add checksum to viking demod

[proxmark3-svn] / common / lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index f5a0310e5521f13ff84a76530aab4891365da256..c8a2c69af82291e8486bd81cbadfb6dab1895fb7 100644 (file)
--- 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