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iOS 藍牙

編輯:IOS開發綜合

藍牙協議本身經歷了從1.0到4.0的升級演變, 最新的4.0以其低功耗著稱,所以一般也叫BLE(Bluetoothlow energy)。

iOS有兩個框架支持藍牙與外設連接。一個是 ExternalAccessory。從ios3.0就開始支持,也是在iphone4s出來之前用的比較多的一種模式,但是它有個不好的地方,External Accessory需要拿到蘋果公司的MFI認證。

另一個框架則是本文要介紹的CoreBluetooth,在iphone4s開始支持,專門用於與BLE設備通訊(因為它的API都是基於BLE的)。這個不需要MFI,並且現在很多藍牙設備都支持4.0,所以也是在IOS比較推薦的一種開發方法。

CoreBluetooth介紹

CoreBluetooth框架的核心其實是兩個東西,peripheral和central, 可以理解成外設和中心。對應他們分別有一組相關的API和類,如下圖所示:

如果你要編程的設備是central那麼你大部分用到,反之亦然。在我們這個示例中,金融刷卡器是peripheral,我們的iphone手機是central,所以我將大部分使用上圖中左邊部分的類。使用peripheral編程的例子也有很多,比如像用一個ipad和一個iphone通訊,ipad可以認為是central,iphone端是peripheral,這種情況下在iphone端就要使用上圖右邊部分的類來開發了。

服務和特征

有個概念有必要先說明一下。什麼是服務和特征呢(service and characteristic)?

每個藍牙4.0的設備都是通過服務和特征來展示自己的,一個設備必然包含一個或多個服務,每個服務下面又包含若干個特征。特征是與外界交互的最小單位。比如說,一台藍牙4.0設備,用特征A來描述自己的出廠信息,用特征B來與收發數據等。

服務和特征都是用UUID來唯一標識的,UUID的概念如果不清楚請自行google,國際藍牙組織為一些很典型的設備(比如測量心跳和血壓的設備)規定了標准的service UUID(特征的UUID比較多,這裡就不列舉了),如下:

#define      BLE_UUID_ALERT_NOTIFICATION_SERVICE   0x1811  
 #define     BLE_UUID_BATTERY_SERVICE   0x180F  
 #define     BLE_UUID_BLOOD_PRESSURE_SERVICE   0x1810  
 #define     BLE_UUID_CURRENT_TIME_SERVICE   0x1805  
 #define     BLE_UUID_CYCLING_SPEED_AND_CADENCE   0x1816  
 #define     BLE_UUID_DEVICE_INFORMATION_SERVICE   0x180A  
 #define     BLE_UUID_GLUCOSE_SERVICE   0x1808  
 #define     BLE_UUID_HEALTH_THERMOMETER_SERVICE   0x1809  
 #define     BLE_UUID_HEART_RATE_SERVICE   0x180D  
 #define     BLE_UUID_HUMAN_INTERFACE_DEVICE_SERVICE   0x1812  
 #define     BLE_UUID_IMMEDIATE_ALERT_SERVICE   0x1802  
 #define     BLE_UUID_LINK_LOSS_SERVICE   0x1803  
 #define     BLE_UUID_NEXT_DST_CHANGE_SERVICE   0x1807  
 #define     BLE_UUID_PHONE_ALERT_STATUS_SERVICE   0x180E  
 #define     BLE_UUID_REFERENCE_TIME_UPDATE_SERVICE   0x1806  
 #define     BLE_UUID_RUNNING_SPEED_AND_CADENCE   0x1814  
 #define     BLE_UUID_SCAN_PARAMETERS_SERVICE   0x1813  
 #define     BLE_UUID_TX_POWER_SERVICE   0x1804  
 #define     BLE_UUID_CGM_SERVICE   0x181A  

當然還有很多設備並不在這個標准列表裡,比如我用的這個金融刷卡器。藍牙設備硬件廠商通常都會提供他們的設備裡面各個服務(service)和特征(characteristics)的功能,比如哪些是用來交互(讀寫),哪些可獲取模塊信息(只讀)等.

