How do I deal with Error Detection Codes (Checksum, CRC, LRC, BCC, etc.)?
Luckily, most EDCs are fairly obvious. For the major classes of EDCs, here is the documentation for which you need to look: • Checksums “The checksum is calculated by adding up all the bytes from the character after the Start-of-Text character up to and including the End-of-Text character” or “To calculate the checksum, add up the ASCII value of each byte in the message and append it to the end of the message.” • LRCs (also known as BCC or XOR) “The checksum is calculated by XORing all the bytes in the message excluding the Start-of-Header byte.” or “To calculate the CRC, XOR only the data bytes. Ignore the header bytes.” or “To determine the CRC, use a standard BCC calculation on all the bytes in the message.” • CRCs A little more complicated, a CRC applies an algorithm to the sequence of characters. Each algorithm normally uses a “polynomial” and optionally some base number. For example: “The CRC-16 check process is applied to all transmitted bytes expect pad and sync bytes….divide
