Exp60 - An opinionated 60% with arrow keys PCB

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Warning WIP - Functioning prototype not built yet.

• Components ordered (2023-01-06).
• PCB's ordered (2023-01-07).

Link to Keyboard Layout Editor project

Why?

I've always preferred the size of a 60%, but never managed to kick the arrow key addiction. Having tried the dz60 and dz64 from kbdfans (dz64 being my fav), they both have trade-offs I've never been quite happy with.

Design constraints

1. 60% form factor, roughly the same size as a GH60.
2. Arrow cluster
3. Standard 2.25U left shift
4. Standard 1U forward slash / question mark key
5. Bottom row should have CTRL, Fn, GUI, ALT and HYPER keys
6. USB-C
7. Hot-swap
8. Hand solderable

How was this layout chosen?

In order to meet design constraints 2, 3 and 4, the arrow cluster needs to be located next to the forward slash key. The right arrow key only has 0.75U of space to its right, so we have the HHKB-esque gaps at the edges of the bottom row.

To meet design constraint 5, the space bar needs to be shrunk to 2.75U. I've been daily driving a heavily modded HHKB Pro JP since 2017 so this is A-OK to me.

PCB Design choices

1. All SMD components due to limited space.
2. Use atmega32u2-au MCU instead of atmega32u4-au due to limited space (32 vs 48 pins).
3. Large footprint SMD components so everything is more easily hand solderable.

Acknowledgements

• JP60 by ai03

  60%, USB-C, ESD and over voltage/currrent protection.

• Keyboard Matías

  This uses the atmega32u2-au, which is crucial for fitting the MCU and related traces on my PCB.