Custom binary protocol

The custom binary protocol is a flexible format designed to store binary data of varying lengths within a defined limit.

Data:

• Custom data

Format:

<q><N><T><var0><var1>…<varN><cs>

Example:

A custom binary frame with example data, including roll, pitch, and heading (in that order), is shown below in hexedecimal format.

<71><0D><18> <3D><8F><EA><E4> <BE><D4><A1><E9> <43><97><F6><0F> <AD>

Decoded values:

By using hex-to-decimal conversion and the IEEE 754 formula, we can decode the values.

• Byte 0

  • Raw value: 71, decoded value: q (stable data).

• Byte 1

  • Raw value: 0D, decoded value: 3 x number of bytes (per data message) + 1 (token) = 3 x 4 + 1 = 13 = 0D (hexadecimal).

• Byte 2

  • Raw value: 18, decoded value: 18 (hexadecimal) = 24 (decimal). User selected token associated with this configuration.

• Byte 3-6 (roll)

  • Hex to binary: 3D 8F EA E4 = 0011 1101 1000 1111 1110 1010 1110 0100.

  • Roll value = (-1)^s x 1.M x 2^(E-127) = (-1)⁰ x 1.00011111110101011100100₂ x 2^(123−127) = 1.124225616 x 2^-4 = 0.0702641.

  • Due to rounding errors, the final roll angle is 0.07 degrees.

• Byte 7-10 (pitch)

  • Hex to binary: BE D4 A1 E9 = 1011 1110 1101 0100 1000 0001 1110 1001.

  • Pitch value = (-1)^s x 1.M x 2^(E-127) = (-1)¹ x 1.10101001000000111101001₂ x 2^(125−127) = -1.64006 x 2^-2 = −0.410015.

  • Due to rounding errors, the final pitch angle is -0.41 degrees.

• Byte 11-14 (heading)

  • Hex to binary: 43 97 F6 0F = 0100 0011 1001 0111 1111 0110 0000 1111.

  • Heading value = (-1)^s x 1.M x 2^(E-127) = (-1)⁰ x 1.00101111111011000001111₂ x 2^(135−127) = 1.18629 x 2⁸ = 303.69024.

  • Due to rounding errors, the final heading angle is 303.69 degrees.

• Byte 15 (checksum)

  • Raw value: AD, hexadecimal value created from XOR operations of all bytes between token and checksum.