UF2 Bootloaders for STM32

This implements USB mass storage flashing using UF2 format

Build instructions

To build just run make in this folder. This will fetch git submodules if needed and build libopenocm3 (which only happens once).

The binaries will be in build/BOARDNAME. The following files will be built:

• bootloader.elf - for use with JTAG adapters
• bootloader.bin - for direct onboard upgrading
• flasher.uf2 - if you already have a UF2 bootloader, you can just drop this on board and it will update the bootloader
• flasher16.uf2 - this is similar, but if you have an older UF2 bootloader on the board, that expects the app to start at 16k (0x08004000)

Adding board

Start from f401 (for 64 pin package) or f401c (for 48 pin package) generic board. Copy the folder and modify board.h, follow instructions at https://arcade.makecode.com/hardware/adding#generating-bootloader

Pullups on USB data lines

If you have a hardware pull up on USB data line, you may need the following in your board.h file:

#define USB_FORCE_DISCONNECT 1

F412

The F412 has a different USB module. In the board.h you will most likely want to add like this:

#define BL_F412 1

License

License: LGPL for libopencm3, BSD for what was left of the PX4 bootloader (see LICENSE.md), MIT for the UF2 stuff, and ISC for the bits from dapboot.

Credits

This repo was forked from https://github.com/PX4/Bootloader

It contains small bits from https://github.com/devanlai/dapboot, mostly the WebUSB, that has been heavily modified though.

The UF2 stuff was mostly lifted from https://github.com/Microsoft/uf2-samdx1 by way of (non-working) https://github.com/Microsoft/uf2-nrf5

The dmesg subsystem is adapted from https://github.com/lancaster-university/codal-core