Controller2

Custom ATmega32U4 USB HID Gamepad

A custom USB gamepad designed and built around an ATmega32U4 microcontroller. This project started as a breadboard prototype using an Arduino and was developed into a standalone custom PCB, combining embedded firmware, digital and analog inputs, USB HID communication, and PCB design.

Features

Hardware & PCB Design

• Custom ATmega32U4 Design: Designed a standalone gamepad around the ATmega32U4, integrating the microcontroller, clock circuitry, USB interface, programming header, analog inputs, and digital inputs onto a custom PCB.
• USB-C Interface: Implemented a USB-C device interface with 5.1kΩ CC pull-down resistors, 22Ω D+/D− series resistors, and dedicated power decoupling for reliable communication.
• Analog Input System: Integrated analog data processing using the ATmega32U4's ADC channels to provide joystick functionality.
• Power & Decoupling: Distributed the +5V USB supply across the board with local 100nF and bulk 10μF capacitors to reduce noise and add stability.
• External Clock: Implemented a 16MHz crystal oscillator with 22pF load capacitors to provide the ATmega32U4 with a stable system clock.
• ISP Programming: Added a dedicated 6-pin AVR ISP header for directly programming the ATmega32U4 on the custom PCB.
• PCB Layout: Designed the complete schematic and multi-layer PCB layout in KiCad.

Firmware

• Standalone USB HID: Configured the ATmega32U4 as a USB HID gamepad, providing direct PC compatibility without a secondary USB-to-UART bridge or custom PC software.
• Analog Input Handling: Used the ATmega32U4's 10-bit ADC to support 2 analog joysticks across 4 axes (X, Y, Rx, Ry).
• Digital Input Handling: Configured 14 button inputs using the MCU's internal pull-up resistors and active-low logic, eliminating the need for external pull-up components.
• Low-Latency Input: Sampled button and analog inputs at approximately 100 Hz using a 10 ms control loop for responsive controller input.
• Input Mapping: Developed a software mapping between the ATmega32U4 GPIO/ADC pins and the corresponding gamepad buttons and analog axes.

Hardware Specifications

Repository Structure

├── firmware/         # C++ / Arduino controller logic and USB HID descriptors
├── hardware/         # KiCad schematics, PCB board layout, and Gerber manufacturing files
└── README.md         # Project technical summary