We are using Geehy SDK, unfortunately it still does not work.
Wanted to clarify what we are doing, just in case we missed something:
• We’re testing with APM32F003F6U6 board
• PB4 is USART3 TX, PB5 is USART3 RX
• We are compiling with optimizations turned off
• We tried setting USART3->IO & USART3->IO SW manually
But it failed.
Oh, I found the reason.
Because the APM32F003F6P6 chip PB4, PB5 for true open drain I/O, no internal push pull circuit. so when using, if used as an output pin, need to add a pull resistor to VDD outside the pin.
