Skip to content

Latest commit

 

History

History
80 lines (11 loc) · 926 Bytes

checksum.md

File metadata and controls

80 lines (11 loc) · 926 Bytes
Raw

Checksum counting

SEEMS NOT BE CORRECT!

For example: [1000 0100 1001 0010 0100 0100 1000 0000 0000 0000] [0010 0100] [1000 0000] [1010 0000] [0000 0000] [0000 0000 0000 0000 0000 0000] [0000 0000] [1001 0010] (first packet in the table)

  1. Take everything except header and checksum, split for each 8 bits Got: [0010 0100] [1000 0000] [1010 0000] [0000 0000] [0000 0000] [0000 0000] [0000 0000] [0000 0000] or in HEX: 0x24 0x80 0xA0 0x00 0x00 0x00
  2. Reverse order of bits Got: [0010 0100] [0000 0001] [0000 0101] [0000 0000] [0000 0000] [0000 0000] [0000 0000] [0000 0000] or in HEX: 0x24 0x01 0x05 0x00 0x00 0x00
  3. Sum all bytes and modulo 0xff Got: (0x24 + 0x01 + 0x05 + 0x00 + 0x00 + 0x00) % 0xff = 0x2A % 0xff = 0x2A
  4. Add 0x1F, reverse again Got: 0x2A + 0x1F = 0x49. In BIN: [0100 1001]. After reverse the order: [1001 0010]