1 前言
当前有越来越多的可穿戴设备使用了蓝牙4.0 BLE(Bluetooth Low Energy)。对于iOS开发而言,Apple之前专门推出CoreBluetooth的Framework来支持BLE的开发。对于硬件开发有了解的朋友应该知道,在之前使用低版本的蓝牙的设备,要连接到iOS设备上,需要注册MFI,拥有MFI协议才能进行相应的开发。如果大家关注我之前对LEGO EV3的研究,就可以发现,EV3是使用了蓝牙2.1,因此需要MFI协议来进行开发。
本文将一步一步讲解如何使用CoreBluetooth框架来与各种可穿戴设备进行通信,使用 小米手环 来进行基本的测试。
2 开发环境
1 Macbook Pro Mac OS X 10.10
2 Xcode 6.3.2
3 iPhone 5s v8.1
4 小米手环
3 基本流程
要开发蓝牙,需要对整个通讯过程有个基本了解。这里我摘录一些Apple官方的文档Core Bluetooth Programming Guide的图片来加以说明。这个文档其实对于开发的流程写的是非常的清楚,大家最好可以看一下。
3.1 可穿戴设备与iOS互联方式
从上面这幅图可以看到,我们的iOS设备是Central,用来接收数据和发送命令,而外设比如小米手环是Peripheral,向外传输数据和接收命令。我们要做的就是通过Central来连接Peripheral,然后实现数据的接收和控制指令的发送。在做到这一步之后,再根据具体的硬件,对接收到的数据进行parse解析。
3.2 可穿戴设备蓝牙的数据结构
这里用的是心率设备来做说明,每个外设Peripheral都有对应的服务Service,比如这里是心率Service。一个外设可以有不止一个s、Service。每个service里面可以有多个属性Characteristic,比如这里有两个Characteristic,一个是用来测量心率,一个是用来定位位置。
那么很关键的一点是每个Service,每个Characteristic都是用UUID来确定的。UUID就是每个Service或Characteristic的identifier。
大家可以在iPhone上下载LightBlue这个应用。可以在这里查看一些设备的UUID。
在实际使用中,我们都是要通过UUID来获取数据。这点非常重要。
在CoreBluetooth中,其具体的数据结构图如下:
4 Step-By-Step 上手BLE开发
4.1 Step 1 创建CBCentralManager
从名字上大家可以很清楚的知道,这个类是用来管理BLE的。我们也就是通过这个类来实现连接。
先创建一个:
@property (nonatomic,strong) CBCentralManager *centralManager;dispatch_queue_t centralQueue = dispatch_queue_create("com.manmanlai", DISPATCH_QUEUE_SERIAL); self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:centralQueue];
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然后关键在于CBCentralManagerDelegate的使用。这个之后再讲。
4.2 Step 2 寻找CBPeripheral外设
有了CBCentralManager,接下来就是寻找CBPeripheral外设,方法很简单:
[self.centralManager scanForPeripheralsWithServices:@[] options:nil];
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这里的Service就是对应的UUID,如果为空,这scan所有service。
4.3 Step 3 连接CBPeripheral
在上一步中,如果找到了设备,则CBCentralManager的delegate会调用下面的方法:
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
{NSLog(@"name:%@",peripheral); if (!peripheral || !peripheral.name || ([peripheral.name isEqualToString:@""])) { return; } if (!self.peripheral || (self.peripheral.state == CBPeripheralStateDisconnected)) { self.peripheral = peripheral; self.peripheral.delegate = self; NSLog(@"connect peripheral"); [self.centralManager connectPeripheral:peripheral options:nil]; } }
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我们在这里创建了一个CBPeripheral的对象,然后直接连接
CBPeripheral的对象也需要设置delegate.
