SBAA106A June   2020  – August 2021

2. 1Introduction
3. 2Simple Checksum
4. 3CRC
1. 3.1 CRC Generic Computations
1. 3.1.1 Using XOR Bitwise Computation
2. 3.1.2 Using Lookup Tables
5. 4Hamming Code
1. 4.1 Hamming Code Computation
1. 4.1.1 Hamming Code Computation Example
2. 4.1.2 Validation of Transmitted Data
6. 5Summary
7. 6References
8. 7Revision History

#### 4.1.2.2 Checksum Validation

The checksum is computed from the received data and compared to the checksum value transmitted by using a bitwise XOR. A checksum error occurs if a nonzero value is computed from the XOR. The checksum used for the ADS131A0x differs from the computation for the ADS1259 discussed in Section 2.1.

/**
* Computation and verification of the checksum from the Hamming byte.
*
* \details Computation of checksum bits using a checksum bit mask and counting
* the number of bits set in the masked value.
*
* \param    uint32_t in of the value to be computed and compared.
*
* \returns  uint32_t Returns 0 if a match or non-zero for a failure.
*/
uint32_t checkSum(uint32_t in)
{
// Compute the checksum for the data after stripping out the hamming/checksum byte
// compare the the computed checksum with the hamming/checksum byte by XORing
// the result should be '0' for a proper checksum.  Remember to compare after moving
// the checksum left by 1 to place the checksum in the proper position.  Also remove
// all other bits in the compare that are not checksum by ANDing with
// 0x06 (0x03 shifted left by one)
return (in ^ ((countBits(in & CHECKSUM_BIT_MASK) << 1))) & 0x06;
}