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Split Mechanical Low Profile Keyboard Using Arduino Pro Micro

I wanted a standalone keyboard to use with my laptop, which with its small keyboard, pushes my hands together and forces my wrists to bend uncomfortably. I had this idea after learning that the Pro Micro, with its ATmega32U4 microcontroller, has built-in Human Input Device (HID) functionality and keyboard libraries that take care of most of the programming work. Additionally, I wanted the keyboard to work with only the left side plugged in, allowing for better gaming ergonomics.

Design Goals
(High to low priority)

- Split mechanical keyboard with 65%, ortholinear layout
- Powered by Arduino Pro Micro
- Barebones and low profile to mirror laptop keyboard height
- 3.5mm Aux between sides, USB-C to computer
- Low cost (<$100). Amazon alternatives start at $100-120 range
- Mirrored PCB, allowing for a single PCB design
Below is a summary of how I designed and built a custom 60%, ortho-linear, 67-key, splittable mechanical keyboard that runs on Arduino Pro Micros.

- 2x Arduino Pro Micro, USB-C, 5V, 16 MHz
- 2x Custom PCB
- 67x 1N4148 SOD-123 diode
- 67x Kalih Choc low profile, brown
- 2x TRRS 3.5mm through hole jack
- 1x USB-C to USB-A cable, 3ft
- 1x Coiled 4 pole 3.5mm aux cable
- 64x 1u Choc keycaps (if not 3D printing)
- 3x 2u Choc keycaps (if not 3D printing)
- 3x Gateron 2u stabilizer (used for to uniform 2u switch resistance)
- 1x Small slide switch (used to disable typing functionality)
- 1x 10k ohm 1/4 W resistor (used to pull up slide switch)
- 2x Push button, through hole (used to reset micro)
- Soldering iron
- Solder
- PC
- Tweezers”

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