Ok I will assume that this is somehow related to some form of Raspbery Pi project That is the only reason I had been silent, I thought that a spammer had gotten through somehow. Sorry about that, though it does look kind like an ad.
Is not there already a wired switch? I do not know that particular model, though most of them have a wired switch, and that would be the plase to tap into to control the thing. As to the specifics you would have to look at the Garadge Door openers servvice manual.
RPi = The best ARM based RISC OS computer around
More than 95% of posts made from RISC OS on RPi 1B/1B+ computers. Most of the rest from RISC OS on RPi 2B/3B/3B+ computers