BLE：如何获得正确的服务 UUID 和特征 UUID？

Question

I am a new in Bluetooth connection and I want to add second device in my iOS project. I already have one device, and the new device is very similar with first one, but little bit deferent. I have one process for the two devices, and I did not change a lot of code, just created all value for the new device. My all devices have different name and identifier, first device is working fine.

For creating UUID values, I used UUID generator ( https://www.guidgenerator.com/online-guid-generator.aspx ).

class BleConstants: NSObject {
let deviceTwoServiceUUID = “59DE3994-6A63-4654-8FF0-F85C5163B2F5”
let deviceTwoFirstCharacteristicUUID = “59DE3994-6A63-4654-8FF0-F85C5163B2F6”
let deviceTwoSecondCharacteristicUUID = “59DE3994-6A63-4654-8FF0-F85C5163B2F7”
let deviceOneServiceUUID = “A6AF4483-E210-457B-B9D6-B8A621513D1D”
let deviceOneFirstCharacteristicUUID = “A6AF4483-E210-457B-B9D6-B8A621513D2D”
let deviceOneSecondCharacteristicUUID = “A6AF4483-E210-457B-B9D6-B8A621513D2D”
}

class BleManager: NSObject, CBCentralManagerDelegate, CBPeripheralDelegate {
@objc private(set) static var sharedInstance = BleManager()
var cbManager : CBCentralManager? = nil
var currentPeripheral : CBPeripheral? = nil
var secondService : CBService? = nil
var firstService : CBService? = nil
var secondFirstCharacteristic : CBCharacteristic!
var secondSecondCharacteristic : CBCharacteristic!
var firstFirstCharacteristic : CBCharacteristic!
var firstSecondCharacteristic : CBCharacteristic!

func initCentralManager() {
    if cbManager == nil {
        cbManager = CBCentralManager(delegate: self, queue: nil, options: [CBCentralManagerOptionRestoreIdentifierKey : “MyApp”, CBCentralManagerOptionShowPowerAlertKey: true])            
    }

func deinitCentralManager() {
    cbManager = nil
}

func isBluetoothAvailable() -> Bool {
    return cbManager?.state == CBManagerState.poweredOn
}

func scan() {
    if (cbManager != nil && (cbManager?.isScanning)!) {
        return
    }
    
    discoveredPeripherals.removeAll()
    
    let serviceUUIDs = [CBUUID(string: BleConstants.deviceTwoServiceUUID), CBUUID(string: BleConstants.deviceOneServiceUUID)]
    
    cbManager?.scanForPeripherals(withServices: serviceUUIDs,
                                  options: [CBCentralManagerScanOptionAllowDuplicatesKey : 1])
}

func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
    if(!discoveredPeripherals.contains(peripheral)) {
        discoveredPeripherals.append(peripheral)
    }
}

func stopScan() {
    if cbManager != nil && (cbManager?.isScanning)! {
        cbManager?.stopScan()
    }
}

func connect(peripheral: CBPeripheral) {
    if cbManager?.state == CBManagerState.poweredOn {
        if currentPeripheral == nil || currentPeripheral?.state != CBPeripheralState.connected {
            cbManager?.connect(peripheral, options: nil)
        } else {
            cbManager?.cancelPeripheralConnection(peripheral)
        }
    }
}

func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
Device.savePeripheralString(peripheral: peripheral.identifier.uuidString)
    AutoConnect.stop()
DeviceUpdate.updateProgress = .None
Device.isDongleConnected = true
currentPeripheral = peripheral
currentPeripheral?.delegate = self
currentPeripheral?.discoverServices(nil)
disableSleep()
}

func disableSleep() {
    UIApplication.shared.isIdleTimerDisabled = true
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
 if error != nil {
        return
    }

