stm32/tinyusb: Add High-Speed USB support and fix CDC/VBUS issues.

[andrewleech]

Summary

The STM32 port's TinyUSB integration only supports the FS controller. Boards with a HS controller (PYBD_SF6, STM32F429DISC, OLIMEX_H407, or ULPI-based designs) cannot use TinyUSB — the RHPORT configuration is hardcoded to RHPORT 0 / full-speed only.

This PR adds proper RHPORT mode selection in tusb_config.h based on MICROPY_HW_USB_HS and MICROPY_HW_USB_HS_IN_FS board config, routes HS IRQ handlers to the correct RHPORT (including STM32N6 which maps HS to RHPORT 0), and adds VBUS sensing configuration for the HS-in-FS path on STM32F4/F7 (mirroring the existing FS path, with support for both VBDEN and legacy NOVBUSSENS register variants).

Additional issues found and fixed during testing (each is a separate commit and can be split into its own PR if preferred):

• CDC reconnect stall: When a host closes and reopens the CDC serial port (e.g. repeated mpremote connect/disconnect cycles), the IN endpoint can remain stalled from a prior runtime USB disconnect. The device becomes unresponsive until reset. Fixed by clearing endpoint stall on DTR high. Additionally, on DTR low (host close) the TX FIFO is now flushed so stale data from a previous session does not accumulate and block writes on the next connection.

• DFU bootloader serial number mismatch: The TinyUSB serial descriptor uses a raw hex dump of all 12 UID bytes (24-char lowercase), while the legacy USB stack and ST's onboard DFU bootloader use a condensed algorithm that selects 6 bytes with two additions (12-char uppercase). This causes the device to report a different serial number depending on which USB stack is active, breaking tools that identify devices by serial (udev rules, mpremote, dfu-util). Fixed by using the ST DFU bootloader algorithm.

• TinyUSB-specific boot.py template: The factory reset boot.py template references pyb.usb_mode() which does not exist on the TinyUSB stack. A TinyUSB-specific template is added that uses machine.USBDevice with BUILTIN_DEFAULT.

Testing

Built with CFLAGS_EXTRA=-DMICROPY_HW_TINYUSB_STACK=1 for:

• PYBD_SF6 (F7, HS-in-FS) — flashed and verified CDC serial, machine.USBDevice API, filesystem access
• OPENMV_N6 (N6, HS-in-FS) — flashed and verified CDC serial, machine.USBDevice API, filesystem access
• STM32F429DISC (F4, HS-in-FS) — build only
• OLIMEX_H407 (F4, HS-in-FS) — build only
• NUCLEO_H563ZI (H5, FS only) — build only, regression check

ULPI boards (STM32H747I_DISCO) are tested on hardware as part of the original development in micropython#18303 — this branch is split out from that work.

CDC serial throughput (OPENMV_N6, HS link at 480 Mbit/s)

Compared TinyUSB vs legacy USB stack using tests/serial_test.py methodology.

Read (device → host):

bufsize	TinyUSB KB/s	Legacy KB/s	Ratio
256	5198	816	6.4x
512	5490	817	6.7x
1024	6050	811	7.5x
2048	7560	817	9.3x
4096	9448	811	11.6x
8192	8422	815	10.3x
16384	8086	787	10.3x

Write (host → device):

bufsize	TinyUSB KB/s	Legacy KB/s	Ratio
256	186	464	0.4x
512	218	592	0.4x
1024	193	671	0.3x
2048	185	733	0.3x
4096	184	763	0.2x
8192	178	786	0.2x
16384	179	800	0.2x

TinyUSB read is 6-12x faster. Write is 2.5-4.5x slower due to a pre-existing limitation in the TinyUSB CDC stdin path — mp_hal_stdin_rx_chr() reads byte-by-byte through a 512-byte ringbuffer, causing backpressure on the USB OUT endpoint. This affects all TinyUSB ports, not just HS, and is being tracked separately.

Trade-offs and Alternatives

The RHPORT configuration uses #ifndef guards so boards like STM32N6 that pre-define CFG_TUSB_RHPORT0_MODE in mpconfigboard_common.h pass through unchanged. This avoids needing per-family #if chains but means any future HS-capable family (e.g. STM32U5) needs its own board-level override.

[github-actions]

Code size report:

Reference:  docs/develop/porting: Update session log for example port. [9f396bb]
Comparison: stm32/extmod: Use full path for shared/tinyusb/mp_usbd.h include. [merge of f6345b7]
  mpy-cross:    +0 +0.000% 
   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
      esp32:    +0 +0.000% ESP32_GENERIC
     mimxrt:   +48 +0.012% TEENSY40
        rp2:   +32 +0.003% RPI_PICO_W
       samd:   +28 +0.010% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.46%. Comparing base (9f396bb) to head (f6345b7).
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Additional details and impacted files

@@           Coverage Diff           @@
##           master      #26   +/-   ##
=======================================
  Coverage   98.46%   98.46%           
=======================================
  Files         176      176           
  Lines       22811    22811           
=======================================
  Hits        22460    22460           
  Misses        351      351           

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