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.


1 Answer 1


The STM32 used tolerates 5V as input but it's giving 3.3 output, i doubt they'd boost that on the fc

that said if you want to be sure its time to bring out the multimeter, if you don't have one you should get one when tinkering with electronics.

  • $\begingroup$ I have a multimeter - but I'm not sure how to make FC to output a steady high on RX and TX. If it sends data at high baud rate the multimeter will hardly produce proper measure, as I understand. $\endgroup$
    – mvmn
    Nov 28, 2023 at 21:10
  • $\begingroup$ If the multimeter doesn't go higher than the 3.3 you are looking for you should be fine. If you want control over the pad, pinio (in betaflights manual) can help, and if you want accuracy you'll need an oscilloscope where you can see min and max values. $\endgroup$
    – ppetermann
    Nov 30, 2023 at 6:21

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