Infineon XENSIV TLI4971 - Code example CRC calculation

Application Note 23 of 31 Rev. 1.30
2022-03-01
Current Sensor TLI4971
Programming Guide and User Manual
4.5 Code example CRC calculation
//CRC calculation example for Infineon TLI4971 current sensor
//CRC 8 (SAE - J1850) CRC polynomial: x^8 + x^4 + x^3 + x^2 + 1
// len = 18 (EEPROM line 0-17)
#define CRC_POLYNOMIAL 0x1D
#define CRC_SEED 0xAA
//check CRC
bool checkCRC (uint16_t* data, int len) {
uint8_t checkSum = data[2]&0xFF;//CRC lower byte in EEPROM line2
return checkSum == crcCalc(data, len);
}
//read data beginning in EEPROM line 3 to line 17, append line 0 to line 2
uint8_t crcCalc(uint16_t* data, int len) {
uint8_t crcData8[len*2];
for(int i = 0; i < len; i++) {
crcData8[i*2] = ( data[(i+3)%18] >>8 ) & 0xFF;//read upper 8 bit
crcData8[i*2+1] = ( data[(i+3)%18] ) & 0xFF;//read lower 8 bit
}
return crc8(crcData8, len*2-1); //do not include last byte (line 2 lower byte)
}
// CRC calculation
uint8_t crc8(uint8_t *data, uint8_t length) {
uint32_t crc;
int16_t i, bit;
crc = CRC_SEED;
for (i = 0; i < length; i++) {
crc ^= data[i];
for (bit = 0; bit < 8; bit++) {
if ((crc & 0x80) != 0) {
crc <<= 1;
crc ^= CRC_POLYNOMIAL;
} else {
crc <<= 1;
}
}
}
return ~crc; // ~crc = crc^0xFF;
}