iOS藍牙4.0協議簡單介紹

時間  2019-11-21
標籤 ios 藍牙 4.0 協議 簡單 介紹 欄目 iOS 简体版
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iOS開發藍牙4.0的框架是CoreBluetooth，本文主要介紹CoreBluetooth的使用，關於本文中的代碼片斷大多來自github上的一個demo，地址是myz1104/Bluetooth。
在CoreBluetooth中有兩個主要的部分,Central和Peripheral，有一點相似Client Server。CBPeripheralManager 做爲周邊設備是服務器。CBCentralManager做爲中心設備是客戶端。全部可用的iOS設備能夠做爲周邊（Peripheral）也能夠做爲中央（Central），但不能夠同時既是周邊也是中央。
git

通常手機是客戶端， 設備（好比手環）是服務器，由於是手機去鏈接手環這個服務器。周邊（Peripheral）是生成或者保存了數據的設備，中央（Central）是使用這些數據的設備。你能夠認爲周邊是一個廣播數據的設備，他廣播到外部世界說他這兒有數據，而且也說明了能提供的服務。另外一邊，中央開始掃描附近有沒有服務，若是中央發現了想要的服務，而後中央就會請求鏈接周邊，一旦鏈接創建成功，兩個設備之間就開始交換傳輸數據了。
除了中央和周邊，咱們還要考慮他倆交換的數據結構。這些數據在服務中被結構化，每一個服務由不一樣的特徵（Characteristics）組成，特徵是包含一個單一邏輯值的屬性類型。github

Peripheral的實現步驟

首先是建立一個周邊數組

_peripheralManager = [[CBPeripheralManager alloc]initWithDelegate:self queue:nil];

接下來它就會響應代理的peripheralManagerDidUpdateState方法，能夠得到peripheral的狀態等信息，服務器

- (void)peripheralManagerDidUpdateState:(CBPeripheralManager *)peripheral
{
    switch (peripheral.state)
    {
        case CBPeripheralManagerStatePoweredOn:
        {
            [self setupService];
        }
            break;
            
        default:
        {
            NSLog(@"Peripheral Manager did change state");
        }
            break;
    }
}

當發現周邊設備的藍牙是能夠的時候，這就須要去準備你須要廣播給其餘中央設備的服務和特徵了，這裏經過調用setupService方法來實現。
每個服務和特徵都須要用一個UUID（unique identifier）去標識，UUID是一個16bit或者128bit的值。若是你要建立你的中央-周邊App，你須要建立你本身的128bit的UUID。你必需要肯定你本身的UUID不能和其餘已經存在的服務衝突。若是你正要建立一個本身的設備，須要實現標準委員會需求的UUID；若是你只是建立一箇中央-周邊App，我建議你打開Mac OS X的Terminal.app，用uuidgen命令生成一個128bit的UUID。你應該用該命令兩次，生成兩個UUID，一個是給服務用的，一個是給特徵用的。而後，你須要添加他們到中央和周邊App中。如今，在view controller的實現以前，咱們添加如下的代碼：數據結構

static NSString * const kServiceUUID = @"1C85D7B7-17FA-4362-82CF-85DD0B76A9A5";
static NSString * const kCharacteristicUUID = @"7E887E40-95DE-40D6-9AA0-36EDE2BAE253";

下面就是setupService方法app

- (void)setupService
{
    CBUUID *characteristicUUID = [CBUUID UUIDWithString:kCharacteristicUUID];
    
    self.customCharacteristic = [[CBMutableCharacteristic alloc] initWithType:characteristicUUID properties:CBCharacteristicPropertyNotify value:nil permissions:CBAttributePermissionsReadable];
    
    CBUUID *serviceUUID = [CBUUID UUIDWithString:kServiceUUID];
    
    self.customService = [[CBMutableService alloc] initWithType:serviceUUID primary:YES];
    [self.customService setCharacteristics:@[self.customCharacteristic]];
    [self.peripheralManager addService:self.customService];
    
   
}

當調用了CBPeripheralManager的addService方法後，這裏就會響應CBPeripheralManagerDelegate的- (void)peripheralManager:(CBPeripheralManager *)peripheral didAddService:(CBService *)service error:(NSError *)error方法。這個時候就能夠開始廣播咱們剛剛建立的服務了。框架

