757dd492b9
Drop magic adverbs (silently, arguably), a stakes-inflation flourish, and the bold-first Snippets bullets; de-duplicate the "usable artifact, not a checkpoint" line shared by the README and roadmap.
159 lines
11 KiB
Markdown
159 lines
11 KiB
Markdown
# Typoena
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A distraction-free, hackable, DIY writing machine. ESP32-S3 + e-ink + a real
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mechanical keyboard. You write Markdown, you commit, you push. Nothing else
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runs on it.
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> **Status: pre-MVP, hardware on bench.** Display, USB keyboard, live typing
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> with partial refresh, Wi-Fi + TLS, and on-device git push are all verified
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> in spikes. No release has shipped yet — v0.1 is blocked on SD (waiting on a
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> compatible card), the boot splash, and wiring the save/publish path into the
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> app binary. Live per-item status: [`docs/roadmap.md`](docs/roadmap.md) ·
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> failure write-ups: [`docs/postmortems/`](docs/postmortems/README.md).
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---
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## Vision
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A single-purpose appliance that boots into a text editor with a Vim keymap,
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edits Markdown files, and (optionally) pushes them to a git remote (GitHub
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first) over Wi-Fi. No browser, no notifications, no apps. Open lid → write →
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push (or don't) → close lid.
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Two file scopes coexist on the SD card — formal definitions in
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[`CONTEXT.md`](CONTEXT.md):
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- **Tracked** — lives in the git working copy, gets **Published** when the
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user presses `Ctrl-G`.
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- **Local** — never leaves the device. Permanently-private: journal entries,
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scratch, things that aren't anyone else's business. There is no "promote
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to Tracked" gesture — scope is fixed at file creation.
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Same editor, same keymap; the difference is just whether `Ctrl-G` (publish to
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the remote) is offered.
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---
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## Hardware
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**ESP32-S3-N16R8** (16 MB flash, 8 MB PSRAM) · **GDEY0579T93** 5.79″ e-ink
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strip (792×272, ~2.9:1 — biases the UX toward "current line + recent context",
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the writing posture we want) · **Nuphy wired USB keyboard** with the S3 as USB
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host · **microSD over SPI** · **USB-C wall power** for the MVP, battery in
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v0.8.
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Full part table, rationale, and bench status:
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[`docs/hardware.md`](docs/hardware.md). Enclosure — a parametric,
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3D-printable typewriter-body case (OpenSCAD): [`hardware/case/`](hardware/case/README.md).
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---
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## Software stack
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**Language: Rust on `esp-idf-rs` (std).** Every stack decision — language, UI
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strategy, display, git lib, auth, concurrency, storage, power, keyboard
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transport — has an ADR in [`docs/adr.md`](docs/adr.md), including the rejected
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alternatives (Ratatui, Gleam + Shore on AtomVM, C/Arduino — ADR-001/002). How
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each decision is weighted against the user-facing requirements lives in
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[`docs/qfd.md`](docs/qfd.md); the ontology those docs use is defined in
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[`GLOSSARY.md`](GLOSSARY.md). A memory-safety review of the Rust `unsafe`/FFI
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surface (mostly `usb_kbd.rs`) is in [`MEMORY_AUDIT.md`](MEMORY_AUDIT.md).
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| Layer | Choice | Notes |
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| ------------- | --------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| HAL / runtime | `esp-idf-svc`, `esp-idf-hal` | std build: heap, threads, VFS, mbedtls, Wi-Fi stack. |
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| Display | Custom SSD1683 driver (`src/epd.rs`) + `embedded-graphics` | Dual-controller 792×272 panel; dirty-rect partial refresh (~630 ms measured). |
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| UI layer | Custom thin widget layer | Ratatui's API _shape_ without its char-grid terminal model ([ADR-002](docs/adr.md#adr-002-ui-strategy--custom-widgets-on-embedded-graphics-not-ratatui)). |
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| Editor core | Custom, in-tree (`src/editor.rs`) | Modal (Normal / Insert / View / Command), motions, operators + text objects. Plain-ASCII buffer until the v0.2 UTF-8 work. |
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| USB host | `esp-idf` TinyUSB bindings | Boot-protocol HID; verified on hardware (Spike 4). |
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| Git | **libgit2 via `git2`**, built as an esp-idf component with mbedTLS (`firmware/components/libgit2/`) | `gix` was the original pick but can't push over HTTPS — the [ADR-004](docs/adr.md#adr-004-git-implementation--gitoxide-gix) kill-switch fired ([postmortem](docs/postmortems/2026-07-05-spike7-gix-https-push.md)). On-device add → commit → push verified. |
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| TLS | `mbedtls` via `esp-idf` | GitHub HTTPS with the chain checked against embedded roots; ≈35 KB heap measured during handshake (Spike 6). |
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| Auth | HTTPS + GitHub PAT | v0.1 bakes credentials in at build time via `TW_*` env vars; provisioning + at-rest protection is [ADR-011](docs/adr.md#adr-011-credential-provisioning--how-the-pat-reaches-the-device-and-is-protected-at-rest) (open), on-device settings land in v0.9. |
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| Filesystem | FAT on SD (`esp_vfs_fat`) | Working copy lives here. Internal LittleFS holds config. |
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---
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## UX boundaries set by the medium
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E-ink is a brutal honesty filter on UI choices. Hard constraints we design
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around, not against:
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- **No cursor blink.** Kills the panel and the battery.