實現細節

作為一個中心要實現完整的通訊,一般要經過這樣幾個步驟:

建立中心角色—掃描外設(discover)—連接外設(connect)—掃描外設中的服務和特征(discover)—與外設做數據交互(explore and interact)—斷開連接(disconnect)。

1建立中心角色

首先在我自己類的頭文件中要包含CoreBluetooth的頭文件,並繼承兩個協議,代碼如下:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
#import   
CBCentralManager *manager;  
manager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];  

2掃描外設(discover)

代碼如下:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
[manager scanForPeripheralsWithServices:nil options:options];

這個參數應該也是可以指定特定的peripheral的UUID,那麼理論上這個central只會discover這個特定的設備,但是我實際測試發現,如果用特定的UUID傳參根本找不到任何設備,我用的代碼如下:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
NSArray *uuidArray = [NSArray arrayWithObjects:[CBUUID UUIDWithString:@"1800"],[CBUUID UUIDWithString:@"180A"],  
[CBUUID UUIDWithString:@"1CB2D155-33A0-EC21-6011-CD4B50710777"],[CBUUID UUIDWithString:@"6765D311-DD4C-9C14-74E1-A431BBFD0652"],nil];  

[manager scanForPeripheralsWithServices:uuidArray options:options];  

目前不清楚原因,懷疑和設備本身在的廣播包有關。

3連接外設(connect)
當掃描到4.0的設備後,系統會通過回調函數告訴我們設備的信息,然後我們就可以連接相應的設備,代碼如下:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI  
{  

    if(![_dicoveredPeripherals containsObject:peripheral])  
        [_dicoveredPeripherals addObject:peripheral];  

    NSLog(@"dicoveredPeripherals:%@", _dicoveredPeripherals);  
}  

//連接指定的設備  
-(BOOL)connect:(CBPeripheral *)peripheral  
{  
    NSLog(@"connect start");  
    _testPeripheral = nil;  

    [manager connectPeripheral:peripheral  
                       options:[NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:CBConnectPeripheralOptionNotifyOnDisconnectionKey]];  

    //開一個定時器監控連接超時的情況  
    connectTimer = [NSTimer scheduledTimerWithTimeInterval:5.0f target:self selector:@selector(connectTimeout:) userInfo:peripheral repeats:NO];  

    return (YES);  
}  

4掃描外設中的服務和特征(discover)
同樣的,當連接成功後,系統會通過回調函數告訴我們,然後我們就在這個回調裡去掃描設備下所有的服務和特征,代碼如下:

[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral  
{  
    [connectTimer invalidate];//停止時鐘  

    NSLog(@"Did connect to peripheral: %@", peripheral);  
    _testPeripheral = peripheral;  

    [peripheral setDelegate:self];  
    [peripheral discoverServices:nil];  


}  

一個設備裡的服務和特征往往比較多,大部分情況下我們只是關心其中幾個,所以一般會在發現服務和特征的回調裡去匹配我們關心那些,比如下面的代碼:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error  
{  


    NSLog(@"didDiscoverServices");  

    if (error)  
    {  
        NSLog(@"Discovered services for %@ with error: %@", peripheral.name, [error localizedDescription]);  

        if ([self.delegate respondsToSelector:@selector(DidNotifyFailConnectService:withPeripheral:error:)])  
            [self.delegate DidNotifyFailConnectService:nil withPeripheral:nil error:nil];  

        return;  
    }  


    for (CBService *service in peripheral.services)  
    {  

        if ([service.UUID isEqual:[CBUUID UUIDWithString:UUIDSTR_ISSC_PROPRIETARY_SERVICE]])  
        {  
            NSLog(@"Service found with UUID: %@", service.UUID);  
            [peripheral discoverCharacteristics:nil forService:service];  
            isVPOS3356 = YES;  
            break;  
        }  


    }  
}  

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error   
{  

    if (error)   
    {  
        NSLog(@"Discovered characteristics for %@ with error: %@", service.UUID, [error localizedDescription]);  

        if ([self.delegate respondsToSelector:@selector(DidNotifyFailConnectChar:withPeripheral:error:)])  
            [self.delegate DidNotifyFailConnectChar:nil withPeripheral:nil error:nil];  

        return;  
    }  


    for (CBCharacteristic *characteristic in service.characteristics)  
    {  
        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:UUIDSTR_ISSC_TRANS_TX]])  
        {  
            NSLog(@"Discovered read characteristics:%@ for service: %@", characteristic.UUID, service.UUID);  

