This does not seem to work anymore. After I flash the bootloader, ST-LINK Utility v4.5 reports "Unknown firmware type. Don't know hot to upgrade."

The bootloader link above links to the protected bootloader. I believe, this bootloader protects the flash from tampering with, something that people may not want, especially if they want to repurpose their blue pill later. There are also bootloaders, where that flash protection has been disabled: https://github.com/Krakenw/Stlink-Bootloaders

Blue-pill as USB Altera Byte Blaster :-)

https://radiokot.ru/forum/viewtopic.php?f=60&t=130723

Thank you,

The title is changed.

I do not have source codes. I suppose that this is to make sure that the equipment is correct.

I think the title is swapped and the right one is " using blue-pill as st-link".

I also did this long time ago but I always wondered what is the purpose of the resistor devider connected to PA0

I can think of two possibilities:

- The original firmware probably want  to look at the actual I/O rail in the target.  The clones are simplified version from the eval board debugger.  They don't have separate power rails or the level shifting circuits that the full design stand alone "debug pod" version  would have.

- could also be a strapping option to tell the firmware what features it support.  I think that's unlikely due to the amount of unused pins.

As a start, I downloaded the firmware 2.J16.S4

STM32 ST-LINK Utility has updated firmware up to version 2.J25.S4

Everything works stably. In theory, you can take the original scheme on the site STM and check. I did not have such a task.