X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/8949e0458403298a700340bd304f501dd7577fbb..3ea7254a57d1732e72f5d4b7bf21d1d6527faa19:/common/lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index f5a0310e..c8a2c69a 100644
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -597,6 +597,26 @@ int IOdemodFSK(uint8_t *dest, size_t size)
 		return (int) startIdx;
 	}
 	return -5;
+} 
+
+// by marshmellow
+// find viking preamble 0xF200 in already demoded data
+int VikingDemod_AM(uint8_t *dest, size_t *size) {
+	if (justNoise(dest, *size)) return -1;
+	//make sure buffer has data
+	if (*size < 64*2) return -2;
+
+	size_t startIdx = 0;
+	uint8_t preamble[] = {1,1,1,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
+	uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
+	if (errChk == 0) return -4; //preamble not found
+	uint32_t checkCalc = bytebits_to_byte(dest+startIdx,8) ^ bytebits_to_byte(dest+startIdx+8,8) ^ bytebits_to_byte(dest+startIdx+16,8)
+	    ^ bytebits_to_byte(dest+startIdx+24,8) ^ bytebits_to_byte(dest+startIdx+32,8) ^ bytebits_to_byte(dest+startIdx+40,8) 
+	    ^ bytebits_to_byte(dest+startIdx+48,8) ^ bytebits_to_byte(dest+startIdx+56,8);
+	if ( checkCalc != 0xA8 ) return -5;
+	if (*size != 64) return -5;
+	//return start position
+	return (int) startIdx;
 }
 
 // by marshmellow