Maybe diggin a topic a bit, but as for June 2021 :
In library file MyHwSTM32.h one line seems to be lost :
#ifndef MyHwSTM32_h #define MyHwSTM32_h #include <IWatchdog.h> #include <itoa.h> #include <SPI.h> #include <EEPROM.h> <<--- this is necessary to compile agains BluePill
and something like this in platformio.ini
[env:bluepill_f103c8] platform = ststm32 board = bluepill_f103c8 framework = arduino upload_protocol = stlink debug_port = stlink debug_tool = stlink monitor_speed = 115200 monitor_filters = time, default
Just to keep you entertained.