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style(docs): apply oxfmt to README and v0.1 docs

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Julien Calixte
2026-05-14 12:56:13 +02:00
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@@ -23,6 +23,7 @@ components, with the tradeoffs from this file ranked by user-facing weight.
**Scope:** Whole project.
### Context
The firmware needs: USB host, Wi-Fi + TLS, SPI peripherals, a SD filesystem,
and a working git implementation that can push over HTTPS. All on an ESP32-S3
with 8 MB PSRAM. We also want the code to stay refactorable as features pile
@@ -30,21 +31,23 @@ up across nine downstream releases.
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **C / C++ on ESP-IDF** | Reference platform, every peripheral has a driver, fastest path to first pixel. | Refactoring at scale is painful; memory safety is on you. |
| **Rust on `esp-idf-rs` (std)** | First-class Espressif-sponsored Rust support; `std` gives heap / threads / VFS / mbedtls; can use the broader Rust ecosystem (`gitoxide`, `ropey`, `embedded-graphics`). | Larger binary than `no_std`; longer build times; some `unsafe` at FFI seams. |
| **Rust on `esp-hal` (no_std)** | Smallest binary, most "pure" embedded experience. | No `std` = no off-the-shelf git, no easy TLS, would re-implement a lot of plumbing. |
| **Gleam + Shore on AtomVM** | Beautiful language, the user's stated preference. | BEAM on ESP32 is memory-hungry; no bindings for USB host, e-ink, SD, TLS, git in that ecosystem. Two research projects stacked. |
| **MicroPython / CircuitPython** | Fastest to prototype. | Too slow for responsive editing at the latencies e-ink already imposes; GC pauses would surface as dropped keys. |
| **TinyGo** | Modern, ergonomic. | ESP32-S3 support is thinner than Rust's; smaller ecosystem of embedded crates equivalents. |
| Option | Pros | Cons |
| ------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------- |
| **C / C++ on ESP-IDF** | Reference platform, every peripheral has a driver, fastest path to first pixel. | Refactoring at scale is painful; memory safety is on you. |
| **Rust on `esp-idf-rs` (std)** | First-class Espressif-sponsored Rust support; `std` gives heap / threads / VFS / mbedtls; can use the broader Rust ecosystem (`gitoxide`, `ropey`, `embedded-graphics`). | Larger binary than `no_std`; longer build times; some `unsafe` at FFI seams. |
| **Rust on `esp-hal` (no_std)** | Smallest binary, most "pure" embedded experience. | No `std` = no off-the-shelf git, no easy TLS, would re-implement a lot of plumbing. |
| **Gleam + Shore on AtomVM** | Beautiful language, the user's stated preference. | BEAM on ESP32 is memory-hungry; no bindings for USB host, e-ink, SD, TLS, git in that ecosystem. Two research projects stacked. |
| **MicroPython / CircuitPython** | Fastest to prototype. | Too slow for responsive editing at the latencies e-ink already imposes; GC pauses would surface as dropped keys. |
| **TinyGo** | Modern, ergonomic. | ESP32-S3 support is thinner than Rust's; smaller ecosystem of embedded crates equivalents. |
### Decision
**Rust on `esp-idf-rs` (std).** It's the sweet spot: keeps the door open to
the entire Rust ecosystem we need (`gitoxide` especially), gets us threads
and TLS without writing them, and has Espressif as an actual upstream.
### Consequences
- Binary will be in the 1–2 MB range — comfortable in 16 MB flash.
- Build times are real (clean build ~5–10 min). Acceptable.
- Cross-compiling toolchain (`espup`) is one more thing to install.
@@ -64,26 +67,29 @@ the binary-size / build-time costs traded against ecosystem access.
**Scope:** Whole project.
### Context
We need a TUI-like editor (header, edit area, status, palettes later). The
output medium is e-ink: pixel framebuffer with **partial-refresh windows**
aligned to panel-internal regions, ~10× slower than an LCD per region.
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **Ratatui** with a custom backend | Mature widget set, well-known API, lots of community examples. | Built for char-grid terminals over ANSI; per-cell diff fights e-ink's region-refresh model; backend would re-rasterise glyphs from cell-diffs; ~200 KB of binary and a leaky abstraction. |
| **Raw `embedded-graphics` only** | Smallest footprint, full control. | Every screen built from primitives; no widget reuse; status line / palette would each be ad-hoc. |
| **LVGL via Rust bindings** | Full GUI toolkit, themable. | Designed for actively-refreshing colour LCDs; e-ink integration is awkward; way more than we need. |
| **Custom thin widget layer on `embedded-graphics`** | Borrow Ratatui's API ideas (`Layout`, `Block`, `Paragraph`) without its rendering model; dirty-rect tracking aligned to e-ink regions; ~500 LoC. | We own and maintain the layer. |
| Option | Pros | Cons |
| --------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Ratatui** with a custom backend | Mature widget set, well-known API, lots of community examples. | Built for char-grid terminals over ANSI; per-cell diff fights e-ink's region-refresh model; backend would re-rasterise glyphs from cell-diffs; ~200 KB of binary and a leaky abstraction. |
| **Raw `embedded-graphics` only** | Smallest footprint, full control. | Every screen built from primitives; no widget reuse; status line / palette would each be ad-hoc. |
| **LVGL via Rust bindings** | Full GUI toolkit, themable. | Designed for actively-refreshing colour LCDs; e-ink integration is awkward; way more than we need. |
| **Custom thin widget layer on `embedded-graphics`** | Borrow Ratatui's API ideas (`Layout`, `Block`, `Paragraph`) without its rendering model; dirty-rect tracking aligned to e-ink regions; ~500 LoC. | We own and maintain the layer. |
### Decision
**Custom thin widget layer on `embedded-graphics`.** Steal the widget *API
shape* from Ratatui (because it's a good shape) but render directly to a
**Custom thin widget layer on `embedded-graphics`.** Steal the widget _API
shape_ from Ratatui (because it's a good shape) but render directly to a
pixel framebuffer with our own dirty-rectangle tracking sized to the panel's
refresh regions.
### Consequences
- ~500 LoC of widget/layout code we maintain. Worth it.
- We can tune refresh cadence (partial vs full) at the widget level.
- If we later want to render to a terminal for desktop testing, we add a
@@ -101,20 +107,22 @@ Owns the two top-ranked functions (H1 latency, H2 region area) in
**Scope:** v0.1 through v1.0. 10.3" upgrade remains on the v1.x table.
### Context
The screen is the most user-facing hardware choice. It sets the aspect of
the writing experience, the BOM cost, the GPIO budget, the framebuffer size,
and the refresh feel.