- (void)peripheralManager:(CBPeripheralManager *)peripheral didAddService:(CBService *)service error:(NSError *)error
{
    if (error == nil)
    {
        [self.peripheralManager startAdvertising:@{ CBAdvertisementDataLocalNameKey : @"ICServer", CBAdvertisementDataServiceUUIDsKey : @[[CBUUID UUIDWithString:kServiceUUID]] }];
    }
}

固然到這裏，你已經作完了peripheralManager的工做了，中央設備已經能夠接受到你的服務了。不過這是靜止的數據，你還能夠調用- (BOOL)updateValue:(NSData *)value forCharacteristic:(CBMutableCharacteristic *)characteristic onSubscribedCentrals:(NSArray *)centrals方法能夠給中央生成動態數據的地方。async

- (void)sendToSubscribers:(NSData *)data {
  if (self.peripheral.state != CBPeripheralManagerStatePoweredOn) {
    LXCBLog(@"sendToSubscribers: peripheral not ready for sending state: %d", self.peripheral.state);
    return;
  }

  BOOL success = [self.peripheral updateValue:data
                            forCharacteristic:self.characteristic
                         onSubscribedCentrals:nil];
  if (!success) {
    LXCBLog(@"Failed to send data, buffering data for retry once ready.");
    self.pendingData = data;
    return;
  }
}

central訂閱了characteristic的值，當更新值的時候peripheral會調用updateValue: forCharacteristic: onSubscribedCentrals:(NSArray*)centrals去爲數組裏面的centrals更新對應characteristic的值，在更新事後peripheral爲每個central走一遍下面的代理方法ide

- (void)peripheralManager:(CBPeripheralManager *)peripheral central:(CBCentral *)central didSubscribeToCharacteristic:(CBCharacteristic *)characteristic

peripheral接受到一個讀或者寫的請求時，會響應如下兩個代理方法ui

- (void)peripheralManager:(CBPeripheralManager *)peripheral didReceiveReadRequest:(CBATTRequest *)request

- (void)peripheralManager:(CBPeripheralManager *)peripheral didReceiveWriteRequests:(NSArray *)requests

那麼如今peripheral就已經建立好了。

建立一箇中央

建立中央而且鏈接周邊
如今，咱們已經有了一個周邊，讓咱們建立咱們的中央。中央就是那個處理周邊發送來的數據的設備。

self.manager = [[CBCentralManager alloc] initWithDelegate:self queue:dispatch_get_main_queue()];

當Central Manager被初始化，咱們要檢查它的狀態，以檢查運行這個App的設備是否是支持BLE。實現CBCentralManagerDelegate的代理方法：

- (void)centralManagerDidUpdateState:(CBCentralManager *)central
{
    switch (central.state)
    {
        case CBCentralManagerStatePoweredOn:
        {
            [self.manager scanForPeripheralsWithServices:@[ [CBUUID UUIDWithString:kServiceUUID]]
                                                 options:@{CBCentralManagerScanOptionAllowDuplicatesKey : @YES }];
        }
            break;
        default:
        {
            NSLog(@"Central Manager did change state");
        }
            break;
    }
}

當app的設備是支持藍牙的時候，須要調用CBCentralManager實例的- (void)scanForPeripheralsWithServices:(NSArray *)serviceUUIDs options:(NSDictionary *)options方法，用來尋找一個指定的服務的peripheral。一旦一個周邊在尋找的時候被發現，中央的代理會收到如下回調：

- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
{
    
    NSString *UUID = [peripheral.identifier UUIDString];
    NSString *UUID1 = CFBridgingRelease(CFUUIDCreateString(NULL, peripheral.UUID));
    NSLog(@"----發現外設----%@%@", UUID,UUID1);
    [self.manager stopScan];
    
    if (self.peripheral != peripheral)
    {
        self.peripheral = peripheral;
        NSLog(@"Connecting to peripheral %@", peripheral);
        [self.manager connectPeripheral:peripheral options:nil];
    }
}

這個時候一個附帶着廣播數據和信號質量(RSSI-Received Signal Strength Indicator)的周邊被發現。這是一個很酷的參數，知道了信號質量，你能夠用它去判斷遠近。任何廣播、掃描的響應數據保存在advertisementData 中，能夠經過CBAdvertisementData 來訪問它。
這個時候你用能夠鏈接這個周邊設備了，

