Trying to use the raspberry pi to control an Arduino Uno and I'm tyring to ensure nothing breaks when connecting them. I know that the Arduino outputs at 5V while the pi inputs at 3.3V. This requires resistors to decrease the voltage.

What about the other way around? I would like the pi to output a digital signal to the Arduino to have a function run. Common sense suggests that this shouldn't be a problem but I want to make sure that is the case.


The Arduino GPIOs will be fine. Some Arduinos are 3V3, most are 5V. Either way their GPIO will not be damaged by a 3V3 signal from the Pi.

  • thanks that's good to hear. Just have to remember that the system is 1 way. – Hojo.Timberwolf May 15 '18 at 7:48
  • Or buy a 3V3 Arduino. I think some 5V Arduinos can actually be run from a 3V3 supply which in effect also removes the problem both ways. – joan May 15 '18 at 7:53
  • Didn't know 3v3 Arduino existed. I shall take a look. One problem though is the Arduino needs to be compatible with the motor shield. I am hoping to have the pi tracking with the camera and sending signals to the arduino to control a pair of motors. (I Believe I need to attach a 12V supply to the motor shield for the motors) – Hojo.Timberwolf May 15 '18 at 7:57

The answer depends on what you mean by "connecting them".

Normally I use a 3.3V Pro Mini which can be directly connected.

Strictly the Pi GPIO "HIGH" signal is marginal when connected to 5V logic, but usually works. You can use a voltage divider on Pi inputs.

If you need bi-directional use a level converter (which can always be used for one-way).

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