SmartCube is a tiny and customizable desk toy using the ESP8266 D1 Mini. Built entirely from cheap, easy-to-find parts, it can connect to Wi-Fi and can be programmed to do just about anything: show notifications, display the weather, monitor stuff, show a clock, serve a web site, mine crypto, be a virtual pet or whatever else your caffeine-fueled brain can imagine.

Info

This is a hobby project I work on and develop for when I have literally nothing else to do, do not expect regular updates. You are free to clone this and do whatever you like with it
Code: I have a few projects developed for the Cube. You can see the list here on my Gitea
V2: There is also a more powerful version, it's pretty much the same but with extra features and is using ESP32, I only made one of them and I don't like it yet, it needs work.
Case: 3D-printable design included in /hardware directory
Schematics: and assembly instructions are also in the /hardware directory

Bill of Materials
3D-Printing the Case
Assembly Instructions
- Body
- Buttons
- OLED Display
- Buzzer
- Battery Setup
Schematics
GPIO Pin Reference Table
Demo Code Explanation
Tips and tricks

Bill of Materials

Component	Quantity	Description	Notes
Enclosure	1	3D-printed case	3D printable STL files are in `hardware/case/`
ESP8266 D1 Mini	1	Microcontroller module
SSD1306 OLED Display	1	128x64 resolution, I2C interface
6x6 Push Buttons	3 or 4	Tactile push buttons
Resistors (10kΩ)	3 or 4	Pull-down resistors for buttons	Generally any resistor between 1kΩ and 100kΩ will work
20mm Piezo Buzzer	1	Caseless buzzer for audio
Wires	Several	Thin wires for connections	I used wires from inside an old ethernet cable
2x6mm screw	8	Small screws for assembling the case	Does not have to be exactly 6mm long
2x2mm screw	4 (Optional)	Small screws for the front	Mostly for cosmetic purposes
14250 Rechargeable Battery	1 (Optional)	Lithium-ion battery	Make sure it's rechargeable; most 14250 aren't
TP4056 Module	1 (Optional)	Charging and protection circuit	USB connector not required
Resistors (220kΩ and 56kΩ)	1 (Optional)	Voltage divider	For monitoring the battery charge level
Micro Slider Switch (SS-12D00)	1 (Optional)	On/Off switch	Only needed if installing the battery

3D-Printing the Case

The SmartCube case is fully 3D-printable. STL files are included this repository in the /hardware/case/ directory:

File	Description
`SmartCube_Body_3_button.stl`	Main cube body with slots for 3 buttons
`SmartCube_Body_4_button.stl`	Body variant for 4 buttons
`SmartCube_Front.stl`	Front panel for OLED display
`SmartCube_Front_No_Holes.stl`	Front panel variant without decorative screw holes
`SmartCube_Back_Speaker_Side_Hole.stl`	Back panel
`SmartCube_Back_Speaker_Power_Switch.stl`	Back panel variant with power switch slot

Use PLA or PETG
0.2 mm layer hight is more than enough, you can print finer if you want to.
Supports may be required depending on your printer

Assembly Instructions

Body

Push the ESP8266 microcontroller in the ledge on the bottom the cube body, it should 'click in' with the USB-C port facing the hole.

Body with 3 or 4 button slots is available in the hardware/case/

Buttons

At this step, glue the buttons into the top slots and solder resistors to their outputs. You can connect the resistor outputs together, and don't forget to attach an extra wire to the button inputs, this will later be used to connect them to the 3.3V line.

Next, solder all of the button outputs to the microcontroller.

Pin numbers for the buttons (and other components) are defined in the example config, and the schematic for the D1 Mini is here. You don't have to follow my exact pin definitions, but I've found this setup to be the easiest way to assemble and fit everything in. The 3-button variant is the standard. If you decide to go with 4 buttons, you'll need to define the extra pin yourself in the code.

Button Left (PIN_BTN_L): (D6) GPIO12
Button Middle (PIN_BTN_M): (D7) GPIO13
Button Right (PIN_BTN_R): (D8) GPIO15

Finally, solder the GND wire to the resistor outputs and connect 3.3V to the button inputs.

