1、创建一个CBCentralManager实例来进行蓝牙管理；2、搜索扫描外围设备；3、连接外围设备；4、获得外围设备的服务；5、获得服务的特征；6、从外围设备读取数据；7、给外围设备发送（写入）数据。

#import <CoreBluetooth/CoreBluetooth.h>

self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];

/***  --  初始化成功自动调用*  --  必须实现的代理，用来返回创建的centralManager的状态。*  --  注意：必须确认当前是CBCentralManagerStatePoweredOn状态才可以调用扫描外设的方法：scanForPeripheralsWithServices*/
- (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。/*-- 两个参数为Nil表示默认扫描所有可见蓝牙设备。-- 注意：第一个参数是用来扫描有指定服务的外设。然后有些外设的服务是相同的，比如都有FFF5服务，那么都会发现；而有些外设的服务是不可见的，就会扫描不到设备。-- 成功扫描到外设后调用didDiscoverPeripheral*/[self.centralManager scanForPeripheralsWithServices:nil options:nil];}break;default:break;}
}

#pragma mark 发现外设
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *,id> *)advertisementData RSSI:(NSNumber *)RSSI{NSLog(@"Find device:%@", [peripheral name]);if (![_deviceDic objectForKey:[peripheral name]]) {NSLog(@"Find device:%@", [peripheral name]);if (peripheral!=nil) {if ([peripheral name]!=nil) {if ([[peripheral name] hasPrefix:@"根据设备名过滤"]) {[_deviceDic setObject:peripheral forKey:[peripheral name]];// 停止扫描, 看需求决定要不要加
//                    [_centralManager stopScan];// 将设备信息传到外面的页面(VC), 构成扫描到的设备列表if ([self.delegate respondsToSelector:@selector(dataWithBluetoothDic:)]) {[self.delegate dataWithBluetoothDic:_deviceDic];}}}}}
}

// 连接设备(.h中声明出去的接口, 一般在点击设备列表连接时调用)
- (void)connectDeviceWithPeripheral:(CBPeripheral *)peripheral
{[self.centralManager connectPeripheral:peripheral options:nil];
}

#pragma mark 连接外设--成功
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral{//连接成功后停止扫描，节省内存
    [central stopScan];peripheral.delegate = self;self.peripheral = peripheral;//4.扫描外设的服务/**--     外设的服务、特征、描述等方法是CBPeripheralDelegate的内容，所以要先设置代理peripheral.delegate = self--     参数表示你关心的服务的UUID，比如我关心的是"FFE0",参数就可以为@[[CBUUID UUIDWithString:@"FFE0"]].那么didDiscoverServices方法回调内容就只有这两个UUID的服务，不会有其他多余的内容，提高效率。nil表示扫描所有服务--     成功发现服务，回调didDiscoverServices*/[peripheral discoverServices:@[[CBUUID UUIDWithString:@"你要用的服务UUID"]]];if ([self.delegate respondsToSelector:@selector(didConnectBle)]) {// 已经连接[self.delegate didConnectBle];}
}

#pragma mark 连接外设——失败
- (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{NSLog(@"%@", error);
}

#pragma mark 取消与外设的连接回调
- (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{NSLog(@"%@", peripheral);
}

#pragma mark 发现服务回调
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{//NSLog(@"didDiscoverServices,Error:%@",error);CBService * __nullable findService = nil;// 遍历服务for (CBService *service in peripheral.services){//NSLog(@"UUID:%@",service.UUID);if ([[service UUID] isEqual:[CBUUID UUIDWithString:@"你要用的服务UUID"]]){findService = service;}}NSLog(@"Find Service:%@",findService);if (findService)[peripheral discoverCharacteristics:NULL forService:findService];
}

#pragma mark 发现特征回调
/**--  发现特征后，可以根据特征的properties进行：读readValueForCharacteristic、写writeValue、订阅通知setNotifyValue、扫描特征的描述discoverDescriptorsForCharacteristic。**/
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{for (CBCharacteristic *characteristic in service.characteristics) {if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"你要用的特征UUID"]]) {/**-- 读取成功回调didUpdateValueForCharacteristic*/self.characteristic = characteristic;// 接收一次(是读一次信息还是数据经常变实时接收视情况而定, 再决定使用哪个)
//            [peripheral readValueForCharacteristic:characteristic];// 订阅, 实时接收
            [peripheral setNotifyValue:YES forCharacteristic:characteristic];// 发送下行指令(发送一条)NSData *data = [@"硬件工程师给我的指令, 发送给蓝牙该指令, 蓝牙会给我返回一条数据" dataUsingEncoding:NSUTF8StringEncoding];// 将指令写入蓝牙
                [self.peripheral writeValue:data forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];}/**-- 当发现characteristic有descriptor,回调didDiscoverDescriptorsForCharacteristic*/[peripheral discoverDescriptorsForCharacteristic:characteristic];}
}

#pragma mark - 获取值
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{// characteristic.value就是蓝牙给我们的值(我这里是json格式字符串)NSData *jsonData = [characteristic.value dataUsingEncoding:NSUTF8StringEncoding];NSDictionary *dataDic = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:nil];// 将字典传出去就可以使用了
}#pragma mark - 中心读取外设实时数据
- (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{if (characteristic.isNotifying) {[peripheral readValueForCharacteristic:characteristic];} else { NSLog(@"Notification stopped on %@.  Disconnecting", characteristic);NSLog(@"%@", characteristic);[self.centralManager cancelPeripheralConnection:peripheral];}
}

// 上文中发现特征之后, 发送下行指令的时候其实就是向蓝牙中写入数据
// 例:
// 发送检查蓝牙命令
- (void)writeCheckBleWithBle
{_style = 1;// 发送下行指令(发送一条)NSData *data = [@"硬件工程师提供给你的指令, 类似于5E16010203...这种很长一串" dataUsingEncoding:NSUTF8StringEncoding];[self.peripheral writeValue:data forCharacteristic:self.characteristic type:CBCharacteristicWriteWithResponse];
}

#pragma mark 数据写入成功回调
- (void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{NSLog(@"写入成功");if ([self.delegate respondsToSelector:@selector(didWriteSucessWithStyle:)]) {[self.delegate didWriteSucessWithStyle:_style];}
}

// 扫描设备
- (void)scanDevice
{if (_centralManager == nil) {self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];[_deviceDic removeAllObjects];}
}

#pragma mark - 断开连接
- (void)disConnectPeripheral{/**-- 断开连接后回调didDisconnectPeripheral-- 注意断开后如果要重新扫描这个外设，需要重新调用[self.centralManager scanForPeripheralsWithServices:nil options:nil];*/[self.centralManager cancelPeripheralConnection:self.peripheral];
}

#pragma mark - 停止扫描外设
- (void)stopScanPeripheral{[self.centralManager stopScan];
}