Reading an Arduino Pin from a Raspberry Pi Pin

Just want to post this, mainly for my own memory. When helping students at the local STEM school interface an arduino to a Raspberry Pi, they needed to read a 5V Arduino pin with an 3.3V RPI card.

In the past when I’ve done this, I used a level converter:

Arduino/Raspberry Pi via I2C

The school has no such beast and this is a bit complicated to explain to most of the students I’ve been working with. So I decided to use a voltage divider to get the voltage where I needed it.

There is a handy website for just such an occasion:

Voltage Divider Calculator

We put in our requirements and got back the necessary resistors:


We didn’t have a 1.7K, but we did have a 1.8K. Recalculated with 5/1.7/3.3 to see what the output voltage would be – 3.235V. Should be good enough.

So we implemented the interconnect like this and it works fine.


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