Sharing Button input between two microcontrollers

[24602]

Hi All

Ive got a project with two microcontrollers (redundancy)

Button connected to both microcontrollers. Internal pull-ups on the micro inputs. Button goes to GND when closed. This works but not ideal.

What would be the best way of sending that button signal to both controllers in the event that one micro dies or shorts the input HIGH or LOW?

[Jeroen3]

Simple 74 series buffers/inverters with a series resistor at the ouputs.

[Damianos]

Two diodes with the cathodes connected to the button and the anodes, via resistors in series, to the inputs.

[24602]

 Like the attached image?

[Shonky]

Don't you mean Cathodes to the micro instead like attached image?

Your diagram has the cathodes going to the switch.

[ArdWar]

You don't even need any diodes.

Change resistor values to your preference. Keep R1/(R2||R3) small enough to make sure the common point still above V_IH(MIN) when one of the IO stuck low. Beware of "always on" internal pullup like STM32's 40kΩ on reset pin, picking a too high value for R2 and R3 may cause IO pin to not go low enough below V_IL(MAX) when needed.
It was for reset circuit so you probably also don't need the caps, although it's still nice to have for debounce.

[Gyro]

If you want true redundancy, you might want to go for a double pole push button. It might limit your choice a bit but the button contacts are probably one of the less reliable elements in the system.

[DarkMode]

Howdy, from my basic understanding, if the Button Pulls Low (Ground), and the Micro's are both pulling up 'High'. Pushing the Button will draw energy from BOTH pins of the Micro.

I think they will both 'short' and flow the energy to the Ground (via the button), you might have to add a resistor after in the circuit to stop it from Shorting too quickly, but that's my Guess.

Corrections welcome