OLED Display

Screw in the 2x2mm screws and hot glue the SSD1306 to the front part of the cube solder the 4 wires to the OLED display, make sure you have some extra length, 4-5cm should be more than enough

The OLED display must be connected via I2C on pins:

SDA: D2 (GPIO4)
SCL: D1 (GPIO5)
GND: GND
VCC: 3.3V pin or directly to the TP4056 output

Buzzer

Glue in the buzzer to the back part of the cube with superglue

As defined in the example config connect:

the positive wire of the buzzer to the 3.3V
the negative wire to PIN_BUZZER (D3) GPIO0

Battery Setup

The battery is optional. Your SmartCube will work fine when powered via USB; however, adding one makes it portable (and much cuter).

A single 700 mAh 14250 battery lasts about 24 hours. The TP4056 prevents the cell from being completely drained and should protect it from damage.

Although it's not shown in any of the pictures or schematics, both the case and the back cover are updated to include a slot for 8.5mm SPDT slider switch(SS-12D00), in case you actually want to have a power switch instead of letting it run until the battery drains.

Solder the 14250 battery to the TP4056 input pins.
Wire the TP4056 output to the 3.3V pin on the D1 Mini to power the device.
Connect the 5V output pin from the D1 Mini to the TP4056 input port to allow charging through the USB data port on the ESP8266.
(Optional) Add a voltage divider to monitor battery level on the ESP8266 A0 pin:
- R1 = 220kΩ (between battery positive and A0)
- R2 = 56kΩ (between A0 and GND)
  
  This scales the battery voltage safely down for measurement (~0-0.85V).

Schematics

This is the basic drawing of the circuit without the battery

This is the complete circuit including the battery and a voltage divider

GPIO Pin Reference Table

Component	GPIO Pin	PlatformIO / Code Macro
Left Button	D6 (GPIO12)	`PIN_BTN_L`
Middle Button	D7 (GPIO13)	`PIN_BTN_M`
Right Button	D8 (GPIO15)	`PIN_BTN_R`
Buzzer	D3 (GPIO0)	`PIN_BUZZER`
OLED SDA	D2 (GPIO4)	`SDA`
OLED SCL	D1 (GPIO5)	`SCL`
Battery Voltage Divider	A0	`A0`

Demo Code Explanation

This repository contains a basic "Hello, World!" project for the SmartCube.

Getting Started:

Download and install VSCode or VSCodium.
Install the PlatformIO IDE extension.
Clone this repository and open the project folder in VSCode/VSCodium.
PlatformIO will automatically handle environment setup and dependencies when you open the project.

Uploading with PlatformIO

Once you open this git repository in VSCode and install the PlatformIO extension.

You can click on the PlatformIO icon on the left sidebar

In the PlatformIO panel, expand d1_mini_lite → General to reveal the available tasks.

Click Build to compile the firmware, and then click Upload to flash it to your SmartCube.

Project Structure:

All source code is located in the src/ directory. You should start by opening src/main.cpp, which contains the entry point and initialization logic.

What the Code Does:

This demo handles basic system functionality, including:

System initialization
Button input handling
OLED display output configuration
WiFi management

Key Features

WiFi Management

The cubeWifiManager class manages WiFi connectivity seamlessly.
If no known WiFi network is available, it starts a configuration portal and creates an access point (AP), allowing users to connect the SmartCube to a network from another WiFi-enabled device.
The OLED display shows the access point details, such as the AP name and IP address, making the setup process very easy.

Button Handling

Buttons are mapped to specific GPIO pins: PIN_BTN_L (Left), PIN_BTN_M (Middle), and PIN_BTN_R (Right).
The cubeButtonHandler function, executed in the loop(), monitors and interprets button presses, differentiating between short and long presses.

Default Button Actions

Right Button:
- Long Press: Turns the OLED display on (if previously off).
Left + Middle Buttons (Simultaneous Long Press):
- Triggers an ESP8266 reboot, effectively restarting the device.

This is meant to provide a minimal starting point for further development with the SmartCube.

Tips and tricks

It's not as hard to make as it looks.
Battery is the trickiest part to fit in, it's best to put in the case last.
Test if everything works before completely closing the case shut.
Ensure all connections are secure and isolated. Hot glue is your friend and will add extra protection from short circuits and it keep wires in place.
Everything is pretty tightly packed in there and it can be quite a mess.

For questions or additional details, feel free to reach out! I would love to hear some feedback. Good luck and have fun :)

Readme.md

SmartCube