TinyUF2 Bootloader

This repo is cross-platform UF2 Bootloader projects for MCUs based on TinyUSB

.
├── apps              # Useful applications such as self-update, erase firmware
├── lib               # Sources from 3rd party such as tinyusb, mcu drivers ...
├── ports             # Port/family specific sources
│   ├── espressif
│   │   └── boards/   # Board specific sources
│   │   └── Makefile  # Makefile for this port
│   └── mimxrt10xx         
├── src               # Cross-platform bootloader sources files

Features

Supported features are

• Double tap to enter DFU, reboot to DFU and quick reboot from application
• DFU with MassStorage (MSC)
• Self update with uf2 file
• Indicator: LED, RGB, TFT
• Debug log with uart/swd

Not all features are implemented for all MCUs, following is supported MCUs and its feature

MCU	MSC	Double Reset	Self-update	Write Protection	Neopixel	TFT
ESP32 S2/S3	✔	Need RC	✔		✔	✔
K32L2	✔	✔
LPC55	✔	✔			✔
iMXRT	✔	✔	✔		✔
STM32F3	✔	✔			✔
STM32F4	✔	✔	✔	✔	✔

Build and Flash

Following is generic compiling information. Each port may require extra set-up and slight different process e.g esp32s2 require setup IDF.

Compile

To build this for a specific board, we need to change current directory to its port folder

$ cd ports/stm32f4

Then compile with make BOARD=[board_name] all, for example

make BOARD=feather_stm32f405_express all

The required mcu driver submodule if any will be clone automatically if needed.

Flash

flash target will use the default on-board debugger (jlink/cmsisdap/stlink/dfu) to flash the binary, please install those support software in advance. Some board use bootloader/DFU via serial which is required to pass to make command

$ make BOARD=feather_stm32f405_express flash

If you use an external debugger, there is flash-jlink, flash-stlink, flash-pyocd which are mostly like to work out of the box for most of the supported board.

Debug

To compile for debugging add DEBUG=1, this will mostly change the compiler optimization

$ make BOARD=feather_stm32f405_express DEBUG=1 all

Log

Should you have an issue running example and/or submitting an bug report. You could enable TinyUSB built-in debug logging with optional LOG=.

• LOG=1 will print message from bootloader and error if any from TinyUSB stack.
• LOG=2 and LOG=3 will print more information with TinyUSB stack events

$ make BOARD=feather_stm32f405_express LOG=1 all

Logger

By default log message is printed via on-board UART which is slow and take lots of CPU time comparing to USB speed. If your board support on-board/external debugger, it would be more efficient to use it for logging. There are 2 protocols:

• LOGGER=rtt: use Segger RTT protocol
  • Cons: requires jlink as the debugger.
  • Pros: work with most if not all MCUs
  • Software viewer is JLink RTT Viewer/Client/Logger which is bundled with JLink driver package.
• LOGGER=swo: Use dedicated SWO pin of ARM Cortex SWD debug header.
  • Cons: only work with ARM Cortex MCUs minus M0
  • Pros: should be compatible with more debugger that support SWO.
  • Software viewer should be provided along with your debugger driver.

$ make BOARD=feather_stm32f405_express LOG=2 LOGGER=rtt all
$ make BOARD=feather_stm32f405_express LOG=2 LOGGER=swo all