            _readCharacteristic = characteristic;//保存讀的特征  

            if ([self.delegate respondsToSelector:@selector(DidFoundReadChar:)])  
                [self.delegate DidFoundReadChar:characteristic];  

            break;  
        }  
    }  


    for (CBCharacteristic * characteristic in service.characteristics)  
    {  


        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:UUIDSTR_ISSC_TRANS_RX]])  
        {  

            NSLog(@"Discovered write characteristics:%@ for service: %@", characteristic.UUID, service.UUID);  
            _writeCharacteristic = characteristic;//保存寫的特征  

            if ([self.delegate respondsToSelector:@selector(DidFoundWriteChar:)])  
                [self.delegate DidFoundWriteChar:characteristic];  

            break;  


        }  
    }  

    if ([self.delegate respondsToSelector:@selector(DidFoundCharacteristic:withPeripheral:error:)])  
        [self.delegate DidFoundCharacteristic:nil withPeripheral:nil error:nil];  

}  

5與外設做數據交互(explore and interact)

發送數據很簡單,我們可以封裝一個如下的函數:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
//寫數據  
-(void)writeChar:(NSData *)data  
{  
    [_testPeripheral writeValue:data forCharacteristic:_writeCharacteristic type:CBCharacteristicWriteWithResponse];  
}  

_testPeripheral和_writeCharacteristic是前面我們保存的設備對象和可以讀寫的特征。

然後我們可以在外部調用它,比如當然我要觸發刷卡時,先組好數據包,然後調用發送函數:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
-(void)msrRead  
{  

    unsigned char command[512] = {0};  
    unsigned charchar *pTmp;  
    int nSendLen = 0;  
    unsigned char ucCrc[3] = {0};  

    _commandType = COMMAND_MSR_READ;  

    pTmp = command;  


    *pTmp = 0x02;//start  
    pTmp++;  

    *pTmp = 0xc1;//main cmd  
    pTmp++;  

    *pTmp = 0x07;//sub cmd  
    pTmp++;  



    nSendLen = 2;  

    *pTmp = nSendLen/256;  
    pTmp++;  
    *pTmp = nSendLen%256;  
    pTmp++;  

    *pTmp = 0x00;//sub cmd  
    pTmp++;  

    *pTmp = 0x00;//sub cmd  
    pTmp++;  


    Crc16CCITT(command+1,pTmp-command-1,ucCrc);  
    memcpy(pTmp,ucCrc,2);  


    NSData *data = [[NSData alloc] initWithBytes:&command length:9];  
    NSLog(@"send data:%@", data);  
    [g_BLEInstance.recvData setLength:0];  

    [g_BLEInstance writeChar:data];  
}  

比如說,你要交互的特征,它的properties的值是0x10,表示你只能用訂閱的方式來接收數據。我這裡是用訂閱的方式,啟動訂閱的代碼如下:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
//監聽設備  
-(void)startSubscribe  
{  
    [_testPeripheral setNotifyValue:YES forCharacteristic:_readCharacteristic];  
}  

當設備有數據返回時,同樣是通過一個系統回調通知我,如下所示:
[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error  
{  

    if (error)   
    {  
        NSLog(@"Error updating value for characteristic %@ error: %@", characteristic.UUID, [error localizedDescription]);  

        if ([_mainMenuDelegate respondsToSelector:@selector(DidNotifyReadError:)])  
            [_mainMenuDelegate DidNotifyReadError:error];  

        return;  
    }  

    [_recvData appendData:characteristic.value];  


    if ([_recvData length] >= 5)//已收到長度  
    {  
        unsigned charchar *buffer = (unsigned charchar *)[_recvData bytes];  
        int nLen = buffer[3]*256 + buffer[4];  
        if ([_recvData length] == (nLen+3+2+2))  
        {  
            //接收完畢,通知代理做事  
            if ([_mainMenuDelegate respondsToSelector:@selector(DidNotifyReadData)])  
                [_mainMenuDelegate DidNotifyReadData];  

        }  
    }  

}  

6 斷開連接(disconnect)

這個比較簡單,只需要一個API就行了,代碼如下:

[objc] view plain copy 在CODE上查看代碼片派生到我的代碼片
//主動斷開設備  
-(void)disConnect  
{  

    if (_testPeripheral != nil)  
    {  
        NSLog(@"disConnect start");  
        [manager cancelPeripheralConnection:_testPeripheral];  
    }  

} 


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