CoreBluetooth For Central (8)
前言
從2012年接觸CoreBluetooth至今也蠻長一段時間，不過還是純研究，也沒寫出相關的APP。不過，真正理解BLE溝通是在接觸TI CC2540並撰寫相關的程式，回過頭來又再看看CoreBluetooth整個流程與操作其實已經非常完整也較穩定，未來或許會有幾篇CC2540或BLE的相關心得說明。
RSSI
RSSI是Received Signal Strength Indication的縮寫，也就代表接收的訊號深度(強度)，訊號愈好代表連線品質愈好，它的單位是以負值的dBm表示，RSSI愈接近0連線品質愈好，所以-50dBm訊號會比-89dBm來的好。
這篇所要介紹的是如何即時讀取連線中Peripheral的RSSI值，使用方式很簡單，但要配合ReadRSSI與Delegate。
ReadRSSI
每個Pheripheral都會有method ReadRSSI，利用此方式來觸發讀取RSSI的事件後再引發Delegate，當你連線成功後就能執行
[peripheral readRSSI];
告知要進行讀取目前Peripheral的RSSI值，此時會引發Delegate：
iOS 7
- (void)peripheralDidUpdateRSSI:(CBPeripheral *)peripheral error:(NSError *)error {
NSLog(@"name: %@ RSSI:%@",peripheral.name,peripheral.RSSI);
}
iOS 8 以上
因iOS 8後棄用peripheral中的RSSI method，所以delegate直接回傳該peripheral RSSI值
- (void)peripheral:(CBPeripheral *)peripheral didReadRSSI:(NSNumber *)RSSI error:(nullable NSError *)error {
NSLog(@"name: %@ RSSI:%@",peripheral.name,RSSI);
}
BluetoothLE-ReadRSSI
承CoreBluetooth For Central (7)中的範例BluetoothLE-Interact，將它另存成BluetoothLE-ReadRSSI，並修改內容增加讀取RSSI的功能，RSSI的更新在iOS中最好以超過2秒為單位來執行Timer，在此設定為2秒一次。
設定2秒timeout執行程式
範例中在連線完成後會將peripheral相應存至connectPeripheral變數：
- (void)execReadRSSI:(NSTimer *)timer
{
[connectPeripheral readRSSI];
}
連線時啟動Timer
避免重覆執行，執行前先將Timer停止
-(void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral {
:
:
:
:
//增加設定定時的程式碼
//initial timer
[_readRSSITimer invalidate];
_readRSSITimer = [NSTimer scheduledTimerWithTimeInterval:2.0f target:self selector:@selector(execReadRSSI:) userInfo:nil repeats:YES];
NSLog(@"readRSSI Timer start");
}
斷線停止Timer
斷線後會引發didDisconnectPeripheral，所以利用此方式將計時器順便停止：
-(void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error {
NSLog(@"%@",@"disconnect-2");
[_readRSSITimer invalidate];
}
執行結果
此次要連接的依然是Polar H7心跳表示範，連線成功後按下Scan and Connect後會自行找到周邊後自行連線。
連線成功後就能在Log中看到RSSI訊號值，內容像：
2015-11-18 09:32:59.979 BluetoothLE-ReadRSSI[2596:1682965] name: Polar H7 000607 RSSI:-70
以下為整個連線過程及印出RSSI值的過程：
2015-11-18 09:32:56.565 BluetoothLE-ReadRSSI[2596:1682965] UpdateState:PoweredOn
2015-11-18 09:32:57.868 BluetoothLE-ReadRSSI[2596:1682965] Scan And Connect
2015-11-18 09:32:57.888 BluetoothLE-ReadRSSI[2596:1682965] ---advertisementData--start-
2015-11-18 09:32:57.889 BluetoothLE-ReadRSSI[2596:1682965] peripheral
<CBPeripheral: 0x1563bf30, identifier = 8DC3DD90-0C17-1AB9-90FE-E9130DD07B81, name = Polar H7 000607, state = disconnected>
2015-11-18 09:32:57.889 BluetoothLE-ReadRSSI[2596:1682965] advertisementData
{
kCBAdvDataIsConnectable = 1;
kCBAdvDataLocalName = "Polar H7 000607";
kCBAdvDataManufacturerData = <6b000315 00>;
kCBAdvDataServiceUUIDs = (
"Heart Rate"
);
kCBAdvDataTxPowerLevel = 0;
}
2015-11-18 09:32:57.890 BluetoothLE-ReadRSSI[2596:1682965] RSSI
-65
2015-11-18 09:32:57.890 BluetoothLE-ReadRSSI[2596:1682965] ---advertisementData--end-
2015-11-18 09:32:57.890 BluetoothLE-ReadRSSI[2596:1682965] localName:Polar H7 000607
2015-11-18 09:32:57.890 BluetoothLE-ReadRSSI[2596:1682965] stopScan
2015-11-18 09:32:57.891 BluetoothLE-ReadRSSI[2596:1682965] connect to Polar H7 000607
2015-11-18 09:32:57.975 BluetoothLE-ReadRSSI[2596:1682965] connected
2015-11-18 09:32:57.975 BluetoothLE-ReadRSSI[2596:1682965] Connect To Peripheral with name: Polar H7 000607
with UUID:8DC3DD90-0C17-1AB9-90FE-E9130DD07B81
