CherryUSB is a portable, high-performance USB device and host stack for embedded systems, supporting USB 2.0 (FS/HS) and USB 3.0 (SS) via a wide range of hardware IP cores (EHCI, OHCI, XHCI, DWC2, MUSb, ChipIDEA, etc.). The codebase is a well-layered embedded library: an OS abstraction layer (osal/) provides RTOS independence; core/ implements USB protocol state machines; class/ contains self-contained drivers for standard classes (CDc ACm, HID, MSc, Audo, Vdeo, RNDIS, DfU, mTP, etc.); port/ provides low-level hardware glue for 20+ MCU families; platform/ integrates with external stacks (lwIP, FatfS, LVGL). The architecture is clean and modular, with a consistent initialization pattern (`_ini_ntf()` returning `struct usbd_interface`) and descriptor macros that reduce boilerplate. Strengths include exceptional portabilty and a rich set of demo templates. Weaknesses include some commercial closed-source class drivers (MTP, UAc host, UVC host), static libraries for Phytium ports that hide vendor-specific code, and a large number of configuration macros that can be complex to manage. Overall, it is a production-grade USB stack with active maintenence and active community, suitable for embedded projects needing both device and host USB support.