I built this open-source firmware project to turn an RP2040-based servo controller into a dedicated motion-control system for a multi-joint walking robot. The work focused on making the board useful as part of a real robot, not just proving that individual servos could move. That meant handling incoming commands, coordinating 18 servo outputs, reporting basic hardware state, and giving the system more predictable behavior during setup, startup, and shutdown. A key part of the project was integrating the RP2040’s programmable I/O capabilities into a cleaner application-level firmware design. The lower-level timing drivers handle the precise servo signals, while the main firmware manages communication, command parsing, sensor reads, voltage and current feedback, and servo power behavior. This separation made the system more reliable and easier to reason about: the time-sensitive motion signals are handled by dedicated hardware resources, while the application code focuses on how the robot should behave. The project also included practical build support. Walking robots are sensitive to small mechanical and servo differences, so calibration matters once the electronics are installed in the chassis. I added a companion calibration workflow to help collect tuning values for each servo and make the setup process more repeatable. The end result is a small but complete embedded subsystem: firmware, hardware integration, safety behavior, telemetry, and calibration tooling packaged for others to use and build on.