Button input to two microcontrollers isolation needed?

[24602]

Hey All

If I had a single button input going to two microcontrollers (32U4 with internal pull-up) both on different powersupplies. Should a diode be placed between each microcontroller and the button?

Thinking if one wasn't powered it would sink current from the other.

Good/ bad what you all think?

Thanks

[Kim Christensen]

Thinking if one wasn't powered it would sink current from the other.

Yes that would be a problem.
Diodes would work. As long as the diodes' forward voltage drop is low enough that a valid logic state will be present at the MCUs when the button is pushed.
You could also use two NPN transistors and drive the bases via a Vdd connected switch and resistors.

[wizard69]

Hey All

If I had a single button input going to two microcontrollers (32U4 with internal pull-up) both on different powersupplies. Should a diode be placed between each microcontroller and the button?

Thinking if one wasn't powered it would sink current from the other.

Good/ bad what you all think?

Thanks

It should be easy to keep the two completely isolated with a double pole push button.   The other possibility is to use an optical isolator.