mirror of
https://github.com/imjasonh/esp32
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95 lines
4 KiB
Markdown
95 lines
4 KiB
Markdown
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# E-ink display — plan
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The Inland ESP-WROOM-32 dev board doesn't have a software-controllable LED
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(see `notes.txt`), so the visible-output story for this project is an e-ink
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display. This file captures the hardware choice, the Rust graphics stack
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we'll use, and a shortlist of projects to build on top.
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## Hardware
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- **Display**: Inland 2.13" e-ink (Micro Center SKU 632694).
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- 250×122 mono, SPI, ~Waveshare 2.13" rebrand
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- 8-pin male header: `VCC`, `GND`, `DIN`, `CLK`, `CS`, `DC`, `RST`, `BUSY`
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- Pre-soldered headers — no soldering required
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- **Refresh characteristics** (SSD1680 driver, typical for this panel):
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- Full refresh ~2s, with the black/white flash that clears ghosting
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- Partial refresh ~300ms, no flash, but ghosting accumulates
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- Run a full every 5–10 partials
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- No grayscale, no animation. "Update once, look at it for a while."
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- **Supporting hardware**: half-size solderless breadboard, Dupont jumper
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assortment (F-F at minimum). Both boards are 3V3, no level shifter needed.
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Wiring sketch (pins on the ESP32 are conventional for SPI2/HSPI, adjust
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as needed once the panel arrives):
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```
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e-ink ESP32
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----- -----
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VCC -> 3V3
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GND -> GND
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DIN -> GPIO23 (MOSI)
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CLK -> GPIO18 (SCK)
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CS -> GPIO5
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DC -> GPIO17
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RST -> GPIO16
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BUSY -> GPIO4
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```
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## Rust graphics stack
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All `no_std`-friendly, all sit on top of the existing `esp-idf-svc` setup —
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just add deps to `Cargo.toml` and draw onto the display via the
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`embedded-graphics` `DrawTarget` that `epd-waveshare` implements.
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- **`embedded-graphics`** — primitives, base `DrawTarget` trait
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- **`epd-waveshare`** — Waveshare e-ink driver, includes the 2.13" panel
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- **`u8g2-fonts`** — large font collection, far better than the
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embedded-graphics built-ins
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- **`embedded-text`** — text wrapping / multi-line layout in a bounding box
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- **`embedded-layout`** — vertical/horizontal stacking, alignment helpers
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(no Flexbox, but covers most positioning we'll need)
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- **`tinybmp`** — render `include_bytes!`'d 1-bit BMPs as
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embedded-graphics images; the easy path for icons
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- **`embedded-iconoir`** — optional, ready-made Iconoir icons
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Default starting set: `embedded-graphics + u8g2-fonts + embedded-text +
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tinybmp`. Pull in `embedded-layout` once positioning gets tedious.
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### Heavier option: Slint
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[Slint](https://slint.dev/) has an MCU backend with explicit e-ink support.
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Write `.slint` markup, get live layout preview. Workable on the
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ESP32-WROOM-32 but noticeable flash/RAM footprint. Reach for it only if
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iterating on layout becomes a bottleneck with the embedded-graphics stack.
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## Project shortlist
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Ordered by cool : effort ratio.
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1. **Wi-Fi info screen** — weather, next calendar event, GitHub PR count,
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refreshed every 5–10 minutes. **Best first project**: smallest
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end-to-end exercise of Wi-Fi + HTTP + JSON + e-ink rendering. Once it
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works, the rest are variations on the same skeleton.
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2. **Build status badge** — last commit's CI state for one or more repos.
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Sits on the desk, nags when CI breaks.
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3. **Pomodoro timer** — two physical buttons, big "WORK 17:32" / "BREAK
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04:00" text. E-ink wins because no backlight to distract.
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4. **Now-playing card** — Spotify Web API. Refresh slowness fits since
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tracks last minutes.
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5. **Door / desk status sign** — "available / heads-down / on a call",
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toggled from phone via tiny HTTP server on the ESP32. Battery + e-ink
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= days of runtime.
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6. **Home Assistant / MQTT subscriber** — display whatever the home
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automation system publishes.
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7. **Conference badge / desk name tag** — name + handle + QR code,
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updateable over Wi-Fi.
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8. **Status dashboard for a personal service** — uptime, last-deploy
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time, error count from one of Jason's own services.
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## Crate stack already in place
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The current `Cargo.toml` has `esp-idf-svc` 0.51 with `binstart` + `native`
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features, plus `log` and `anyhow`. That covers Wi-Fi, HTTP client, NTP,
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NVS storage. For the e-ink work we just add the embedded-graphics family
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of crates listed above and an SPI driver from `esp-idf-hal`.
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