73 lines
4.5 KiB
Markdown
73 lines
4.5 KiB
Markdown
# Tutte Coxeter 36k
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This is firmware for a Raspberry Pi Pico PR2040 controller monoblock 36 key design
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(split 3x5_3 - three rows of five, and three thumb keys, for each hand). This is a
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*diode-free* design with a sparse 13 by 13 scanning matrix designed using a partial
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[Tutte-Coxeter](https://en.wikipedia.org/wiki/Tutte%E2%80%93Coxeter_graph) graph
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(using only 26 vertices or GPIO pins, with 36 edges or keys - see this
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[blog post](https://astrobeano.blogspot.com/2025/05/ergo-mech-keyboard-wiring-using-tutte-coxeter-graph.html)
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for background, although the final pin selection and trace routing changed).
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This matrix shows the full 15×15 Tutte-Coxeter bipartite scanning matrix with the
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two unused rows and columns last (❌), and the further 9 keys this would allow (⭕)
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if using 30 GPIOs rather than just 26 for a 13×13 scanning matrix. The allocation
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of keys to matrix elements and scanning matrix rows and columns to GPIO pins was
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arbitrary and down to how best to layout the PCB traces:
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| GP | 11 | 10 | 3 | 4 | 7 | 26 | 27 | 28 | 15 | 21 | 19 | 20 | 16 | ❌ | ❌ |
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|---:|:--:|:--:|:-:|:-:|:-:|:--:|:--:|:--:|:--:|:--:|:--:|:--:|:--:|:--:|:--:|
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| 12 | / | | | | | | F | | | | | | | | ⭕ |
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| 8 | P | L | | | | | | | | | | A | | | |
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| 9 | | . | , | | | | | | | | | | | ⭕ | |
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| 1 | | | K | I | | | | | | E | | | | | |
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| 6 | | | | M | H | | | | | | | | | | ⭕ |
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| 2 | | U | | | Y | T | | | | | | | | | |
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| 22 | | | | | | G | B | | | | | | L3 | | |
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| 0 | | | O | | | | W | R | | | | | | | |
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| 13 | | | | | N | | | D | R2 | | | | | | |
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| 14 | ; | | | | | | | | R1 | S | | | | | |
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| 18 | | | | | | B | | | | X | L2 | | | | |
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| 17 | | | | | | | | C | | | L1 | Z | | | |
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| 5 | | | | J | | | | | | | | Q | R3 | | |
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| ❌ | | | | | | | | | ⭕ | | | | ⭕ | ⭕ | |
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| ❌ | | | | | | | | | | | ⭕ | | | ⭕ | ⭕ |
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The keys here are labeled as per Qwerty, with L1, L2, L3, R3, R2, and R1 for the thumbs:
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| Q | W | E | R | T | | Y | I | O | U | P |
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|:-:|:-:|:--:|:--:|:--:|:-:|:--:|:--:|:--:|:-:|:-:|
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| A | S | D | F | G | | H | J | K | L | ; |
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| Z | X | C | V | B | | N | M | , | . | / |
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| | | L1 | L2 | L3 | | R3 | R2 | R1 | | |
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The firmware follows the `LAYOUT_split_3x5_3` QMK community layout convention, making it much
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easier to use with an existing layout like Miryoku.
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The first physical PCB for this was designed using the [Gamma Omega
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keyboard](https://github.com/unspecworks/gamma-omega) footprint from Ergogen.
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That is intended for use with the same Raspberry Pi Pico YD-RP2040 microcontroller
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board in order to fit the same 3D printed case, including reset button placement.
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* Keyboard Maintainer: [Peter J. A. Cock](https://github.com/peterjc)
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* Hardware Supported: Tutte Coxeter 36k (single PCB) with Raspberry Pi Pico
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* Hardware Availability: https://github.com/unspecworks/gamma-omega/tree/main/tc36k
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Make example for this keyboard (after setting up your build environment):
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make tutte_coxeter_36k:default
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Flashing example for this keyboard:
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make tutte_coxetter_36k:default:flash
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See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
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## Bootloader
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Enter the bootloader in 3 ways:
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* **Bootmagic reset**: Hold down the key at (0,0) in the matrix (bottom right key, Qwerty `/`) and plug in the keyboard
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* **Physical reset button**: Briefly press the button on the back of the controller (if physically accessible)
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* **Keycode in layout**: Press the key mapped to `QK_BOOT` if it is available
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