# typewriter A distraction-free, hackable, DIY writing machine. ESP32-S3 + e-ink + a real mechanical keyboard. You write Markdown, you commit, you push. Nothing else runs on it. > Status: pre-MVP. Hardware not yet on bench. Bring-up in progress. --- ## Vision A single-purpose appliance that boots into a text editor with a Vim keymap, edits Markdown files, and (optionally) pushes them to a git remote (GitHub first) over Wi-Fi. No browser, no notifications, no apps. Open lid → write → push (or don't) → close lid. Two file scopes coexist on the SD card: - **Tracked** — lives in the git working copy, gets committed and pushed. - **Local** — never leaves the device. Drafts, journal entries, scratch, things that aren't ready or aren't anyone else's business. Same editor, same keymap; the difference is just whether `Ctrl-G` (commit & push) is offered. --- ## Hardware | Part | Choice | Why | |---|---|---| | MCU | **ESP32-S3-N16R8** (16 MB flash, 8 MB octal PSRAM) | USB OTG host (for the keyboard), Wi-Fi, BLE, dual core @ 240 MHz, plenty of PSRAM for git pack data and screen buffer. Best-supported Rust target in the ESP family. | | Display | **Waveshare 7.5" V2 SPI (800×480)** for MVP | Partial refresh works, well-supported by `epd-waveshare`, low power, no IT8951 controller board needed. Upgrade path: 10.3" + IT8951 once UX is proven. | | Keyboard | **Nuphy Air60/Halo65 wired USB-C** | ESP32-S3 acts as USB host via TinyUSB. BLE-HID is a fallback but contends with Wi-Fi for radio time during push. | | Storage | microSD over SPI | Holds both the git working copy (`/sd/repo/`) **and** the local-only scratch space (`/sd/local/`). Internal flash is for firmware + config only. | | Power | **USB-C wall power for MVP**, 18650 + IP5306 in Phase 3 | Measure power profile on real hardware before sizing the battery. E-ink + sleep should give multi-day battery life but battery introduces charging, safety, and BMS complexity we don't need on day one. | | Enclosure | 3D-printed, hinged lid | Phase 4 concern. | **Why not the 10.3" parallel screen for MVP:** IT8951 driver is fine but adds ~$80 BOM and parallel pins eat the GPIO budget we want for SD + status LEDs. Start cheap, prove the loop, then upgrade. --- ## Software stack **Language: Rust on `esp-idf-rs` (std).** Decision is load-bearing — see the rejected alternatives below. | Layer | Crate / Component | Notes | |---|---|---| | HAL / runtime | `esp-idf-svc`, `esp-idf-hal` | std build, gives us heap, threads, VFS, mbedtls, Wi-Fi stack. | | Display | `embedded-graphics` + `epd-waveshare` | Pixel framebuffer with partial-refresh regions. We track dirty rects ourselves. | | Editor core | Custom, in-tree | Rope buffer (`ropey`), mode state machine, Vim keymap table. | | TUI-style layout | Custom thin layer (~500 LoC) | API inspired by Ratatui (`Layout`, `Block`, `Paragraph`) but renders directly to `embedded-graphics`. See below. | | USB host | `esp-idf` TinyUSB bindings | Boot-protocol HID is enough for the keyboard. | | Git | `gitoxide` (`gix`) | Pure-Rust, modular. We only need add / commit / push (smart HTTP). No libgit2, no mbedtls glue beyond what `esp-idf` already gives us. | | TLS | `mbedtls` via `esp-idf` | Used for GitHub HTTPS. ~120 KB heap during handshake — fits in PSRAM. | | Auth | GitHub Personal Access Token in encrypted NVS | SSH on embedded is painful; HTTPS+PAT is the pragmatic path. | | Filesystem | FAT on SD (`esp_vfs_fat`) | Working copy lives here. Internal LittleFS holds config. | ### Why not Ratatui Ratatui assumes a **character-grid terminal** with an ANSI backend. E-ink is a **pixel framebuffer with partial-refresh windows**. The right primitive for e-ink is dirty-rectangle tracking aligned to the panel's refresh regions — Ratatui's per-cell diff model fights this. We can borrow its widget *API shape* (it's a good one) without dragging in the terminal abstraction. Net saving: probably 200 KB of binary and a lot of pretending the screen is a VT100. ### Why not Gleam + Shore BEAM doesn't run on ESP32. AtomVM does, but: memory budget is tight, Gleam-on- AtomVM is bleeding-edge, and there are no bindings for USB host / e-ink / SD / TLS / git in that ecosystem. Shore is also terminal-oriented, so the same impedance mismatch as Ratatui applies. Building this on Gleam would be a research project stacked on a research project. Revisit in 2-3 years. ### Why not C / Arduino Workable, well-trodden, fastest path to a blinking screen. But this is a project I want to keep evolving — Rust's refactoring leverage and type safety pay off the moment we start adding modes, palette, search, etc. --- ## UX boundaries set by the medium E-ink is a brutal honesty filter on UI choices. Hard constraints we design around, not against: - **No cursor blink.