In this video Hugatry shared detailed instructions of how to use the STM32F103C8T6 as an USB device with virtual serial port:
Cheap STM32F103C8T6 development board
Blue STM32F103C8T6 development boards, also known as “BluePill”, are cheap way to get started with 32bit ARM microcontrollers. The STM32 development board can sometimes be bought for less than $2 and ST-LinkV2 compatible programmer and debugger doesn’t cost much more than that either.
The STM32F103C8T6 has nice amount of flash and RAM, runs at 72MHz and best of all: It has built-in USB. It is possible to program these STM32 boards to act as an USB devices, without “FTDI chip”. In this post and in the embedded video I will teach step by step how to use the STM32F103C8T6 as an USB device, in particular a virtual serial port.
More details at Hugatry’s HackVlog.