上一篇簡單介紹了藍芽的部分基礎知識，詳細的東西大家可以去github上搜babyBluetooth，裡面有一些學習資料

iOS連線外設的流程

• 建立中心管理者
• 掃描外設 discoverPeripheral
• 連線外設 connectPeripheral
• 掃描外設中的服務和特徵 discoverServices discoverCharacteristics
  
  • 獲取外設的services
  • 獲取外設service中的characteristics
  • 獲取characteristic的值value、descriptor的value
• 與外設做資料互動 write、read
• 訂閱characteristic的通知notify
• 斷開連線 disconnected

實現步驟

1、匯入CoreBluetooth標頭檔案，建立中心管理類，設定代理

#import <CoreBluetooth/CoreBluetooth.h>
@interface ViewController : UIViewController<CBCentralManagerDelegate>
@interface ViewController (){
    //系統藍芽裝置管理物件，可以把他理解為主裝置，通過他，可以去掃描和連結外設
    CBCentralManager *manager;
    //用於儲存被發現裝置
    NSMutableArray *peripherals;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    /*
     設定主裝置的委託,CBCentralManagerDelegate
        必須實現的：
        - (void)centralManagerDidUpdateState:(CBCentralManager *)central;//主裝置狀態改變的委託，在初始化CBCentralManager的適合會開啟裝置，只有當裝置正確開啟後才能使用
        其他選擇實現的委託中比較重要的：
        - (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI; //找到外設的委託
        - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral;//連線外設成功的委託
        - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//外設連線失敗的委託
        - (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//斷開外設的委託
    */
     //初始化並設定委託和執行緒佇列，最好一個執行緒的引數可以為nil，預設會就main執行緒
     manager = [[CBCentralManager alloc]initWithDelegate:self queue:dispatch_get_main_queue()];
 

2、掃描外設（discover），掃描外設的方法我們放在centralManager成功開啟的委託中，因為只有裝置成功開啟，才能開始掃描，否則會報錯。
所以當重新連線外設時，都不會成功，因為states還沒開啟；一般自己寫藍芽，這個地方要處理一下，連線的時候判斷一下，還未開啟就重連，一直等到PoweredOn

-(void)centralManagerDidUpdateState:(CBCentralManager *)central{
        switch (central.state) {
            case CBCentralManagerStateUnknown:
                NSLog(@">>>CBCentralManagerStateUnknown");
                break;
            case CBCentralManagerStateResetting:
                NSLog(@">>>CBCentralManagerStateResetting");
                break;
            case CBCentralManagerStateUnsupported:
                NSLog(@">>>CBCentralManagerStateUnsupported");
                break;
            case CBCentralManagerStateUnauthorized:
                NSLog(@">>>CBCentralManagerStateUnauthorized");
                break;
            case CBCentralManagerStatePoweredOff:
                NSLog(@">>>CBCentralManagerStatePoweredOff");
                break;
            case CBCentralManagerStatePoweredOn:
                NSLog(@">>>CBCentralManagerStatePoweredOn");
                //開始掃描周圍的外設
                /*
                 第一個引數nil就是掃描周圍所有的外設，掃描到外設後會進入
                      - (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI;
                 */
                [manager scanForPeripheralsWithServices:nil options:nil];
                break;
            default:
                break;
        }
    }

    //掃描到裝置會進入方法
    -(void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{

        NSLog(@"當掃描到裝置:%@",peripheral.name);
        //接下來可以連線裝置

    }
 

3、連線外設
有一點注意，找到的peripheral必須被持有：(比如新增到陣列、賦值給另一個被持有的變數)，否則CBCentralManager中也不會儲存這個peripheral，那麼CBPeripheralDelegate中的方法也不會被呼叫

