XRUSB

A truly tiny and beautiful, ultra-fast and modern USB stack for embedded systems.

Introduction

XRUSB is a standalone, modern C++ USB protocol stack. It is provided both as a LibXR subtree and as an independent repository. XRUSB focuses on portability, high performance, and easy integration.

Key Features

• Modern C++ Implementation: Written in C++17, using classes and template-based modular encapsulation for easy extension.
• Lock-Free Data Structures: All data transfers and event handling are lock-free and thread-safe for maximum efficiency.
• Double Buffering Mechanism: Fully utilizes hardware/software double buffers and DMA. Alternating read/write greatly increases data throughput.
• Dynamic Endpoint Allocation: Endpoints are allocated on demand during enumeration; multiple classes can automatically manage and reuse endpoints to avoid resource waste.
• One-Time Memory Allocation: All memory is determined at compile time and allocated once at construction. No redundant space is reserved for strings/descriptors.
• Interrupt-Driven: Operates fully by hardware interrupts, with no reliance on polling or background threads.
• Interrupt-Safe: Driver functions can be called directly from ISR (Interrupt Service Routine).
• Optimized Memory Copy: Achieves higher throughput for bulk transfers and descriptor processing.

Device Drivers

This repository only contains platform-independent stack code. For platform-specific device drivers, please refer to the corresponding drivers in libxr, such as:

• driver/st/stm32_usb_ep.cpp
• driver/ch/ch32_usb_endpoint_otghs.cpp

Note:

• USB-DEVICE below refers to the native USB device controller path used by XRUSB.
• Mainline libxr currently provides CDC-JTAG on ESP32-C3/ESP32-C6 via driver/esp/esp_cdc_jtag.*; this is a separate dedicated USB Serial/JTAG UART backend, not the generic XRUSB device-controller path.

Support Status

Device Stack

Protocol	Status	Notes
CDC-ACM	Supported	Implemented as LibXR’s UART class
HID	Supported	Only standard keyboard/mouse and remote controller; other types require you to derive your own
UAC	Supported	Currently implements a UAC 1.0 microphone only
GSUSB	Supported (CAN/FDCAN)	Driverless SocketCAN on Linux
DAPLINK V2	Supports (SWD interface only)	Can be used with Keil/OpenOCD

Host Stack

TODO

Platform Support

Platform	Phy	Status	Test Device
STM32	USB_DEVICE_FS	Supported	STM32F103
STM32	USB_DRV_FS	Supported (Device)	STM32G431
STM32	USB_OTG_FS	Supported (Device)	STM32F407
STM32	USB_OTG_HS	Supported (Device)	STM32F407/STM32H750
CH32	USB_DEVICE_FS	Supported	CH32V203
CH32	USB_OTG_FS	Supported (Device)	CH32V307/CH32V203/CH32V208
CH32	USB_OTG_HS	Supported (Device)	CH32V307

Documentation

Released together with the LibXR documentation.