2015-11-18 09:32:57.975 BluetoothLE-ReadRSSI[2596:1682965] readRSSI Timer start
2015-11-18 09:32:58.271 BluetoothLE-ReadRSSI[2596:1682965] didDiscoverServices:
2015-11-18 09:32:58.271 BluetoothLE-ReadRSSI[2596:1682965] ====Polar H7 000607
2015-11-18 09:32:58.272 BluetoothLE-ReadRSSI[2596:1682965] =========== 4 of service for UUID 8DC3DD90-0C17-1AB9-90FE-E9130DD07B81 ===========
2015-11-18 09:32:58.272 BluetoothLE-ReadRSSI[2596:1682965] Service found with UUID: Heart Rate
2015-11-18 09:32:58.273 BluetoothLE-ReadRSSI[2596:1682965] Service found with UUID: Device Information
2015-11-18 09:32:58.273 BluetoothLE-ReadRSSI[2596:1682965] Service found with UUID: Battery
2015-11-18 09:32:58.274 BluetoothLE-ReadRSSI[2596:1682965] Service found with UUID: 6217FF49-AC7B-547E-EECF-016A06970BA9
2015-11-18 09:32:58.331 BluetoothLE-ReadRSSI[2596:1682965] =========== 2 Characteristics of Heart Rate service
2015-11-18 09:32:58.331 BluetoothLE-ReadRSSI[2596:1682965] 2A37
2015-11-18 09:32:58.332 BluetoothLE-ReadRSSI[2596:1682965] 找到 心跳測量屬性
2015-11-18 09:32:58.332 BluetoothLE-ReadRSSI[2596:1682965] 2A38
2015-11-18 09:32:58.333 BluetoothLE-ReadRSSI[2596:1682965] 找到 心跳測量位置屬性
2015-11-18 09:32:58.333 BluetoothLE-ReadRSSI[2596:1682965] === Finished set notification ===
2015-11-18 09:32:58.570 BluetoothLE-ReadRSSI[2596:1682965] =========== 7 Characteristics of Device Information service
2015-11-18 09:32:58.571 BluetoothLE-ReadRSSI[2596:1682965] System ID
2015-11-18 09:32:58.571 BluetoothLE-ReadRSSI[2596:1682965] Model Number String
2015-11-18 09:32:58.572 BluetoothLE-ReadRSSI[2596:1682965] Serial Number String
2015-11-18 09:32:58.572 BluetoothLE-ReadRSSI[2596:1682965] Firmware Revision String
2015-11-18 09:32:58.572 BluetoothLE-ReadRSSI[2596:1682965] Hardware Revision String
2015-11-18 09:32:58.572 BluetoothLE-ReadRSSI[2596:1682965] Software Revision String
2015-11-18 09:32:58.572 BluetoothLE-ReadRSSI[2596:1682965] Manufacturer Name String
2015-11-18 09:32:58.573 BluetoothLE-ReadRSSI[2596:1682965] === Finished set notification ===
2015-11-18 09:32:58.630 BluetoothLE-ReadRSSI[2596:1682965] =========== 1 Characteristics of Battery service
2015-11-18 09:32:58.631 BluetoothLE-ReadRSSI[2596:1682965] Battery Level
2015-11-18 09:32:58.631 BluetoothLE-ReadRSSI[2596:1682965] === Finished set notification ===
2015-11-18 09:32:58.779 BluetoothLE-ReadRSSI[2596:1682965] =========== 1 Characteristics of 6217FF49-AC7B-547E-EECF-016A06970BA9 service
2015-11-18 09:32:58.780 BluetoothLE-ReadRSSI[2596:1682965] 6217FF4A-B07D-5DEB-261E-2586752D942E
2015-11-18 09:32:58.781 BluetoothLE-ReadRSSI[2596:1682965] === Finished set notification ===
2015-11-18 09:32:58.900 BluetoothLE-ReadRSSI[2596:1682965] 0 bpm
2015-11-18 09:32:58.959 BluetoothLE-ReadRSSI[2596:1682965] 位置: 胸部
2015-11-18 09:32:59.919 BluetoothLE-ReadRSSI[2596:1682965] 89 bpm
2015-11-18 09:32:59.979 BluetoothLE-ReadRSSI[2596:1682965] name: Polar H7 000607 RSSI:-70
2015-11-18 09:33:00.909 BluetoothLE-ReadRSSI[2596:1682965] 89 bpm
2015-11-18 09:33:01.929 BluetoothLE-ReadRSSI[2596:1682965] 92 bpm
2015-11-18 09:33:01.978 BluetoothLE-ReadRSSI[2596:1682965] name: Polar H7 000607 RSSI:-71
2015-11-18 09:33:02.950 BluetoothLE-ReadRSSI[2596:1682965] 96 bpm
2015-11-18 09:33:03.940 BluetoothLE-ReadRSSI[2596:1682965] 97 bpm