I recently purchased a BigTreeTech mini e3 V1.2 controller for my custom built 3D printer (as opposed to an pre-purchased ender 3). In doing so, I ran into the problem that the endstops I have been using have three wires: Power, Ground, and signal. The mini e3 V1.2 that I purchased uses endstop connections that only have two pins. This can be seen in the schematic below on the bottom right of the controller. I don't know where to buy endstops that only have two pins and have not been able to find anything online. If anybody knows where these can be bought or how the 3 pinned endstops are supposed to be wired up it would be much appreciated.
You do not need to connect the red (+) wire of the endstops. The controller board uses a technique to ensure the signal is 3.3 V or ground, see the top left schematics of this link (will insert an image later!). Specifics about this technology is found here and is explained as using a pull up resistor.
What happens is that the signal is always reported as triggered, unless the endstop connects the signal wire to ground.
This link shows that only ground and signal are required (will insert an image later!).