How to determine contacts to jump a SMD button on garage door remote?

Question

I am attempting to control my garage door remote using a Raspberry Pi controlled relay. I have done this in the past with other remotes (i.e. the relay part is not an issue), but my new house's garage door remote uses SMD/membrane switches and the contacts of the buttons aren't visible, so I can't figure out what points to short to emulate the button press.

The specific remote in question is a 'Padors PTR416', which uses the HCS301 chip. The chip's operation is detailed here (excerpt screenshot below): https://ww1.microchip.com/downloads/en/devicedoc/21143b.pdf

From the circuit/pin descriptions I figured that shorting between pin 1 (switch input 0) and pin 8 (positive voltage) would do it for button 0, but it does not send the signal or turn on the signal LED.

I'm not an electrical engineer and I'm at the limit of my understanding, so if anyone has any pointers that would be great. I do not have a multimeter to test, if necessary I'll get one, but I'm hoping it can be figured out without. I haven't experimented too much as I don't want to damage the remote.

Answer 1

Given you know the IC being used and it's pinout, it should be pretty easy to work out which switch is which.

Pins 1 through 4 (pin 1 is the one with the white dot on the IC) are your four switch inputs.

Probe the voltage between each of these pins and ground (pin 5), then repeat the measurement for each switch being pressed. You should find that each button changes the voltage on one of the pins.