### Options considered
| Option | Size / Res | Aspect | Pros | Cons |
|---|---|---|---|---|
| **GDEY0579T93 + DESPI-c579** | 5.79" / 792×272 | 2.9:1 strip | SPI, partial refresh, small framebuffer (~27 KB), Freewrite-style narrow viewport, low power, low GPIO use. | Only ~11 visible lines of edit area; less context on screen. |
| **Waveshare 7.5" V2** | 7.5" / 800×480 | 5:3 page | More lines visible, well-supported by `epd-waveshare` out of the box. | Bigger BOM, bigger framebuffer (~48 KB), more conventional / less typewriter-feeling. |
| **Waveshare 10.3" + IT8951** | 10.3" / 1872×1404 | 4:3 | Real "page" experience; great for long-form. | +$80 BOM; parallel bus eats GPIO; IT8951 adds a controller board; overkill for v0.1. |
| **2.9" / 4.2" smaller panels** | varied | varied | Cheap, common. | Too cramped for a typewriter; status bars eat the screen. |
| Option | Size / Res | Aspect | Pros | Cons |
| ------------------------------ | ----------------- | ----------- | ----------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------- |
| **GDEY0579T93 + DESPI-c579** | 5.79" / 792×272 | 2.9:1 strip | SPI, partial refresh, small framebuffer (~27 KB), Freewrite-style narrow viewport, low power, low GPIO use. | Only ~11 visible lines of edit area; less context on screen. |
| **Waveshare 7.5" V2** | 7.5" / 800×480 | 5:3 page | More lines visible, well-supported by `epd-waveshare` out of the box. | Bigger BOM, bigger framebuffer (~48 KB), more conventional / less typewriter-feeling. |
| **Waveshare 10.3" + IT8951** | 10.3" / 1872×1404 | 4:3 | Real "page" experience; great for long-form. | +$80 BOM; parallel bus eats GPIO; IT8951 adds a controller board; overkill for v0.1. |
| **2.9" / 4.2" smaller panels** | varied | varied | Cheap, common. | Too cramped for a typewriter; status bars eat the screen. |
### Decision
**GDEY0579T93 driven over SPI via the DESPI-c579 breakout.** The strip
aspect biases UX toward "current line + recent context" — the writing
posture we actually want. Small framebuffer keeps PSRAM free for git pack
@@ -122,6 +130,7 @@ data. The DESPI-c579 is a passive level-shifter / FPC adapter, not an active
controller — same SPI driver model as any other e-paper.
### Consequences
- Visible edit area is ~11 lines. UI design must embrace this (no
multi-pane, no large headers). See
[v0.1 product → screen layout](v0.1-mvp-product.md#screen-layout).
@@ -140,28 +149,31 @@ controller — same SPI driver model as any other e-paper.
**Scope:** Whole project, all releases.
### Context
The device must do `add`, `commit`, `push` over the network. Optionally
later: `fetch`, `pull`, `branch`. The library must compile against
`esp-idf-rs` (std, mbedtls available).
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **`libgit2-sys`** (C bindings) | Battle-tested, comprehensive, well-known. | C dependency complicates cross-compile to ESP32-S3; needs mbedtls glue; binary size; less Rust-idiomatic. |
| **`gitoxide` (`gix`)** | Pure Rust, modular crates (we only depend on what we use), idiomatic API, active development. | Smart-HTTP push path is newer than libgit2's; PSRAM allocation patterns less battle-tested on embedded. |
| **Hand-rolled HTTP + pack** | Smallest possible footprint. | Reinventing git internals; pack delta + ref discovery + index updates are not weekend work. |
| **Shell out to `git` binary** | Trivial. | There is no `git` binary on the ESP32-S3. |
| Option | Pros | Cons |
| ------------------------------ | --------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------- |
| **`libgit2-sys`** (C bindings) | Battle-tested, comprehensive, well-known. | C dependency complicates cross-compile to ESP32-S3; needs mbedtls glue; binary size; less Rust-idiomatic. |
| **`gitoxide` (`gix`)** | Pure Rust, modular crates (we only depend on what we use), idiomatic API, active development. | Smart-HTTP push path is newer than libgit2's; PSRAM allocation patterns less battle-tested on embedded. |
| **Hand-rolled HTTP + pack** | Smallest possible footprint. | Reinventing git internals; pack delta + ref discovery + index updates are not weekend work. |
| **Shell out to `git` binary** | Trivial. | There is no `git` binary on the ESP32-S3. |
### Decision
**`gitoxide`.** Modular means we pull only `gix-pack`, `gix-protocol`,
`gix-transport`, etc. — not 200 KB of features we don't use. Pure Rust
removes a class of cross-compile pain. The smart-HTTP path is validated in
spike 7 *before* we commit to integration; if it fails on the device, we
spike 7 _before_ we commit to integration; if it fails on the device, we
fall back to `libgit2-sys` for v0.1 (documented as the kill-switch in the
risk table).
### Consequences
- We become an early-ish embedded user of `gitoxide`; bugs reported back
upstream.
- Auth via PAT in an Authorization header — no SSH (see ADR-005).
@@ -179,25 +191,28 @@ and [risks table](v0.1-mvp-technical.md#risks-and-how-well-know-they-bit-us).
**Scope:** v0.1 through at least v0.9.
### Context
The device must authenticate to GitHub (or other git remotes) to push.
Auth has to be: enterable on a tiny screen-less first-run flow, storable
on-device, and reasonably secure for a personal appliance.
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **HTTPS + PAT** | Trivial to implement; PAT is a string the user pastes during captive-portal setup; works with `gitoxide` smart-HTTP. | Long-lived secret on device; PAT rotation is manual. |
| **HTTPS + OAuth device flow** | No secret typed by hand; user approves on github.com. | Adds an OAuth client app to maintain; token still has to live on device; more first-run UX work. |
| **SSH** | No PAT; per-device deploy keys. | SSH on embedded is heavy (host-key handling, key generation); `gitoxide`'s SSH transport story is less mature than HTTPS; users would have to register the public key on GitHub anyway. |
| **GitHub App with installation token** | Strongest model, rotating credentials. | Massive overhead for a single-user device. |
| Option | Pros | Cons |
| -------------------------------------- | -------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **HTTPS + PAT** | Trivial to implement; PAT is a string the user pastes during captive-portal setup; works with `gitoxide` smart-HTTP. | Long-lived secret on device; PAT rotation is manual. |
| **HTTPS + OAuth device flow** | No secret typed by hand; user approves on github.com. | Adds an OAuth client app to maintain; token still has to live on device; more first-run UX work. |
| **SSH** | No PAT; per-device deploy keys. | SSH on embedded is heavy (host-key handling, key generation); `gitoxide`'s SSH transport story is less mature than HTTPS; users would have to register the public key on GitHub anyway. |
| **GitHub App with installation token** | Strongest model, rotating credentials. | Massive overhead for a single-user device. |
### Decision
**HTTPS + PAT.** Stored in internal LittleFS, encrypted with a key derived
from the chip's eFuse so a stolen SD card alone is not enough. Captive
portal accepts the PAT during first-run setup.
### Consequences
- The user must generate a PAT with `repo` scope. Documented in
[v0.1 product → first-run flow](v0.1-mvp-product.md#first-run-provisioning-flow).
- PAT is never logged. Validated in code review.
@@ -214,25 +229,28 @@ portal accepts the PAT during first-run setup.
**Scope:** v0.1 through at least v1.0.
### Context
The firmware has several concurrent concerns: USB input, Wi-Fi maintenance,
screen rendering, occasional git operations. None of them are I/O-bound at
the scale where async wins. The number of "tasks" is bounded and small (≤ 8).
