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Battery (firmware + server, disabled by default): new battery.c reads a 2x200k voltage divider via ADC oneshot with curve-fitting calibration (the ESP32-C6's scheme), maps through a piecewise LiPo discharge curve, and restores the pin to button duty after each read -- the settled XIAO ESP32-C6 design shares the back button's GPIO0/A0, time-shared per wake. Skipped entirely when on mains (a 2x100k VBUS divider into a spare digital pin -- the 5V pin is dead on battery power, so presence = mains, where the charging voltage would read misleadingly full) or when the reading is implausible. The manage overlay gains a battery region (static outline glyph + "NN%", below the manage QR, all menu levels), and the device POSTs to the new /frame/battery endpoint after a successful fetch; the server stores percent + as-of timestamp, exposed via /api/queue and shown in the web UI. FRAME_BATTERY_ADC_GPIO / FRAME_VBUS_SENSE_GPIO default to -1 (fully inert on the dev board); compile-verified both disabled and enabled, hardware bring-up deferred until the ordered XIAO + batteries arrive. Orientation (server-side only): new config setting + web UI dropdown (landscape / portrait / landscape_flipped / portrait_flipped). Photos are composed/cropped at the logical hanging shape (portrait crops at 480x800, so face-aware crops match how the frame actually hangs), then rotated losslessly into the panel's native 800x480 byte layout after dithering -- the device never knows. Face-label anchors are transformed through the same rotation (logical_to_native()) so they stay attached to faces on rotated frames. Known documented limitation: the on-device manage overlay still renders in native orientation, so it appears sideways on a portrait-hung frame (QRs scan at any rotation; text reads sideways).
ESPresso Frame
A DIY e-ink photo frame: an ESP32-C6 pulls photos from your Immich library and displays them on a 7.3" full-color e-paper panel, waking on a timer to refresh and spending the rest of its time in deep sleep.
- No cables to a computer, no SD card shuffling. Provisioning is a captive portal with a QR code drawn on the panel itself -- scan, join, fill in your WiFi and server address, done.
- The frame never decodes an image. A small self-hosted server does all the work (pulling from Immich, cropping, dithering, packing into the panel's exact pixel format) and hands the device a stream it can write straight to SPI. The ESP32-C6 has no PSRAM and not much SRAM to spare -- keeping it a dumb display client is what makes that workable.
- Crops toward faces, not just the center, using face bounding boxes Immich already computed for its own People feature -- no bundled face detector.
- Refresh interval and album are configurable from a web UI, no reflashing needed to change them.
Hardware
- ESP32-C6 dev board (8MB flash)
- Waveshare 7.3" E Ink Spectra 6 (E6) panel -- 800x480, 6-color, SPI
See docs/hardware.md for wiring and
docs/architecture.md for how the two halves talk
to each other.
Getting started
server/-- run the FastAPI server first (Docker Compose, points at your Immich instance). Seeserver/README.md.firmware/-- build and flash the ESP32-C6, then scan the QR codes it draws on first boot to provision it. Seefirmware/README.md.
Repo layout
firmware/ ESP-IDF project for the ESP32-C6
server/ FastAPI server: Immich -> crop/dither/pack -> the frame
docs/ Wiring and architecture notes
License
MIT -- see LICENSE. A few small pieces of vendored
third-party code (a QR code generator, a bitmap font table) keep their
own permissive licenses; see LICENSE for details.
Built with substantial assistance from Claude Code.