xiao 75% keyboard

Details

Motivation of this keyboard is I want compact, small keyboard with dedicated PageUp/PageDown key. Most of small keyboards mapped Fn+Up/Down for PageUp/PageDown but I fed up pressing Fn key for PageUp and PageDown!! Pointing device is also quite handy when I want to click something while typing.

86 Kailh mini choc switches for keyboard keys.
2 Kailh X Switches for mouse buttons.
1 Top-up JT8P analog stick for pointing device.
Seeed XIAO as controller.
LED under each keyboard keys.

XIAO has 11 IO pins. I used 10 IOs for key matrix and 1 IO for analog input to read X/Y of analog stick.
By using charlieplexing technique, 10×9 switch matrix can be created. 2 cells of matrix are used to power analog stick.
External slide switch tunrs on/off LEDs as there wasn't enough pins to controll LED.

I'll describe a bit how analog stick is sensed.
The analog stick I used is simply pair of potentiometer. To read position, connect VCC to one end, connect GND to the other end, and read divided voltage using analog input.

Above circuit uses 2 analog inputs, but I have only 1 analog input. So connect 2 IOs to potentionmeters via diode like below image.

If D10=H and D9=L, A1 value is position of X. If D10=L and D10=H, A1 value is position of Y.

Components

86 × Kailh PG1232 mini choc switch keyboard switches

2 × Kailh PG1425 X switch mouse buttons

1 × TOP-UP JT8P-3.2T-B10K-1-16Y pointing device

1 × Seeed XIAO Seeed XIAO

88 × 1N4148W SOD-123 SMD switching diode

Project Logs

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Keycaps arrived
teru • 11/12/2022 at 11:34 • 0 comments

I ordered keycaps to 3d print service 2 weeks ago and I have keycaps now. Below photo is keyboard with keycaps.

It seems like I have done all what I planned.
Create keycap
teru • 11/05/2022 at 11:25 • 0 comments

My keyboard's pitch of key switch is 16mm by 16mm. This means there isn't producted keycap for my keyboard. Natural option recently is 3D print the keycaps.

There is some people published keycaps for low pitch keyboards at marketplace on https://make.dmm.com/, well-known 3D print service in Japan. e.g. YKNキーキャップセット(Chocスイッチ 15x15mmキーピッチ用) or Choc 向け挟ピッチ16mm 薄型キーキャップ（50個）.

I liked YKNキーキャップ but it doesn't contain enough keycaps for my keyboard. I also wanted to keycap same size as kailh mini choc keyswitch, 14.5mm×13.5mm. So I tried to create keycaps using FreeCAD.

My first attempt is applying chamfer to box on FreeCAD but it was boring.

I tried Loft tool found while searching for a way to create better model against sketches I draw roughly and it unexpectedly worked well.
Completed firmware
teru • 11/03/2022 at 13:03 • 0 comments

I think I finished writing firmware.

Since QMK dosen't support XIAO m0 (SAMD21), I wrote simple keyboard firmware on arduino and Adafruit TinyUsb.

Code is available on github: https://github.com/ktmizugaki/xiao-75-keyboard/tree/main/prog/

it may not be trivial to build the firmware as I am using unusual setup.
Implemented switches
teru • 10/23/2022 at 02:25 • 0 comments

Switches bought from aliexpress arrived.

Implemented switches.

Quickly tested and all keys worked.
I got a light
teru • 10/19/2022 at 12:07 • 0 comments

My board shines.