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **`std::thread` + channels** | Boring, debuggable, stack traces work, no executor to tune; ESP-IDF FreeRTOS underneath is well-understood. | Each thread costs 8–32 KB stack depending on workload; not zero-cost like async. |
| **`embassy` async** | Trendy, ergonomic, low memory per task. | `esp-idf-rs` and `embassy` don't mix cleanly; adopting embassy means dropping `std` and rewriting against `esp-hal` (ADR-001 reversed). |
| **`tokio` on `esp-idf-rs`** | Familiar async. | Heavy executor, oversized for ≤ 8 tasks, mbedtls/`gitoxide` integration would need a lot of glue. |
| **Single-threaded event loop** | Smallest memory. | Long-running ops (git push, full refresh) block input. |
| Option | Pros | Cons |
| ------------------------------ | ----------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------- |
| **`std::thread` + channels** | Boring, debuggable, stack traces work, no executor to tune; ESP-IDF FreeRTOS underneath is well-understood. | Each thread costs 8–32 KB stack depending on workload; not zero-cost like async. |
| **`embassy` async** | Trendy, ergonomic, low memory per task. | `esp-idf-rs` and `embassy` don't mix cleanly; adopting embassy means dropping `std` and rewriting against `esp-hal` (ADR-001 reversed). |
| **`tokio` on `esp-idf-rs`** | Familiar async. | Heavy executor, oversized for ≤ 8 tasks, mbedtls/`gitoxide` integration would need a lot of glue. |
| **Single-threaded event loop** | Smallest memory. | Long-running ops (git push, full refresh) block input. |
### Decision
**`std::thread` + `crossbeam-channel`.** Five tasks (`usb`, `wifi`, `ui`,
`render`, `git`). Editor state behind a single `Mutex`. No `await`, no
runtime to tune, no colour-of-functions problem.
### Consequences
- ~76 KB of stack space across the five task stacks (8 + 8 + 16 + 12 + 32
KB — see [v0.1 technical → threads / tasks](v0.1-mvp-technical.md#threads--tasks)
for the breakdown). Comfortable in the ESP32-S3's 512 KB internal SRAM.
@@ -248,25 +266,28 @@ runtime to tune, no colour-of-functions problem.
**Scope:** Whole project.
### Context
Two storage needs: a large, removable, growable area for the git working
copy and notes; and a small, durable, never-removed area for device config
(Wi-Fi credentials, PAT, remote URL).
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **SD (FAT) for working copy + LittleFS (internal) for config** | Plays to each medium's strengths; user can pop the SD to read on desktop; config can't be lost by yanking the card. | Two filesystems to manage. |
| **All on SD** | One filesystem. | Config disappears if SD is removed; PAT on FAT is harder to protect than on encrypted NVS. |
| **All in internal flash** | Single medium; encrypted. | 16 MB flash limits notes growth; no desktop-side access; SD slot becomes pointless. |
| **SPIFFS for everything** | Single FS, well-known on ESP32. | SPIFFS isn't great with large files; no removability. |
| Option | Pros | Cons |
| -------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------ |
| **SD (FAT) for working copy + LittleFS (internal) for config** | Plays to each medium's strengths; user can pop the SD to read on desktop; config can't be lost by yanking the card. | Two filesystems to manage. |
| **All on SD** | One filesystem. | Config disappears if SD is removed; PAT on FAT is harder to protect than on encrypted NVS. |
| **All in internal flash** | Single medium; encrypted. | 16 MB flash limits notes growth; no desktop-side access; SD slot becomes pointless. |
| **SPIFFS for everything** | Single FS, well-known on ESP32. | SPIFFS isn't great with large files; no removability. |
### Decision
**FAT on SD for `/sd/repo/` and `/sd/local/`. LittleFS on internal flash
for `/nvs/config.toml`.** PAT inside config is encrypted with an eFuse-
derived key.
### Consequences
- User can plug the SD into a laptop and read/edit files there.
Discouraged but possible.
- Config survives SD reformatting.
@@ -283,6 +304,7 @@ derived key.
**Scope:** v0.1 only. Revisited in ADR-future at v0.8.
### Context
"DIY typewriter" suggests portability, which suggests battery. But battery
adds: charging circuit, BMS, thermal margin, soft power switch, lid-close
detection, sleep states. Each of those has its own bring-up cost.
@@ -296,11 +318,13 @@ detection, sleep states. Each of those has its own bring-up cost.
- **LiPo + dedicated charger IC + buck/boost.** More control, more parts.
### Decision
**Wall power only for v0.1.** Battery is its own phase (v0.8) once the
power profile of "boot + type + idle + push" is measured on real hardware.
Sizing a battery before measuring is guessing.
### Consequences
- v0.1 device is tethered. Not the final aesthetic, but the right MVP —
scope is in [v0.1 product → out of scope](v0.1-mvp-product.md#out-of-scope-for-v01).
- We can decide cell capacity from real numbers in v0.8, not specs sheets.
@@ -315,23 +339,26 @@ Sizing a battery before measuring is guessing.
**Scope:** v0.1 through at least v1.0.
### Context
The Nuphy keyboard speaks both wired USB-C (HID) and Bluetooth LE (HID).
The ESP32-S3 has USB OTG (host capable) and BLE 5. Either transport works.
### Options considered
| Option | Pros | Cons |
|---|---|---|
| **USB host (TinyUSB)** | Keyboard draws no battery of its own; ESP32-S3 powers it through the host port; standard boot-protocol HID is well-supported; no radio contention with Wi-Fi during push. | One more USB connector on the enclosure; cable between device and keyboard (or shared chassis). |
| **BLE-HID** | No cable; keyboard can be slightly remote from the device. | Keyboard has its own battery to manage; BLE shares the 2.4 GHz radio with Wi-Fi, so a `Ctrl-G` push contends with input; pairing UX is more first-run work. |
| **UART receiver (custom keyboard firmware)** | Lowest latency, simplest stack. | Requires reflashing the Nuphy or building a passthrough; not viable as a product choice. |
| Option | Pros | Cons |
| -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **USB host (TinyUSB)** | Keyboard draws no battery of its own; ESP32-S3 powers it through the host port; standard boot-protocol HID is well-supported; no radio contention with Wi-Fi during push. | One more USB connector on the enclosure; cable between device and keyboard (or shared chassis). |
| **BLE-HID** | No cable; keyboard can be slightly remote from the device. | Keyboard has its own battery to manage; BLE shares the 2.4 GHz radio with Wi-Fi, so a `Ctrl-G` push contends with input; pairing UX is more first-run work. |
| **UART receiver (custom keyboard firmware)** | Lowest latency, simplest stack. | Requires reflashing the Nuphy or building a passthrough; not viable as a product choice. |
### Decision
**USB host (TinyUSB) for v0.1.** BLE-HID is kept as a documented fallback
if TinyUSB host turns out unstable
([spike 4](v0.1-mvp-technical.md#hardware-bring-up-order) is the gate).
### Consequences
- Enclosure design must include a USB-A or USB-C port for the keyboard.
