Prototyping a case for Wafer

How the thinnest keyboard could be without a fancy case?

Right after my first PCB layout, I had one question:
How thin can this keyboard actually be… in real life?

So I teamed up with a friend from my makerspace who knew the Fusion, and we started quick case prototyping, just to test the shape and vibe. I wished to have infused stands, so the screws would be visible only from the bottom.

Of course the first prints were... humbling,

we made the display enclosure on a case smaller than the display itself lol.
We didn’t notice for almost a week, because the 3D model we used (nice!view breakout) was way smaller than the real PCB

Then we hit the next issue, electronics are taking a plenty of space.
They don't just take area, they take height. So we had to redesign cutouts and internal pockets way more aggressively than we thought.

And since my Corne already had that “snap together” feel, we decided to add flat round magnets too

However, despite all the early mistakes, we got 5mm on the thinnest part and 8mm in a display area. It was actually really thin

Later we squeezed it even more and pushed the thinnest section down to ~4 mm.

“I’ll just borrow Mikoto…” (and learn the Right way)

I started with the most beginner move possible, zero knowledge, peak confidence.

My plan was simple:

• take the Mikoto MCU layout,
• "borrow" this schematic,
• add a nice!view display
• add a basic keyboard matrix learned from Joe Scotto video
• and jump straight into routing

From here I also decided to use a soft-off button instead of physical battery switch, this decision was actually decent

Mikoto is the open-source ready to jlcpcb production devboard

There was one tiny catch though: Mikoto is basically a bare MCU. And "bare" means: you are responsible for all painful stuff, decoupling, routing near the nrf52840... and scariest part: the antenna.

Think I accounted that?
keep thinking.

Layouting the first in my life PCB took me almost 3 weeks, and before I even went to place the components, I'd have to fix all of my board outline

first layout of Wafer

Of course I later figured out that this will obviously wont work well

some of my beginner mistakes:

this is a 6-layer PCB, and my routing still scares me.

I guess I was trying to add extra capacitance or what?

I picked a completely random 2.4 GHz antenna footprint and hoped it would work.

later I remade this board 2 more times from scratch.
Don't be like me.

Ergogen (March 2025): Just not another split

So from this point, I would journal and show everything I did to make Wafer (at least from what I remember)

I didn't have any plan at all, I just had that itch: "I want my own board with stagger". Back then I'd already built a third split and finally wireless low-profile Corne a few months ago, so I wasn't new to split keyboards... but PCBs were like a rabbit hole to me. I knew how to print, solder, flash my own ZMK config, But how about designing the boards itself? Eww...

So I just outlined my hand and sketched my first concept, and i remember thinking: "Hey that's hella nice!".
At this point i already knew that I want to 36 keys, the perfect for minimalistic keyboard that I got used to.

Then I discovered Ergogen, and it felt like cheating (in a good way)

First concept, i still like the personality of this of this outline shape

Thanks to the Ben Wallack video I found Ergogen: basically a programmable way to design keyboard layouts that can output KiCad files. For me as a beginner, that sounded so unreal.

The moment of the "ultra-thin" idea

While I was playing with layouts, something kept bothering me, something that I have seen in all DIY builds (including my own)

Devboards take an unnecessary amount of space. And it still looks unserious.
The stack usually ends up like: shield PCB, battery, devboard, display…
It works, it’s easy, but why am I wasting so much volume just because of the MCU pin headers, while I still have relatively small battery?

I wanted to get rid of this Sandwich as much as I could, I want a keyboard that is clean, with no "good enough" compromise

If the devboard is the reason the build is thick, why not to place the components on the shield? (and make a cutout for the battery)

It is a really simple idea, absolutely not new to any manufacturing but to that time I barely seen any split keyboard with it so far...

Maybe I should have a look at something else than reddit lol.

first wafer outline

Some Photos

I’m at the very last stage of Wafer, but I’m currently a bit stuck while I iterate on the case design and dial with a better manufacturing than JLCCNC. The electronics are working, now it’s all about getting the enclosure to fit and feel exactly the way I designed it. In the meantime, here are a few photos I managed to take along the way

CNC Milled Cases

The Wafer case is the most “mechanical” part of the project: an ultra-thin CNC-machined aluminum enclosure where the top piece acts like a clean frame/plate with cutouts for the PG1316S switches, and the bottom piece is a tight pocket for the electronics with dedicated space for the battery/magnets and all the openings for USB-C and the side soft-off button. I spent a lot of time dialing in the CAD so everything fits within a few millimeters and still feels solid and seamless — but real manufacturing can sometimes “mess up” even with good drawings: tool wear, fixturing/baseline shifts, tolerance stackups, or finishing (like blasting/anodizing) can push critical dimensions out of spec. That’s basically what happened on my first run, so it’s just another iteration: verify the problem areas, tighten the tolerances/inspection points, adjust the model if needed, and re-order to get the case to the level I originally designed it for.

Soldering the PCBs

Part of the board (the charger section and most of the tiny SMD passives) was assembled at the factory via PCBA, but I still had to hand-solder the “hard” parts myself, the PG1316S ultra-thin switches and the ISP1807 module. Doing that by hand was honestly tougher than I expected because of the fine pitch, precise alignment, and the amount of manual work involved, but in the end everything seated properly and the board came to life. As a finishing touch, I also made antenna-area covers with my logo using AMS multi-material printing

Firmware with ZMK and Zephyr modules

I modified ZMK for Wafer so the battery percentage comes straight from the nPM1300 PMIC, instead of relying on the usual “battery sensor” path: I added a dedicated battery reporting mode where ZMK talks to the PMIC over I²C, triggers a VBAT ADC measurement by writing to the nPM1300 “task” register, waits briefly for the conversion, then reads back the ADC result from the PMIC registers (MSB/LSB), reconstructs the raw value, converts it to millivolts, and finally feeds that into ZMK’s normal mV → % LiPo curve so the charge level shows up consistently in the UI/widgets and everywhere ZMK reports battery. I implemented this before the official ZMK 4.1 release, but on the same 4.1 codebase, so it stays easy to rebase and keep upstream-compatible.
I'm going to implement this solution for others, and merge changes to ZMK main soon

The Schematic with custom PMIC

This is my third revision PCB Schematic, last versions were using NICENANO v2 internals which are really outdated to this time.
This is the current Wafer schematic: the main MCU is an nRF52840 module (ISP1807) for low-power BLE/USB and running ZMK/Zephyr, paired with an nPM1300 PMIC that handles USB-C charging for a 250mAh LiPo, fuel gauging, and multiple regulated power rails for the rest of the board. The keyboard uses a Matrix and will feature 36 key layout, plus USB ESD/TVS protection, SWD Tag connect for JLink flashing custom bootloader for debugging, reset/soft-off controls, a status LED, and a connector for a small display (nice!view-style).

I also switched from a traditional power switch to a MCU-controlled soft-off button so the battery can keep charging at all times while still letting me fully use the soft-off feature; this will be implemented as a small side-mounted push button