📚 BookCounter

A tiny physical book-reading tracker built around an ESP32 e-ink display. Press a button every time you finish a book — the count is saved forever, even when the battery dies.

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Demo

Finished a book	Reset animation

Front	Side

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Features

• E-ink display — readable in sunlight, no backlight drain
• Up button — increments count with a confetti burst animation
• Down button (short press) — decrements count
• Down button (long press, 1.5 s) — resets to zero with a T-Rex walking in and chomping the number away
• Persistent NVS storage — count survives power cuts and battery swaps
• Light sleep between presses — long battery life

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Hardware

Part	Link
Heltec Vision Master E213 V1.1 (ESP32 + 2.13" e-ink)	AliExpress
Li-Po battery	AliExpress
Tactile button	Amazon UK

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3D Printed Case

Print files are in the PrintFiles/ folder. Also available on Creality Cloud.

File	Description
3MF/BookCounterWithArrows.3mf	Ready-to-slice 3MF with both panels (recommended)
Front Panel v7.stl	Front panel with button cutout and display window
Back Panel V5.stl	Back panel / battery cover
Step/front new button.step	Editable STEP source for the front panel
Step/Back Panel v5.step	Editable STEP source for the back panel

Print in your filament of choice — no supports needed.

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Software Setup

1. Install Arduino IDE

Download and install the Arduino IDE (version 2.x recommended).

2. Add the Heltec ESP32 board package

1. Open File → Preferences
2. Paste the following URL into the Additional boards manager URLs field:

   https://resource.heltec.cn/download/package_heltec_esp32_index.json
   

3. Open Tools → Board → Boards Manager, search for Heltec ESP32, and install it

3. Install required libraries

Open Tools → Manage Libraries and install the following:

Library	Install name	Notes
Heltec eInk Modules	heltec-eink-modules	Drives the e-ink display — provides EInkDisplay_VisionMasterE213V1_1
Preferences	(built-in)	Part of the ESP32 Arduino core — no separate install needed

The ESP32 light-sleep functions used in the code (esp_light_sleep_start, esp_sleep_enable_gpio_wakeup, gpio_wakeup_enable) are also part of the ESP32 Arduino core and require no extra libraries.

4. Upload

1. Open BookCounterdino/BookCounterdino.ino
2. Go to Tools → Board and select Heltec Vision Master E213
3. Select the correct COM port under Tools → Port
4. Click Upload

Pin mapping

GPIO	Role
17	UP button (active low, internal pull-up)
39	DOWN button (active low, external 10 kΩ pull-up required — see note below)

Important — GPIO 39 has no internal pull-up: GPIO 39 on the ESP32 is an input-only pin that does not support internal pull-up resistors. INPUT_PULLUP is silently ignored for this pin. Without an external pull-up, the pin floats and the DOWN button (and sometimes the UP button) will stop responding after a cold power-on.

Fix: Solder a 10 kΩ resistor between the GPIO 39 pin and the 3.3 V pin on the board. One leg to 3.3 V, the other leg to GPIO 39. The button itself is wired between GPIO 39 and GND as normal — no other changes needed.

3.3V ──┤10kΩ├── GPIO 39 ──── Button ──── GND

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How It Works

Power on ──► display saved count

UP press ──► count++ ──► confetti animation ──► display new count
DOWN short ──► count-- ──► display new count
DOWN long  ──► count = 0 ──► T-Rex CHOMP animation ──► display 0

Between presses: ESP32 light sleep (GPIO wake-up)

Count is stored in NVS (Preferences library) under the key bookctr/count so it persists across reboots and battery changes.

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License

MIT — do whatever you like with it.