Jacek Fedorynski Creates a Mouse Hat and Human Trackball

Turning a baseball cap and a gym ball into computer input devices.

Jacek Fedorynski has recently created an air mouse, a device that attaches to a hat and functions like an actual mouse. Hat mouse, you ask? Instead of controlling it with hand movements, it requires you to use your head. Based on Adafruit’s Feather nRF52840 Sense, this air mouse works by reading accelerometer, gyroscope and magnetometer data, and connects via Bluetooth to run on Windows, Mac and Linux.

It goes through a sensor fusion algorithm to get orientation and yaw, and pitch values are used to place the cursor on the screen. Absolute cursor positioning helps to ensure any head orientation correlates to a cursor’s position. To reset the center position, the “user switch” button needs to be pressed on the board. I’m cringing thinking of how still I would have to hold my head in critical selecting scenarios. But, it’s still cool. Auto-aim on the horizon?

The Feather board can be powered with a Li-Po battery or via the USB port, which is where a power bank can be used. However, this mouse isn’t able to perform button clicks just yet. For now, the device employs a USB footswitch as a clicking mechanism. (The footswitch is an underdeveloped interface, in my opinion.) A sip-and-puff switch might work better, depending on how the user moves. The Feather nRF52840 contains a bunch of sensors that are used for the orientation. The pressure sensor, microphone, or even light sensor can be utilized to create head-operated switches.

Fedorynski also created a human trackball. It’s basically a gym ball that functions as a trackball. This device consists of an nRF52832 Bluetooth chip, an MPU-92509DOF sensor, a built-in battery charging circuit, and a Li-Po battery. For this project, the board was attached to the gym ball using scotch tape.

The sensor fusion algorithm was done with Adafruit’s library, implementing Sebastain Madgwick’s sensor fusion algorithm. Additionally, Sandeep Mistry’s Arduino core was used for the nRF52832 chip and the BLEPeripheral library for Bluetooth. The board was then programmed from Nordic’s nRF52 development kit.

It also contains a calibration sketch for the magnetometer, which uses Bluetooth aerial to transfer data. The gym ball can’t do any button clicks, so a foot switch hooked up to a Digispark helps to compliment this feature. This trackball performs similarly to a joystick. As it tilts to the right, the cursor follows that direction as long as it stays in that place and doesn’t move when it’s brought back to its original spot. All of this is radical, can’t wait to see what the next versions look like.

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