V2.5.1 MSGFLTR pipe bug correction
Version 2.5 includes a bug correction in parameters validation on the MSGFLTR pipe that blocked function 2.
You need the tkg-hid-bootloader firmware here :
https://github.com/TheKikGen/stm32-tkg-hid-bootloader/blob/master/F1/bootloader_only_binaries/tkg_hid_generic_pc13.bin
Flash it with st-link at 0x08000000. This new bootloader doesn"t need any driver.
Unplug the st-link stick, plug the Bluepill to USB, then use TKG-FLASH.EXE provided in that release to flash the 128K or the 64k bluepill version. The 128K firmware should work on a 64K Bluepill most of the time. If it is not the case, try the 64K firmware version.
Prebuilt binaries are compiled for the tkg-hid-bootloader since the 2.5 version.