Inside a knockoff Wii Nunchuk

wpid-IMAG1125.jpgAs part of the Lightsaber project, I’ve been looking for a low pin count way to add control since the ATTiny85 that I’m using only has 6 IO pins. For the prototype I connected a button and a potentiometer to a pin each. I’d like to have an accelerometer and another button or two, but that uses up pins pretty quickly. However, if I hang all the controls off an i2c bus, then I only need to use two IO pins.

The Wii Nunchuk just happens to be an i2c bus. It also happens to have 4 inputs built into it: 2 buttons, a 2-axis joystick and a 3 axis accelerometer. That’s pretty close to everything  I want. It also aggregates reading all of those sensor inputs into a single i2c transaction which means less work for the ATTiny85 software.

Official Wii Nunchuks aren’t the cheapest things in the world. Even 8 years after the Wii was first released, a genuine Nintendo Nunchuk is £15. That blows my budget for this project. I can however order replica Nunchuks via Aliexpress for a mere £2.95 each including shipping. I ordered a lot of 5 to experiment a couple of weeks ago and they arrived today.

For such a low price I was not expecting much, and indeed, my expectation were met. They work, I’ll say that much for them, but I wouldn’t want to use them for actually playing a game. Button presses don’t always make contact and feel a bit sloppy. I’m not too worried about that though because I’m going to gut them for the electronics and throw away the plastic.

More troublesome though is that the clones don’t behave in exactly the same as an official Nintendo Nunchuk. In fact, in the lot of 5 I purchased I seem to have two different variants, each of which behaves differently. Two of them I was able to get working completely by following the instructions in this forum post. The other three are recognized by the new code, but the event reports are still encrypted. I need to do some debugging to figure out what else is needed.

Inside the Nunchuk
Inside the Nunchuk
Electronics from two difference Nunchuk clones
Electronics from two difference Nunchuk clones

Cracking the case open, it’s clear that the plastic moulding is a direct copy of the Nintendo part. The boards in both versions have exactly the same outline as the Nintendo one and all the plastic looks identical. One of them even uses the Nintendo tri-wing screws. The boards themselves look designed to be as cheap as possible. The main controller is an anonymous die-on-board held with a blob of epoxy. Soldering quality is marginal at best.

Not that any of this bothers me. If I can get it mounted inside the Lightsaber hilt then it will do the job nicely for less than it would cost to buy each button and sensor individually.

2 thoughts on “Inside a knockoff Wii Nunchuk”

  1. That is pretty cool, love your lightsaber! Its pretty awesome that with enough know how you can open up electronics and have them bend to your will. I love the fact that you ran into a problem then found the answer on a random forum somewhere. Shows how incredible the internet really is.

    I got here while researching how to do a project of my own that I can’t get to the bottom off. I was wondering if you could give me some advice?

    Do you know what would be the best way to: add 2 buttons to a Nunchuck, replace its analogue stick with a clickable analogue stick, then have the extra buttons, original buttons and motion controls interface with a PC via USB?

    1. Creating a USB HID (Human interface device) isn’t all that hard to do. There are lots of Arduino projects that you can use as a starting point. For example:

      I would get yourself an Arduino Leonardo to start playing with and wire up a couple of buttons. Google for example joystick Arduino sketches to make those buttons show up as USB joystick button presses. Once you have that working then you can connect a Nunchuk via an I2C bus and pass the joystick, buttons and accelerometer values through.

      Actually replacing the analogue stick with a clickable one is rather more ambitious though since you need to get it to fit into the existing Nunchuk enclosure. That’s more of a mechanical mounting problem than anything.

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