The Phoenix LTX Accessory Protocol uses blocks to transmit data.
Blocks have the following format:
|BDataN||Block data (optional)|
Each element in the block is one 8-bit byte.
The checksum is calculated as follows:
- Initialize the checksum to 0xFF.
- Subtract each byte of block data from the checksum.
- Underflows wrap around from 0x00 to 0xFF.
A simple way to verify the checksum is to subtract it as well. If it is valid, the result will be 0.