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First things first: Don't forget to read the originalREADME.md of the parent project.

This is a fork ofdmitrystu's greatsboot_stm32 bootloader, which is a beautiful piece of software, with a few modifications to make it act similarly likerogerclarkmelbourne'sSTM32duino-bootloader, adapt the nifty little RTC magic number feature fromSerasidis'STM32 HID-Bootloader, and thus provide better compatiblity to theSTM32duino Arduino Core - especially when developing withPlatformIO and VSCode.

For downloading firmwares to your Blackpill via USB you can simply do the little finger dance and you're fine... kind of... unless you're some lazy dude like me, who doesn't want to do the extraequilibristics to fiddle around with the board all the time while coding. Having a pretty weak pull-down connected to BOOT1 with a far higher resistance than my thick clumsy fingers doesn't help neither.

Since the STM32F103 doesn't have a USB-capable bootloader in ROM,Roger wrote theSTM32duino-bootloader for the Bluepill andST-Link Baite-Clones, which always starts up after resetting the board and then proceeds to the user application after a short timeout. This way the host can toggle the DTR "pin" of the USB-serial which is detected by theSTM32duino Arduino Core and triggers a reset of the board like theMaple boards first implemented this.

The beforementionedHID Bootloader, which isonly partly supported by PlatformIO'sST STM32-platform, andRoger'sSTM32duino-bootloader additionally implementchecking a register of the RTC's backup domain to determine whether the bootloader should beforce-entered orskipped completely after the reset, which can be controlled by the user application and is also reflected in theSTM32duino Arduino Core. See itsbootloader.c for more details.

To complete the whole and round it nicelyWeAct especially made theirHID Bootloader incompatible withSerasidis'STM32 HID-Bootloader from which it was forked and their Blackpills are usually shipped with. Yay!I'm lovin' it!

So what would be nice is a standard dfu-capable bootloader that can easily be entered automatically using your development IDE and is supported by the standard STM32-Arduino Framework.So here you go!

• The DFU protocol (sboot)
• Application offsets 0x2000 and 0x4000 in flash(it can actually be quite tiny depending on the selected features)
• Automatically entering the bootloader after power-on (STM32duino-bootloader)
• Entering the bootloader by double-clicking the reset-button (sboot)
• Entering the bootloader by holding down a user-button (all)
• Force-entering the bootloader when no firmware is detected (STM32duino-bootloader)
• Force-entering or force-skipping the bootloader by
  • RTC magic number (HID/STM32duino Bootloader) or
  • magic number in SRAM (sboot)
• Automatically exiting the bootloader and running the firmware after various configurable timeouts
• Encrypted firmware downloads (sboot)
• Verifying the checksum of the firmware (sboot)
• A nervously flashing LED while in bootloader
• Each of the features above can be enabled/disabled separatelyNot all combinations make sense! You choose! (userconfig.h)

• ST-DfuSe extensions
• STM32F103 MCU targets (Bluepills,Baite-STLinks)
• Being badly incompatible to everything else (WeAct HID-Bootloader)

• Simply just power up your board
• Toggle the DTR "pin" of the USB-serial interface
• Write RTC_MAGIC_NUMBER_BOOTLOADER into register 4 of the RTC backup domain (RTC->BKP4R) and issue a (whatever) reset
• Write DFU_BOOTKEY at DFU_BOOTKEY_ADDR (RAM top by default) and make a software reset
• Assert DFU_BOOTSTRAP_PIN on DFU_BOOTSTRAP_PORT on startup
• Make a double reset during the DFU_DBLRESET_MS period
• Overwrite the first four bytes of your user firmware

Inexamples/hello_world you can find a very basic example on how to use this bootloader for your daily work withPlatformIO and VSCode.

What isArduino IDE?