TinyUSB — Open-Source Cross-Platform USB Stack for Embedded Systems

Introduction

TinyUSB is an open-source USB stack in C for embedded microcontrollers. It provides device and host functionality across RP2040, STM32, nRF, ESP32-S2/S3, and many other chip families with a portable driver abstraction.

What TinyUSB Does

• Implements USB device classes: CDC, MSC, HID, MIDI, Audio, and vendor-specific
• Provides USB host support for enumerating and talking to attached devices
• Abstracts chip-specific USB registers behind a portable driver layer
• Ships with ready-to-build examples for dozens of boards
• Runs bare-metal or integrates with an RTOS

Architecture Overview

Three layers separate concerns: chip-specific drivers at the bottom, a core protocol engine handling standard requests and endpoint management in the middle, and class drivers exposing application-level APIs on top. A lightweight event queue dispatches callbacks outside ISR context, keeping interrupt handlers short.

Self-Hosting & Configuration

• Add TinyUSB as a submodule or copy the source into your project
• Set the MCU family and board in tusb_config.h or via build defines
• Enable only the USB classes you need to minimize flash and RAM
• Call tud_task() or tuh_task() from your main loop or RTOS thread
• Build with Make, CMake, or integrate into your IDE project

Key Features

• Supports 20+ MCU families from multiple vendors
• Device and host stacks in one codebase
• Minimal CDC build fits under 16 KB of flash
• Extensive examples: CDC serial, mass storage, HID, MIDI, composite
• Active community with regular releases and broad CI

Comparison with Similar Tools

• STM32 USB Library — tightly coupled to STM32 HAL; not portable to other chips
• Zephyr USB subsystem — powerful but requires the full Zephyr RTOS and build system
• LUFA — well-documented; limited to Atmel AVR and XMEGA chips
• CherryUSB — similar scope; newer with fewer supported MCUs and examples

FAQ

Q: Which MCUs are supported? A: RP2040, STM32 (F0/F1/F4/H7/L4 and others), nRF52/nRF53, ESP32-S2/S3, LPC, SAMD, Renesas, and more. See the hw/bsp directory for the full list.

Q: Can I use it without an RTOS? A: Yes. Call its task function from your main loop and it processes events cooperatively.

Q: How do I make a composite USB device? A: Enable multiple class drivers in tusb_config.h and write a composite descriptor with interfaces for each class. The cdc_msc example demonstrates this.

Q: Does it support USB 3.x? A: No. It supports USB 2.0 full-speed and high-speed where hardware allows.

Sources

• Repository: https://github.com/hathach/tinyusb
• Documentation: https://docs.tinyusb.org/