Pomodoro Cube
A Pomodoro timer with a physical cube that can be rotated to start, pause, and reset the timer.
Overview
The Smart Pomodoro Cube is a handheld productivity device built from the ground up to explore embedded systems, custom electronics, and industrial design. It functions as a distraction-free Pomodoro timer driven entirely by its physical orientation. When placed on its custom magnetic pogo-pin dock, it transforms into an interactive hub featuring a virtual pet (Tamagotchi), productivity tracker, and digital clock.
Every element—the custom KiCad PCB, the 3D-printed enclosure, the analog circuitry, and the CircuitPython firmware—was specifically designed to fit inside the highly constrained volume of a standard Rubik’s Cube.
Key Features
- Standalone Operation: Features a real-time clock, orientation-based timer selection, countdown progress bar, and battery/temperature monitoring.
- Magnetic Charging Dock: Enables cable-free charging via pogo pins and seamlessly transitions the cube into docked mode.
- Interactive Dock Modes: Unlocks a 15-minute quick timer, an interactive Tamagotchi pet (with petting animations), and long-term productivity statistics.
Demonstrations
Standalone Cube
Interactive Charging Dock
Engineering Highlights
Analog Button Multiplexing
Because the magnetic pogo-pin interface is strictly limited to four physical connections (5V, GND, 3.3V, Data), it was impossible to dedicate separate GPIO pins to the four dock buttons. To solve this, I engineered a resistor ladder that multiplexes all four buttons into a single analog data line, using distinct voltage thresholds to determine which button was pressed.
Safe Battery Monitoring
To accurately read the 3.7V LiPo battery (which peaks at 4.2V, exceeding the ESP32’s safe limits), I implemented a hardware voltage divider. It steps the voltage down by half before reaching the ADC, allowing software to accurately calculate the remaining battery percentage without hardware damage.
State-Machine Architecture
The CircuitPython firmware is built on a memory-efficient Finite State Machine (FSM), cleanly separating the standalone logic (Clock/Timer) from the docked logic (Tamagotchi/Stats) to prevent memory fragmentation and ensure smooth sprite animations.
Hardware & Tools
- MCU & UI: Seeed Studio XIAO ESP32-C3, 1.28" Round GC9A01 IPS Display
- Sensors: MPU6050 (Orientation Detection), External RTC Module
- Power & Connectivity: 3.7V LiPo Battery, Magnetic Pogo Pins
- Electronics: Custom KiCad PCB (Cube Mainboard), Custom Perfboard (Dock Circuitry)