So lets Design a Schematic in Kicad

What do we need:

Power Supply:

I decided to use a well known Low Drop out Voltage Regulator: RT9013.

Key features: Low DropOut Voltage, low quiescent current. This is important for battery operations

Keys to press:

I decided to go go for Cherry MX Keys RED. They have a perfect press and work quite stable: Side fasct: The can be illuminated with an LED from underneath

 To save some IO Pins I decided to arrange the keys in a 3x3 matrix

Some RGB-LEDs because Ble light makes everything better

My typically used SK6812 or WS2812 do not fit under the MX Keys. Therefore I searched a lot and found a better fitting RGB LED

SK6812-Mini: They are small and perfectly fit in a hole under the keys. And most important they work with fast LED.