# 0.21.0

*June 29, 2026*

## General

### New MCUs and Boards

- Add HPMicro HPM6xxx support with HPM6750EVK2 board
- Add NXP RW61x (RW612, ChipIdea high-speed) support
- Add Artery AT32F45x series support
- Add STM32C5 series support
- Add Espressif ESP32-S31 (high-speed) support
- Add WCH CH582/CH583 (USBFS) support
- Add CH32V103 USB device support (combined-control USBFS) with CH32V103C8T6 Bluepill board
- Add FreeRTOS support for RP2040/RP2350
- New boards: nRF54LM20-DK, WeAct STM32H743, EK-TM4C1294XL, STM32H747-DISCO, NUCLEO-H533RE
- Migrate i.MX RT to the new `mcux-devices-rt` SDK package

### Code Quality and Build

- Major refactor of dedicated hardware-FIFO (HWFIFO) handling: omit per-endpoint RAM buffers on ports with a dedicated hardware FIFO, add stride-aware FIFO access, and store raw bytes in `tusb_fifo`
- Reduce code size via control/descriptor and stream refactors, and remove `snprintf` usage
- Remove IAR toolchain support from the Make build; add IAR warning flags and resolve warnings in CMake
- Fix Zephyr build with nrfx v4, C++/`-Werror=extra` builds, and various `-Wconversion` warnings
- Update FatFS to R0.16
- Fix the fuzzing harness
- Various BSP fixes (STM32H5 UID read with ICACHE, STM32F411 Black Pill HSE, RT1011 data cache, Teensy)

### Documentation

- Add a README for every example and `build-doc` tooling
- Add Sponsors section and `FUNDING` configuration
- Various README/doc fixes (FTDI host, STM32C071 Nucleo URL, Supported CPUs table)

## API Changes

- Add `is_isr` parameter to `dcd_edpt_xfer`, `dcd_edpt_xfer_fifo`, `usbd_edpt_xfer` and `usbd_edpt_xfer_fifo`
- Remove the no-FIFO mode from the endpoint stream API
- Add `tud_vendor_write_clear()` to forcefully clear the TX buffer
- Add `tud_midi_n_demux_stream_read()` cable-aware MIDI stream read
- Add `CFG_TUH_HID_SET_PROTOCOL_ON_ENUM` host HID option
- Add `CFG_TUSB_DEBUG_BREAKPOINT` hook for `TU_BREAKPOINT`
- Add ThreadX OSAL support
- `tud_task_ext()` / `tuh_task_ext()` now limit the number of events processed per call
- Replace `CFG_TUD_NET_ENDPOINT_SIZE` with the descriptor-based endpoint size

## Device Stack

### USBD Core

- Refactor and validate device descriptor handling; move control transfer handling into `usbd.c`
- Use the EP0 buffer directly when large enough; clamp EP0 OUT data copy to the control buffer
- Fix stream write logic/racing without FIFO; fix zero `wLength` control request
- Fix ISO OUT endpoint failure on alt-setting MPS change

### Audio

- Fix `audiod_open` with MIDI interfaces
- Fix big-endian bitfield guards for audio structs and endian-safe `wValue`/`wIndex` extraction in UAC2 examples

### CDC

- Remove `tud_cdc_configure`
- Fix CDC echo test issue on i.MX RT and fast MCUs

### HID

- Bound item size to remaining length in the report-descriptor parser
- Remove host enumeration assumption; add `CFG_TUH_HID_SET_PROTOCOL_ON_ENUM`

### MIDI

- Add USB-MIDI 2.0 device and host class drivers
- Add cable-aware stream read `tud_midi_n_demux_stream_read()`
- Fix MIDI host issue

### MSC

- Skip the command stage if the OUT endpoint is stalled
- Cap `tud_msc_scsi_cb` buffer size to the endpoint buffer size

### MTP

- Fix transfer completion detection for exact-length packets; queue ZLP when needed
- Fix premature phase change after a short OUT transfer; fixes in `add_string`

### Network (NCM)

- Fix NCM state on restart
- Support `SetEthernetPacketFilter` and `SetNtbInputSize` requests
- Add a weak callback for the initial link state

### Video (UVC)

- Fix VC interface parsing when `bNumEndpoints` != 0
- Assert the `usbd_edpt_iso_activate()` result

### DFU

- Fix the DFU functional descriptor version (1.0.1 → 1.1.0)

