I ordered the Xteink X4 not knowing about CrossPoint and I was so disappointed with the included firmware:

- Almost no formatting on the ebooks you upload (no bold text, missing glyphs, no images/cover art) - The book had to be rendered before being uploaded. I suspect they were uploading series of bitmaps. - This meant if you wanted to change portrait/landscape or change font size/type you had to re-render the book - Bitmap fonts were very ugly.

Overall it was barely workable. More of a proof of concept. The CrossPoint firmware on the other hand:

- Actually renders books as you would expect, in a pleasing manner, formatting and all - Much more reader configuration on device: font settings, margin, spacing, alignment, progress display - Update via USB or OTA - Multiple ways to get your books: Connect to your Calibre library to push or pull books (thanks for introducing me to Calibre!), USB, Wireless file transfer - Sync progress via KOReader

It's the best gift the community could give to the manufacturer. With only the default firmware my X4 would have been in the junk drawer within a week, but now I carry it every day, I've shown it to so many people. It's a marvel. With the news about them attempting to lock it down I can't recommend it anymore. Why would they do that?

Really nice device, I'm just waiting for a version with front light.

I'm quite frustrated to hear that Xteink have decided to block firmwware being changed on some devices. I can only imagine the reason would be consumers who look for support after something went wrong but it's frustrating for those of us who just want an open eink device.

I ordered the Xteink X4 not knowing about CrossPoint and I was so disappointed with the included firmware:

Overall it was barely workable. More of a proof of concept. The CrossPoint firmware on the other hand:

Really nice device, I'm just waiting for a version with front light.

Front light would make it the perfect device. I use it on the go everywhere now, to limit the distractions inherent with trying to read from my phone. But in bed having to pull out a book light or a headlight is an annoying step that risks disturbing my partner.

The S4 is the new version coming soon with a front light.

Supposedly already bypassed. But yes, moving entirely out of step with what seems to be making these devices popular! https://www.reddit.com/r/xteinkereader/comments/1t1wtya/dont...

The S4 is the new version coming soon with a front light.

Ah yes but that one is probably going to be much more expensive as it runs android and more powerful hardware. It won't support crosspoint-reader then either :'( Though you could install KOReader then, which is a good alternative. It also seems to lack page turn buttons.

But I read there's also an "X4 v2 pro" coming with frontlight: https://www.joshualowcock.com/xteink/xteink-x4-v2-pro-xteink...

So I'm waiting to see which one will be the best price/quality in this regard.

I bought the book lights that they sell along with the device and they're perfect for it. They include an adapter so they magnetically attach to the back, or they can clip to the folio.

But I read there's also an "X4 v2 pro" coming with frontlight: https://www.joshualowcock.com/xteink/xteink-x4-v2-pro-xteink...

So I'm waiting to see which one will be the best price/quality in this regard.

I bought the book lights that they sell along with the device and they're perfect for it. They include an adapter so they magnetically attach to the back, or they can clip to the folio.

Meh I used those with my old Kindle 2nd edition. It had a really nice leather case with a solder slide out light.

But it wasn't nearly as good as the front light ones that came later.

Meh I used those with my old Kindle 2nd edition. It had a really nice leather case with a solder slide out light.

But it wasn't nearly as good as the front light ones that came later.

CrossPoint Reader

Firmware for the Xteink X4 e-paper display reader (unaffiliated with Xteink). Built using PlatformIO and targeting the ESP32-C3 microcontroller.

CrossPoint Reader is a purpose-built firmware designed to be a drop-in, fully open-source replacement for the official Xteink firmware. It aims to match or improve upon the standard EPUB reading experience.

Motivation

E-paper devices are fantastic for reading, but most commercially available readers are closed systems with limited customisation. The Xteink X4 is an affordable, e-paper device, however the official firmware remains closed. CrossPoint exists partly as a fun side-project and partly to open up the ecosystem and truly unlock the device's potential.

CrossPoint Reader aims to:

Provide a fully open-source alternative to the official firmware.
Offer a document reader capable of handling EPUB content on constrained hardware.
Support customisable font, layout, and display options.
Run purely on the Xteink X4 hardware.

This project is not affiliated with Xteink; it's built as a community project.

Features & Usage

EPUB parsing and rendering (EPUB 2 and EPUB 3)
Image support within EPUB
Saved reading position
File explorer with file picker
- Basic EPUB picker from root directory
- Support nested folders
- EPUB picker with cover art
Custom sleep screen
- Cover sleep screen
Wifi book upload
Wifi OTA updates
KOReader Sync integration for cross-device reading progress
Configurable font, layout, and display options
- User provided fonts
- Full UTF support
Screen rotation

Multi-language support: Read EPUBs in various languages, including English, Spanish, French, German, Italian, Portuguese, Russian, Ukrainian, Polish, Swedish, Norwegian, and more.

