上一篇简单介绍了蓝牙的部分基础知识，详细的东西大家可以去github上搜babyBluetooth，里面有一些学习资料

iOS连接外设的流程

• 建立中心管理者
• 扫描外设 discoverPeripheral
• 连接外设 connectPeripheral
• 扫描外设中的服务和特征 discoverServices discoverCharacteristics
  
  • 获取外设的services
  • 获取外设service中的characteristics
  • 获取characteristic的值value、descriptor的value
• 与外设做数据交互 write、read
• 订阅characteristic的通知notify
• 断开连接 disconnected

实现步骤

1、导入CoreBluetooth头文件，建立中心管理类，设置代理

#import <CoreBluetooth/CoreBluetooth.h>
@interface ViewController : UIViewController<CBCentralManagerDelegate>
@interface ViewController (){
    //系统蓝牙设备管理对象，可以把他理解为主设备，通过他，可以去扫描和链接外设
    CBCentralManager *manager;
    //用于保存被发现设备
    NSMutableArray *peripherals;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    /*
     设置主设备的委托,CBCentralManagerDelegate
        必须实现的：
        - (void)centralManagerDidUpdateState:(CBCentralManager *)central;//主设备状态改变的委托，在初始化CBCentralManager的适合会打开设备，只有当设备正确打开后才能使用
        其他选择实现的委托中比较重要的：
        - (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI; //找到外设的委托
        - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral;//连接外设成功的委托
        - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//外设连接失败的委托
        - (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//断开外设的委托
    */
     //初始化并设置委托和线程队列，最好一个线程的参数可以为nil，默认会就main线程
     manager = [[CBCentralManager alloc]initWithDelegate:self queue:dispatch_get_main_queue()];

2、扫描外设（discover），扫描外设的方法我们放在centralManager成功打开的委托中，因为只有设备成功打开，才能开始扫描，否则会报错。
所以当重新连接外设时，都不会成功，因为states还没打开；一般自己写蓝牙，这个地方要处理一下，连接的时候判断一下，还未打开就重连，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");
                //开始扫描周围的外设
                /*
                 第一个参数nil就是扫描周围所有的外设，扫描到外设后会进入
                      - (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI;
                 */
                [manager scanForPeripheralsWithServices:nil options:nil];
                break;
            default:
                break;
        }
    }

    //扫描到设备会进入方法
    -(void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{

        NSLog(@"当扫描到设备:%@",peripheral.name);
        //接下来可以连接设备

    }

3、连接外设
有一点注意，找到的peripheral必须被持有：(比如添加到数组、赋值给另一个被持有的变量)，否则CBCentralManager中也不会保存这个peripheral，那么CBPeripheralDelegate中的方法也不会被调用

    //扫描到设备会进入方法
    -(void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{

        //接下连接我们的测试设备，如果你没有设备，可以下载一个app叫lightbule的app去模拟一个设备
        //这里自己去设置下连接规则，我设置的是P开头的设备
               if ([peripheral.name hasPrefix:@"P"]){
               /*
                   一个主设备最多能连7个外设，每个外设最多只能给一个主设备连接,连接成功，失败，断开会进入各自的委托
                - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral;//连接外设成功的委托
                - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//外设连接失败的委托
                - (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error;//断开外设的委托
                */

                //找到的设备必须持有它，否则CBCentralManager中也不会保存peripheral，那么CBPeripheralDelegate中的方法也不会被调用！！
                [peripherals addObject:peripheral];
                //连接设备
               [manager connectPeripheral:peripheral options:nil];
           }

    }


    //连接到Peripherals-成功
    - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
    {
        NSLog(@">>>连接到名称为（%@）的设备-成功",peripheral.name);
    }

    //连接到Peripherals-失败
    -(void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
    {
        NSLog(@">>>连接到名称为（%@）的设备-失败,原因:%@",[peripheral name],[error localizedDescription]);
    }

    //Peripherals断开连接
    - (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{
        NSLog(@">>>外设连接断开连接 %@: %@\n", [peripheral name], [error localizedDescription]);

