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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
commit 07b5a3c3ba
3 changed files with 19 additions and 17 deletions
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28
common/crc16.c
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@ -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;
}