FOCsy PCB

PCB design for the FOCsy balance robot - a FOC-driven two-wheeled balancing robot prototype.

Project Overview

FOCsy is a prototype platform for validating FOC (Field-Oriented Control) driven balance robots. This PCB integrates:

• 2x SimpleFOC Mini motor drivers for 2208 gimbal motors
• Sensor integration for IMU and encoders
• Power management for battery operation
• ESP32 interface

This project serves as a stepping stone to the Strider robot, a more advanced wheel-leg platform with:

• SCS2332/STS3032/STS3215 servos for hip pitch
• 2208 motors on ankle
• Jetson Orin Nano compute module

Hardware Specifications

• Motor Drivers: 2x SimpleFOC Mini
• Motors: 2x 2208 80T gimbal motors
• Encoders : 2x AS5600 (I²C) module
• MCU module: Waveshare ESP32-S3-Touch-LCD-3.5 built around ESP32-S3
  • Sensors: QMI8658 (datasheet)
• Power: 3s 18650
  • BMS 3S 20A
  • IP2369 45W 2S to 6S Battery Charging Discharger Module

Repository Structure

FOCsy_PCB/
├── README.md              # This file
├── LICENSE                # Project license
├── .gitignore             # Git ignore rules
├── FOCsy.kicad_pro        # KiCad project file
├── FOCsy.kicad_sch        # Main schematic
├── FOCsy.kicad_pcb        # PCB layout
├── symbols/               # Custom schematic symbols
│   └── FOCsy.kicad_sym
├── footprints/            # Custom footprints
│   └── FOCsy.pretty/
├── 3dmodels/              # 3D models for visualization
├── fabrication/           # Manufacturing outputs
│   ├── gerbers/           # Gerber files
│   ├── bom/               # Bill of Materials
│   └── assembly/          # Assembly files
└── docs/                  # Documentation
    ├── images/            # Schematic captures, renders
    └── mechanical/        # Mechanical drawings

Library Management

This project uses local, self-contained libraries

• All custom symbols, footprints, and 3D models are stored within the repository
• Relative paths ensure portability across machines
• No external library dependencies needed for collaborators

Getting Started

Prerequisites

• KiCad 8.0 or later (KiCad 9 recommended)
• Git

Clone and Open

git clone https://github.com/chitoku/FOCsy_PCB.git
cd FOCsy_PCB
# Open FOCsy.kicad_pro in KiCad

Version Control Workflow

Branch Strategy

• main - Stable releases matching fabricated boards
• dev - Active development
• Feature branches for major changes

Commit Guidelines

Use descriptive commit messages:

add: power supply schematic
route: motor driver traces
fix: correct SimpleFOC Mini pinout
doc: add mechanical clearance notes

Releases

Tag versions that match manufactured boards:

git tag v0.1-proto1
git push --tags

Manufacturing

Fabrication outputs are generated for releases only. See fabrication/ folder for:

• Gerber files
• Bill of Materials (BOM)
• Pick-and-place files
• Assembly notes

Development Roadmap

• Schematic design
  • Power supply circuit
  • SimpleFOC Mini integration
  • Sensor interfaces
  • Microcontroller connections
• PCB Layout
  • Component placement
  • Power routing
  • Signal routing
  • Ground planes
• Review and validation
• Prototype fabrication
• Testing and iteration

Related Projects

This project is part of a larger robotics development path:

1. FOCsy (this project) - FOC balance robot prototype
2. Strider (future) - Advanced wheel-leg robot with enhanced compute

License

This project is licensed under the MIT License - see the LICENSE file for details.

MIT is used for simplicity and permissiveness in this educational/research prototype.
Future projects (e.g., Strider) may consider hardware-specific licenses like CERN-OHL.

Contributing

This is currently a personal research project. Feel free to open issues for questions or suggestions.

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Last Updated: November 2025