Bluetooth Low Energy (BLE) 📱

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title: Bluetooth (BLE) publish: true date: 2025-01-27 12:00:00 update: 2025-01-27 12:00:00 description: Learn how to use Bluetooth Low Energy with tinyCore categories:

• advanced
• connectivity

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tinyCore includes built-in Bluetooth Low Energy (BLE) support, allowing you to create wireless projects that connect to phones, computers, and other devices.

What is BLE?

Bluetooth Low Energy is a wireless communication protocol designed for:

• Low power consumption - Perfect for battery-powered projects
• Short-range communication - Typically 10-100 meters
• Simple data exchange - Ideal for sensors, controllers, and IoT devices

Key Features

✅ What tinyCore BLE Can Do

• Phone Connectivity - Connect to iOS and Android apps
• Data Transfer - Send sensor data to your phone
• Remote Control - Control tinyCore from your phone
• Notifications - Send alerts and status updates
• Custom Apps - Create your own mobile applications

📱 Common Use Cases

• Smart Home Devices - Control lights, sensors, and appliances
• Wearable Projects - Fitness trackers, smart watches
• Remote Sensors - Environmental monitoring
• Game Controllers - Custom input devices
• IoT Devices - Internet of Things applications

Getting Started

Prerequisites

1. tinyCore Board - Any tinyCore variant
2. Arduino IDE - With ESP32 board support
3. Mobile Device - iOS or Android for testing

Basic BLE Server Example

#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

// BLE Service and Characteristic UUIDs
#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"

BLEServer* pServer = NULL;
BLECharacteristic* pCharacteristic = NULL;
bool deviceConnected = false;

// Connection callback
class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
      Serial.println("Device connected!");
    }

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;
      Serial.println("Device disconnected!");
      // Restart advertising
      pServer->getAdvertising()->start();
    }
};

void setup() {
  Serial.begin(115200);

  // Initialize BLE
  BLEDevice::init("tinyCore BLE");
  pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());

  // Create BLE Service
  BLEService *pService = pServer->createService(SERVICE_UUID);

  // Create BLE Characteristic
  pCharacteristic = pService->createCharacteristic(
                      CHARACTERISTIC_UUID,
                      BLECharacteristic::PROPERTY_READ |
                      BLECharacteristic::PROPERTY_WRITE |
                      BLECharacteristic::PROPERTY_NOTIFY
                    );

  // Add descriptor for notifications
  pCharacteristic->addDescriptor(new BLE2902());

  // Start the service
  pService->start();

  // Start advertising
  BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
  pAdvertising->addServiceUUID(SERVICE_UUID);
  pAdvertising->setScanResponse(false);
  pAdvertising->setMinPreferred(0x0);
  BLEDevice::startAdvertising();

  Serial.println("BLE Server ready! Waiting for connections...");
}

void loop() {
  if (deviceConnected) {
    // Send data every second
    String data = "Hello from tinyCore!";
    pCharacteristic->setValue((uint8_t*)data.c_str(), data.length());
    pCharacteristic->notify();
    delay(1000);
  }
}

Advanced Features

Custom Services and Characteristics

Create your own BLE services for specific applications:

// Custom service for sensor data
#define SENSOR_SERVICE_UUID "12345678-1234-1234-1234-123456789abc"
#define TEMPERATURE_CHAR_UUID "87654321-4321-4321-4321-cba987654321"

BLEService* pSensorService;
BLECharacteristic* pTemperatureChar;

Data Formats

Send different types of data:

// Send sensor readings
float temperature = 23.5;
uint8_t tempBytes[4];
memcpy(tempBytes, &temperature, 4);
pTemperatureChar->setValue(tempBytes, 4);
pTemperatureChar->notify();

Security Features

Implement pairing and encryption:

// Enable security
BLESecurity *pSecurity = new BLESecurity();
pSecurity->setAuthenticationMode(ESP_LE_AUTH_REQ_SC_BOND);
pSecurity->setCapability(ESP_IO_CAP_OUT);
pSecurity->setInitEncryptionKey(ESP_BLE_ENC_KEY_MASK | ESP_BLE_ID_KEY_MASK);

Project Examples

1. RGB Mood Light Controller

Control RGB LEDs from your phone:

// RGB LED pins
#define RED_PIN 25
#define GREEN_PIN 26
#define BLUE_PIN 27

// BLE characteristic for RGB values
BLECharacteristic* pRGBChar;

void setup() {
  // Initialize RGB pins
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);

  // Setup BLE (similar to basic example)
  // ...

  // Create RGB characteristic
  pRGBChar = pService->createCharacteristic(
    RGB_CHAR_UUID,
    BLECharacteristic::PROPERTY_WRITE
  );
}

void loop() {
  // Handle RGB updates in BLE callback
}

2. Sensor Data Logger

Send sensor data to your phone:

// Send IMU data
void sendIMUData() {
  if (deviceConnected) {
    // Read IMU
    float accelX, accelY, accelZ;
    // ... read sensor data ...

    // Create JSON-like string
    String data = "{\"accel\":{\"x\":" + String(accelX) +
                  ",\"y\":" + String(accelY) +
                  ",\"z\":" + String(accelZ) + "}}";

    pCharacteristic->setValue((uint8_t*)data.c_str(), data.length());
    pCharacteristic->notify();
  }
}

Mobile App Development

Using BLE Scanner Apps

For testing, use these free apps:

• nRF Connect (Android/iOS)
• BLE Scanner (Android)
• LightBlue (iOS)

Creating Custom Apps

Use these frameworks for custom mobile apps:

• React Native with react-native-ble-plx
• Flutter with flutter_blue_plus
• Native iOS with CoreBluetooth
• Native Android with BluetoothLe

Troubleshooting

Common Issues

1. Device Not Found

   • Check if BLE is enabled on your phone
   • Ensure tinyCore is advertising
   • Try restarting the BLE stack

2. Connection Drops

   • Check signal strength
   • Reduce data transmission frequency
   • Implement reconnection logic

3. Data Corruption

   • Use proper data formatting
   • Implement checksums
   • Check characteristic properties

Debug Tips

// Enable BLE debugging
#define CONFIG_BT_NIMBLE_ROLE_PERIPHERAL 1
#define CONFIG_BT_NIMBLE_ROLE_CENTRAL 1

// Monitor connection status
void printConnectionStatus() {
  Serial.print("Connected devices: ");
  Serial.println(deviceConnected ? "1" : "0");
}

Performance Optimization

Power Management

// Reduce power consumption
BLEDevice::setMTU(23); // Use smaller packets
pAdvertising->setMinInterval(0x20); // Slower advertising
pAdvertising->setMaxInterval(0x40);

Data Throughput

// Optimize for high data rates
#define BLE_MTU_SIZE 512
BLEDevice::setMTU(BLE_MTU_SIZE);

Next Steps

• Explore ESP-NOW - For device-to-device communication
• Learn WiFi - For internet connectivity
• Check out User Projects - See what others have built
• Join the Community - Get help on Discord

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Ready to build wireless projects? Start with the RGB Mood Light Tutorial or explore other connectivity options!