Sunday, March 6, 2011

Digging into an Xbox controller

We're trying to add a rapid-fire button to a Xbox controller, and the first step is taking it apart. This isn’t quick and easy, as it requires a special tool, a T8 Torx security driver. Some people have been able to use normal T8 drivers if they break off a little tiny post inside the screw head. We didn't have much luck and ordered the special tool online.

Once we had the tool, we spent a morning working on the controllers. After removing a bunch of screws, they separate into halves along with a lot of buttons, rubber pads and small trim pieces to sort and store in a safe place. We also removed the 'rumble packs', which are motors with off-center weights that vibrate during play.

The rapid-fire modification adds a new button that works as if you're pressing the fire trigger many times. We had to drill a hole in the base of the controller to mount it. We first started with a smaller pilot hole, and then carefully expanded to 1/4" to match the button. The plastic is soft and may twist and tear easily, so we used a hand drill and went slow.

The holes were not perfect but the button retaining nut covers up the imperfections. We made sure this was good and secure, as it's tough to tighten these once the whole thing is re-assembled.

Next we soldered two wires to the button.

One wire goes to a contact that's part of the trigger itself. The second goes to a small Light Emitting Diode (LED) that lights up to indicate "player 1" is using the controller. Soldering the wire here was trouble … the LED is a very small component, so the copper pad to solder and attach the wire is tiny. We struggled a bit getting this to attach and remain fixed as we re-assembled the controller, but using a fleck of flux helped. 

The wires on the board have to be carefully positioned between all the buttons, rubber pads and joysticks. We nibbled away a little bit of plastic near the new rapid-fire button to make a space it could fit into. This plastic used to hold the rumble pack on the right side, but that can't be re-installed because we need the space for the button. The second rumble pack went back in normally.

Finally, we managed to get everything back together and could test it out.

Our results were mixed at best. Both controllers still worked, with the exception of the "Player One" LED which did not light up any more. I think the LED or the tiny copper traces on the circuit board may have been damaged trying to attach the wire. The original triggers and other controls are OK, so we didn't destroy anything major. The new rapid-fire button, however, doesn't do rapid-fire. It behaves just like a single-shot trigger, firing once.

Some of the blog posts and information on the web talks about this problem, so we're going to have to dig deeper. Games may be programmed to ignore rapid fire, or more likely, our circuit isn't working or doing what it needs. We'll have to look more carefully at what is going on and how to trigger it faster.

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