CrossDink is a fork of CrossInk, which is itself a fork of CrossPoint Reader. It keeps CrossInk's fonts, reader features and reading stats, and rebuilds the firmware around the dual-core ESP32-S3 in the newer Xteink and Seeed readers.
The project started as DualPoint, a plan to put the S3's second core to work. It is now CrossDink.
CrossDink runs only on ESP32-S3 readers:
- Xteink X4 Pro
- Xteink X4 Classic
- Seeed Studio Sticky
The ESP32-C3 Xteink X3 and X4 are not supported. For those, use CrossInk.
- Use both cores. The screen, the reader's background work, networking and input each get their own task, so page turns and taps don't wait on indexing, image decoding or transfers.
- Assume PSRAM. With the ESP32-C3 limits gone, large buffers, caches and Wi-Fi buffers live in PSRAM, which keeps internal RAM free for the things that need it.
- Spend less power while idle. The Sticky and X4 Pro drop into automatic light sleep between loop ticks, and the Wi-Fi screens idle in modem sleep between transfers.
- Write to the SD card less. Progress, stats and session state are written only when something changed, and in small in-place slots.
- Stay in sync with CrossInk. Upstream CrossInk and CrossPoint changes are merged in regularly, so their reader features keep arriving here.
- Second-core work:
- chapters are inflated on the second core the first time they open;
- JPEG and PNG images in books are decoded there;
- the next page is drawn ahead there, right after a page is shown;
- the next chapter is indexed there near the end of a chapter.
- Input: buttons and touch are read on their own task, woken by the input lines, so presses and swipes made while the device is busy are queued instead of lost.
- Faster File Transfer: File Transfer and Calibre Connect serve requests on their own task, so transfers keep flowing while the screen redraws.
- Fewer reboots around Wi-Fi: entering and leaving File Transfer, OPDS, KOReader Sync or Nearby Transfer no longer restarts the device when there is enough memory.
- Light sleep: the X4 Pro firmware uses automatic light sleep. Buttons, touch, the frontlight and USB serial keep working.
- Faster Library and USB Drive:
- the Library index is kept between visits and starts building in the background after a restart;
- USB Drive reads ahead while it sends data.
- Frontlight gestures: brightness and warmth follow your finger while you drag, in 1% steps.
- Smaller firmware: leaner built-in TTF fonts, minified web pages and no wolfSSL debug strings save several hundred KB of flash.
- New name and logo: CrossDink has a two-drop logo on the boot screen and web portal. It keeps its data in
/.crossdinkand reads CrossInk's/.crosspointwithout changing it, so settings, reading progress, stats and stats backups carry over from CrossInk; caches, covers and thumbnails are rebuilt.
See CHANGELOG.md for the full list.
 Font: Bitter, Size: 12 pt, Margin: 15 |
 Reading Stats with custom front button mapping shown |
- Fonts: Lexend Deca and Bitter as reader fonts, and Inter for the UI. Scalable TTF sizes from 8 pt to 22 pt are included, and more families can be installed from the SD card (see SD Card Fonts).
- Glyphs: music notation, selected Cyrillic, and the CJK fallback ranges Project Hail Mary needs.
- Themes:
MinimalandDashboardthemes and sleep screens. - Text formatting: strikethrough, thicker underlines,
<hr>section breaks, redaction-style text and simple tables. - Reader tools: bookmarks, Focus Reading, Guide Dots, Force Paragraph Indents, auto page turn (5-120 s) and an in-book menu for reader options.
- Reading stats and finished books: reading stats (books finished, time, sessions, pages per minute), which can also be your sleep screen. You can mark books as finished and move them to a Read folder.
- Sync between devices: stats sync and reading progress sync between two devices.
- Controls and Library: remappable buttons and shortcuts (see Controls), and a searchable Library with sort options.
Reader options are documented in Reader Features.
CrossDink runs on a microcontroller, so very large folders or complex EPUBs can be slower than they would be on a phone, tablet, or desktop app.
- Keep folders under about 200 files. For the smoothest browsing, aim for 50-100 files per folder.
- Having 1000+ books on the SD card is fine if they are split into smaller folders, such as by author, series, genre, or read/unread status.
- Avoid putting every book in the SD card root. The file browser has to scan and sort the current folder before it can show it.
- Text-first EPUBs are the best fit. Large image-heavy EPUBs, scanned books, comics, and omnibus files with thousands of sections may load slowly or fail under memory pressure.
- As a rough target, EPUBs under 20 MB tend to work the best. Files over 50 MB may still work, but they are more likely to be slow or memory-sensitive, especially if they contain many large images.
- If an EPUB is unusually slow, try optimizing it with the built-in web optimizer (via File Transfer) before copying it to the SD card: remove unused high-resolution images, split very large omnibus files, and avoid embedding multiple full font families when possible.
- Use a reliable SD card and leave some free space. CrossDink stores settings, reading progress, cache files, stats, and generated book data on the card.
Build and flash from source with PlatformIO (see below). The flashing and revert steps in Installation also apply, as long as you use a CrossDink .bin built for your device.
Once CrossDink is installed, later builds can be flashed with SD Card Firmware Update in Settings, or uploaded over File Transfer.
CrossDink uses PlatformIO for building and flashing firmware. See Getting Started for prerequisites, clone setup, and validation commands.
Nix/NixOS users can enter the development shell with either nix develop (flakes) or nix-shell:
nix develop -f nix
# or
nix-shell nixTo flash a connected device, enable PlatformIO's udev rules in your NixOS configuration:
services.udev.packages = with pkgs; [ platformio-core.udev ];After rebuilding the system configuration, reconnect the device or reload udev rules.
Connect your device to your computer via a USB cable. Before the first build, initialize the repository's submodules (including freeink-sdk):
git submodule update --init --recursiveThen flash the firmware using the environment for your device:
| Device | Environment |
|---|---|
| Xteink X4 Pro | x4-pro |
| Xteink X4 Classic | x4-classic |
| Seeed Studio Sticky | sticky |
Each has a -debug variant with extra logging.
pio run -e x4-pro --target uploadIf PlatformIO reports PackageException: Can not create a symbolic link for freeink-sdk/libs/hardware/BatteryMonitor, not a directory, the freeink-sdk submodule is not initialized. Run the submodule command above and retry.
See Testing and Debugging for serial logging, simulator checks, static analysis, and bug-report guidance.
CrossDink is a personal project and does not accept pull requests. Reader features that would benefit everyone belong upstream in CrossInk or CrossPoint.
CrossDink is built on the work of CrossInk by uxjulia and CrossPoint Reader and its contributors. If you enjoy the reader features, please consider supporting CrossInk's development on Ko-fi.