[nic547]

STM32 MCUs are 3V3, not 5V right?

Arduino really isn't great with naming, a Uno can be an AVR or ARM based board, now either 3V3 or 5V based and also a SBC rather than just a MCU.

[geerlingguy]

I think to Arduino, Uno just means 'Uno form factor, with shield pins in the same place'

[chimpontherun]

Which is kind of sad, since the Uno pinout is horrible for high-speed signals

[the__alchemist]

Depends on the MCU, but generally STM32 is 1.7-3.6V

[0x457]

STM32 is 3v3 logic.

[HeyLaughingBoy]

Yes, but many (most?) of them are 5V-tolerant.