Xbox 360 Thumbstick Hack Question


#1

Hello everyone,

I have a question about how the thumbstick on the Xbox 360 pad works. What I want to do is to restrict the thumbstick to only up and down movement. I was thinking I could desolder the mechanism from the bottom side, remove the entire stick assembly from the pcb, somehow cover or block the contacts for left and right then resolder the assembly back.

Does anyone have any experience removing these things? Or, even better, do any of you gamepad gurus have a better idea? I’ve got one practically ruined MadCatz pcb that I can experiment with, and as soon as I’m able to I will…but I was hoping for any support I could get going in.

Thank you as always for any advice you can offer.

Jonathon “Pac” Maness


#2

Do you want to prevent the stick from physically moving left/right or only stop it from sending those signals? If the latter I’m thinking it should be enough to just desolder the X-axis potentiometer and replace it with a resistor corresponding to the potentiometer’s value when the stick is in neutral position.


#3

I feel good because I sort of understand what you said but I have NO clue on how I would do that. Stopping the signal or stopping it from physically moving in those directions…either one is ok. Basically, if I pull back and left, I’d like it to only register back. Same with up and right or any combination of up/down and left/right. In fact, I don’t need left or right to be active at all.

I am past befuddled at this point. Could be the pain medicine, could the lack of sleep…most likely it’s BioShock + all of the above + I’m sort of a moron about electronics. Not a moron really, just unedumakated.

I’m looking at the thumbstick, and I think I know what you mean kind of. Desolder the bit that shows what position the X-axis is in and put a resistor there. How would I make it register null (is that the right term?)?


#4

Not trying to insult you or anything, but why would you want to do that? Just curious.


#5

Find the pot that controls the axis you want. There’ll be three solder points for the pot. Use your multimeter and doublecheck that the left and right pins are connecteced to the left and right pins of the pot for the other axis on that stick.
If the solder points for the pots look like this:
1
2
3
456

Then there is a good chance that 4 is connected to 1, 6 is connected to 3, or 4 is connected to 3 and 6 is connected to one. Write this down.

Youre gonna cut the left and right traces where they go to the pot. Leave the middle one alone. Find two resistors of the same value (doesn’t really matter, but 1K ohm is probably a good size to use.) and connect the left and right pins of the OTHER pot to the middle pin of your modded pot through the resistors.


#6

While we’re at it, is there a straightforward was to outboard an analog stick “click” button?

Ie, I solder on a momentary pushbutton, and when I press that button, it sends an analog stick “click”? There’s a non-fighting-game reason for this. :slight_smile:


#7

Sure, just run the wires from the click switch to your second button.
Now, if you want to do it and have the stick not click anymore, THATS difficult.
Even though the audible click only happens when its pressed down, the click button is still pressed as long as the stick is pressed in. Just like every other momentary switch.


#8

Yeah, that’s fine. In fact I would prefer both to work. :slight_smile:


#9

I’m looking at the traces on the board of the MadCatz pcb, and from this one it appears that value 3 on the axis I want cut goes to a value 3 on the good axis and 6 goes to six. The very left solder point (or right depending how you look I suppose) almost appears to be a ground.

What you are describing sort of reminds me of the solution I read somewhere for hacking the shoulder buttons. Is that because they are both sensitive to how far they are pushed vs. just being clicked buttons?


#10

Correct. Almost all controllers use potentiometers for their analog stuff, both triggers and analog sticks. Pots have one low pin (usually connected to ground), one high pin (usually connected to the power source, like +5v) and a pin in the middle called the wiper. It acts as a voltage divider; the voltage on the wiper pin will always be somewhere between the low pin and the high pin. If the wiper is closer to the low pin than the high pin, it will be a lower voltage.

Because the wiper will be in the very middle when in neutral, the voltage will be exactly in the middle of the low and high. If the low is 0 volts, and the high is 5 volts, the wiper will be at 2.5 volts. The PCB sees this voltage, and knows immediately where the stick is.

cutting the traces to the pot makes it ignore whatever the pot says. Connecting it to high and low with an identical resistor makes the voltage at the wiper in between the high and low voltage. PCB sees that, and thinks the analog is always in the middle.


#11

What would happen if I were just to remove the potentiometer altogether? Would there be an explosion or would it simply just not register at all?


#12

Then the line would be floating. When the PCB checked the voltage on that line, the only voltage would be random induced noise. If its anything like the Dreamcast pads I took apart, it would either be randomly fluttering all over the place, or locked all of the way in one direction.


#13

You took apart a Dreamcast pad? You…you…you…monster! :slight_smile:

What would happen if, say, I removed the pot altogether and ran a resistor from the hypothetical 5 v to the 0 v holes? Would the PCB interpret that as neutral, or would it freak out again?

See, my concern is putting resistors into the same solder point on the board that is already being used by the “measuring” post of the pot and the posts for the working potentiometer’s lines. Won’t it get a little crowded in there or should there be room to solder in two or three posts through one hole? Also, can’t I just use the lines that I snipped the “left” and “right” of the modded pot’s for the voltage for the regulators or do they have to come from the working potentiometer’s posts?

Sorry for all the questions, but this is pretty interesting to me and I’m trying to pick brains before I go destroy another good generic Xbox 360 pad in the name of science (and in the name of destroying good generic Xbox 360 pads!).


#14

That’s be fine. Problem is, with those metal cases, its sometimes difficult

It may get a bit crowded.

You should have cut the traces going to the left and right posts, so theres no voltage going to the pot.

Or, if its possible on your pad, you cen see about just cutting or menting the post that goes from the analog assembly to the post. Hot glue the pot to center and make sure the pot is disconnected from the analog stick.