Controlling Nintendo 3DS

So I'm trying to control the button inputs of a Nintendo 3DS with the arduino sending PWM 5V pulses from ports 2 through 9 to the UP,DOWN,LEFT,RIGHT and A,B,X,Y buttons of the 3DS but I clearly don't know basic electronics because it's not doing anything.

The LED bargraph is just so I can see which buttons are being pressed by the arduino when it finally gets working and the buttons on the side are to control an LCD screen that I've yet to set up.

But just basically how do I connect the cable from the 3DS to these PWM ports so that a 5V signal from the arduino will actually trigger the button and make the 3DS think it's been pressed?

Thanks and feel free to mock my ignorance, I just need a little help.

Any circuit needs two wires it looks like you only have one. You need to wire the ground of your 3DS to the ground of your arduino as well as any signal.

However before you do are you sure that the 3DS works on 5V? If it only works on 3v3 you could blow it up giving it 5V. Also it is normally a logic LOW that corresponds to a button press.