I want to connect an Arduino to Raspberry Pi through a USB-TTL converter like this one:


My doubt would be about logic voltage. I know that Arduino works with 5V logic, while Raspberry Pi does with 3.3V and is non-tolerant. So, how should the wiring be done?

I'm not intending to connect any weird stuff to the Raspberry. To the Raspberry Pi is only going to go the usb-end of the adapter.

My adapter does not have a serial number to identify it, but its main chip does, it is this:


I just want to avoid damaging the Pi through USB. I don't know if supplying 5V through it might damage it, though.

Basically just want to know if should be this:

enter image description here

Or this:

enter image description here

References I used for documenting:

  • I am suspicious of any Instructables post. Many are poor quality. There are plenty of good Pi tutorials on this site & raspberrypi.org.
    – Milliways
    Nov 10, 2022 at 21:42

3 Answers 3


First that device is NOT TTL (it would be CMOS).

No one can tell what it does from a picture. You need to check the specifications. Many (most?) such devices actually output 3.3V logic.

IMPORTANT DO NOT connect ANY power pins 3.3 or 5V to the Pi!

  • The USB chip my adapter uses is sparkfun.com/datasheets/IC/cp2102.pdf seems like the adapter does not have serial number. I was not asking about how to wire something to the pi. The pi is going to only get the usb-end plugged.
    Nov 10, 2022 at 22:14
  • If you are planning to connect USB to the Pi the Question makes no sense. USB is 5V. NOTE the Instructables post is pin connections to the Pi.
    – Milliways
    Nov 10, 2022 at 22:44
  • Yes, I thought that, but I concerned when I read about Pi not being 5V tolerant. Sorry for my ignorance. Could you confirm only with my latest updates on the question? I posted my wiring options.
    Nov 10, 2022 at 22:51
  • I EDITED the post, as you might see. My question is intended to AVOID damaging the RASPBERRY.
    Nov 10, 2022 at 22:56

Connect like this:

Arduino - USB Serial
Txd     - Rxd
Rxd     - Txd
GND     - GND

Do NOT connect any power pins.

  • Yup, that was exactly the way to do it. Thanks.
    Nov 12, 2022 at 19:32

Well, after getting better documented and performing tests, I got the right wiring for avoid damaging the Raspberry Pi and getting the desired serial communication as expected.

USB standard gives 5V max output (considering the possible threshold) which by design would not damage the Pi. Which is not the case for GPIOs, where if you would like to do something similar, you should use a level shifter since those are not 5V tolerant.

Here is the right wiring:


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