USB serial is a good way to go

Note: let’s use “F103” as shorthand to avoid typing “STM32F103C8T6” all the time The F103 has a built-in ROM-based boot loader, so there’s no risk of ever damaging it, but it’s quite limited since it can only deal with a serial connection on the USART1 pins (PA9 for TX and PA10 for RX). There is no way to reflash an empty or messed-up F103 from USB. In addition, every ARM chip has either JTAG hardware built-in, or its low-pincount variant, called SWD.