My bluetooth controller emulates an xbox 360 controller, but, even if it reports 16 buttons, it actually has 15 buttons. It doesn't have the home button.
There's a way to map a different key combination to open the overlay?
Also: looks like the maker of my controller cheaped out a little bit with electronics, so start+select can't be pressed at the same time (if you press one, the other will be depressed)