Read (High/Low) Arduino Output with an Raspberry GPIO Input Port

Question

I want to trigger events on the raspberry (3) with an Arduino. Because of very contrary statements to this, i am kinda Lost. Arduino outputs 5V, that should be read by an Input of the Raspberry. Just slow Low/High Values, kinda like Buttons presses.

Different Possibilities I found:

• Voltage Divider from 5v to 3,3v for Raspberry Pi (for example: 10k and 18k, for ~3v on the Input): That would the way that I think it is the easiest. But I stumbled over a lot of statements that say they would not recommend that, because of burned GPIOs. And the pullups of the Raspberry GPIO should be a problem. Later I found that the raspberry has software set able pull up/down resistors. It feels like lots of people don't know that they can disable them?

• Voltage Level Breakout boards: That would be the easy way to go, but costs money and I don't need a bidirectional connection.

• Levelshifter ICs: self explanatory.

• Circtuit with a Transitor: Self explanatory, that would be my choice if Voltage Divider don't work.

So perhaps you can explain me what fact is against using a Voltage divider to connect these two boards. I just want to understand the issue, if there is one. :)

Cheers Michael

Answer 1

As you said, a resistive divider would be the easiest. Clamp diodes are cheap to add and provide extra protection.

^{simulate this circuit – Schematic created using CircuitLab}

If you are using different power supplies for each of the devices and want isolation between them, you can use a common optocoupler such as 4N25, PC817, etc..

^{simulate this circuit}