Firmware

Each of the four brains runs its own firmware, developed and versioned independently.

Brain	Part	Firmware / OS
Raspberry Pi 5	Main Computer	Raspberry Pi OS — an older release, chosen to keep driver support simple
Pico 2	Legs & Balance	C++
XIAO RP2350	Head	C++
Nano Every	Torso	C++

The three microcontrollers are all programmed in C++. The Pi 5 is the odd one out: it runs Linux (Raspberry Pi OS) rather than embedded firmware — see Main Computer → System for its OS configuration and services.

One repository per part

Each part — Main Computer, Legs & Balance, Head, Torso — lives in its own repository, so each can be built and worked on independently of the others. The internal buses are the contracts that keep them compatible with each other.