Unicomp's Model M Buckling Spring Keyboards Get a Hackable Upgrade: A Raspberry Pi Pico Controller

Recently-produced buckling spring keyboards come with a now-QMK-compatible Raspberry Pi Pico-based controller, as an added bonus.

Gareth Halfacree
8 months ago β€’ Retro Tech / HW101

Keyboard enthusiasts have made a welcome discovery in recently-manufactured Unicomp buckling spring mechanical keyboards: a move to a new USB controller board design which uses an extremely-hackable Raspberry Pi Pico as its brains β€” making it compatible with the QMK open-source controller firmware project and unlocking full customizability.

"For many years, enthusiasts have been asking for reprogrammable Model M keyboards from Unicomp," explains pseudonymous mechanical keyboard fan Admiral Shark of the shift, in a post brought to our attention by Adafruit. "Thanks to the unfortunate 2022 discontinuation of the Cypress microcontroller Unicomp previously used for its USB keyboards, Unicomp keyboards are now [mostly] reflashable thanks to their selection of the RP2040-based Raspberry Pi Pico as the heart of its new generation of USB controller cards."

As a potted history: IBM shipped two main families of mechanical keyboards which used a buckling spring mechanism to provide tactile feedback, the Model F and the later cost-reduced Model M. These are, according to their proponents, some of the best keyboards around, but long out-of-production β€” until Unicomp stepped in to build new Model M boards, featuring modern USB connectivity but retaining the pleasing clunk of the buckling spring mechanism.

Since June 2023, following the discontinuation of the microcontroller around which the keyboards' original controller had been built, Unicomp has been using a new controller board design β€” and soldered right on top is a Raspberry Pi Pico, the $4 dual-core development board from Raspberry Pi. This is of particular interest to tinkerers: the Vial-QMK variant of the QMK open-source keyboard firmware has been ported to the new boards by Purdea Andrei, providing full customization of the keyboards' functionality.

"The two new Unicomp controller cards are 'Aristides' as a replacement for 'Ruffian' and 'Justify/Mike Smith' as a replacement for 'AP1,'" Admiral Shark explains. "Aristides (in keeping with Unicomp's PCB naming convention) is named after the racehorse that won the first Kentucky Derby in 1875 and is intended for 101-105 key and 122-key keyboards that require pressure-fit connection to their membrane assemblies."

"Justify is named after the thirteenth winner of the American Triple Crown," Admiral Shark continues, "and serves as the motherboard of the new Mini M controller card supporting the Pico, two 74LVC138AD demultiplexers (under the daughterboard), right Triomate (membrane flex cable) socket and USB port. Mike [Smith] is named after the jockey who rode Justify to the Triple Crown and is a daughterboard attached to Justify that has the left Triomate socket and four LVC125A quadruple bus buffer gates."

Details of how to find out if your Unicomp keyboard has the new Raspberry Pi Pico-based controller are available in Admiral Shark's post on the subject β€” along with information on ordering a replacement controller to upgrade existing boards.

Main article image courtesy of Unicomp.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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