10 +528,17 @@ int DetectStrongNRZClk(uint8_t *dest, size_t size, int peak, int low){
                        lastWasHigh = (dest[i] >= peak);
                        if (i-transition1 < lowestTransition) lowestTransition = i-transition1;
                        transition1 = i;
+               } else if (dest[i] < peak && dest[i] > low) {
+                       transitionSampleCount++;
                }
        }
        if (lowestTransition == 255) lowestTransition = 0;
        if (g_debugMode==2) prnt("DEBUG NRZ: detectstrongNRZclk smallest wave: %d",lowestTransition);
+       // if less than 10% of the samples were not peaks (or 90% were peaks) then we have a strong wave
+       if (transitionSampleCount / size < 10) {
+               *strong = true;
+               lowestTransition = getClosestClock(lowestTransition);
+       }
        return lowestTransition;
 }
 
@@ -550,7 +558,9 @@ int DetectNRZClock(uint8_t dest[], size_t size, int clock, size_t *clockStartIdx
        int peak, low;
        if (getHiLo(dest, loopCnt, &peak, &low, 90, 90) < 1) return 0;
 
-       int lowestTransition = DetectStrongNRZClk(dest, size-20, peak, low);
+       bool strong = false;
+       int lowestTransition = DetectStrongNRZClk(dest, size-20, peak, low, &strong);
+       if (strong) return lowestTransition;
        size_t ii;
        uint8_t clkCnt;
        uint8_t tol = 0;