game controller mod?

I got the idea from acidmods spitfire mod http://www.acidmods.com/forum/index.php?topic=17385.0 I'm thinking of doing it just for fun, probably on an xbox controller (not 360) that's emulating a 360. Obviously I wouldn't need anything crazy for rapid fire, but I'm thinking of adding macros and stuff. If I was more experienced/had a PIC flahser I would do it with a PIC, but for now it looks like I'll have a bunch of wires going to an arduino.

Just a few questions: -I'll probably use the battery pack, or maybe plug it into the wall, unless there's some way to power the arduino through the USB's +5 (not a full usb plug though) -If i use a different source, I would be connecting my outputs to one side of the switch for whichever buttons I decide to use. Is there any problem with connecting on PS's +5v to another (controller)'s ground?

I'm not too good with this circuitry crap, so I'd like to know what kind of things I would need to consider before doing this.

Thanks

I'm pretty new myself, but I think I can answer your questions.

  1. If you have a regulated 5V supply available you can connect it straight to the 5V and ground ports on the Arduino header and power it that way. No need to cobble together a bogus USB connector just to supply 5V. But be sure it really is a regulated 5V supply, and not an unregulated supply straight from a wall wart, etc.

  2. If you're going to have one device providing a 5V logic signal to the other device they are going to need a common ground.

well it's 5v from a usb powered from a computer so I imagine it's regulated.

To make a common ground wouldn't connect the +5 and gnd to gnd serve to do this?

Thanks

No! Do not connect +5 Volts to Ground. That would be a short circuit. Connect Ground on the power supply to Ground on the Arduino.

haha I know, I mean connect 5v to 5v and gnd to gnd.

Another question. I made a simple app using analog read to measure potential. 1023 being 5 volts. Since the controller is plugged into usb I feel safe to say that I won't get a damage voltage. I plugged the arduino to my computer and the controller into my xbox, then on analog 5 I pulled it down and touched it to pieces of metal to read the potential.. How is this working? Don't they need common ground, or is the common ground the fact that they're both plugged into the wall?

Another question is how can I best find the ground pin on the controller? there's 5 going into the usb (xbox uses 1 extra for Vsync). this is a cheapo brand controller so I'm hesitant to trust the wire colours (although 5v seems to be red)

Final question is if buttons are activated with 2.5volts would a simple voltage divider 1k and 1k do the trick?

Thanks