Flow 75

Flow 75 — Programmer's Layered Keyboard

A premium, programmer-focused 75% mechanical keyboard designed for maximum cognitive flow and zero hand displacement.

The Core Concept

Traditional keyboards force software developers to constantly lift and stretch their hands to reach symbols, arrows, navigation keys, and mouse controls. Flow 75 brings full ergonomic layer power into a standard 75% unibody form factor using a 3-way split spacebar and an intuitive Left-Column Modifier Cascade.

graph TD
    %% Styling
    classDef spacebar fill:#2d3748,stroke:#4a5568,stroke-width:2px,color:#fff,font-weight:bold;
    classDef layer fill:#3182ce,stroke:#2b6cb0,stroke-width:2px,color:#fff;
    classDef standard fill:#4a5568,stroke:#2d3748,stroke-width:2px,color:#fff;
    
    subgraph The 3-Way Split Spacebar
        direction LR
        LS[Left Space<br>2.25u]:::spacebar
        C[Center Key<br>1.25u]:::spacebar
        RS[Right Space<br>2.75u]:::spacebar
        
        LS -->|Hold| IL((INPUT LAYER<br>Symbols & Operators)):::layer
        C -->|Tap| ENT((Fast ENTER)):::standard
        RS -->|Hold| AL((ACTION LAYER<br>Vim, Mods, Nav)):::layer
    end

    subgraph Left-Column Modifier Cascade
        direction LR
        P1[Physical Caps Lock]:::standard -->|Maps to| M1(SHIFT<br>Zero-stretch):::layer
        P2[Physical L-Shift]:::standard -->|Maps to| M2(CTRL<br>Comfort reach):::layer
        P3[Physical L-Ctrl]:::standard -->|Maps to| M3(CAPS LOCK<br>Cornered):::layer
    end

Key Highlights

• Left Space (INPUT): Tap for space, hold for programming symbols ({, }, [, ], (, ), =, etc.) mapped directly on the home row.
• Right Space (ACTION): Tap for space, hold for VIM navigation (I/J/K/L), word jumps, text edits (delete word, copy/paste, undo), and mouse emulation.
• Center Key (ENTER): Fast thumb Enter without moving the right pinky off the home row.
• Left-Column Shift: Caps Lock becomes Shift, Left Shift becomes Control, Left Ctrl becomes Caps Lock.
• Dumb / Game Mode: A dedicated physical switch (or secondary firmware chord) to instantly switch to a standard ANSI layout for gaming or sharing.
• Ambient Pomodoro LED: Hardware-level focus sprint indicator (25m focus / 5m rest) embedded beneath the center key.
• Plug & Play: Powered by QMK firmware. No background software or drivers required.

Repository Structure

flow_75/
├── .gemini/             # Workspace rules, guidelines, and context
├── docs/                # Architectural guides, firmware instructions, and history
│   ├── 01_system_architecture.md      # Concept, hardware specs, and layers mental model
│   ├── 02_keymap_and_layers.md        # Exact keymap matrix, Input & Action logic
│   ├── 03_firmware_and_compilation.md # QMK environment setup and flashing instructions
│   └── CHANGELOG.md                   # Iteration history and bug fixes
├── firmware/
│   └── qmk/             # QMK firmware source, rules, config, and keymaps
├── hardware/            # Hardware design assets (KiCad schematics, CAD case models)
│   ├── pcb/
│   ├── cad/
│   └── keycaps/
├── tools/
│   └── simulator/       # Reserved for future browser keymap simulator
├── brainstorming/       # Initial ideation records and Six Hats debates
│   ├── ideation_memory_input.md
│   ├── ideation_memory_action.md
│   ├── six_hats_debate_input.md
│   ├── six_hats_debate_action.md
│   └── roadmap.md
└── README.md

Roadmap

Phase 0: Ideation & Concept Validation (In Progress)

• Initial Brainstorming & Six Hats debate
• Core Concept Definition (3-way split spacebar, Modifier cascade)
• INPUT Layer Definition (Symbols & Operators mapping)
• ACTION Layer Definition (Vim nav, text mutations, mouse emulation)
• Base Layer Layout finalization (ANSI layout confirmed)
• Finalize Architecture & Keymap Specification documentation

Phase 1: Firmware & Frankenstein Prototype (Completed)

• Setup QMK Environment and scaffold flow_75 project
• Draft Base Layer Matrix in C
• Implement INPUT & ACTION Layers logic
• Flash and validate on a commercial split-space board (Frankenstein prototype)
• Initial tuning of Tap-Hold mechanics (TAPPING_TERM, PERMISSIVE_HOLD)

Phase 2: User Testing & Calibration

• 2-week daily driving feedback loop
• Timing optimization (zero space-lag vs false triggers)
• Refine text mutation macros (e.g., delete line, undo/redo)

Phase 3: Hardware Engineering (PCB & MCU)

• Component Selection (RP2040 MCU, Kailh hotswap sockets, ESD protection)
• KiCad Schematics drafting (MCU, USB, Matrix, LED)
• Custom Pomodoro LED circuit design
• PCB Layout & Routing

Phase 4: Industrial Design & Enclosure

• 75% unibody footprint definition (gasket mount)
• CNC Aluminum Chassis CAD modeling (STEP/STL)
• Custom side-printed keycap geometry and SVG legend art

Phase 5: Production & Launch

• Order initial PCB and CNC prototype batch
• Assembly & QA testing
• Finalize Open Source release and build guides

Contributing

Flow 75 is an open-source project and we welcome contributions from the community! Whether you want to optimize the QMK firmware, tweak the layer maps, or contribute to the PCB design, please check out our Contributing Guidelines first.

Please note that this project is released with a Code of Conduct. By participating in this project you agree to abide by its terms.

License

Flow 75 uses a dual-licensing model:

• Hardware designs: CERN Open Hardware Licence Version 2 - Permissive (CERN-OHL-P)
• Firmware & Software: GNU General Public License v2.0 (GPL-2.0)

See the LICENSE file for full details.