TinyUF2 Bootloader

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

.
├── lib               # Sources from 3rd party such as tinyusb, mcu drivers ...
├── ports             # Port/family specific sources
│   ├── esp32s2       
│   │   └── boards/   # Board specific sources
│   │   └── Makefile  # Makefile for this port
│   └── mimxrt10xx         
├── src               # Cross-platform bootloader sources files

Features

TODO more docs later

• Support ESP32-S2, iMXRT10xx, LPC55xx, STM32F3, STM32F4
• Self update with update file in uf2 format
• Indicator: LED, RGB
• Debug log with uart/swd
• Double tap to enter DFU, reboot to DFU and quick reboot from application

Build and Flash

Requirements

• GCC cross compiler and Make

Compile

Firstly clone this repo and its submodules with

$ git clone --recurse-submodules https://github.com/adafruit/tinyuf2

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

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 out only message from bootloader project, while LOG=2 print more information with TinyUSB stack information events as well (note: it is quite a bit). LOG=3 or higher is not used yet.

$ 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