I need to connect a Raspberry Pi and an Arduino Uno through serial communication and decided to follow this guide, which mentions the use of a voltage divider.

I understand the connection to the Raspberry Pi GPIO requires 3.3V but I also plan to power the Raspberry Pi from the Ardunio's 5v output pin.

What's the safest approach to achieve this and the recommended current? Thanks.

  • Are you talking about powering the PI via its 5v pin, or powering the it from the Arduino 5v pin? Yes you need a voltage divider, you might get away with a resistor network, but a proper one would be better. – Code Gorilla Apr 8 '18 at 7:14
  • I mean powering the pi from the Ardunio's 5v output pin. The real question here is how I'm supposed to establish connections between pi-arduino when the gpio pins require 3.3v and I need to power the pi with 5v – Adewunmi Apr 8 '18 at 7:20
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    Depending on what pi it is you need 2.5A, which an Arduino can not provide. You need to connect the gnd pins to provide a common ground to allow them to communicate. The Arduino will send 5v signals into the voltage divider and these will be dropped to 3.3v for the pi, and then the process will be reversed. AliExpress or eBay will have loads for sale, they cost about $0.5 each. – Code Gorilla Apr 8 '18 at 7:28
  • Thanks alot. You've made a couple of things clear to me. If I have a 5V, 2.5A power source to be connected to a pi pin and I also need to connect the 3.3v from the voltage divider to a pin, is it safe to have two voltage sources into the pi? – Adewunmi Apr 8 '18 at 7:54
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    Yo should connect the 5v 2.5A PSU via the power input micros USB socket on the Pi rather than the 5V pin. I don't know for certain, but the chances are that the socket is better protected against over/under voltage, reverse polarity, etc. If you use the power in pins of the GPIO connector (if there are any) then you need to be 100% certain you are correct otherwise you will fry your Pi, and fried Pi smells bad. If you use the power socket the 3.3V will also be provided by the circuitry and all will be good. – Code Gorilla Apr 9 '18 at 11:24
  1. You CAN NOT reliably power any model Pi from the Arduino 5V output.

  2. You can interconnect the Arduino serial to the Pi using a voltage divider or (preferably) a level converter, as suggested in the linked article. (I might add that the linked article contains a number of errors which will not work on recent Pi models).

Better still you can use a USB connection, to provide serial communication to the Arduino, AND you can power the Arduino from the Pi (I often do this).

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