    //掃描到裝置會進入方法
    -(void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{

        //接下連線我們的測試裝置，如果你沒有裝置，可以下載一個app叫lightbule的app去模擬一個裝置
        //這裡自己去設定下連線規則，我設定的是P開頭的裝置
               if ([peripheral.name hasPrefix:@"P"]){
               /*
                   一個主裝置最多能連7個外設，每個外設最多隻能給一個主裝置連線,連線成功，失敗，斷開會進入各自的委託
                - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral;//連線外設成功的委託
                - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//外設連線失敗的委託
                - (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//斷開外設的委託
                */

                //找到的裝置必須持有它，否則CBCentralManager中也不會儲存peripheral，那麼CBPeripheralDelegate中的方法也不會被呼叫！！
                [peripherals addObject:peripheral];
                //連線裝置
               [manager connectPeripheral:peripheral options:nil];
           }

    }


    //連線到Peripherals-成功
    - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
    {
        NSLog(@">>>連線到名稱為（%@）的裝置-成功",peripheral.name);
    }

    //連線到Peripherals-失敗
    -(void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
    {
        NSLog(@">>>連線到名稱為（%@）的裝置-失敗,原因:%@",[peripheral name],[error localizedDescription]);
    }

    //Peripherals斷開連線
    - (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{
        NSLog(@">>>外設連線斷開連線 %@: %@\n", [peripheral name], [error localizedDescription]);

    }

4、掃描外設中的服務和特徵(discover)
裝置連線成功後，就可以掃描裝置的服務了，同樣是通過委託形式，掃描到結果後會進入委託方法。但是這個委託已經不再是主裝置的委託（CBCentralManagerDelegate），而是外設的委託（CBPeripheralDelegate）,這個委託包含了主裝置與外設互動的許多 回叫方法，包括獲取services，獲取characteristics，獲取characteristics的值，獲取characteristics的Descriptor，和Descriptor的值，寫資料，讀rssi，用通知的方式訂閱資料等等。

5、獲取外設的services

    //連線到Peripherals-成功
    - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
    {
        NSLog(@">>>連線到名稱為（%@）的裝置-成功",peripheral.name);
        //設定的peripheral委託CBPeripheralDelegate
        //@interface ViewController : UIViewController<CBCentralManagerDelegate,CBPeripheralDelegate>
        [peripheral setDelegate:self];
        //掃描外設Services，成功後會進入方法：-(void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{
        [peripheral discoverServices:nil];

    }

    //掃描到Services
    -(void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{
        //  NSLog(@">>>掃描到服務：%@",peripheral.services);
        if (error)
        {
            NSLog(@">>>Discovered services for %@ with error: %@", peripheral.name, [error localizedDescription]);
            return;
        }

        for (CBService *service in peripheral.services) {
                         NSLog(@"%@",service.UUID);
                         //掃描每個service的Characteristics，掃描到後會進入方法： -(void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
                         [peripheral discoverCharacteristics:nil forService:service];
                     }
    }

6、獲取外設的Characteristics,獲取Characteristics的值，獲取Characteristics的Descriptor和Descriptor的值

    //掃描到Characteristics
 -(void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{
     if (error)
     {
         NSLog(@"error Discovered characteristics for %@ with error: %@", service.UUID, [error localizedDescription]);
         return;
     }

     for (CBCharacteristic *characteristic in service.characteristics)
     {
         NSLog(@"service:%@ 的 Characteristic: %@",service.UUID,characteristic.UUID);
     }

     //獲取Characteristic的值，讀到資料會進入方法：-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
     for (CBCharacteristic *characteristic in service.characteristics){
         {
             [peripheral readValueForCharacteristic:characteristic];
         }
     }

     //搜尋Characteristic的Descriptors，讀到資料會進入方法：-(void)peripheral:(CBPeripheral *)peripheral didDiscoverDescriptorsForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
     for (CBCharacteristic *characteristic in service.characteristics){
         [peripheral discoverDescriptorsForCharacteristic:characteristic];
     }


 }

//獲取的charateristic的值
-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{
    //打印出characteristic的UUID和值
    //!注意，value的型別是NSData，具體開發時，會根據外設協議制定的方式去解析資料
    NSLog(@"characteristic uuid:%@  value:%@",characteristic.UUID,characteristic.value);

