STEMBuddy Arduino Library

Turn your phone into virtual hardware for ESP32 projects.

STEMBuddy lets your ESP32 control virtual LEDs, LCDs, servos, motors, buzzers, and oscilloscopes on the STEM Buddy Android app over BLE. The app can also send virtual sensor data and button inputs back to your ESP32 — no physical components needed.

How It Works

ESP32 (your code)  ──BLE──>  Phone (STEM Buddy app)
    buddy.led.on()           Virtual LED lights up
    buddy.lcd.print("Hi")   Virtual LCD shows text
    buddy.servo.setAngle(90) Virtual servo animates

Phone (sensors/inputs) ──BLE──>  ESP32
    Accelerometer, light      buddy.sensor.temperature()
    Buttons, sliders, dpad    buddy.input.slider(0)

Your phone becomes the component. Students don't need to buy LEDs, LCDs, or sensors — just an ESP32 and the free app.

Installation

Arduino Library Manager (recommended)

1. Open Arduino IDE
2. Go to Sketch > Include Library > Manage Libraries...
3. Search for STEMBuddy
4. Click Install

Manual Install

1. Download this repository as a ZIP
2. In Arduino IDE, go to Sketch > Include Library > Add .ZIP Library...
3. Select the downloaded ZIP file

PlatformIO

Add to your platformio.ini:

lib_deps = hacktronics/STEMBuddy-Arduino

Quick Start

#include <STEMBuddy.h>

STEMBuddy buddy;

void setup() {
    buddy.begin("My Project");   // Start BLE with device name
}

void loop() {
    buddy.update();              // Process BLE messages

    if (buddy.isConnected()) {
        buddy.led.setColor(255, 0, 0);  // Red
        buddy.led.on();
        delay(1000);
        buddy.led.off();
        delay(1000);
    }
}

Virtual Components

Outputs (ESP32 → Phone)

Component	Object	Example
LED / RGB LED	buddy.led	buddy.led.setColor(r, g, b)
LCD Display	buddy.lcd	buddy.lcd.print(0, 0, "Hello!")
Servo Motor	buddy.servo	buddy.servo.setAngle(90)
DC Motor	buddy.motor	buddy.motor.run(200)
Buzzer	buddy.buzzer	buddy.buzzer.tone(440)
Oscilloscope	buddy.scope	buddy.scope.plot(value)
Text-to-Speech	buddy.tts	buddy.tts.speak("Hello")
Serial Terminal	buddy.terminal	buddy.terminal.print("debug info")
Notifications	buddy.notify	buddy.notify.send("Alert!", "Details here")
Piano	buddy.piano	buddy.piano.noteOn(60, 100)
Audio	buddy.audio	buddy.audio.play("alert.mp3")
Relay	buddy.relay	buddy.relay.on()
Home Switches	buddy.sw	buddy.sw.set(0, true)

Inputs (Phone → ESP32)

Component	Object	Example
Virtual Sensors	buddy.sensor	buddy.sensor.temperature()
Buttons / Sliders / D-Pad	buddy.input	buddy.input.slider(0)
Camera	buddy.camera	buddy.camera.capture()
NFC	buddy.nfc	buddy.nfc.tagPresent()

Examples

The library includes ready-to-use examples:

• LEDBlink — Blink a virtual LED with color changes
• LCDHello — Display text on a virtual LCD
• ServoSweep — Sweep a virtual servo back and forth
• MotorControl — Control virtual DC motor speed
• BuzzerMelody — Play a melody on the virtual buzzer
• SensorRead — Read virtual sensor data from the phone
• MotionDetect — React to phone motion sensor
• Compass — Use phone magnetometer as a compass

Open them in Arduino IDE via File > Examples > STEMBuddy.

Requirements

• Board: ESP32 (any variant with BLE support)
• Arduino Core: arduino-esp32 v2.0+
• App: STEM Buddy on Android

Protocol

See PROTOCOL.md for the full BLE command protocol specification.

License

MIT License — see LICENSE for details.

Links

• STEM Buddy App
• CodeSkool
• Hacktronics