UF2 bootloader for STM32F103

This project was initially forked off https://github.com/devanlai/dapboot though the DFU functionality has been removed and replaced with a USB Mass Storage with UF2 support

Boards with this bootloader can be programmed at https://maker.makecode.com using web interface using a graphical programming language or TypeScript (JavaScript with Types).

Flashing bootloader from binaries

You will need a STLink/v2 (or other debugger) to flash it.

• https://github.com/mmoskal/uf2-stm32f103/releases
• download the latest ZIP file (uf2-stm32f103-vX.Y.Z.zip)
• run: openocd -f interface/stlink-v2.cfg -f target/stm32f1x.cfg -c "program uf2boot-BLUEPILL.bin verify reset exit 0x8000000"
• see if BLUEPILL drive appears; if not reset the board; the LED should be fading in and out about once per second

Build instructions

The default target is a generic STM32F103 dev board with an LED on PC13, commonly referred to as a "bluepill" board.

To build other targets, you can override the TARGET variable when invoking make.

make clean
make TARGET=STLINK

Targets

Target Name	Description	Link
BLUEPILL	Cheap dev board	http://wiki.stm32duino.com/index.php?title=Blue_Pill
MAPLEMINI	LeafLabs Maple Mini board and clone derivatives	http://wiki.stm32duino.com/index.php?title=Maple_Mini
STLINK	STLink/v2 hardware clones	https://wiki.paparazziuav.org/wiki/STLink#Clones
PXT32	MakeCode Arcade console (currently disabled on Arcade site)	https://arcade.makecode.com

Flash instructions

The make flash target will use openocd to upload the bootloader to an attached board. By default, the Makefile assumes you're using a STLink v2 based probe, but you can override this by overriding OOCD_INTERFACE variable. For example:

make OOCD_INTERFACE=interface/cmsis-dap.cfg flash

Overriding defaults

Local makefile settings can be set by creating a local.mk, which is automatically included.

Here is an example local.mk that changes the default target to the STLink/v2 and uses an unmodified STLink/v2 to flash it.

TARGET ?= STLINK
OOCD_INTERFACE ?= interface/stlink-v2.cfg

Using the bootloader

Building for the bootloader

The bootloader occupies the lower 16KiB of flash, so your application must offset its flash contents by 16KiB. This can be done by modifying your linker script or flags as appropriate.

Switching to the bootloader

The bootloader can be built to look for arbitrary patterns, but the default for the STM32F103 target looks for a magic value stored in the RTC backup registers. Writing the magic value and then resetting will run the bootloader instead of the main application.

WebUSB

The WebUSB isn't currently supported.

Licensing

All contents of the dapboot project are licensed under terms that are compatible with the terms of the GNU Lesser General Public License version 3.

Non-libopencm3 related portions of the dapboot project are licensed under the less restrictive ISC license, except where otherwise specified in the headers of specific files.

The UF2 parts are licensed under MIT.

See the LICENSE file for full details.