Serial Port not working on bluepill STM32F103C8T6 + FTDI + PlatformIO

Hello, I am currently trying to make my stm32 + FTDI so make the serial port working.
with the following circuit:

I managed to make it working on the arduino IDE with the following configration:


And using Serial1 in the code.

Note that for uploading I use a ST-LINK V2 adapter

Now this is my platformIO config for this project

PlatfromIO does show the good serial port but I cannot find how to print anything

You explicitly enable the USB Serial (CDC), so by default Serial will go to USB device. Not via UART (PA9/10).

What src/main.cpp code are you running on the STM32?


This is my code, nothing complicated

The constructor arguments look wrong, shouldn’t they be PA9 and PA10 instead of PA_9, PA_10?

To my knowledge, they are the same, but replacing them changes nothing

Okay, indeed both the int version (PA9) and PinName enum (PA_9) are accepted. But RX and TX are reversed.

PA9 = Serial1 TX and PA10 = Serial1 RX

the constructor wants

aka, RX first, then TX.

So you should write

HardwareSerial Serial1(PA10, PA9);

Okay yes, my mistake.

how should I fix that ?
When I remove the problematic line, the code doesn’t compile

I wonder what should my platform.ini look like