- The Nuphy's own battery is irrelevant when wired — saves the user a
charging surface.

222
docs/qfd.md
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@@ -1,7 +1,7 @@
# Quality Function Deployment
Translates what the device must *be* (user-facing requirements) into what it
must *do* (engineering functions) and what we must *build* (components).
Translates what the device must _be_ (user-facing requirements) into what it
must _do_ (engineering functions) and what we must _build_ (components).
Surfaces the few targets that dominate the design and the conflicts between
them. Every decision cell points back to [`adr.md`](adr.md).
@@ -21,20 +21,20 @@ weights: **9** strong, **3** medium, **1** weak, blank none.
What a user (= me) values about the device, with importance weights on a
1–10 scale. Source columns point at the doc the requirement comes from.
| ID | Requirement | Weight | Source |
|-----|---------------------------------------------------|:------:|--------|
| W1 | Sub-second visible response to typing | 10 | [product → story 2](v0.1-mvp-product.md#user-stories), [README → UX](../README.md#ux-boundaries-set-by-the-medium) |
| W2 | `Ctrl-G` reliably lands a commit on GitHub | 9 | [product → story 4](v0.1-mvp-product.md#user-stories) |
| W3 | Pulling power never corrupts the file | 10 | [product → story 5](v0.1-mvp-product.md#user-stories), [acceptance](v0.1-mvp-product.md#acceptance-criteria) |
| W4 | One-shot first-run setup, never repeated | 7 | [product → story 1](v0.1-mvp-product.md#user-stories) |
| W5 | Quick boot to a writing cursor | 6 | [product → acceptance](v0.1-mvp-product.md#acceptance-criteria) (≤ 5 s) |
| W6 | Long sessions without crash / lag / drift | 9 | [product → acceptance](v0.1-mvp-product.md#acceptance-criteria) (1 h soak) |
| W7 | Distraction-free, single-purpose surface | 8 | [README → vision](../README.md#vision) |
| W8 | E-ink-honest UI (no blink, no animation, no flash spam) | 7 | [README → UX](../README.md#ux-boundaries-set-by-the-medium) |
| W9 | Refactorable across nine downstream releases | 8 | [roadmap](roadmap.md) |
| W10 | Hackable / DIY-shaped BOM and code | 5 | [README → vision](../README.md#vision) |
| W11 | Multi-day battery life (v0.8 onward) | 4 | [roadmap → v0.8](roadmap.md#v08--power-battery--sleep--) |
| W12 | Local-only file scope coexists with git scope (v0.5+) | 5 | [README → scopes](../README.md#vision), [roadmap → v0.5](roadmap.md#v05--file-palette--multi-file--) |
| ID | Requirement | Weight | Source |
| --- | ------------------------------------------------------- | :----: | ------------------------------------------------------------------------------------------------------------------ |
| W1 | Sub-second visible response to typing | 10 | [product → story 2](v0.1-mvp-product.md#user-stories), [README → UX](../README.md#ux-boundaries-set-by-the-medium) |
| W2 | `Ctrl-G` reliably lands a commit on GitHub | 9 | [product → story 4](v0.1-mvp-product.md#user-stories) |
| W3 | Pulling power never corrupts the file | 10 | [product → story 5](v0.1-mvp-product.md#user-stories), [acceptance](v0.1-mvp-product.md#acceptance-criteria) |
| W4 | One-shot first-run setup, never repeated | 7 | [product → story 1](v0.1-mvp-product.md#user-stories) |
| W5 | Quick boot to a writing cursor | 6 | [product → acceptance](v0.1-mvp-product.md#acceptance-criteria) (≤ 5 s) |
| W6 | Long sessions without crash / lag / drift | 9 | [product → acceptance](v0.1-mvp-product.md#acceptance-criteria) (1 h soak) |
| W7 | Distraction-free, single-purpose surface | 8 | [README → vision](../README.md#vision) |
| W8 | E-ink-honest UI (no blink, no animation, no flash spam) | 7 | [README → UX](../README.md#ux-boundaries-set-by-the-medium) |
| W9 | Refactorable across nine downstream releases | 8 | [roadmap](roadmap.md) |
| W10 | Hackable / DIY-shaped BOM and code | 5 | [README → vision](../README.md#vision) |
| W11 | Multi-day battery life (v0.8 onward) | 4 | [roadmap → v0.8](roadmap.md#v08--power-battery--sleep--) |
| W12 | Local-only file scope coexists with git scope (v0.5+) | 5 | [README → scopes](../README.md#vision), [roadmap → v0.5](roadmap.md#v05--file-palette--multi-file--) |
---
@@ -43,23 +43,23 @@ What a user (= me) values about the device, with importance weights on a
Measurable characteristics. Targets are v0.1 unless noted. Direction column
shows what "better" looks like (↑ higher, ↓ lower, → fixed).
| ID | Function | Dir | v0.1 target | v1.0 target |
|-----|-------------------------------------------------------|:---:|--------------------------|-----------------------|
| H1 | Keypress → glyph latency | ↓ | ≤ 200 ms | ≤ 150 ms |
| H2 | Partial-refresh region area per keystroke | ↓ | ≤ 1 text line (~22 px h) | same |
| H3 | Full-refresh cadence (clears ghosting) | → | 1 per 20 partials | tuned by panel temp |
| H4 | Cold boot → cursor ready | ↓ | ≤ 5 s | ≤ 3 s |
| H5 | Continuous-typing endurance (no drop, no leak) | ↑ | ≥ 1 h | ≥ 8 h |
| H6 | `Ctrl-G` push success rate on healthy Wi-Fi | ↑ | ≥ 95 % | ≥ 99 % |
| H7 | Push end-to-end (one-file commit) | ↓ | ≤ 30 s | ≤ 10 s |
| H8 | Save survives power loss after status confirms | → | 100 % | 100 % |
| H9 | PSRAM heap headroom during push | ↑ | ≥ 1 MB free at peak | same |
| H10 | Firmware binary size | ↓ | ≤ 2 MB | ≤ 1.5 MB |
| H11 | Stack budget across all tasks | ↓ | ≤ 80 KB (sum) | same |
| H12 | Wi-Fi reconnect on transient outage | ↓ | ≤ 30 s | ≤ 10 s |
| H13 | Idle / typing / push current draw | ↓ | measured only | sized for >2 days |
| H14 | Module count / public-API surface (refactor proxy) | → | ≤ 8 modules | same |
| H15 | Build time (clean, release) | ↓ | ≤ 10 min | ≤ 7 min |
| ID | Function | Dir | v0.1 target | v1.0 target |
| --- | -------------------------------------------------- | :-: | ------------------------ | ------------------- |
| H1 | Keypress → glyph latency | ↓ | ≤ 200 ms | ≤ 150 ms |
| H2 | Partial-refresh region area per keystroke | ↓ | ≤ 1 text line (~22 px h) | same |
| H3 | Full-refresh cadence (clears ghosting) | → | 1 per 20 partials | tuned by panel temp |
| H4 | Cold boot → cursor ready | ↓ | ≤ 5 s | ≤ 3 s |
| H5 | Continuous-typing endurance (no drop, no leak) | ↑ | ≥ 1 h | ≥ 8 h |
| H6 | `Ctrl-G` push success rate on healthy Wi-Fi | ↑ | ≥ 95 % | ≥ 99 % |
| H7 | Push end-to-end (one-file commit) | ↓ | ≤ 30 s | ≤ 10 s |
| H8 | Save survives power loss after status confirms | → | 100 % | 100 % |
| H9 | PSRAM heap headroom during push | ↑ | ≥ 1 MB free at peak | same |
| H10 | Firmware binary size | ↓ | ≤ 2 MB | ≤ 1.5 MB |
| H11 | Stack budget across all tasks | ↓ | ≤ 80 KB (sum) | same |
| H12 | Wi-Fi reconnect on transient outage | ↓ | ≤ 30 s | ≤ 10 s |
| H13 | Idle / typing / push current draw | ↓ | measured only | sized for >2 days |
| H14 | Module count / public-API surface (refactor proxy) | → | ≤ 8 modules | same |
| H15 | Build time (clean, release) | ↓ | ≤ 10 min | ≤ 7 min |
---
@@ -69,21 +69,21 @@ Reading: row × column cell is how strongly the function (H) advances the
requirement (W). Importance at the bottom is `Σ(weight × strength)` — the
weighted vote on which functions deserve the most engineering attention.
