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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

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    \$\begingroup\$ A voltage divider is ok, if you want extra protection you can add clamp diodes to 3.3V. Alternatively, you can use a 3.3V Arduino for example with a series resistor. Will they be far away from each other? Are you using different power supplies..? \$\endgroup\$ – Wesley Lee Nov 22 '16 at 13:46
  • \$\begingroup\$ Power Supplies are the same and the the boards lay next to each other. Do you mean Zener diode with clamp diodes? ok, my fault. I searched google for "clamp diodes" and only got bad hits. "clamp diode" did the trick... Thanks for your help! :) \$\endgroup\$ – Polle Nov 30 '16 at 10:33
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As you said, a resistive divider would be the easiest. Clamp diodes are cheap to add and provide extra protection.

schematic

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..

schematic

simulate this circuit

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  • \$\begingroup\$ Thanks for the useful insight, helped a lot! The Optocoupler is actually a good Idea for that situation. I will take the route with the voltage divider + diodes, thought. \$\endgroup\$ – Polle Nov 30 '16 at 10:38
  • \$\begingroup\$ @Polle -- glad that I could help, good luck! \$\endgroup\$ – Wesley Lee Nov 30 '16 at 11:22

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