Free Ink

Free Ink is an open-source collective building the software, firmware and hardware for e-paper readers, with every layer shipped in the open. It's three separate projects that stack:

The star distribution tells you the actual shape of the thing: CrossPoint is the project with users — replacement firmware for cheap Xteink readers — and the SDK is the recent attempt (June 2026) to generalize what CrossPoint learned so the same codebase can drive other panels and boards.

The SDK's design bet

Every device-specific detail lives behind small injectable interfaces: display controller, waveforms and LUTs, GPIOs, bus speeds, touch, frontlight, audio. Firmware calls one generic API — EInkDisplay, InputManager, BatteryMonitor, SDCardManager, BoardConfig — and gets device-specific behavior underneath.

The consequence they lead with is the interesting one: new devices are data, not code. Adding a board means adding a profile and a driver config supplying pins, geometry, waveforms and voltages as values, rather than editing the generic driver. Per-device tuning stays out of the shared code path, and related devices can share one firmware build with runtime detection, while a genuinely new controller slots in as a standalone driver behind the same facade.

Builds compose along two axes, devices × capabilities: touch, frontlight, color and audio are flag-gated and default on only where a device needs them, so each binary stays tight. Capacitive touch covers CHSC6x and GT911 controllers; the frontlight is PWM with warm/cool control.

One detail worth keeping for anyone doing embedded TLS: SecureNet bundles wolfSSL compiled from source for TLS 1.3 + PSA, bypassing the stubbed system mbedTLS, specifically so the reader can reach TLS-1.3-only servers — KOReader's sync service being the motivating case. That's a concrete instance of a vendor SDK's stubbed crypto forcing you to carry your own stack.

Reader features

EPUB 2 and 3 with embedded CSS applied, laid out in your chosen font, size and margins, with pages cached to SD on first open so reopening is near-instant. Noto Serif and Noto Sans built in plus any font from the SD card, with control over size, spacing, margins, hyphenation, alignment and anti-aliasing. A WiFi upload server so you can drop EPUBs in from a browser or send straight from Calibre, plus KOReader sync for position across devices. Bookmarks that remember page and reading percentage. A bionic-reading mode that bolds word-openings, with grayscale anti-aliasing and tiled rendering for fast page turns. Full RTL layout for Hebrew and Arabic, and translated menus in Spanish, French, German, Italian, Portuguese, Russian, Ukrainian, Polish and more.

de-link

The open hardware core: a compact, hand-solderable ESP32-S3 board with published KiCad schematics and a full BOM, buildable for around $60. ESP32-S3 at 240 MHz dual-core with WiFi, BLE, 16 MB flash and optional PSRAM; 24-pin SPI e-paper for GoodDisplay panels from 3.97″ up through 7.5″ and larger; microSD over 4-bit SDMMC; bring-your-own LiPo charged over USB-C with an MCP73832 charge controller and DW01A + FS8205A cell protection; an optional series-LED frontlight with cool/warm PWM control; dual 4-switch resistor ladders plus reset.

Assessment

The appeal is the whole-stack openness — books as plain files on an SD card in open formats, permissively licensed software and firmware, a published BOM and a swappable battery so you repair rather than landfill, and no accounts or subscriptions. That's a coherent answer to the same ownership complaint that motivates paper-computer, from the hardware side rather than the workflow side.

The realistic read: CrossPoint is usable today if you own an Xteink X3 or X4, and e-reader-ipp-printer is a worked example of extending it: an X3 that accepts IPP print jobs from macOS. The SDK is seven weeks old with 38 stars and its generalization claim is unproven across boards it wasn't extracted from — the hard part of a hardware abstraction is the second and third vendor's panel, not the first. de-link hasn't been pushed to since April 2026 and carries no license file, which matters for open hardware.

On watchlist — the SDK is the piece to watch, and the question is whether "new devices are data, not code" survives a controller family GoodDisplay didn't make.

MIT (SDK and CrossPoint). Site: https://freeink.org · SDK: https://github.com/Free-Ink/freeink-sdk