While trackballs haven’t been common since the mid-‘90s, they are seeing a bit of a resurgence among people who spend a lot of time at their computers. I’ve been using trackball mice exclusively for more than a decade now and I firmly believe that it has helped to prevent repetitive stress injuries (RSI). Trackball mice come in a variety of forms, but most resemble a standard mouse with a ball positioned by the thumb or index finger positions. Some have a large centrally-placed ball and tend to be popular among video editors. Jacek Fedoryński designed a very clever trackball mouse in the latter style that ingeniously encloses the electronics within the ball itself.
Your typical trackball mouse has electronics that work in almost exactly the same way as a regular optical mouse. The only difference is that the optical sensor points towards the ball instead of downwards towards the desk. Fedoryński took a completely different approach when he designed his custom trackball mouse. The large ball is sealed and contains all of the electronics — the base only has bearings and there are no external wires. Instead of optically detecting movement in two dimensions, his mouse has a gyroscope to monitor the ball’s orientation in three-dimensional space. It updates very quickly, so rotating the ball will change the values for each axis. An algorithm then translates that into 2D mouse movements that are sent to the computer via Bluetooth.
The primary component in the mouse is an Adafruit Feather Bluetooth Sense, which contains a Nordic Semiconductor nRF52840 SoC with a Cortex-M4 processor and a built-in BLE radio. The board also has onboard sensors, including an LSM6DS33 accelerometer/gyroscope and a LIS3MDL magnetometer. Also inside of the trackball is a 500mAh LiPo battery with a wireless charging coil. A custom charging station lets Fedoryński top off the battery and also has magnets to trigger Reed switches in the ball for calibration. The normal base has only a few zirconium oxide ball bearings. The charging base, normal base, and trackball are all 3D-printed, with the ball being sealed with glue. That ball was also thoroughly sanded to make it roll as smoothly as possible on the bearings in the base. There are no mouse buttons, but Fedoryński’s custom keyboard has extra keys that he uses to send mouse clicks. If this mouse intrigues you, Fedoryński has made the code and STL files available so you can make your own!