https://stm32duinoforum.com/forum/wiki_subdomain/index_title_Bootloader.html

https://github.com/rogerclarkmelbourne/STM32duino-bootloader

https://www.electronicshub.org/how-to-upload-stm32f103c8t6-usb-bootloader/

https://github.com/rogerclarkmelbourne/Arduino_STM32