Sucralose

Sucralose

Sucralose is a wireless, 50-key split keyboard built around Kailh PG1316S ultra-low-profile switches. One reversible PCB serves both halves.

Rev. 2

Rev. 2 keeps the Rev. 1 key layout and adds:

• A 7th column on both halves: four Kailh PG1316M switches sit on a strip outboard of the pinky column. Their narrow keycaps, mounted in portrait, minimize the added width. The strip is a breakaway section, so you can snap it off and keep a 42-key board.
• A larger battery cutout: the bigger opening in the PCB allows a slimmer battery cover.
• Pads for a slide switch and reset button: both are on the board edge.

The two halves stacked are now under 13.5 mm tall.

Hardware

• Switches: Kailh PG1316S, 21 per half, on a 17 mm pitch to fit their smaller keycaps.
• 7th column: Kailh PG1316M, 4 per half, on the breakaway strip. The firmware runs with or without it.
• Controller: Seeed XIAO nRF52840 Plus, running ZMK.
• Display: nice!view, soldered flush to keep the stack low.
• Power: a LiPo pouch in a corner cutout beside the key field, a JST-PH connector, and a side slide switch. An optional side reset button is also supported.
• PCB: 1 mm thick, so the full stack stays in ultra-low-profile range.

Design

• Layout: the column splay is inspired by chalk. The 1.5u outer thumb key comes from the Corne.
• Reversible: each half uses the same board, flipped.
  • The XIAO footprint puts a land on both copper layers at every pin. Each layer carries the net that pin needs when the module is mounted on that side.
  • The nice!view header can't do that because its pins are plated through-holes. Four solder jumpers per side select its pin order instead.
• Serviceable switches: the PG1316S contacts sit under the switch body. The custom footprint uses plated through-holes so each joint can be reflowed from the underside.

Custom Footprints

These live in lib/footprints.pretty/. The files ending in _sucralose were drawn for this board.

• PG1316S: a reversible footprint with plated through-holes and locating-pin holes. It builds on mikefive's footprints and marbastlib's.
• PG1316M: a reversible footprint with plated through-hole terminals, derived from libmodulo's.
• XIAO nRF52840 Plus: a reversible version of Seeed's official single-sided footprint.
• nice!view: a dual-sided header, plus chevron solder jumpers for net selection.
• Alps SSSS811101 power switch: front and back versions, checked against ceoloide's footprints.
• Other parts: a reversible B3U reset button and SOD-123 diodes.

Case

case/out/ has STL files for the partial covers: a battery cover and battery plate, left and right XIAO covers, and a screen cover. It also has left and right reference DXFs showing the outline, keycap clearances, and M1 screw holes.

Firmware

This repo is also the ZMK module for the board: firmware/ holds the sucralose_left / sucralose_right shield. See firmware/README.md for how to build it.

License

Sucralose is released under the MIT License.

The key switch layout is the exception. To the extent it is unchanged from chalk by maurzo, that layout stays under chalk's CC BY-NC-SA 4.0 license. Third-party files in reference/ and the footprints derived from upstream libraries also keep their own licenses.

Credits

• Corne: foostan/crkbd, CC-BY-4.0.
• Key switch layout: maurzo/chalk by maurzo, CC-BY-NC-SA-4.0.
• PG1316S footprints: mikeholscher/zmk-config-mikefive and ebastler/marbastlib, CERN-OHL-P.
• PG1316M footprint and 3D model: dennisleexyz/libmodulo, GPL-3.0.