# 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. ![](./docs/images/cover.jpg) ## 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 truely 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 - [x] EPUB parsing and rendering (EPUB 2 and EPUB 3) - [ ] Image support within EPUB - [x] Saved reading position - [x] File explorer with file picker - [x] Basic EPUB picker from root directory - [x] Support nested folders - [ ] EPUB picker with cover art - [x] Custom sleep screen - [x] Cover sleep screen - [x] Calendar Mode (automated image display from URL) - [x] Wifi book upload - [x] Wifi OTA updates - [x] Configurable font, layout, and display options - [ ] User provided fonts - [ ] Full UTF support - [x] Screen rotation See [the user guide](./USER_GUIDE.md) for instructions on operating CrossPoint. ## Calendar Mode Calendar Mode transforms your CrossPoint Reader into an automated display that periodically fetches and displays a BMP image from a URL. This is useful for: - Calendar/schedule displays - Weather dashboards - Information displays - Digital signage ### How It Works 1. When enabled, the device wakes from deep sleep on a timer (1-24 hours configurable) 2. Connects to saved WiFi network 3. Fetches a BMP image from the configured URL 4. Displays the image as the sleep screen 5. Returns to deep sleep until the next refresh ### Configuration In **Settings**, you'll find: | Setting | Description | |---------|-------------| | **Calendar Mode** | Enable/disable the feature (ON/OFF) | | **Calendar Refresh (hours)** | How often to refresh (1-24 hours) | | **Calendar Server URL** | URL that returns a BMP image | | **Test Calendar Now** | Immediately test the fetch and display | ### Image Requirements The server URL must return a valid BMP image: - **Format**: BMP (Windows bitmap) - **Bit depth**: 1, 2, 8, 24, or 32 bpp (8-bit grayscale recommended) - **Dimensions**: 480 x 800 pixels (device screen size) - **Orientation**: Top-down (negative height in BMP header) recommended ### Setting Up a Server You'll need a server that generates and serves BMP images. Example options: - **Cloudflare Worker**: Serverless function that generates images on-demand - **Local server**: Python/Node.js script serving static or dynamic images - **Static hosting**: Pre-generated images on any web server The device makes a simple HTTP GET request to the URL and expects raw BMP data in response. ### Power Consumption Calendar Mode uses ESP32-C3 deep sleep between refreshes: - Deep sleep: ~10-20µA - Active (WiFi + fetch): ~100-150mA for ~10-30 seconds With a 4-hour refresh interval, expect several months of battery life. ## Installing ### Web (latest firmware) 1. Connect your Xteink X4 to your computer via USB-C 2. 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) 1. Connect your Xteink X4 to your computer via USB-C 2. Download the `firmware.bin` file from the release of your choice via the [releases page](https://github.com/daveallie/crosspoint-reader/releases) 3. Go to https://xteink.dve.al/ and flash the firmware file using the "OTA fast flash controls" section 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. ### Manual See [Development](#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/daveallie/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. ```sh pio run --target upload ``` ## 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_` │ ├── 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](./docs/file-formats.md). ## Contributing Contributions are very welcome! If you're looking for a way to help out, take a look at the [ideas discussion board](https://github.com/daveallie/crosspoint-reader/discussions/categories/ideas). If there's something there you'd like to work on, leave a comment so that we can avoid duplicated effort. ### To submit a contribution: 1. Fork the repo 2. Create a branch (`feature/dithering-improvement`) 3. Make changes 4. 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](https://github.com/atomic14/diy-esp32-epub-reader), which was a project I took a lot of inspiration from as I was making CrossPoint.