### Printer

- Add the USB Printer device class driver

### Vendor

- Omit the endpoint buffer for ports with a dedicated hardware FIFO

## Host Stack

- Fully asynchronous host code: remove blocking delays from `tuh_task_ext()`, respect its `timeout_ms`, and avoid stalling one device while another enumerates
- Add an async control-transfer FIFO so queued control transfers are dispatched instead of dropped
- Hub enumeration reliability improvements; add MTT hub support
- Support full-speed host with a high-speed PHY (DWC2)
- Fix FTDI host multi-channel loop
- CDC host: use a local control buffer; fix `cdch_open` typo
- Big-endian host support for SETUP packet handling
- Use `TUSB_ROLE_HOST` in host stack initialization

## Controller Driver (DCD & HCD)

### DWC2

- Add `dcd_configure` for FIFO config and DWC2 deinit support
- Support full-speed host operation on a high-speed PHY
- Vbus sensing enhancement; do not modify FS PHY registers on HS PHY (ESP32-P4)
- Fix HCD TX FIFO full check, ISO IN endpoint disabled after incomplete transfer, and EP0 status completion before SETUP
- Submit SETUP on SETUP_DONE and handle v3.10a spurious RX_COMPLETE (STM32L476)
- HCD: correct HFIR for low-speed devices via internal FS PHY; fix split-IN NAK storm and UART starvation (STM32F723)

### FSDEV (STM32 / CH32)

- Add FSDEV host (HCD) driver
- Refactor FSDEV; share the PMA errata delay helper between DCD/HCD with overridable timing
- Fix single-buffered isochronous endpoint cases, STM32U0 data stride, and PMA pointer advance on ring-buffer wrap
- Fix CH32V20x enumeration by enabling the D+ pull-up; work around CH32 EP0 premature OUT ACK
- Do not enable the unused USB wakeup EXTI IRQ (F1/F3/G4/L1)

### MUSB

- Enhance driver: double packet, EP0 refactor, fix DATAEND race with EP0
- Fix ZLP IN transfer, RXRDY clearing, and defer EP0 SETUP during the DATA_IN/STATUS race

### RP2040 / RP2350

- Refactor RP2 driver
- HCD rework: EPX for non-interrupt endpoints and ping-pong double buffering
- Fix RP2350 hard fault in unaligned memcpy to USB DPRAM
- Host: fix OUT-data control transfers sending DATA0 instead of DATA1

### CH32 USBFS / USBHS (WCH)

- Fix dropped bulk OUT packets by re-arming the EP_RX_CTRL state (usbfs)
- Fix endpoint stall length index and clear-stall response (usbhs)
- Fix CH32V103 hard fault

### RUSB2 / SAMx7x

- Fix RUSB2 FIFO write
- Refresh `dcd_samx7x`

### New host controllers

- Add NXP IP3516 HCD (EHCI-like)
- Add MTT (multi-TT) hub support

### nRF5x

- Request HFCLK in `USB_EVT_READY` to fix the post-SoftDevice deadlock

## Testing

- Expand Hardware-in-the-Loop (HIL) coverage (MTP, audio, throughput; nanoch32v203, ch32v103, stm32u083nucleo, tm4c123x) and post pass/fail/skip HIL reports as PR comments
- Add MemBrowse code-size CI integration and size-difference reporting
- Add automated Claude Code PR review and bug-fix CI workflows
- Add `hil`, `code-size`, `pvs`, `usbmon` and `build-doc` developer skills

## Contributors

Thanks to everyone who contributed to this release: @Alex-Schaefer, @alt-0191, @andrewleech, @armusin, @bdolgov, @BrentK-ADI, @ceedriic, @chenzhihong007, @dangfan, @DavidKorczynski, @dinsfire64, @dxbjavid, @embedded-ideas, @felhub, @gab-k, @gabChouin, @HakanL, @hathach, @HiFiPhile, @igi540, @IntegraSources, @kira-live, @LeZerb, @michael-membrowse, @michaelajax, @mickabrig7, @Milek7, @morse-cedricvandenbergh, @nminaylov, @non-bin, @Phozer, @remiberthoz, @renjieah, @rhgndf, @RobertDaleSmith, @roma-jam, @sauloverissimo, @sgrunza-at-BadgerMeter, @sidcha, @StefanOroel, @Tails86, @thamul, @tore-espressif, @UMRnInside, @ValentiWorkLearning, @verylowfreq, @wjklimek1, @YixingShen, @zhiqiang-ch, @zjzhang-cn.