Bluetooth Low Energy (BLE)

BLE Overview:

• Designed for low power, short-burst data transmission
• Uses GATT (Generic Attribute Profile) protocol
• Operates in 2.4GHz band
• Connection range typically 10-30m
• Not compatible with Classic Bluetooth

Key Components:

1. GATT Hierarchy:

Profile
└── Service (identified by UUID)
    └── Characteristic (identified by UUID)
        └── Value (actual data)

2. Roles:

• Peripheral (Microcontroller): Advertises and provides data
• Central (Android phone): Scans and consumes data

Implementation Steps:

1. Microcontroller Side:

// Example using Arduino BLE library
#include <ArduinoBLE.h>
 
// Define Service UUID
BLEService myService("180D");
 
// Define Characteristic
BLECharacteristic myCharacteristic("2A37", 
    BLERead | BLENotify, 
    sizeof(float));
 
void setup() {
    BLE.begin();
    BLE.setLocalName("MyDevice");
    BLE.setAdvertisedService(myService);
    myService.addCharacteristic(myCharacteristic);
    BLE.addService(myService);
    BLE.advertise();
}
 
void loop() {
    // Update data
    float value = getSensorData();
    myCharacteristic.writeValue(value);
}

2. Android App Side:

// Basic structure for Android BLE implementation
class BleManager {
    private val bluetoothAdapter: BluetoothAdapter
    private val scanner: BluetoothLeScanner
    
    // Scan for devices
    private fun startScan() {
        scanner.startScan(scanCallback)
    }
    
    // Connect to device
    private fun connect(device: BluetoothDevice) {
        device.connectGatt(context, false, gattCallback)
    }
    
    // GATT callback
    private val gattCallback = object : BluetoothGattCallback() {
        override fun onCharacteristicChanged(
            gatt: BluetoothGatt,
            characteristic: BluetoothGattCharacteristic
        ) {
            // Handle received data
            val data = characteristic.value
        }
    }
}

Important Considerations:

1. Permissions:

• Android requires location permission for BLE scanning
• Android 12+ requires specific Bluetooth permissions

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

2. Data Transfer Methods:

• Read: One-time data request
• Write: Send data to peripheral
• Notify/Indicate: Continuous updates from peripheral

3. Best Practices:

• Keep payload size small (20 bytes recommended)
• Implement reconnection logic
• Handle connection state changes
• Consider battery impact
• Implement proper error handling

4. Common Issues:

• Connection timeouts
• Device discovery problems
• Permission handling
• Android device variations
• Background operation limitations

5. Power Optimization:

• Use appropriate advertising intervals
• Minimize connection interval when possible
• Disconnect when not needed
• Use notification instead of polling

6. Security:

• Consider BLE pairing
• Implement encryption if needed
• Use bonding for trusted devices
• Validate data integrity

This overview should give you a starting point for implementing BLE communication. The exact implementation details will depend on your specific microcontroller and requirements.