| | H1 lat | H2 area | H3 cad | H4 boot | H5 soak | H6 push% | H7 push s | H8 dura | H9 heap | H10 bin | H11 stk | H12 wifi | H13 mA | H14 mod | H15 build |
|-------|:------:|:-------:|:------:|:-------:|:-------:|:--------:|:---------:|:-------:|:-------:|:-------:|:-------:|:--------:|:------:|:-------:|:---------:|
| W1 (10) | **9** | 9 | 3 | | 3 | | | | 1 | | 1 | | | | |
| W2 (9) | | | | | | **9** | 3 | | 9 | | | 9 | | | |
| W3 (10) | | | | | | | | **9** | | | | | | | |
| W4 (7) | | | | | | 3 | | | | | | 3 | | 1 | |
| W5 (6) | | | | **9** | | | | | | 3 | | | | | |
| W6 (9) | 3 | | 3 | | **9** | 3 | | 3 | 9 | | 3 | 3 | | | |
| W7 (8) | 3 | 3 | 3 | | | | | | | | | | 3 | 1 | |
| W8 (7) | 1 | 9 | **9** | | | | | | | | | | | | |
| W9 (8) | | | | | | | | | | 1 | 1 | | | **9** | 3 |
| W10 (5) | | | | | | | | | | 3 | | | 1 | 3 | 1 |
| W11 (4) | | | | | | | | | | | | | **9** | | |
| W12 (5) | | | | | | 1 | | 3 | | | | | | 3 | |
| **Σ** | **138**| **174** | **126**| **54** | **108** | **132** | **27** | **147** | **162** | **38** | **41** | **120** | **74** | **115** | **29** |
| | H1 lat | H2 area | H3 cad | H4 boot | H5 soak | H6 push% | H7 push s | H8 dura | H9 heap | H10 bin | H11 stk | H12 wifi | H13 mA | H14 mod | H15 build |
| ------- | :-----: | :-----: | :-----: | :-----: | :-----: | :------: | :-------: | :-----: | :-----: | :-----: | :-----: | :------: | :----: | :-----: | :-------: |
| W1 (10) | **9** | 9 | 3 | | 3 | | | | 1 | | 1 | | | | |
| W2 (9) | | | | | | **9** | 3 | | 9 | | | 9 | | | |
| W3 (10) | | | | | | | | **9** | | | | | | | |
| W4 (7) | | | | | | 3 | | | | | | 3 | | 1 | |
| W5 (6) | | | | **9** | | | | | | 3 | | | | | |
| W6 (9) | 3 | | 3 | | **9** | 3 | | 3 | 9 | | 3 | 3 | | | |
| W7 (8) | 3 | 3 | 3 | | | | | | | | | | 3 | 1 | |
| W8 (7) | 1 | 9 | **9** | | | | | | | | | | | | |
| W9 (8) | | | | | | | | | | 1 | 1 | | | **9** | 3 |
| W10 (5) | | | | | | | | | | 3 | | | 1 | 3 | 1 |
| W11 (4) | | | | | | | | | | | | | **9** | | |
| W12 (5) | | | | | | 1 | | 3 | | | | | | 3 | |
| **Σ** | **138** | **174** | **126** | **54** | **108** | **132** | **27** | **147** | **162** | **38** | **41** | **120** | **74** | **115** | **29** |
### Top engineering priorities (from importance)
@@ -114,7 +114,7 @@ The roof shows where pushing one function pushes another the wrong way.
**`– –`** strong conflict.
| | H1 | H2 | H3 | H4 | H5 | H6 | H7 | H8 | H9 | H10 | H11 | H12 | H13 | H14 | H15 |
|---------|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|
| ------- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| **H1** | — | ++ | – | | + | | | | | | | | – | | |
| **H2** | | — | ++ | | | | | | | | | | + | | |
| **H3** | | | — | | | | | | | | | | + | | |
@@ -137,7 +137,7 @@ The roof shows where pushing one function pushes another the wrong way.
second pile up ghosting faster, demanding earlier full refreshes —
visible flashes that hurt H8 perception and H1 burst behaviour. The
ADR-003 strip aspect is the structural answer: a small framebuffer makes
*both* cheaper, not one at the expense of the other. The runtime answer
_both_ cheaper, not one at the expense of the other. The runtime answer
is render §H3: schedule full refreshes on idle ≥ 1 s (v0.1 tech doc).
- **H9 heap ↔ H10 binary size** (strong). std + gitoxide + mbedtls inflate
both. We chose to spend on these (ADR-001, ADR-004) because 16 MB flash
@@ -170,44 +170,44 @@ constrains the choice.
