In addition to a “Blue Pill,” you will need a 3.3V USB to serial converter. I used a SparkFun Serial Basic configured for 3.3V. Only the TX and RX pins and, optionally, power will be used, so you should be able to use a standard FTDI board as well.
Be careful! Some serial converter boards put out 5V as VCC even when set to 3.3V mode. Applying 5V to the 3.3V main supply line of a Blue Pill will kill it.
Lots of pins on the STM32F103C8T6 are purported to be 5V tolerant, but the main DC isn't. I don't know if TX/RX are.
There is a 5V input on the Blue Pill and a USB connector that can power the board from 5V. These go through a small 3.3V regulator.
GNDpins of the Blue Pill.
3.3pin of the Blue Pill (or
5Vif your serial converter board puts out 5V even in 3.3V mode).
Under the Tools menu, make the following selections:
To put the device into “use” mode, move the top jumper back to 0 (left) position.
Note that the stm32duino.com domain has gone down, apparently because it exceeded the host's traffic limit. Whether it will return is unclear. Project development on GitHub is active.
https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_index.json. However, this list is incompatible with the list at