Starbie

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What exactly is it?

Starbie is a small interactive device built around the XIAO ESP32-C3. It uses a bunch of sensors and other components to make it actually do stuff.

Some of the things packed into it:

• Movement detection using the MPU6050.
• Temperature and humidity readings using the DHT11.
• An OLED display to show information.
• An RGB LED for visual feedback.
• Cherry MX switches for physical input.

Why I built it

I made Starbie for HalfLife, following their Week 1 PCB design tutorial.

Since this is my second hardware project, I wanted to build something a bit more interesting than my first one. Starbie is a tiny motion-controlled digital pet, basically a desktop Tamagotchi (totally not a Starboy).

And yeah, I'm also trying to get that 3D printer prize lol. HalfLife gives me a reason to actually design, build and document my projects instead of leaving them as ideas.

The Schematic

The schematic was made in KiCad and shows how all the components are connected to the XIAO ESP32-C3.

The PCB Design

I designed the board using KiCad, with a custom shape and footprints for the components.

Fabrication

Here's the final manufacturing quote and preview from JLCPCB before it becomes reality:

Firmware

The firmware is written for the XIAO ESP32-C3 and handles Starbie's sensors, display, RGB LED and buttons. It reads movement data from the MPU6050 and temperature and humidity from the DHT11, with the OLED used to display information.

Controls

Starbie has two buttons.

Both buttons are debounced in software (30 ms).

Tilt menu

1. Press Button 1 to open the menu. The way you are holding Starbie at that moment becomes the centre.
2. Tilt Starbie. The MPU6050 accelerometer moves a ball around the screen. The screen is split into four sectors by two diagonal lines: NAP (top), PLAY (right), FEED (bottom) and PET (left).
3. The sector in the direction you tilt is highlighted. A small dead zone in the middle means nothing is highlighted until you tilt past it.
4. Press Button 1 again to confirm. If nothing is highlighted, nothing happens and the menu stays open.
5. Pressing Button 2 while the menu is open leaves the menu without choosing anything and shows the stats screen instead.

Which physical tilt direction moves the ball to which sector depends on how the MPU6050 is mounted. If the ball moves the wrong way, change SWAP_MPU_AXES, MENU_X_DIRECTION or MENU_Y_DIRECTION at the top of Starbie.ino.

Each action changes the pet's three stats (each stays between 0 and 100):

Shake: on the pet screen, shaking Starbie gives +5 joy, −2 energy and −1 fullness, wakes a sleeping pet, and has a 0.65 second cooldown. Shaking does nothing while the menu or stats screen is open.

Stats are saved to flash after every action and every shake, so Starbie remembers them after a reset. Stats do not drain over time; they only change when you use the menu or shake Starbie.

Status LED

The RGB LED shows Starbie's mood. The firmware checks the stats in this order and shows the first one that matches:

If more than one stat is low, the first row that matches wins (yellow, then blue, then red). The LED is on/off only (no dimming or colour mixing), and yellow is red and green on together.

Stats screen

Press Button 2 to see Starbie's JOY, ENERGY and FULL bars with their numbers, plus the room temperature (°C) and humidity (%) from the DHT11. If the DHT11 has not produced a reading yet, the screen shows --. The temperature and humidity are display-only; they do not affect the pet or the LED.

Bill Of Materials

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