Update README.md

[proxmark3-svn] / common / lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index d2e0fca42b4cab88ae4995575a482a5afe3ca021..7690004707881cd230f566afeed40aa7d49abe6c 100644 (file)
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -10,8 +10,8 @@
 //
 // NOTES: 
 // LF Demod functions are placed here to allow the flexability to use client or
-// device side. Most BUT NOT ALL of these functions are currenlty safe for 
-// device side use currently. (DetectST for example...)
+// device side. Most BUT NOT ALL of these functions are currently safe for 
+// device side use. (DetectST for example...)
 //
 // There are likely many improvements to the code that could be made, please
 // make suggestions...
@@ -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;
@@ -1767,22 +1777,53 @@ int IOdemodFSK(uint8_t *dest, size_t size, int *waveStartIdx) {
 } 
 
 // redesigned by marshmellow adjusted from existing decode functions
-// indala id decoding - only tested on 26 bit tags, but attempted to make it work for more
-int indala26decode(uint8_t *bitStream, size_t *size, uint8_t *invert) {
-       //26 bit 40134 format  (don't know other formats)
-       uint8_t preamble[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1};
-       uint8_t preamble_i[] = {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0};
-       size_t startidx = 0; 
-       if (!preambleSearch(bitStream, preamble, sizeof(preamble), size, &startidx)){
-               // if didn't find preamble try again inverting
-               if (!preambleSearch(bitStream, preamble_i, sizeof(preamble_i), size, &startidx)) return -1;
+// indala id decoding
+int indala64decode(uint8_t *bitStream, size_t *size, uint8_t *invert) {
+       //standard 64 bit indala formats including 26 bit 40134 format
+       uint8_t preamble64[] = {1,0,1,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 1};
+       uint8_t preamble64_i[] = {0,1,0,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 0};
+       size_t startidx = 0;
+       size_t found_size = *size;
+       bool found = preambleSearch(bitStream, preamble64, sizeof(preamble64), &found_size, &startidx);
+       if (!found) {
+               found = preambleSearch(bitStream, preamble64_i, sizeof(preamble64_i), &found_size, &startidx);
+               if (!found) return -1;
                *invert ^= 1;
-       } 
-       if (*size != 64 && *size != 224) return -2;
+       }
+       if (found_size != 64) return -2;
        if (*invert==1)
-               for (size_t i = startidx; i < *size + startidx; i++) 
+               for (size_t i = startidx; i < found_size + startidx; i++) 
+                       bitStream[i] ^= 1;
+
+       // note: don't change *size until we are sure we got it... 
+       *size = found_size;
+       return (int) startidx;
+}
+
+int indala224decode(uint8_t *bitStream, size_t *size, uint8_t *invert) {
+       //large 224 bit indala formats (different preamble too...)
+       uint8_t preamble224[] = {1,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,1};
+       uint8_t preamble224_i[] = {0,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,0};
+       size_t startidx = 0;
+       size_t found_size = *size;
+       bool found = preambleSearch(bitStream, preamble224, sizeof(preamble224), &found_size, &startidx);
+       if (!found) {
+               found = preambleSearch(bitStream, preamble224_i, sizeof(preamble224_i), &found_size, &startidx);
+               if (!found) return -1;
+               *invert ^= 1;
+       }
+       if (found_size != 224) return -2;
+       if (*invert==1 && startidx > 0)
+               for (size_t i = startidx-1; i < found_size + startidx + 2; i++) 
                        bitStream[i] ^= 1;
 
+       // 224 formats are typically PSK2 (afaik 2017 Marshmellow)
+       // note loses 1 bit at beginning of transformation...
+       // don't need to verify array is big enough as to get here there has to be a full preamble after all of our data
+       psk1TOpsk2(bitStream + (startidx-1), found_size+2);
+       startidx++;
+
+       *size = found_size;
        return (int) startidx;
 }