Bootloader Upgrade on Stlink
============================

Beside accessing the SWD pins direct like explained on
https://embdev.net/articles/STM_Discovery_as_Black_Magic_Probe
an updated bootloader can also be programmed via DFU. This requires three
steps:
1. Prepare bootloader update
Normal BMP has to be replaced by the upgrade programm:
 dfu-util -s 0x08002000:leave -D dfu_upgrade.bin
Wait until Dual color led flashes red, indicating DFU is active for the
bootloader.

2. Flash new bootloader
 dfu-util -s 0x08000000 -D blackmagic_dfu.bin
Wait until Dual color led flashes green, indicating bootloader is active.

If not, unplug USB, keep black reset button pressed, replug USB.
Wait until Dual color led flashes green.

3. Flash BMP
 dfu-util -s 0x08002000:leave:force -D blackmagic.bin