Monbit

A tiny ESP32-based digital monster pet with an e-ink display that evolves over time based on care, sleep cycles, and randomness.

Motivation

Monbit is a personal project created to learn embedded development, hardware prototyping, and product design.

The goal is not only to create a device, but also to explore the full product development process. From firmware and electronics to CAD design and physical prototype.

I want to document the entire journey, sharing both successes and failures, to create a resource for others interested in similar projects.

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Documentation

• Roadmap
• Development Log
• Hardware Notes
• Game Design
• UI Design

Current Progress

Current Version: v0.0.4 (2026-07-13)

Firmware

• ESP32 bring-up
• Project architecture (modular source files)
• E-Ink display communication
• Basic UI rendering
• Partial display refresh
• 3-button input system
• Button debouncing
• Monster state system
• Monster actions (Feed / Play / Sleep)
• Automatic monster tick system
• Persistent storage (save/load)
• Audio subsystem
• Menu system
• Battery management
• Deep sleep
• Sprite rendering

Hardware

• Components selected
• ESP32 tested
• E-Ink display tested
• Buttons tested (breadboard)
• First enclosure front prototype designed (front lid, far from final)
• Audio amplifier connected
• Speaker connected
• Battery integrated
• Charging module integrated
• Power switch integrated
• Accelerometer integrated
• Permanent wiring
• First fully assembled prototype
• Final enclosure designed

Gameplay

• Basic monster stats
• Monster actions
• Time-based stat changes
• Beep when button is pressed
• Naming the monster
• Monster sprite and animations
• Monster emotions
• Growth/aging system
• Evolution
• Random events
• Game balancing

Documentation

• README
• Roadmap
• Devlog
• Project versioning
• Wiring diagrams
• Hardware BOM
• Build instructions

Milestones

v0.0.1 — Hello Hardware

Completed:

• ESP32-C3 configured with PlatformIO
• USB serial debugging enabled
• E-Ink display connected and initialised
• First successful display render (MONBIT v0.0.1)

Update:

• basic GUI setup
• connected first button

v0.0.2 — Buttons

Completed:

• Buttons are detected and affect the stats
  • LEFT button => eat
  • MIDDLE button => play
  • RIGHT button => sleep
• Screen has two options for refresh - full or partial
• When the button is pressed, the screen refreshes partially (without the big blink)
• Happiness renamed to Fun

v0.0.3 - Storage

Completed:

• Every tick (currently 10 seconds), the hunger, fun and energy are changed by 1
• Every time the button is pressed, the current state of the Monster is saved to Flash
• When rebooted, the data is loaded

v0.0.4 - Audio

Completed:

• Audio subsystem added
• Beep when button is pressed

Hardware

Core components:

• ESP32-C3 SuperMini ?

• WeAct 1.54" E-Ink Display

• 500mAh LiPo Battery

• TP4056 USB-C Charging Module ?

• Tactile Buttons

• MAX98357A Audio Amplifier

• Speaker

• MPU6050 Accelerometer

Software

Development environment:

• C++
• Arduino Framework
• PlatformIO
• Visual Studio Code

Libraries:

• GxEPD2
• FreeMonoBold0pt7bt
• i2s

Gallery

Wiring & Setup

Display & GUI

Buttons

Enclosure

Repository Structure

monbit/
├── firmware/     # ESP32 firmware (PlatformIO)
│   ├── include/
│   ├── lib/
│   ├── src/
│   ├── test/
│   └── platformio.ini
├── hardware/     # Hardware notes & measurements
│   ├── hardware_notes.md
│   └── measurements.md
├── design/       # CAD files (enclosure STLs)
├── docs/         # Design notes
│   ├── game_design.md
│   └── ui_design.md
├── photos/       # Build & progress photos
├── DEVLOG.md
├── ROADMAP.md
├── LICENSE
└── README.md

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