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- **Typing latency target: ≤ 200 ms** from keypress to glyph on screen, using
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partial refresh on the affected line only.
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- **Full refresh every ~20 partials** to clear ghosting. User-visible flash —
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schedule it on pauses (>1 s of no input).
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- **No smooth scrolling.** Page-style jumps only.
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- **No animations.** Anywhere.
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- **Render only changed lines**, not the viewport.
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---
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## Roadmap
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Releases are frequent, and every version is a usable artifact rather than a
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checkpoint. Per-version scope, current `[x]`/`[~]` marks, and the Macroplan
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source live in [`docs/roadmap.md`](docs/roadmap.md).
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| Version | Theme | One-liner |
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| ------------------------------------------------------- | ------------ | -------------------------------------------- |
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| [v0.1](docs/roadmap.md#v01--mvp-it-writes-it-pushes--) | MVP | Boots, edits one file, `Ctrl-G` pushes. |
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| [v0.2](docs/roadmap.md#v02--vim-navigation--) | Vim nav | Normal/Insert, motions, line numbers. |
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| [v0.2.5](docs/roadmap.md#v025--international-input--) | Intl input | US-Intl dead keys: à é ê ç, `'`+space = `'`. |
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| [v0.3](docs/roadmap.md#v03--vim-editing--) | Vim edit | `dd yy p`, undo/redo, counts. |
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| [v0.4](docs/roadmap.md#v04--visual-mode--ex-commands--) | Visual + ex | `v V`, `:w :q :e` command line. |
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| [v0.5](docs/roadmap.md#v05--file-palette--multi-file--) | Files | `Ctrl-P` over `/repo` + `/local`, buffers. |
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| [v0.6](docs/roadmap.md#v06--markdown-affordances--) | Markdown | Headings, list continuation, soft-wrap. |
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| [v0.7](docs/roadmap.md#v07--search--better-git--) | Search + git | `/` search, `:Gpull`. |
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| [v0.8](docs/roadmap.md#v08--power-battery--sleep--) | Power | 18650 + sleep + lid switch. |
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| [v0.9](docs/roadmap.md#v09--robustness--) | Robustness | Crash-safe writes, reconnect, settings. |
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| [v1.0](docs/roadmap.md#v10--polish--) | Polish | Boot ≤ 3 s, fonts, themes, enclosure, guide. |
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| [v1.x](docs/roadmap.md#v1x--stretch--nice-to-have) | Stretch | 10.3″ panel, multi-remote, stats, BLE. |
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---
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## Repo layout
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```
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/firmware Rust crate, esp-idf-rs target
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(SD card mounted at runtime contains /repo and /local)
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/src
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main.rs app binary — editor + display + USB (SD/git not wired yet)
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editor.rs modal editor core: buffer, modes, keymap, :commands
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epd.rs SSD1683 dual-controller e-ink driver
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usb_kbd.rs TinyUSB host glue, HID → key events
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/bin on-device spike binaries (sd_fat, wifi_tls, git_push,
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git_sync, git_smoke)
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/components/libgit2 libgit2 as an esp-idf CMake component (mbedTLS);
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source vendored as a git submodule
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build.rs bakes TW_* env vars (Wi-Fi, PAT, author) — v0.1 config path
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/spikes desktop spikes (spike7 git push proof, pre-device)
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/docs ADRs, QFD, hardware, roadmap, per-version specs,
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spikes.md, postmortems/, notes/
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/hardware enclosure — parametric OpenSCAD case (case/) + renders
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CONTEXT.md project glossary — Tracked / Local / Save / Publish, and
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the principles that fall out of them
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GLOSSARY.md methodology glossary — the WHAT / Function /
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Characteristic / Metric / Target ontology layers
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package.json pnpm + oxfmt — formatting toolchain for docs/JSON
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```
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---
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## Open questions / risks (tracked, not yet resolved)
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- [ ] SD on the bench: the 133 GB card rejects CMD59; waiting on a genuine
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≤32 GB card ([postmortem](docs/postmortems/2026-07-05-spike3-sd-cmd59.md)).
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- [ ] Heap fragmentation over a long writing session with the PSRAM allocator.
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- [ ] Real-world e-ink ghosting with the current partial-refresh cadence.
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- [~] Use-after-free freeing the in-flight USB transfer on keyboard unplug —
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fixed in code, pending an on-device hot-plug run to confirm
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([`MEMORY_AUDIT.md`](MEMORY_AUDIT.md) finding #1).
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Retired risks ([gix push](docs/postmortems/2026-07-05-spike7-gix-https-push.md),
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TinyUSB HID stability, TLS heap, libgit2-on-xtensa) and how they died:
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[`docs/spikes.md`](docs/spikes.md) and
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[`docs/postmortems/`](docs/postmortems/README.md).
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These get resolved by writing code, not by deciding harder.
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