How to select ONE board to download code?

I have two stm32 boards, but platformio report an error when I connecting two boards on my PC to download demo. How can I select one of these boards to download demo in platformio?

Which is what exactly?

What’s the platformio.ini?

You answered none of my two questions :frowning:

I need exact error output and your platformio.ini.

I see.

Duplicate of

Thanks, I will try it.