X-Git-Url: http://cvs.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/bf8328e92802fd5f2b63a038ac0b3fc0eeac8581..c07b79fcbf72f530cbff5bc1e49c12bff311f50f:/common/lfdemod.c?ds=sidebyside

diff --git a/common/lfdemod.c b/common/lfdemod.c
index 14478319..79c99f73 100644
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -592,40 +592,41 @@ uint32_t bytebits_to_byte(uint8_t* src, int numbits)
 
 int IOdemodFSK(uint8_t *dest, size_t size)
 {
-	static const uint8_t THRESHOLD = 140;
     uint32_t idx=0;
     //make sure buffer has data
     if (size < 66) return -1;
     //test samples are not just noise
-	uint8_t justNoise = 1;
-	for(idx=0;idx< size && justNoise ;idx++){
-		justNoise = dest[idx] < THRESHOLD;
-	}
-	if(justNoise) return 0;
-
-	// 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;
-			}
-		}
-	}
+    uint8_t testMax=0;
+    for(idx=0;idx<65;idx++){
+        if (testMax<dest[idx]) testMax=dest[idx];
+    }
+    idx=0;
+    //if not just noise
+    if (testMax>20){
+        // 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;
 }