}

//搜尋到Characteristic的Descriptors
-(void)peripheral:(CBPeripheral *)peripheral didDiscoverDescriptorsForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{

    //打印出Characteristic和他的Descriptors
     NSLog(@"characteristic uuid:%@",characteristic.UUID);
    for (CBDescriptor *d in characteristic.descriptors) {
        NSLog(@"Descriptor uuid:%@",d.UUID);
    }

}
//獲取到Descriptors的值
-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForDescriptor:(CBDescriptor *)descriptor error:(NSError *)error{
    //打印出DescriptorsUUID 和value
    //這個descriptor都是對於characteristic的描述，一般都是字串，所以這裡我們轉換成字串去解析
    NSLog(@"characteristic uuid:%@  value:%@",[NSString stringWithFormat:@"%@",descriptor.UUID],descriptor.value);
}   

7、把資料寫到Characteristic中

//寫資料
-(void)writeCharacteristic:(CBPeripheral *)peripheral
            characteristic:(CBCharacteristic *)characteristic
                     value:(NSData *)value{

    //打印出 characteristic 的許可權，可以看到有很多種，這是一個NS_OPTIONS，就是可以同時用於好幾個值，常見的有read，write，notify，indicate，知知道這幾個基本就夠用了，前連個是讀寫許可權，後兩個都是通知，兩種不同的通知方式。
    /*
     typedef NS_OPTIONS(NSUInteger, CBCharacteristicProperties) {
     CBCharacteristicPropertyBroadcast                                              = 0x01,
     CBCharacteristicPropertyRead                                                   = 0x02,
     CBCharacteristicPropertyWriteWithoutResponse                                   = 0x04,
     CBCharacteristicPropertyWrite                                                  = 0x08,
     CBCharacteristicPropertyNotify                                                 = 0x10,
     CBCharacteristicPropertyIndicate                                               = 0x20,
     CBCharacteristicPropertyAuthenticatedSignedWrites                              = 0x40,
     CBCharacteristicPropertyExtendedProperties                                     = 0x80,
     CBCharacteristicPropertyNotifyEncryptionRequired NS_ENUM_AVAILABLE(NA, 6_0)        = 0x100,
     CBCharacteristicPropertyIndicateEncryptionRequired NS_ENUM_AVAILABLE(NA, 6_0)  = 0x200
     };

     */
    NSLog(@"%lu", (unsigned long)characteristic.properties);


    //只有 characteristic.properties 有write的許可權才可以寫
    if(characteristic.properties & CBCharacteristicPropertyWrite){
        /*
            最好一個type引數可以為CBCharacteristicWriteWithResponse或type:CBCharacteristicWriteWithResponse,區別是是否會有反饋
        */
        [peripheral writeValue:value forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];
    }else{
        NSLog(@"該欄位不可寫！");
    }


}

8、訂閱Characteristic的通知
一般在discoverCharacteristic的代理中，發現了型別是notify的characteristic，直接就可以訂閱了

    //設定通知
-(void)notifyCharacteristic:(CBPeripheral *)peripheral
            characteristic:(CBCharacteristic *)characteristic{
    //設定通知，資料通知會進入：didUpdateValueForCharacteristic方法
    [peripheral setNotifyValue:YES forCharacteristic:characteristic];

}

//取消通知
-(void)cancelNotifyCharacteristic:(CBPeripheral *)peripheral
             characteristic:(CBCharacteristic *)characteristic{

     [peripheral setNotifyValue:NO forCharacteristic:characteristic];
}

9、斷開連線(disconnect)

    //停止掃描並斷開連線
-(void)disconnectPeripheral:(CBCentralManager *)centralManager
                 peripheral:(CBPeripheral *)peripheral{
    //停止掃描
    [centralManager stopScan];
    //斷開連線
    [centralManager cancelPeripheralConnection:peripheral];
}

iOS中藍芽模組OTA升級（YModem協議）