bootlin-nunchuk's Introduction

Nunchuk Driver

A sample Linux I2C driver for the Nintendo Wii Nunchuk (RVL-004). The driver supports the following inputs using the input subsystem:

Z Button
C Button
Joystick (X and Y)

This project is based on Bootlin's embedded Linux trainings (see References section below).

Tested on BeagleBone Black hardware running mainline Linux version 5.10.179.

Hardware

BeagleBone Black
Nintendo Wii Nunchuk
UEXT connector for Wii Nunchuck

Building the kernel module

To cross-compile, run the following command (using a cross-compiling toolchain provided by Ubuntu as an example):

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-

Device Tree

To enable Nunchuk functionality on your board, add the following entry to the device tree:

&i2c1 {
	pinctrl-names = "default";
	pinctrl-0 = <&i2c1_pins>;
	
	status = "okay";
	clock-frequency = <100000>;
	
	joystick@52 {
		compatible = "nintendo,nunchuk";
		reg = <0x52>;
	};
};

Nunchuk

Connect the Nunchuk to the I2C1 bus of the BeagleBone Black board (pins 17 and 18 of P9, see pinout). The Nunchuk should show up at address 0x52:

# i2cdetect -r 1
i2cdetect: WARNING! This program can confuse your I2C bus
Continue? [y/N] y
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- 52 -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Load the kernel module to verify the driver finds the device: