[TokyoDrift] built an adapter that allows you to connect a PlayStation 2 controller to a PlayStation Portable. It’s a bit different from similar hacks as this adapter doesn’t require any hardware alteration to the PSP or the controller. To do so, a plug-in is used on the PSP firmware side of things. The adapter then makes use of video out and PS2 controller extension cables, along with an ATmega8 microcontroller to handle the signals between the two devices. We posted a picture of the guts because we like that king of thing but the finished project is nicely housed inside of a project box.

http://hackaday.com/2010/04/23/plays...o-psp-adapter/