Components (with anchoring ADR):
| ID | Component | ADR |
|-----|----------------------------------------------|------------|
| C1 | ESP32-S3-N16R8 SoC | ADR-001, ADR-008 |
| C2 | `esp-idf-rs` (std) + ESP-IDF | ADR-001 |
| C3 | `std::thread` + `crossbeam-channel` | ADR-006 |
| C4 | PSRAM allocator wrapper | ADR-001 |
| C5 | GDEY0579T93 + DESPI-c579 panel | ADR-003 |
| C6 | `embedded-graphics` + e-paper driver | ADR-002, ADR-003 |
| C7 | Custom widget / dirty-rect layer | ADR-002 |
| C8 | `ropey` rope buffer | ADR-001 (ecosystem) |
| C9 | TinyUSB host (`esp-idf` bindings) | ADR-009 |
| C10 | FAT on microSD | ADR-007 |
| C11 | LittleFS on internal flash | ADR-007 |
| C12 | `gitoxide` (`gix-*`) | ADR-004 |
| C13 | mbedtls TLS (via ESP-IDF) | ADR-005 |
| C14 | HTTPS + GitHub PAT auth | ADR-005 |
| C15 | eFuse-derived encryption key | ADR-005, ADR-007 |
| C16 | USB-C wall PSU | ADR-008 |
| ID | Component | ADR |
| --- | ------------------------------------ | ------------------- |
| C1 | ESP32-S3-N16R8 SoC | ADR-001, ADR-008 |
| C2 | `esp-idf-rs` (std) + ESP-IDF | ADR-001 |
| C3 | `std::thread` + `crossbeam-channel` | ADR-006 |
| C4 | PSRAM allocator wrapper | ADR-001 |
| C5 | GDEY0579T93 + DESPI-c579 panel | ADR-003 |
| C6 | `embedded-graphics` + e-paper driver | ADR-002, ADR-003 |
| C7 | Custom widget / dirty-rect layer | ADR-002 |
| C8 | `ropey` rope buffer | ADR-001 (ecosystem) |
| C9 | TinyUSB host (`esp-idf` bindings) | ADR-009 |
| C10 | FAT on microSD | ADR-007 |
| C11 | LittleFS on internal flash | ADR-007 |
| C12 | `gitoxide` (`gix-*`) | ADR-004 |
| C13 | mbedtls TLS (via ESP-IDF) | ADR-005 |
| C14 | HTTPS + GitHub PAT auth | ADR-005 |
| C15 | eFuse-derived encryption key | ADR-005, ADR-007 |
| C16 | USB-C wall PSU | ADR-008 |
Function-to-component matrix (9 strong / 3 medium / 1 weak):
| | C1 SoC | C2 std | C3 thr | C4 PSR | C5 EPD | C6 eg | C7 wid | C8 rope | C9 USB | C10 SD | C11 LFS | C12 gix | C13 TLS | C14 PAT | C15 efs | C16 PSU |
|-------|:------:|:------:|:------:|:------:|:------:|:-----:|:------:|:-------:|:------:|:------:|:-------:|:-------:|:-------:|:-------:|:-------:|:-------:|
| H1 lat | 3 | 1 | 9 | 3 | 9 | 9 | 9 | 3 | 9 | | | | | | | |
| H2 area | | | | | 9 | 9 | 9 | | | | | | | | | |
| H3 cad | | | | | 9 | 3 | 9 | | | | | | | | | |
| H4 boot | 3 | 9 | 3 | 1 | 3 | | | | | 9 | 3 | | | | | |
| H5 soak | 3 | 3 | 3 | 9 | 1 | | | 9 | 9 | 3 | | 3 | 3 | | | |
| H6 push% | | 3 | | | | | | | | | | 9 | 9 | 9 | | |
| H7 push s| | | 3 | 1 | | | | | | 3 | | 9 | 9 | | | |
| H8 dura | | 3 | | | | | | | | 9 | 9 | | | | | |
| H9 heap | 3 | 3 | | 9 | | | | 3 | | | | 9 | 9 | | | |
| H10 bin | | 9 | 1 | | | 3 | 3 | 3 | 3 | | | 9 | 3 | | | |
| H11 stk | | | 9 | | | | | | 3 | | | 3 | | | | |
| H12 wifi | 3 | 9 | | | | | | | | | | | 3 | | | |
| H13 mA | 9 | | 1 | | 9 | | | | 3 | 3 | | | | | | 9 |
| H14 mod | | 3 | 3 | | | 3 | 9 | 3 | | | | 9 | | | | |
| H15 build| | 9 | | | | | | | | | | 9 | 3 | | | |
| | C1 SoC | C2 std | C3 thr | C4 PSR | C5 EPD | C6 eg | C7 wid | C8 rope | C9 USB | C10 SD | C11 LFS | C12 gix | C13 TLS | C14 PAT | C15 efs | C16 PSU |
| --------- | :----: | :----: | :----: | :----: | :----: | :---: | :----: | :-----: | :----: | :----: | :-----: | :-----: | :-----: | :-----: | :-----: | :-----: |
| H1 lat | 3 | 1 | 9 | 3 | 9 | 9 | 9 | 3 | 9 | | | | | | | |
| H2 area | | | | | 9 | 9 | 9 | | | | | | | | | |
| H3 cad | | | | | 9 | 3 | 9 | | | | | | | | | |
| H4 boot | 3 | 9 | 3 | 1 | 3 | | | | | 9 | 3 | | | | | |
| H5 soak | 3 | 3 | 3 | 9 | 1 | | | 9 | 9 | 3 | | 3 | 3 | | | |
| H6 push% | | 3 | | | | | | | | | | 9 | 9 | 9 | | |
| H7 push s | | | 3 | 1 | | | | | | 3 | | 9 | 9 | | | |
| H8 dura | | 3 | | | | | | | | 9 | 9 | | | | | |
| H9 heap | 3 | 3 | | 9 | | | | 3 | | | | 9 | 9 | | | |
| H10 bin | | 9 | 1 | | | 3 | 3 | 3 | 3 | | | 9 | 3 | | | |
| H11 stk | | | 9 | | | | | | 3 | | | 3 | | | | |
| H12 wifi | 3 | 9 | | | | | | | | | | | 3 | | | |
| H13 mA | 9 | | 1 | | 9 | | | | 3 | 3 | | | | | | 9 |
| H14 mod | | 3 | 3 | | | 3 | 9 | 3 | | | | 9 | | | | |
| H15 build | | 9 | | | | | | | | | | 9 | 3 | | | |
### Read across, not down
@@ -219,7 +219,7 @@ Function-to-component matrix (9 strong / 3 medium / 1 weak):
`libgit2-sys` if spike 7 fails). It's also why H9 sits in the top three
priorities — `gitoxide`'s memory profile is the unknown.
- **C2** (std runtime) sits underneath almost everything, but it's the
*enabler* (H4 boot, H10 binary, H12 Wi-Fi) rather than the bottleneck.
_enabler_ (H4 boot, H10 binary, H12 Wi-Fi) rather than the bottleneck.
Reversing ADR-001 would force re-deciding ADR-004, ADR-005, ADR-006,
ADR-007 all at once — they're a single decision in three drawers.
@@ -230,21 +230,21 @@ Function-to-component matrix (9 strong / 3 medium / 1 weak):
Pulled from §3 importance and §4 conflicts, in priority order. These are
the numbers spikes 2–7 must validate before integration starts.
