I want to connect SpeedyBee F405 V3 to a Raspberry Pi via UART.

Raspberry Pi uses 3.3 volt for GPIO, so it sounds like connecting a 5 volt UART to it may damage it - and most online documentation recommends to check for this.

But I can't find any information on what voltage does SpeedyBee F405 V3 use in it's UART ports. Is it 3.3V or 5V or something else?

UPD: Experimentally, it worked for people with Raspberry Pi - so I assumed it must be 3.3V and did the same, and so far my Raspberry Pi 4 hasn't burned. So I presume it is 3.3V - but I was unable to find any documentation that would clearly state so.