This is a ball-balancing robot that I designed from scratch.

Apart from the mirror trick, which increases the camera's field of view, the robot includes another key innovation: the "finger-follower" feature. The finger position is tracked on the robot's touchscreen, and the ball follows it in real time. By watching the display, it appears as though the ball continuously "lands" underneath the finger.

The system is based on Raspberry Pi components: a Raspberry Pi 4B+ as the main controller, a PiCamera V3 Wide, and three RP2040-Zero boards that control three TMC2209 (silent) stepper drivers.

The Raspberry Pi 4B+ communicates with the three RP2040-Zero boards via a custom I²C protocol.

The system processes more than 110 FPS and controls the platform at 17–25 Hz.

The 7-inch touchscreen display (sponsored by ELECROW), together with the GUI application, makes the robot particularly enjoyable to use. The GUI also exposes several calibration parameters, such as the PID gains, which can be adjusted in real time, making the tuning process much more user-friendly and educational.

To minimize wiring and reduce the possibility of connection errors, the robot uses a custom PCB (sponsored by PCBWay) that fits onto the Raspberry Pi as a HAT. This board essentially acts as a hub, connecting all the other boards together.

The project is complemented by extensive documentation (a PDF file of approximately 150 pages) covering many aspects of the build, including: the BOM, 3D printing, PCB assembly, wood base preparation, Raspberry Pi and RP2040 setup, initial testing, full assembly (27 steps with photos), GUI operation, PID tuning, I²C protocol details, configuration parameters, troubleshooting, and a Q&A section.