| Rank | Function | Target | Watched on | If we miss it |
|------|----------------|----------------------|-----------------------|-----------------------------------------------|
| 1 | H2 region area | ≤ 1 line per keypress| spike 2 + spike 5 | Increase font size to shrink per-glyph dirty rect (ADR-003 consequence) |
| 2 | H9 PSRAM heap | ≥ 1 MB free at push peak | spike 7 | ADR-004 kill-switch → `libgit2-sys`; cap rope at 128 KB |
| 3 | H8 durability | 100 % survive power yank after status | bench HIL | Re-evaluate ADR-007 (move config to internal NVS only) |
| 4 | H1 latency | ≤ 200 ms keypress→glyph | spike 5 | Larger partial-refresh region; render multi-char bursts |
| 5 | H6 push % | ≥ 95 % on healthy Wi-Fi | spike 6 + spike 7 | TLS cipher trim; reconnect backoff tuning |
| 6 | H3 cadence | full every ~20 partials | spike 2 | Adjust per panel temperature; defer flash to idle ≥ 1 s |
| 7 | H4 boot | ≤ 5 s to cursor | integration smoke | Trim startup logging; lazy-mount SD after splash |
| 8 | H5 soak | 1 h no leak / no drop| 1 h bench soak | Glyph-cache eviction; PSRAM heap-fragmentation review |
| Rank | Function | Target | Watched on | If we miss it |
| ---- | -------------- | ------------------------------------- | ----------------- | ----------------------------------------------------------------------- |
| 1 | H2 region area | ≤ 1 line per keypress | spike 2 + spike 5 | Increase font size to shrink per-glyph dirty rect (ADR-003 consequence) |
| 2 | H9 PSRAM heap | ≥ 1 MB free at push peak | spike 7 | ADR-004 kill-switch → `libgit2-sys`; cap rope at 128 KB |
| 3 | H8 durability | 100 % survive power yank after status | bench HIL | Re-evaluate ADR-007 (move config to internal NVS only) |
| 4 | H1 latency | ≤ 200 ms keypress→glyph | spike 5 | Larger partial-refresh region; render multi-char bursts |
| 5 | H6 push % | ≥ 95 % on healthy Wi-Fi | spike 6 + spike 7 | TLS cipher trim; reconnect backoff tuning |
| 6 | H3 cadence | full every ~20 partials | spike 2 | Adjust per panel temperature; defer flash to idle ≥ 1 s |
| 7 | H4 boot | ≤ 5 s to cursor | integration smoke | Trim startup logging; lazy-mount SD after splash |
| 8 | H5 soak | 1 h no leak / no drop | 1 h bench soak | Glyph-cache eviction; PSRAM heap-fragmentation review |
The two not-in-MVP rows but already-shaped-by-design:
| — | H13 current | Measured only in v0.1 | bench multimeter | Cell sizing for v0.8 is data-driven, not spec-sheet |
| — | H11 stacks | Sum ≤ 80 KB | static analysis | Was off-by-2x in ADR-006 pre-fix — corrected in §7 |
| — | H13 current | Measured only in v0.1 | bench multimeter | Cell sizing for v0.8 is data-driven, not spec-sheet |
| — | H11 stacks | Sum ≤ 80 KB | static analysis | Was off-by-2x in ADR-006 pre-fix — corrected in §7 |
---
@@ -252,19 +252,19 @@ The two not-in-MVP rows but already-shaped-by-design:
Plain-language summary of what we accepted in exchange for what.
| Tradeoff | Got | Paid | ADR |
|-------------------------------------------------------|-------------------------------|-------------------------------|---------|
| std (esp-idf-rs) over no_std (esp-hal) | Heap, threads, VFS, mbedtls, gitoxide-compatible | +1 MB binary, +5–10 min builds | ADR-001 |
| Custom widget layer over Ratatui | Dirty-rects aligned to e-ink regions; 200 KB binary back | 500 LoC we own and maintain | ADR-002 |
| 5.79" strip panel over 7.5" page or 10.3" reader | 27 KB framebuffer, fast partial refresh, "Freewrite" UX | Only ~11 visible lines | ADR-003 |
| `gitoxide` over `libgit2-sys` | Pure Rust, modular, no FFI cross-compile pain | Smart-HTTP path is newer; PSRAM profile unproven (spike 7) | ADR-004 |
| HTTPS + PAT over OAuth device-flow or SSH | First-run UX fits in a captive-portal form | Long-lived secret on device; manual rotation in v0.1 | ADR-005 |
| `std::thread` over `embassy` or `tokio` | Boring, debuggable, real stack traces; no exec to tune | ~76 KB total stack across 5 tasks | ADR-006 |
| FAT-on-SD + LittleFS-on-flash split | Desktop can read SD; config survives SD reformat | Two filesystems to manage; FAT's power-loss weakness mitigated by atomic-rename | ADR-007 |
| Wall power for v0.1, battery deferred | Measure real draw before sizing the cell | Tethered MVP; not the final aesthetic | ADR-008 |
| USB host (TinyUSB) over BLE-HID | No radio contention with Wi-Fi during push; keyboard powered from the device | One more USB connector on enclosure | ADR-009 |
| Tradeoff | Got | Paid | ADR |
| ------------------------------------------------ | ---------------------------------------------------------------------------- | ------------------------------------------------------------------------------- | ------- |
| std (esp-idf-rs) over no_std (esp-hal) | Heap, threads, VFS, mbedtls, gitoxide-compatible | +1 MB binary, +5–10 min builds | ADR-001 |
| Custom widget layer over Ratatui | Dirty-rects aligned to e-ink regions; 200 KB binary back | 500 LoC we own and maintain | ADR-002 |
| 5.79" strip panel over 7.5" page or 10.3" reader | 27 KB framebuffer, fast partial refresh, "Freewrite" UX | Only ~11 visible lines | ADR-003 |
| `gitoxide` over `libgit2-sys` | Pure Rust, modular, no FFI cross-compile pain | Smart-HTTP path is newer; PSRAM profile unproven (spike 7) | ADR-004 |
| HTTPS + PAT over OAuth device-flow or SSH | First-run UX fits in a captive-portal form | Long-lived secret on device; manual rotation in v0.1 | ADR-005 |
| `std::thread` over `embassy` or `tokio` | Boring, debuggable, real stack traces; no exec to tune | ~76 KB total stack across 5 tasks | ADR-006 |
| FAT-on-SD + LittleFS-on-flash split | Desktop can read SD; config survives SD reformat | Two filesystems to manage; FAT's power-loss weakness mitigated by atomic-rename | ADR-007 |
| Wall power for v0.1, battery deferred | Measure real draw before sizing the cell | Tethered MVP; not the final aesthetic | ADR-008 |
| USB host (TinyUSB) over BLE-HID | No radio contention with Wi-Fi during push; keyboard powered from the device | One more USB connector on enclosure | ADR-009 |
### Conflicts left explicitly *unresolved* by v0.1
### Conflicts left explicitly _unresolved_ by v0.1
These are the live tensions we are watching, not deciding harder:
@@ -304,7 +304,7 @@ and is not load-bearing.
- When a new ADR lands, add its components to §5 and re-score any
function-row whose dominant component changed.
- When a spike returns numbers, update §6's "Target" or "Watched on"
columns — this is the doc that *should* feel out of date if measured
columns — this is the doc that _should_ feel out of date if measured
reality drifts from estimates.
- The WHATs change rarely; the HOWs change with each release; the
matrices are recomputed when either side changes.

18
docs/v0.1-mvp-product.md
View File

@@ -147,14 +147,14 @@ don't fight it.
