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Modified kermit crc to use existing crc calc code

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This commit is contained in:
marshmellow42 2015-06-05 22:39:56 -04:00
parent c2c7f6c271
commit 07b5a3c3ba
3 changed files with 19 additions and 17 deletions
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7
client/cmddata.c
View file

@ -1515,14 +1515,13 @@ int CmdFDXBdemodBI(const char *Cmd){
uint32_t crc16 = bytebits_to_byteLSBF(BitStream+64,16);
uint32_t extended = bytebits_to_byteLSBF(BitStream+80,24);
uint64_t rawid = ((uint64_t)bytebits_to_byteLSBF(BitStream,32)<<32) | bytebits_to_byteLSBF(BitStream+32,32);
uint64_t rawid = ((uint64_t)bytebits_to_byte(BitStream,32)<<32) | bytebits_to_byte(BitStream+32,32);
uint8_t raw[8];
num_to_bytes(rawid, 8, raw);
uint8_t *raw_ptr = SwapEndian64(raw, 8, 4);
if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(raw_ptr,8));
if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(raw,8));
uint16_t calcCrc = crc16_ccitt_kermit(raw_ptr, 8);
uint16_t calcCrc = crc16_ccitt_kermit(raw, 8);
PrintAndLog("Animal ID: %04u-%012llu", countryCode, NationalCode);
PrintAndLog("National Code: %012llu", NationalCode);
PrintAndLog("CountryCode: %04u", countryCode);

28
common/crc16.c
View file

@ -8,7 +8,6 @@
#include "crc16.h"
unsigned short update_crc16( unsigned short crc, unsigned char c )
{
unsigned short i, v, tcrc = 0;
@ -44,16 +43,19 @@ uint16_t crc16_ccitt(uint8_t const *message, int length) {
}
uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) {
if (length == 0) return 0;
uint32_t crc = 0, q = 0;
uint8_t c;
for (int i = 0; i < length; i++){
c = message[i];
q = (crc ^ c ) & 0xF;
crc = (crc >> 4) ^ (q * 0x1081);
q = (crc ^ (c >> 4)) & 0xF;
crc = (crc >> 4) ^ (q * 0x1081);
}
return crc;
return bit_reverse_uint16(crc16(message, length, 0x0000, 0x1021));
}
uint16_t bit_reverse_uint16 (uint16_t value) {
const uint16_t mask0 = 0x5555;
const uint16_t mask1 = 0x3333;
const uint16_t mask2 = 0x0F0F;
const uint16_t mask3 = 0x00FF;
value = (((~mask0) & value) >> 1) | ((mask0 & value) << 1);
value = (((~mask1) & value) >> 2) | ((mask1 & value) << 2);
value = (((~mask2) & value) >> 4) | ((mask2 & value) << 4);
value = (((~mask3) & value) >> 8) | ((mask3 & value) << 8);
return value;
}

1
common/crc16.h
View file

@ -13,4 +13,5 @@ unsigned short update_crc16(unsigned short crc, unsigned char c);
uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t polynomial);
uint16_t crc16_ccitt(uint8_t const *message, int length);
uint16_t crc16_ccitt_kermit(uint8_t const *message, int length);
uint16_t bit_reverse_uint16 (uint16_t value);
#endif