** Kills the panel and the battery. - **Typing latency target: ≤ 200 ms** from keypress to glyph on screen, using partial refresh on the affected line only. - **Full refresh every ~20 partials** to clear ghosting. User-visible flash — schedule it on pauses (>1 s of no input). - **No smooth scrolling.** Page-style jumps only. - **No animations.** Anywhere. - **Render only changed lines**, not the viewport. --- ## Roadmap Frequent releases. Each version is a usable artifact, not a checkpoint. ### v0.1 — MVP: "it writes, it pushes" — [ ] The minimum thing that justifies the hardware existing. Full design: [product](docs/v0.1-mvp-product.md) · [technical](docs/v0.1-mvp-technical.md). - [ ] ESP32-S3 boots, e-ink shows splash + boot log - [ ] USB host enumerates the Nuphy, key events reach the editor - [ ] One hard-coded file (`/sd/repo/notes.md`) opens on boot - [ ] Insert-only editing (no modes yet), backspace, enter, arrow keys - [ ] Line wrap, no line numbers yet - [ ] Save on `Ctrl-S` → SD - [ ] Wi-Fi credentials via captive portal on first boot, stored in NVS - [ ] `Ctrl-G` runs: `git add notes.md && git commit -m "wip" && git push` to a pre-configured remote, using a PAT entered during setup - [ ] Partial refresh on edits; full refresh on save Out of scope: Vim, palette, multiple files, branches, conflict handling. ### v0.2 — Vim navigation — [ ] - [ ] Mode state machine (Normal / Insert), mode indicator in status line - [ ] Movement: `h j k l`, `w b e`, `0 $`, `gg G`, `Ctrl-d Ctrl-u` - [ ] `i a o O A` to enter Insert - [ ] `Esc` returns to Normal - [ ] Line numbers (absolute) in the left gutter ### v0.3 — Vim editing — [ ] - [ ] `x dd yy p P`, `dw dd d$`, repeat with `.` - [ ] Undo / redo (`u`, `Ctrl-r`) — bounded history in PSRAM - [ ] Numeric prefixes (`3dd`, `5j`) ### v0.4 — Visual mode + ex commands — [ ] - [ ] Visual char (`v`) and line (`V`) modes, `y d c` on selections - [ ] `:` command line: `:w :q :wq :e ` - [ ] Status line shows file path, dirty flag, mode ### v0.5 — File palette + multi-file — [ ] - [ ] `Ctrl-P` opens fuzzy file palette over **both** `/sd/repo/` and `/sd/local/`, with a scope marker (e.g. `[git]` / `[local]`) per result - [ ] Open, switch, close buffers (keep ≤ 3 in memory) - [ ] `:e` and palette share the same recent-files list - [ ] `:enew` creates a new file — prompts for scope (tracked vs local) - [ ] `Ctrl-G` is disabled / hidden when the current buffer is local-scope ### v0.6 — Markdown affordances — [ ] - [ ] Heading lines bolded in render - [ ] List continuation on Enter inside `- ` / `1. ` - [ ] Soft-wrap at word boundaries - [ ] Optional column ruler at 80 ### v0.7 — Search + better git — [ ] - [ ] `/` forward search, `n N` - [ ] `:Gpull` (fetch + fast-forward only; refuse on conflict and surface it) - [ ] `:Gbranch` to switch branches; refuse with dirty tree - [ ] Commit message prompt instead of hard-coded `"wip"` ### v0.8 — Power: battery + sleep — [ ] - [ ] Measure idle / typing / push current draw on bench - [ ] 18650 + IP5306 charge board, soft power switch - [ ] Light sleep on idle > 30 s (keyboard interrupt wakes) - [ ] Deep sleep on lid close (reed switch); restore cursor + buffer - [ ] Battery indicator in status line ### v0.9 — Robustness — [ ] - [ ] Crash-safe writes (write to `.tmp`, fsync, rename) - [ ] Recover from interrupted push (re-attempt on next save) - [ ] SD card removal / reinsert handling - [ ] Wi-Fi reconnect with backoff - [ ] Settings screen: SSID, PAT rotation, default remote, commit author ### v1.0 — Polish — [ ] - [ ] Boot time ≤ 3 s to usable cursor - [ ] Font selection (at least one serif + one mono) - [ ] Enclosure design files in `hardware/` - [ ] User guide ### v1.x — Stretch / nice-to-have - 10.3" panel upgrade via IT8951 - Multiple remotes / repos - Spell-check (dictionary in flash, naive) - Stats: words today, streak - Theme: light / dark (inverted e-ink) - BLE-HID fallback for wireless keyboards --- ## Repo layout (planned) ``` /firmware Rust crate, esp-idf-rs target (SD card mounted at runtime contains /repo and /local) /src editor/ rope buffer, modes, keymap render/ embedded-graphics + dirty rects git/ gitoxide wrapper, auth usb/ TinyUSB host glue fs/ SD + NVS build.rs sdkconfig.defaults /hardware BOM, schematic, enclosure (later) /docs ADRs, power measurements ``` --- ## Open questions / risks (tracked, not yet resolved) - [ ] `gix-clone` + `gix-pack` smart-HTTP push working on `esp-idf-rs` with mbedtls — needs an early spike before locking the stack. - [ ] TinyUSB host stability with arbitrary HID descriptors (Nuphy reports consumer-control keys we may need to ignore). - [ ] Heap fragmentation over a long writing session with PSRAM allocator. - [ ] Real-world e-ink ghosting with current partial-refresh cadence. These get resolved by writing code, not by deciding harder.