## Error UX
| Failure | What the user sees |
|---|---|
| No SD card on boot | "no SD card — insert one and reboot" |
| SD card mounted but `/sd/repo` missing | drop back into first-run setup |
| Wi-Fi won't connect | status shows `Wi-Fi ✗`; editing still works; `Ctrl-G` shows "no network" |
| `Ctrl-G` push rejected (auth, non-fast-forward, etc.) | status shows reason; commit stays local; user can retry |
| File write fails | status flashes "save failed"; buffer stays dirty |
| Keyboard disconnects | header shows `⌨ ✗`; editing pauses; reconnects automatically |
| Failure | What the user sees |
| ----------------------------------------------------- | ------------------------------------------------------------------------ |
| No SD card on boot | "no SD card — insert one and reboot" |
| SD card mounted but `/sd/repo` missing | drop back into first-run setup |
| Wi-Fi won't connect | status shows `Wi-Fi ✗`; editing still works; `Ctrl-G` shows "no network" |
| `Ctrl-G` push rejected (auth, non-fast-forward, etc.) | status shows reason; commit stays local; user can retry |
| File write fails | status flashes "save failed"; buffer stays dirty |
| Keyboard disconnects | header shows `⌨ ✗`; editing pauses; reconnects automatically |
No modal dialogs. Errors live in the status line. The editor is never blocked
from accepting keystrokes (except during the partial-refresh frame itself).
@@ -199,7 +199,7 @@ place to check before declaring an item done.
## Non-goals as success criteria
These are deliberately *not* measured in v0.1:
These are deliberately _not_ measured in v0.1:
- Boot time below 3 s (Phase 1 target).
- Battery life (no battery yet).

60
docs/v0.1-mvp-technical.md
View File

@@ -42,13 +42,13 @@ blocked by I/O.
### Threads / tasks
| Task | Core | Stack | Responsibility |
|---|---|---|---|
| `usb_task` | 0 | 8 KB | TinyUSB host loop, decode HID reports, post `KeyEvent`s |
| `wifi_task` | 0 | 8 KB | Provisioning AP or station mode; expose status |
| `ui_task` | 1 | 16 KB | Consume `KeyEvent`s, mutate editor state, enqueue render |
| `render_task` | 1 | 12 KB | Drain render queue, do partial/full refresh on EPD |
| `git_task` | 1 | 32 KB | Triggered by `Ctrl-G`; runs gitoxide commit + push |
| Task | Core | Stack | Responsibility |
| ------------- | ---- | ----- | -------------------------------------------------------- |
| `usb_task` | 0 | 8 KB | TinyUSB host loop, decode HID reports, post `KeyEvent`s |
| `wifi_task` | 0 | 8 KB | Provisioning AP or station mode; expose status |
| `ui_task` | 1 | 16 KB | Consume `KeyEvent`s, mutate editor state, enqueue render |
| `render_task` | 1 | 12 KB | Drain render queue, do partial/full refresh on EPD |
| `git_task` | 1 | 32 KB | Triggered by `Ctrl-G`; runs gitoxide commit + push |
All inter-task communication is via `crossbeam-channel` or `std::sync::mpsc`
bounded queues. The editor state is `Arc<Mutex<EditorState>>`; the lock is
@@ -117,15 +117,15 @@ stack decision (e.g. fall back to libgit2; switch to a separate SD SPI bus).
### `keymap` — v0.1 keymap table
| Key | Action |
|---|---|
| printable | insert char |
| `Backspace` | delete char before cursor |
| `Enter` | insert `\n` |
| Key | Action |
| --------------- | --------------------------------- |
| printable | insert char |
| `Backspace` | delete char before cursor |
| `Enter` | insert `\n` |
| `←` `→` `↑` `↓` | move cursor (visual lines for ↑↓) |
| `Home` `End` | line start / end |
| `Ctrl-S` | save |
| `Ctrl-G` | save (if dirty) + commit + push |
| `Home` `End` | line start / end |
| `Ctrl-S` | save |
| `Ctrl-G` | save (if dirty) + commit + push |
Anything else is ignored in v0.1.
@@ -198,14 +198,14 @@ PSRAM heap during push is a top-3 watched metric — see
ESP32-S3-N16R8: 512 KB SRAM + 8 MB PSRAM. We budget conservatively.
| Region | Approx | Use |
|---|---|---|
| Internal SRAM | ~120 KB | task stacks, DMA buffers, hot code paths |
| Internal SRAM | ~80 KB | mbedtls runtime (TLS handshake working set) |
| PSRAM | ~128 KB | EPD framebuffer (792×272×1 ≈ 27 KB) + shadow + glyph cache |
| PSRAM | ~512 KB | rope buffer + edit history headroom |
| PSRAM | ~1.5 MB | gitoxide working set during push (pack delta, etc.) |
| PSRAM | rest | heap headroom |
| Region | Approx | Use |
| ------------- | ------- | ---------------------------------------------------------- |
| Internal SRAM | ~120 KB | task stacks, DMA buffers, hot code paths |
| Internal SRAM | ~80 KB | mbedtls runtime (TLS handshake working set) |
| PSRAM | ~128 KB | EPD framebuffer (792×272×1 ≈ 27 KB) + shadow + glyph cache |
| PSRAM | ~512 KB | rope buffer + edit history headroom |
| PSRAM | ~1.5 MB | gitoxide working set during push (pack delta, etc.) |
| PSRAM | rest | heap headroom |
PSRAM is the default for `Box::new` via a custom allocator wrapper; DMA-able
allocations must explicitly request internal SRAM (epd-waveshare needs this
@@ -264,13 +264,13 @@ does not implement key rotation.
Mirrored as live conflicts in
[qfd.md §7 "Conflicts left explicitly unresolved by v0.1"](qfd.md#7-tradeoffs-and-their-why-linked-to-adrs).
| Risk | Symptom we'd see | Fallback |
|---|---|---|
| `gix` smart-HTTP push doesn't work on `esp-idf-rs` mbedtls | spike 7 fails | switch to `libgit2-sys` (C, well-trodden) for v0.1 only |
| TinyUSB host drops HID reports under load | dropped keystrokes during fast typing | enable larger USB rx buffer; if still bad, fall back to BLE-HID for v0.1 |
| EPD partial refresh slower than 200 ms | typing feels laggy | reduce font size to shrink dirty area; or render multi-char bursts |
| TLS heap pressure on PSRAM | OOM during push | tune mbedtls to smaller cipher suites; force GC of glyph cache before push |
| SD + EPD on same SPI bus collide | corruption on save during render | move SD to a separate SPI peripheral (ESP32-S3 has two) |
| Risk | Symptom we'd see | Fallback |
| ---------------------------------------------------------- | ------------------------------------- | -------------------------------------------------------------------------- |
| `gix` smart-HTTP push doesn't work on `esp-idf-rs` mbedtls | spike 7 fails | switch to `libgit2-sys` (C, well-trodden) for v0.1 only |
| TinyUSB host drops HID reports under load | dropped keystrokes during fast typing | enable larger USB rx buffer; if still bad, fall back to BLE-HID for v0.1 |
| EPD partial refresh slower than 200 ms | typing feels laggy | reduce font size to shrink dirty area; or render multi-char bursts |
| TLS heap pressure on PSRAM | OOM during push | tune mbedtls to smaller cipher suites; force GC of glyph cache before push |
| SD + EPD on same SPI bus collide | corruption on save during render | move SD to a separate SPI peripheral (ESP32-S3 has two) |
Every one of these is detected by a spike before integration starts — we are
not finding them at the end.