ESP32 C3 EReader

ESP32 E-Reader

A custom-built e-ink reading device based on the ESP32-C3, designed for everyday use. Built around a 4.2" e-ink display with a frontlight for reading in the dark environment, running a modified version of the Crosspoint open-source firmware adapted for custom hardware. The goal was to build a capable, low-cost alternative to commercial e-readers with full control over both hardware and software.

Hardware License

The hardware designs in /Hardware are licensed under the CERN-OHL-W v2.

Hardware

Building your own? See the Build guide for step-by-step assembly instructions.

PCB stack-up

F.Cu     — signal
GND      — full ground plane
PWR      — power distribution
B.Cu     — signal

Ground pour with stitching vias on both outer layers. EMI-sensitive boost converter traces kept compact.

Power rails

Power management

Three operating states optimized for battery life:

The device enters Sleep automatically after a display update completes. Deep sleep is only used when powered off via the power button.

Controls

Firmware

Based on Crosspoint Reader with modifications for custom hardware and 4MB flash constraint.

What's changed from upstream

• HalFrontlight — new HAL driver for PWM-controlled frontlight via TPS61169
• HalPowerManager — smaller tweaks
• HalGPIO — GPIO, button layout adapted to custom PCB
• partitions_4mb.csv — custom partition scheme to fit 4MB flash (replaces upstream 16MB default)
• platformio.ini — 4MB build configuration
• Display refresh — modified refresh handling for Good Display 4.2" panel compatibility
• Dictionary — English → Hungarian word lookup in the EPUB reader (see Dictionary)

See docs/4mb-build/ for detailed documentation on the 4MB build process and known issues.

Dictionary

Long-press Confirm (0.5 s) in an EPUB to enter dictionary mode. The four front buttons become a cursor:

The translation (a few Hungarian words) appears in a popup, any button closes it.

The dictionary is a file on the SD card, /dict/en-hu.dic (about 4 MB, 118 000 word forms incl. inflections). It is built on a PC with scripts/build_dict.py from Wiktionary (via kaikki.org) with FreeDict eng-hun as a fallback; the script documents the steps and the file format. Wiktionary data is CC BY-SA 4.0, FreeDict eng-hun is GPL-2.0+.

Repository structure

ESP32_E-Reader/
├── Hardware/
│   ├── 3D CAD/                 — enclosure 3D models
│   ├── Bill Of Materials/      — BOM spreadsheets
│   ├── PCB/                    — KiCad project (Rev. B)
│   ├── REV-A/                  — Rev. A schematic/layout reference
│   └── LICENSE                 — CERN-OHL-W v2
├── Datasheets of Components/    — component datasheets (PDF)
└── Software/
    └── crosspoint-reader/       — firmware (fork of Crosspoint Reader)
        ├── src/                 — application source (activities, UI)
        ├── lib/                 — internal libraries (Epub engine, GfxRenderer, HAL, I18n)
        ├── open-x4-sdk/         — Xteink X4 community SDK (submodule)
        ├── docs/                — build docs, file formats, 4mb-build notes
        ├── scripts/             — build/codegen/debugging scripts
        ├── test/                — unit tests
        ├── platformio.ini       — build configuration
        └── LICENSE              — MIT

Build

Requirements

• PlatformIO
• ESP32-C3 board with 4MB flash

Steps

git clone https://github.com/IS7V4N/ESP32_E-Reader.git
cd ESP32_E-Reader
git submodule update --init --recursive
~/.platformio/penv/bin/pio run -e 4mb -t upload

License

/Hardware are licensed under the CERN-OHL-W v2.

Firmware modifications follow the license of the upstream Crosspoint Reader project.