Avisaro Online Documentation - Wiki
CRC Computation
The CRC value of the packet commands can ether be ignored (0x00, 0x00) or used. This is the method the CRC is calculated for the packet commands:
(Note: This example is written for "little endian" machines - such as a PC or many microcontroller.)
#define INIT_CRC 0xffff
const UINT16 crc_tab[16] =
{
0x0000, 0x1081, 0x2102, 0x3183,
0x4204, 0x5285, 0x6306, 0x7387,
0x8408, 0x9489, 0xA50A, 0xB58B,
0xC60C, 0xD68D, 0xE70E, 0xF78F
};
// crc_update as macro
#define CRC_UPDATE(crc, d)\
{\
crc = (crc >> 4) ^ crc_tab[(crc ^ d) & 0x000f];\
crc = (crc >> 4) ^ crc_tab[(crc ^ (d >> 4)) & 0x000f];\
}
---------------------------------------------------
1. crc initialisieren:
UINT16 crc = INIT_CRC;
2. dann für alle bytes:
CRC_UPDATE (crc, byte[n]);
3. das Ergebnis bitweise invertieren. Fertig.
crc = ~crc;
const UINT16 crc_tab[16] =
{
0x0000, 0x1081, 0x2102, 0x3183,
0x4204, 0x5285, 0x6306, 0x7387,
0x8408, 0x9489, 0xA50A, 0xB58B,
0xC60C, 0xD68D, 0xE70E, 0xF78F
};
// crc_update as macro
#define CRC_UPDATE(crc, d)\
{\
crc = (crc >> 4) ^ crc_tab[(crc ^ d) & 0x000f];\
crc = (crc >> 4) ^ crc_tab[(crc ^ (d >> 4)) & 0x000f];\
}
---------------------------------------------------
1. crc initialisieren:
UINT16 crc = INIT_CRC;
2. dann für alle bytes:
CRC_UPDATE (crc, byte[n]);
3. das Ergebnis bitweise invertieren. Fertig.
crc = ~crc;