Gonnecting GPIO of one microcontroller directly to another microcontoller

[xibriz]

I have a remote control that I want to connect a ESP8266 to trigger some of the remote buttons.
Originally I though to just use a relay and solder onto the buttons of the remote control.

But after opening it I see that the remote control uses a L24YK with 6 input pins that is triggered when pulled to GND.

L24YK and ESP8266 are both 3.3V chips, could I just ditch the relay and connect a pulled up GPIO from the ESP directly to the L24YK and just pull it low when I want to simulate a button press?

Or do I risk breaking something when setting the input pin of the L24YK to high?

[DrDiettrich]

Use of optocouplers is recommended, instead of relays. Such isolation prevents e.g. problems when a remote control button is pressed accidentally.

[xibriz]

Thanks for the response.

I have relays with optocouplers, but if I understand you correct one solution is to just ditch the relays and only use optocouplers?

I was hoping to use the same power source to drive the remote and the ESP.

So in your opinion, I risk breaking something with this schema?

[DrDiettrich]

You risk to kill a GPIO output by pressing a key, shorting the output to Gnd. At least the GPIO pins should not be outputs unless a key press shall be simulated.

[Paul_B]

Put a diode with cathode to the ESP in series with each of the connections. It can only pull down the button input, not pull it up.

[xibriz]

Appreciate the help DrDiettrich and Paul__B.

If any of you want to take my highly advanced schematic and add the least number of parts that would be great