PCB-Design

Prototype Keyboard design project "Orions Hands V0.1"

Contains a custom mechanical keyboard PCB design keyboard-pcb and firmware keyboard-code.

Key Features:

• NKRO support over USB using a RP Pico and Rust
• Custom layout with pushable rotary encoder consumer controls over USB (vol +/-, pause, next/prev track)
• I2C display (SSD1309) with embedded-graphics
• Multicore for efficiency/speed (core0: keyboard/usb hid, core1: display/other)

Tests:

Tested on Windows and MacOS - check keyboard-code

IMPORTANT!

1. The space on the front side of the pcb on the right is reserved for a small I2C display.

2. The rp pico usb micro-b connector is only slightly accessible after soldering - this is because the intention is to extend the connector, using usb-c or an alternative 4 wire connector, away from the controller. The connector can then be case mounted for more freedom of positioning. This extension of the connector can be done in 2 ways:

   • slightly more fiddly way (my solution), plugging in a stripped usb micro-b cable into the controller -> the other end can then be connected to a usb-c breakout board or alternative 4 pin connector (the rotary encoders clips may have to be clipped to give some more room). The wires end up on the bottom of keyboard.
   • solder a connection for usb-c on the back of the rp pico (care not to break solder pads) -> demonstrated here: usb-c mod for rp pico. The wires will end up on the top of the keyboard. The PCB has a cutout to make these pads easily accessible. If you would like to put the connector on the back of the keyboard using this method it may be convenient to have a hole in the pcb for connector wires to go to the back rather than over the side of the pcb.

3. Some keycaps are not standard sizes: caps lock is stepped; backspace and enter keys are 0.5u shorter than standard; and '#/~' keys are 0.25u shorter than standard - these decisions were made to make the keyboard cleaner/more compact and so that the space bar is the only key that needs to have a stabiliser! The disadvantage is the keys can be more difficult to buy/re-use. Some keys have also been removed to keep most commonly used keys - feel free to change it!

To Improve:

• Use pull up resistors rather than relying on pi pico internal pull ups

Inspiration and key resources:

• The Switch Matrix - PCB Design for Mechanical Keyboards - important for understanding how a keyboard matrix works
• Keyboard layout editor - useful for figuring out your layout
• Keyboard PCB Design Guide - good for general guidance and set up for making keyboard PCB's in KiCAD - note: this is for a macropad, not for a key matrix; this guide uses a bare bones mcu not a development board; the latest version of KiCAD is best to use contrary to the guide (it has improved a lot) -> despite the issues it is very good for general understanding, required schematics/footprints for keyboards and tips/tricks in KiCAD
• KiCAD RP Pico - a great resource for the schematic, footprints and 3D model of the rp pico for use in KiCAD
• usbd-human-interface-device (rp pico Rust crate) - great crate for usb hid! Much (the core) of the firmware is based on this crate and examples within
• Ben Eater's youtube videos on keyboards - someone has put together a playlist of these: Ben Eater keyboard interface (playlist)
• For better understanding of how it comes together I would also recommend reading: some documentation on the rp pico; about usb hid protocols; about mechanical switch debounce; about n-key roll over (NKRO) for usb hid keyboards; about pushable rotary encoders; about the Rust language; how spi/i2c works for adding external devices (Ben Eater also has some videos on this); about multicore on rp pico in Rust