Leveraging the Wii Nuncuck Library
Tod E. Kurt generated one of the first blog articles that discussed how to send and decode I2C commands to the Wii Nunchuck using an Arduino UNO in February 2008. He created a nunchuck library as well as produced a wii chuck adapter to easily interface with existing Wii nunchuck controllers (eliminating the need to use extension cable adapters for interfacing). From his work, numerous makers have extended his library and modified it to deal with both "original" as well as "third-party" Wii nunchuck controllers. Much of his work and others inspired a Wii nunchuck library by Tim Teatro discussed in his blog on February 2012. Other Wii nunchuck libraries might exist, but I plan to use Tim's Wii nunchuck library as a basis for the iTapStick project. To learn more about what has been done with various Wii nunchuck libraries check out the blogs from both Tod and Tim.
Leveraging the Adafruit Pro Trinket Mouse Library
Mike Barela has a great article on using the Pro Trinket as a USB HID Mouse based on the Adafruit Pro Trinket mouse library. Since the Pro Trinket does not actually have a USB interface chip, he shows how you can leverage the V-USB library to emulate a USB HID Mouse based on this library. Please review the article by Mike for more background information about this library.
The iTapStick Project
A combination of the Wii nunchuck library and the Pro Trinket Mouse library provides the foundation for creating the iTapStick USB Mouse Stick for Wii Nunchuk Controllers. This project was motivated from playing the OFDP video game found on Steam for the PC. The YouTube video showing the game in action is shown below.
Rather than using the left and right mouse buttons or an XBox controller for playing the game, why not use Wii nunchuck controllers. If we can program the "Z" button to represent a left mouse click for one nunchuck and a right mouse click for the other nunchuck, the fun factor of OFDP dramatically increases. While we are at it, let's use the joystick on the nunchuck to control the mouse position so we can select various areas of the map. With these features combined with two wireless wii nunchucks, the Nunchuket Wii Nunchuck to mouse USB interface stick was born!