I have been looking into this.
I bought a RATGDO 2.5 and was disappointed to open my gate motor and see the contacts weren’t easily laid out. I have been digging. As stated above, the SBC seems to be the golden ticket for dry contacts.
(taken from manual)
The Expansion Board is seemingly the easiest option to get access to limiters for Open and Close but at $150 it’s not really my first choice. Model: LiftMaster Expansion Board (UL325)
The black box in the bottom right hand corner is what I think would be the easiest access to what you’d need for a dry contact RATGDO.
But this isn’t too feasible due to cost.
I want to dig into what the color wires on the arm do.
Now, I haven’t tested this yet but I stumbled across this video (https://youtu.be/T5quqEr5-_U?t=594) where a guy is repairing his LA400 opener and it gives a pretty good view of the limit switches on the inside of the arm. It looks like the Brown and White Wires are Limit switches and the Yellow might be the common line. In the next few days when I get a chance I am going to take a multimeter and see what the terminals on the gate board say at different positions.
I’m hoping we can get a reading out of these colored wires going to the operator.
My 3rd RATGDO is still on it’s way and I’m not willing to rip my other 2 out of the other doors to test this. If anyone makes progress, please update me!