[self.manager connectPeripheral:peripheral options:nil];

它會響應下面的代理方法，

- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
    NSLog(@"----成功鏈接外設----");
    [self.peripheral setDelegate:self];
    [self.peripheral discoverServices:@[ [CBUUID UUIDWithString:kServiceUUID]]];
}

訪問周邊的服務
上面的CBCentralManagerDelegate代理會返回CBPeripheral實例，它的- (void)discoverServices:(NSArray *)serviceUUIDs方法就是訪問周邊的服務了，這個方法會響應CBPeripheralDelegate的方法。

- (void)peripheral:(CBPeripheral *)aPeripheral didDiscoverServices:(NSError *)error
{
    NSLog(@"----didDiscoverServices----Error:%@",error);
    if (error)
    {
        NSLog(@"Error discovering service: %@", [error localizedDescription]);
        [self cleanup];
        return;
    }
    
    for (CBService *service in aPeripheral.services)
    {
        NSLog(@"Service found with UUID: %@", service.UUID);
        if ([service.UUID isEqual:[CBUUID UUIDWithString:kServiceUUID]])
        {
            [self.peripheral discoverCharacteristics:@[[CBUUID UUIDWithString:kCharacteristicUUID],[CBUUID UUIDWithString:kWrriteCharacteristicUUID]] forService:service];
        }
    }
}

在上面的方法中若是沒有error，能夠調用discoverCharacteristics方法請求周邊去尋找它的服務所列出的特徵，它會響應下面的方法

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
{
    if (error)
    {
        NSLog(@"Error discovering characteristic: %@", [error localizedDescription]);
        return;
    }
    if ([service.UUID isEqual:[CBUUID UUIDWithString:kServiceUUID]])
    {
        for (CBCharacteristic *characteristic in service.characteristics)
        {
            NSLog(@"----didDiscoverCharacteristicsForService---%@",characteristic);
            if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kCharacteristicUUID]])
            {
                [peripheral readValueForCharacteristic:characteristic];
                [peripheral setNotifyValue:YES forCharacteristic:characteristic];
            }
            
            if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kWrriteCharacteristicUUID]])
            {
                writeCharacteristic = characteristic;
            }
            
        }
    }
}

這個時候peripheral能夠調用兩個方法，
[peripheral readValueForCharacteristic:characteristic]這個是讀特徵值的，會響應- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error；

[peripheral setNotifyValue:YES forCharacteristic:characteristic];會響應- (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error；

- (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    if (error)
    {
        NSLog(@"Error changing notification state: %@", error.localizedDescription);
    }
    
    // Exits if it's not the transfer characteristic
    if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kCharacteristicUUID]] )
    {
        // Notification has started
        if (characteristic.isNotifying)
        {
            NSLog(@"Notification began on %@", characteristic);
            [peripheral readValueForCharacteristic:characteristic];
        }
        else
        { // Notification has stopped
            // so disconnect from the peripheral
            NSLog(@"Notification stopped on %@.  Disconnecting", characteristic);
            [self.manager cancelPeripheralConnection:self.peripheral];
        }
    }
}

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    NSLog(@"----Value---%@",characteristic.value);
    if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kCharacteristicUUID]])
    {

        if (writeCharacteristic)
        {
            Byte ACkValue[3] = {0};
            ACkValue[0] = 0xe0; ACkValue[1] = 0x00; ACkValue[2] = ACkValue[0] + ACkValue[1];
            NSData *data = [NSData dataWithBytes:&ACkValue length:sizeof(ACkValue)];
            [self.peripheral writeValue:data
                      forCharacteristic:writeCharacteristic
                                   type:CBCharacteristicWriteWithoutResponse];
        }
    }
}

在上面的方法中，- (void)writeValue:(NSData *)data forCharacteristic:(CBCharacteristic *)characteristic type:(CBCharacteristicWriteType)type是一個對周邊設備寫數據的方法，它會響應下面的方法

- (void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    NSLog(@"---didWriteValueForCharacteristic-----");
    if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kWrriteCharacteristicUUID]])
    {
        NSLog(@"----value更新----");

    }
}

這樣，中央設備也實現了讀寫數據的功能了。

另外，github上有一個封裝的第三方開源藍牙框架，地址是kickingvegas/YmsCoreBluetooth

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