See the user guide for instructions on operating CrossPoint, including the KOReader Sync quick setup.

For more details about the scope of the project, see the SCOPE.md document.

Installing

Web (latest firmware)

Connect your Xteink X4 to your computer via USB-C and wake/unlock the device
Go to https://xteink.dve.al/ and click "Flash CrossPoint firmware"

To revert back to the official firmware, you can flash the latest official firmware from https://xteink.dve.al/, or swap back to the other partition using the "Swap boot partition" button here https://xteink.dve.al/debug.

Web (specific firmware version)

Connect your Xteink X4 to your computer via USB-C
Download the firmware.bin file from the release of your choice via the releases page
Go to https://xteink.dve.al/ and flash the firmware file using the "OTA fast flash controls" section

Command line (specific firmware version)

Install esptool :

pip install esptool

Download the firmware.bin file from the release of your choice via the releases page
Connect your Xteink X4 to your computer via USB-C.
Note the device location. On Linux, run dmesg after connecting. On MacOS, run :

log stream --predicate 'subsystem == "com.apple.iokit"' --info

Flash the firmware :

esptool.py --chip esp32c3 --port /dev/ttyACM0 --baud 921600 write_flash 0x10000 /path/to/firmware.bin

Change /dev/ttyACM0 to the device for your system.

Manual

See Development below.

Development

Prerequisites

PlatformIO Core (pio) or VS Code + PlatformIO IDE
Python 3.8+
USB-C cable for flashing the ESP32-C3
Xteink X4

Checking out the code

CrossPoint uses PlatformIO for building and flashing the firmware. To get started, clone the repository:

git clone --recursive https://github.com/crosspoint-reader/crosspoint-reader

# Or, if you've already cloned without --recursive:
git submodule update --init --recursive

Flashing your device

Connect your Xteink X4 to your computer via USB-C and run the following command.

pio run --target upload

Debugging

After flashing the new features, it’s recommended to capture detailed logs from the serial port.

First, make sure all required Python packages are installed:

python3 -m pip install pyserial colorama matplotlib

after that run the script:

# For Linux
# This was tested on Debian and should work on most Linux systems.
python3 scripts/debugging_monitor.py

# For macOS
python3 scripts/debugging_monitor.py /dev/cu.usbmodem2101

Minor adjustments may be required for Windows.

Internals

CrossPoint Reader is pretty aggressive about caching data down to the SD card to minimise RAM usage. The ESP32-C3 only has ~380KB of usable RAM, so we have to be careful. A lot of the decisions made in the design of the firmware were based on this constraint.

Data caching

The first time chapters of a book are loaded, they are cached to the SD card. Subsequent loads are served from the cache. This cache directory exists at .crosspoint on the SD card. The structure is as follows:

.crosspoint/
├── epub_12471232/       # Each EPUB is cached to a subdirectory named `epub_<hash>`
│   ├── progress.bin     # Stores reading progress (chapter, page, etc.)
│   ├── cover.bmp        # Book cover image (once generated)
│   ├── book.bin         # Book metadata (title, author, spine, table of contents, etc.)
│   └── sections/        # All chapter data is stored in the sections subdirectory
│       ├── 0.bin        # Chapter data (screen count, all text layout info, etc.)
│       ├── 1.bin        #     files are named by their index in the spine
│       └── ...
│
└── epub_189013891/

Deleting the .crosspoint directory will clear the entire cache.

Due the way it's currently implemented, the cache is not automatically cleared when a book is deleted and moving a book file will use a new cache directory, resetting the reading progress.

For more details on the internal file structures, see the file formats document.

Contributing

Contributions are very welcome!

If you are new to the codebase, start with the contributing docs.

If you're looking for a way to help out, take a look at the ideas discussion board. If there's something there you'd like to work on, leave a comment so that we can avoid duplicated effort.

Everyone here is a volunteer, so please be respectful and patient. For more details on our governance and community principles, please see GOVERNANCE.md.

To submit a contribution:

Fork the repo
Create a branch (feature/dithering-improvement)
Make changes
Submit a PR

CrossPoint Reader is not affiliated with Xteink or any manufacturer of the X4 hardware.

Huge shoutout to diy-esp32-epub-reader by atomic14, which was a project I took a lot of inspiration from as I was making CrossPoint.

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