    }

4、扫描外设中的服务和特征(discover)
设备连接成功后，就可以扫描设备的服务了，同样是通过委托形式，扫描到结果后会进入委托方法。但是这个委托已经不再是主设备的委托（CBCentralManagerDelegate），而是外设的委托（CBPeripheralDelegate）,这个委托包含了主设备与外设交互的许多 回叫方法，包括获取services，获取characteristics，获取characteristics的值，获取characteristics的Descriptor，和Descriptor的值，写数据，读rssi，用通知的方式订阅数据等等。

5、获取外设的services

    //连接到Peripherals-成功
    - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
    {
        NSLog(@">>>连接到名称为（%@）的设备-成功",peripheral.name);
        //设置的peripheral委托CBPeripheralDelegate
        //@interface ViewController : UIViewController<CBCentralManagerDelegate,CBPeripheralDelegate>
        [peripheral setDelegate:self];
        //扫描外设Services，成功后会进入方法：-(void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{
        [peripheral discoverServices:nil];

    }

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

        for (CBService *service in peripheral.services) {
                         NSLog(@"%@",service.UUID);
                         //扫描每个service的Characteristics，扫描到后会进入方法： -(void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
                         [peripheral discoverCharacteristics:nil forService:service];
                     }
    }

6、获取外设的Characteristics,获取Characteristics的值，获取Characteristics的Descriptor和Descriptor的值

    //扫描到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);
     }

     //获取Characteristic的值，读到数据会进入方法：-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
     for (CBCharacteristic *characteristic in service.characteristics){
         {
             [peripheral readValueForCharacteristic:characteristic];
         }
     }

     //搜索Characteristic的Descriptors，读到数据会进入方法：-(void)peripheral:(CBPeripheral *)peripheral didDiscoverDescriptorsForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
     for (CBCharacteristic *characteristic in service.characteristics){
         [peripheral discoverDescriptorsForCharacteristic:characteristic];
     }


 }

//获取的charateristic的值
-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{
    //打印出characteristic的UUID和值
    //!注意，value的类型是NSData，具体开发时，会根据外设协议制定的方式去解析数据
    NSLog(@"characteristic uuid:%@  value:%@",characteristic.UUID,characteristic.value);

}

//搜索到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);
    }

}
//获取到Descriptors的值
-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForDescriptor:(CBDescriptor *)descriptor error:(NSError *)error{
    //打印出DescriptorsUUID 和value
    //这个descriptor都是对于characteristic的描述，一般都是字符串，所以这里我们转换成字符串去解析
    NSLog(@"characteristic uuid:%@  value:%@",[NSString stringWithFormat:@"%@",descriptor.UUID],descriptor.value);
}   

7、把数据写到Characteristic中

//写数据
-(void)writeCharacteristic:(CBPeripheral *)peripheral
            characteristic:(CBCharacteristic *)characteristic
                     value:(NSData *)value{

    //打印出 characteristic 的权限，可以看到有很多种，这是一个NS_OPTIONS，就是可以同时用于好几个值，常见的有read，write，notify，indicate，知知道这几个基本就够用了，前连个是读写权限，后两个都是通知，两种不同的通知方式。
    /*
     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的权限才可以写
    if(characteristic.properties & CBCharacteristicPropertyWrite){
        /*
            最好一个type参数可以为CBCharacteristicWriteWithResponse或type:CBCharacteristicWriteWithResponse,区别是是否会有反馈
        */
        [peripheral writeValue:value forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];
    }else{
        NSLog(@"该字段不可写！");
    }


}

8、订阅Characteristic的通知
一般在discoverCharacteristic的代理中，发现了类型是notify的characteristic，直接就可以订阅了

    //设置通知
-(void)notifyCharacteristic:(CBPeripheral *)peripheral
            characteristic:(CBCharacteristic *)characteristic{
    //设置通知，数据通知会进入：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、断开连接(disconnect)

    //停止扫描并断开连接
-(void)disconnectPeripheral:(CBCentralManager *)centralManager
                 peripheral:(CBPeripheral *)peripheral{
    //停止扫描
    [centralManager stopScan];
    //断开连接
    [centralManager cancelPeripheralConnection:peripheral];
}

iOS中蓝牙模块OTA升级（YModem协议）

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