[FAQ] TPS2HCS10-Q1: CRC Calculation Function Example

Tool/software:

The TPS2HCS10-Q1 device has an optional cyclic redundancy check (CRC) feature to ensure each SPI frame (SPI Format: COPL = 0, CPHA = 1) is transmitted and received properly. This CRC calculation is based on the CRC-4-ITU standard, with a polynomial of x⁴ + x + 1 and a starting value of 1111. For more information, see the TPS2HCS10-Q1 data sheet. Please see below a code example on how to calculate the CRC bits:

uint8_t crc_encode(uint8_t send_rec_bytes[3])
{
  uint8_t crc_start = 0x0F;
  uint8_t crc_polynomial = 0x03;
  uint8_t crc_result = crc_start;
  uint8_t bitnum = 0;
  uint8_t bytenum = 0; 

for(bytenum = 0; bytenum < 3; bytenum++)
  {
    for(bitnum = 0; bitnum < 8; bitnum++)
    {
      if((((send_rec_bytes[bytenum] >> (7-bitnum)) & 0x01) ^ ((crc_result & 0x08) >> 3)) > 0)
        crc_result = crc_polynomial ^ ((crc_result << 1) & 0x0F);

      else
        crc_result = (crc_result << 1) & 0x0F;
    }

  }

  for(bitnum = 0; bitnum < 4; bitnum++)
  {
    if(((crc_result & 0x08) >> 3) > 0)
      crc_result = crc_polynomial ^ ((crc_result << 1) & 0x0F);
    else
      crc_result = (crc_result << 1) & 0x0F;
  }
  return crc_result;
}