Douglas Engelbart gave “The Mother of All Demos” in 1968, introducing concepts such as the computer mouse, highlighting text, and hyperlinking documents, which profoundly impacted computing.

Less well-remembered, however, was Engelbart’s chording keyset, a five-button keyboard-like device that allows the input of characters when pressed in specific combinations. Russ Nelson wanted to bring awareness to the forgotten device with his entry in the Odd Inputs and Peculiar Peripherals contest.

Consisting of a Teensy 4.1, a custom PCB, and five mechanical key switches, all wrapped up in a custom enclosure housing the five keys, the hardware is actually quite simple. The Teensy’s USB Host capabilities are leveraged to incorporate mouse inputs before passing fused key codes to a PC, expanding the 5 buttons’ 32 combinations (enough for A-Z) to 256 thanks to the three additional buttons on the mouse. Further information, as well as source code and schematics can be found on the project’s Hackaday page.