Pseudonymous maker "Skycode22" is putting together a family of 3D-printed open source trackball devices, starting with the OpenTrack and OpenEx — the latter owing its inspiration to Kensington's classic Expert design.
Each model in the Open* trackball family, which eschew modern optical mice and the moving of one's hand in favor of rolling a physical ball with finger or thumb, is powered by the open source QMK firmware more commonly seen in custom keyboards. Here, though, it drives the trackball, optional scroll wheel, and up to four buttons.
The first model unveiled, the OpenTrack, uses an unusual layout with the ball located at the far end where the fingers can roll it and the two buttons — which use full-size keyboard-style key caps on mechanical switches — are off to the side for thumb use. "This is [Revision] 1," Skycode22 explains of the initial prototype. "[Revision] 2 will have the scroll wheel built in as well."
Just over a week later Skycode22 showed off a second design, a direct homage to the Kensington Expert trackball. Here, the ball is located dead center and surrounding by a physical scroll ring, while four buttons are positioned at each corner.
"Currently I'm just using a humble [Arduino] Pro Micro with the [Microchip] ATmega32U4," Skycode22 writes of the trackballs' internals, "and the sensor I'm using is the [PixArt] PMW3360, I believe. It could be used with any sensor or microcontroller configuration as long as the firmware matches up. Currently there is no PCB and all the components are held in place with hot glue."
Skycode22 has published code and STL files for 3D printing for both the OpenEx and OpenTrack to GitHub under an unspecified open source license.