4.4 Step 4 寻找Service
如果Peripheral连接成功的话,就会调用delegate的方法:
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{if (!peripheral) {return;}[self.centralManager stopScan]; NSLog(@"peripheral did connect"); [self.peripheral discoverServices:nil]; }
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我们这里先停止Scan,然后让Peripheral外设寻找其Service。
4.5 Step 5 寻找Characteristic
找到Service后会调用下面的方法:
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{NSArray *services = nil;if (peripheral != self.peripheral) { NSLog(@"Wrong Peripheral.\n"); return ; } if (error != nil) { NSLog(@"Error %@\n", error); return ; } services = [peripheral services]; if (!services || ![services count]) { NSLog(@"No Services"); return ; } for (CBService *service in services) { NSLog(@"service:%@",service.UUID); [peripheral discoverCharacteristics:nil forService:service]; } }
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我们根据找到的service寻找其对应的Characteristic。
4.6 Step 6 找到Characteristic后读取数据
找到Characteristic后会调用下面的delegate方法:
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
{NSLog(@"characteristics:%@",[service characteristics]);NSArray *characteristics = [service characteristics]; if (peripheral != self.peripheral) { NSLog(@"Wrong Peripheral.\n"); return ; } if (error != nil) { NSLog(@"Error %@\n", error); return ; } self.characteristic = [characteristics firstObject]; //[self.peripheral readValueForCharacteristic:self.characteristic]; [self.peripheral setNotifyValue:YES forCharacteristic:self.characteristic];
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这里我们可以使用readValueForCharacteristic:来读取数据。如果数据是不断更新的,则可以使用setNotifyValue:forCharacteristic:来实现只要有新数据,就获取。
4.7 Step 7 处理数据
读到数据后会调用delegate方法:
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{NSData *data = characteristic.value;// Parse data ...}
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4.8 Step 8 向设备写数据
这个很简单,只要使用:
[self.peripheral writeValue:data forCharacteristic:self.characteristic type:CBCharacteristicWriteWithResponse];
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data是NSData类型。
5 实验
使用小米手环实验,得到如下结果:
2015-06-10 16:52:31.607 KetherDemo[13786:1792995] scaning device 2015-06-10 16:52:33.474 KetherDemo[13786:1793032] name:<CBPeripheral: 0x1700e4380, identifier = 6FF833E3-93C1-28C6-CBC0-74A706AAAE31, name = LS_SCA16, state = disconnected> 2015-06-10 16:52:33.475 KetherDemo[13786:1793032] connect peripheral 2015-06-10 16:52:37.538 KetherDemo[13786:1793031] peripheral did connect 2015-06-10 16:52:37.984 KetherDemo[13786:1793031] service:FEE7 2015-06-10 16:52:37.985 KetherDemo[13786:1793031] service:Device Information 2015-06-10 16:52:38.099 KetherDemo[13786:1793032] characteristics:( "<CBCharacteristic: 0x17409c250, UUID = FEC8, properties = 0x20, value = (null), notifying = NO>", "<CBCharacteristic: 0x17409c200, UUID = FEC7, properties = 0x8, value = (null), notifying = NO>" ) 2015-06-10 16:52:38.100 KetherDemo[13786:1793032] Kether did connect 2015-06-10 16:52:38.101 KetherDemo[13786:1793032] Kether did connect 2015-06-10 16:52:38.280 KetherDemo[13786:1793031] characteristics:( "<CBCharacteristic: 0x17009f270, UUID = Manufacturer Name String, properties = 0x2, value = (null), notifying = NO>", "<CBCharacteristic: 0x17009f2c0, UUID = Model Number String, properties = 0x2, value = (null), notifying = NO>", "<CBCharacteristic: 0x17009f310, UUID = Serial Number String, properties = 0x2, value = (null), notifying = NO>", "<CBCharacteristic: 0x17009eb90, UUID = Hardware Revision String, properties = 0x2, value = (null), notifying = NO>", "<CBCharacteristic: 0x17009f0e0, UUID = Firmware Revision String, properties = 0x2, value = (null), notifyi`` = NO>",
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6 小结
通过上面的方法,我们就可以轻松的对BLE进行开发。实际上比想象的要简单。