Setting Up a Mac Mini as a BLE Peripheral Device Using Core Bluetooth Framework

Understanding the Core Bluetooth Framework for Peripheral Devices

Introduction

The Core Bluetooth framework provides a powerful and efficient way to interact with Bluetooth Low Energy (BLE) devices on Apple platforms. One of the key features of the Core Bluetooth framework is its ability to enable devices as BLE peripherals, allowing them to advertise their presence and transmit data to other devices. In this article, we will explore how to set up a Mac Mini as a BLE peripheral device using the Core Bluetooth framework.

Prerequisites

Before diving into the details, it’s essential to have a basic understanding of the Core Bluetooth framework and its components. Here are some key concepts to keep in mind:

CBPeripheral: Represents a BLE peripheral device.
CBPeripheralManager: Manages the connection between the Apple platform and a BLE peripheral device.
CBPeripheralDelegate: A protocol that defines methods for handling events related to a CBPeripheral.

Setting Up the Core Bluetooth Framework

To set up the Core Bluetooth framework, you need to create an instance of CBPeripheralManager and delegate it to the class that will handle the event notifications. The following code snippet demonstrates how to initialize the CBPeripheralManager:

- (CBPeripheralManager *)peripheralManager {
    if (_peripheralManager == nil) {
        _peripheralManager = [[CBPeripheralManager alloc] initWithDelegate:self queue:nil];
    }
    return _peripheralManager;
}

This code snippet initializes the CBPeripheralManager instance and assigns it to a class property named _peripheralManager. The delegate is set to the current object, which means that all events related to the BLE peripheral device will be handled by this object.

Defining the CBPeripheralDelegate Protocol

The CBPeripheralDelegate protocol defines methods for handling events related to a CBPeripheral. In order to handle these events, you need to implement the following methods:

connectionUpdate: Called when a new connection is established or terminated.
readValueForKey: Called when a read request is sent to the device.
writeValue: Called when a write request is sent to the device.

Here’s an example implementation of the CBPeripheralDelegate protocol:

- (void)connectionUpdate:(CBConnection *)connection {
    // Handle connection events here
}

- (void)valueChangedForKey:(NSString *)key {
    // Handle value changes here
}

- (void)writeValue:(NSData *)data forKey:(NSString *)key {
    // Handle write requests here
}

Enabling BLE Peripheral Mode

To enable the Mac Mini as a BLE peripheral device, you need to create an instance of CBPeripheral and set it as the central device. The following code snippet demonstrates how to do this:

- (void)setupBLEPeripheral {
    // Create a new CBPeripheral instance
    CBPeripheral *peripheral = [[CBPeripheral alloc] init];
    
    // Set up the peripheral's properties
    peripheral.name = @"MyLEDevice";
    peripheral.description = @"MyLEDevice Description";
    peripheral.power = CBCurrentLinkPowerHigh;
    peripheral.serviceUUIDs = @[@("00002a37-0000-1000-8000-00805f9b34fb")];
    peripheral.clientConnection = nil;
    
    // Set the peripheral as the central device
    [self.peripheralManager addPeripheral:peripheral desiredServices:nil];
}

This code snippet creates a new instance of CBPeripheral and sets up its properties. The power property is set to CBCurrentLinkPowerHigh, which means that the device will transmit data at maximum power level. The serviceUUIDs array contains the UUID for the service that you want to advertise.

Advertising BLE Services

To advertise a BLE service, you need to create an instance of CBService and add it to the peripheral’s services. The following code snippet demonstrates how to do this:

- (void)createService {
    // Create a new CBService instance
    CBService *service = [[CBService alloc] initWithServiceType:@"MyLEService" UUID@[0x02, 0xA3, 0x37, 0x00, 0x00, 0x80, 0x00, 0x05, 0xF9, 0xB3, 0x34, 0xFB]];
    
    // Set up the service's properties
    service.characteristicCount = 1;
    service.dataType = CBAttributeDataTypeUnsignedInteger;
    
    // Add the service to the peripheral's services
    [self.peripheralManager addService:service];
}

This code snippet creates a new instance of CBService and sets up its properties. The serviceType parameter is set to "MyLEService", which is the UUID for the service that you want to advertise.

Writing Data to BLE Services

To write data to a BLE service, you need to create an instance of CBCharacteristic and add it to the service’s characteristics array. The following code snippet demonstrates how to do this:

- (void)writeData {
    // Create a new CBCharacteristic instance
    CBCharacteristic *characteristic = [[CBCharacteristic alloc] initWithService:service characteristicType:CBCharacteristicPropertyWrite characteristicsProperties:nil];
    
    // Set up the characteristic's properties
    characteristic.dataType = CBAttributeDataTypeUnsignedInteger;
    characteristic.valueLength = 1;
    
    // Write data to the characteristic
    [self.peripheralManager writeValue:[NSData dataWithBytes:(const void *)1 length:1] forCharacteristic:characteristic onSubordinate:service];
}

This code snippet creates a new instance of CBCharacteristic and sets up its properties. The characteristicType parameter is set to CBCharacteristicPropertyWrite, which means that the characteristic can be written to.

Reading Data from BLE Services

To read data from a BLE service, you need to create an instance of CBCharacteristic and add it to the service’s characteristics array. The following code snippet demonstrates how to do this:

- (void)readData {
    // Create a new CBCharacteristic instance
    CBCharacteristic *characteristic = [[CBCharacteristic alloc] initWithService:service characteristicType:CBCharacteristicPropertyRead characteristicsProperties:nil];
    
    // Read data from the characteristic
    [self.peripheralManager readValueForKey:characteristic];
}

This code snippet creates a new instance of CBCharacteristic and sets up its properties. The characteristicType parameter is set to CBCharacteristicPropertyRead, which means that the characteristic can be read.

Conclusion

In this article, we have explored how to set up a Mac Mini as a BLE peripheral device using the Core Bluetooth framework. We have discussed the key components of the Core Bluetooth framework and provided code snippets to demonstrate how to initialize the CBPeripheralManager instance, define the CBPeripheralDelegate protocol, enable BLE peripheral mode, advertise BLE services, write data to BLE services, and read data from BLE services.