InkDeck

InkDeck

A pocket e-paper e-reader with physical page-turn buttons, weeks of battery life, and books loaded over Wi-Fi.

What is InkDeck?

InkDeck is a DIY e-reader about the size of a paperback (153 × 72 × 23.5 mm). It has a 4.7" e-paper screen that looks like printed paper, so it's easy on the eyes and readable in sunlight, and it keeps the page on screen even with the power off.

It's built around a LilyGo T5 4.7" E-Paper S3 board (ESP32-S3 + 960 × 540 e-paper + microSD slot), plus a custom grip PCB I designed in KiCad. The grip board sits beside the screen under your right thumb and has:

• 3 buttons: PREV, NEXT and MENU
• A coin vibration motor for a little buzz on each page turn
• A slide power switch between the battery and the LilyGo

It reads EPUB and .txt books from the microSD card, and you can add books from your phone over Wi-Fi without taking the card out. Everything fits in a 3D-printed case I modelled in Fusion 360.

Why I built it

I like reading on e-paper, but most e-readers only work properly with one company's book store, and the cheaper ones only have a touchscreen. I wanted real buttons I can press with one thumb while holding it in one hand, like turning a page.

Building it myself means it reads my own DRM-free books (Project Gutenberg, Standard Ebooks) with no account or store. I can also change anything I want, from how long the buttons are held to how the pages look.

It was also a good way to learn about low-power design, which a phone or laptop never makes you think about:

• picking pins that can wake the chip from deep sleep
• dealing with strapping pins
• making e-paper and a battery work together

Features

• 4.7" 960 × 540 e-paper with 16 grey levels: easy to read, and the page stays on screen with zero power
• Reads EPUB (converted once, then opens instantly) and .txt books
• Physical buttons: tap for the next or previous page, hold to jump a chapter
• Haptic feedback: a different buzz for page turns, chapter jumps, errors and sleep
• Deep sleep after 10 minutes, then MENU wakes it on the same page
• Wi-Fi upload: the reader makes its own hotspot, so a phone can add or delete books
• Remembers your page in every book
• Battery % in the footer, and it shows "please charge" and sleeps when nearly flat
• One-handed grip with the buttons under your thumb

How it works

flowchart LR
    subgraph Grip["Grip PCB"]
        BTN["PREV / NEXT / MENU buttons"]
        MOT["Vibration motor via AO3400"]
        SW["Power switch"]
    end
    subgraph LilyGo["LilyGo T5 4.7-inch S3"]
        ESP["ESP32-S3 firmware"]
        EPD["E-paper 960 x 540"]
        SD["microSD card"]
        ADC["Battery ADC IO14"]
    end
    BAT["LiPo battery"]
    PHONE["Phone or laptop"]

    BTN -->|GPIO 10 39 48| ESP
    ESP -->|GPIO 45| MOT
    BAT --> SW --> LilyGo
    BAT -.-> ADC --> ESP
    SD <-->|SPI| ESP
    ESP -->|parallel bus| EPD
    PHONE <-->|Wi-Fi hotspot| ESP

The e-paper, SD card and touch use almost every GPIO on the LilyGo. Only 4 are free, so the grip PCB uses exactly 4 signals through a 6-pin JST-SH cable:

Controls

While MENU is held, the motor buzzes at 1 s and again at 3 s, so you can feel which action you'll get before letting go.

Firmware

Written in PlatformIO (Arduino framework) with LilyGo's e-paper library. The full explanation with diagrams and code snippets is in firmware/FIRMWARE.md.

EPUB reader: an EPUB is a ZIP file full of web pages. The first time a book is opened, the firmware:

1. reads the ZIP's file list
2. finds content.opf (title + chapter order)
3. unzips each chapter with the decoder built into the ESP32-S3's ROM
4. removes the HTML tags and saves plain text to the SD card

After that the book opens instantly. Every chapter starts on a new page.

Pages: a greedy word-wrap fills each line with words until the next one doesn't fit. Where every page starts is saved on the SD card, so the footer can show Ch 3/27 57 / 312 70% and going back a page is instant.

Deep sleep: the e-paper keeps the page visible with no power, so the reader looks the same asleep. MENU wakes it:

while (digitalRead(PIN_BTN_MENU) == LOW) delay(10);   // never sleep while MENU is held
esp_sleep_enable_ext0_wakeup(GPIO_NUM_10, 0);         // MENU wakes it up
esp_deep_sleep_start();

Haptics:

Testing: the parts haven't arrived yet, so the EPUB converter and a simulation of the whole firmware (fake buttons, screen and SD card) are tested on a computer, in firmware/pc_tests.

Custom PCB

Designed in KiCad: a 25 × 67 mm two-layer grip board that sits beside the LilyGo inside the case. Power is on the front layer, button signals on the back, with ground fill on both sides. It passes DRC with 0 errors, 0 unconnected.

• Power: battery in → slide switch → battery out to the LilyGo's battery socket
• Buttons: 3 × 6 mm tact switches. MENU has a 10k pull-up so it still works in deep sleep
• Motor driver: AO3400 MOSFET with a 1N4148 flyback diode and a 10k gate pull-down
• Connector: 6-pin JST-SH (J3) to the LilyGo GPIOs

Enclosure

Modelled in Fusion 360 with user parameters, so it can be updated once the real parts are measured. It's 3 printed parts:

1. Front shell: screen window, 3 button holes lined up with the grip PCB, standoffs for the PCB, and cut-outs for the power switch, USB-C and microSD
2. Back cover: holds the battery behind the screen and the motor behind the grip, with a raised ridge so it's comfy to hold
3. Button caps (×3): plungers that reach the tact switches, with a flange so they can't fall out

The grip is on the right so your thumb reaches the buttons, and USB-C is on the left so the cable doesn't get in the way.

Exploded view

Shows how the screen, grip PCB, battery, motor, printed parts and screws fit together. The parts list, step-by-step assembly and wiring are in CAD/ASSEMBLY.md.

Renders

The screen window, USB-C, microSD and battery sizes are placeholders and will be checked against the real parts before the final print.

Bill of materials

All parts are from AliExpress except the custom PCB, which comes from JLCPCB. Prices are approximate AUD and change with sales, exchange rates and shipping. Many small parts only come in packs, so you'll have spares. Where a listing has several options (value, size, pin count, pack size), pick the one in the Part column.

Electronics

Enclosure

Total

Charging is through the LilyGo's own USB-C port, so any phone charger and USB-C cable works.

AliExpress listings change often. If a link stops working, search AliExpress for the exact part name in the table (e.g. "LilyGo T5 4.7 S3", "AO3400").

Repository layout

InkDeck/
├── README.md
├── JOURNAL.md               ← build log, day by day
├── PCB/                     ← KiCad project + Gerbers (grip PCB)
├── CAD/
│   ├── ASSEMBLY.md          ← parts list, assembly steps, wiring
│   ├── step/  stl/          ← printable parts + assemblies
│   └── images/              ← exploded view, renders, drawing
└── firmware/
    ├── platformio.ini
    ├── FIRMWARE.md          ← how everything in the code works
    ├── src/                 ← the firmware
    └── pc_tests/            ← EPUB + firmware tests that run on a computer

Acknowledgements

• LilyGo for the T5 4.7" board and the LilyGo-EPD47 e-paper library
• Built with KiCad, Fusion 360 and PlatformIO
• Free books: Project Gutenberg and Standard Ebooks
• AI assistance (Claude) was used for planning, guidance, the firmware and its tests.