    if let services = peripheral.services {

        for service in services {
            if service.uuid.uuidString == BleConstants.deviceTwoServiceUUID {
        Device.dongleType = port.second
                    secondService = service
                peripheral.discoverCharacteristics(nil, for: service)
        }
            if service.uuid.uuidString == BleConstants.deviceOneServiceUUID {
        Device.dongleType = port.first
                firstService = service
                peripheral.discoverCharacteristics(nil, for: service)
            } else {
                Log.bt("didDiscoverServices for peripheral not found \(peripheral.identifier.uuidString)")
            }
        }
    }
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {

    for characteristic in service.characteristics! {
        if characteristic.uuid.uuidString == BleConstants.deviceOneFirstCharacteristicUUID {
     firstCharacteristic = characteristic
        }  
    else if characteristic.uuid.uuidString == BleConstants.deviceOneSecondCharacteristicUUID {
           firstSecondCharacteristic = characteristic
        else if characteristic.uuid.uuidString == BleConstants.deviceTwoFirstCharacteristicUUID {
            secondFirstCharacteristic = characteristic
        } else if characteristic.uuid.uuidString == BleConstants.deviceTwoSecondCharacteristicUUID {
    secondSecondCharacteristic = characteristic
        } else {
            Log.bt("didDiscoverCharacteristics not found \(characteristic.uuid.uuidString)")
        }
    }
    
    if Device.dongleType == .deviceTwo {
         openPortDeviceTwo()
    } else {
        openPortDeviceOne()
    }
}

}

Data from logs:

For first device:

1. isBluetoothAvailable()
2. scan()
3. CentralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String: Any], rssi RSSI: NSNumber) (peripheral <CBPeripheral: 0x267hg5670, identifier = 98HG761CE-56C3-K767-26HJ-E51BA678Gh56, name = DeviceOne, state = disconnected)
4. CentralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String: Any], rssi RSSI: NSNumber)
5. scan()
6. CentralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String: Any], rssi RSSI: NSNumber) (peripheral <CBPeripheral: 0x267hg5670, identifier = FJ1478HJ-EH8J-6709-1FH0-1456HGJ0BC901, name = SecondDevice, state = disconnected>)
7. stopScan()
8. connect(peripheral: CBPeripheral) (currentPeripheral nil, currentPeripheral nil)
9. CentralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral
10. centralManager(_:didConnect:) - didConnectPeripheral FJ1478HJ-EH8J-6709-1FH0-1456HGJ0BC901 Second device
11. savedPeripheralString FJ1478HJ-EH8J-6709-1FH0-1456HGJ0BC901 Second device
12. Bluetooth stop() currentPeripheral Optional(<CBPeripheral: 0x2jk875fe0, identifier = FJ1478HJ-EH8J-6709-1FH0-1456HGJ0BC901, name = SecondDevice, state = connected>)
13. disableSleep()
14. peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?)
15. peripheral(_:didDiscoverServices:) - didDiscoverServices for peripheral FJ1478HJ-EH8J-6709-1FH0-1456HGJ0BC901
16. peripheral(_:didDiscoverServices:) - didDiscoverServices for peripheral.services Optional([<CBService: 0x2jkki2dc0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5>, <CBService: 0xhj67c240, isPrimary = YES, UUID = Device Information>]) [<CBService: 0x5678f2dc0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5>, <CBService: 0x28186c240, isPrimary = YES, UUID = Device Information>], peripheral.services is Optional([<CBService: 0xhjy62dc0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5>, <CBService: 0x2hju7240, isPrimary = YES, UUID = Device Information>])) service.uuid.uuidString is 59DE3994-6A63-4654-8FF0-F85C5163B2F5 and services is [<CBService: 0xhj7892dc0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5>, <CBService: 0xhjk678340, isPrimary = YES, UUID = Device Information>]
17. peripheral(_:didDiscoverServices:) - didDiscoverServices SecondDevice 59DE3994-6A63-4654-8FF0-F85C5163B2F5
18. peripheral(_:didDiscoverServices:) - didDiscoverServices for peripheral not found FJ1478HJ-EH8J-6709-1FH0-1456HGJ0BC901

For second device:

1. isBluetoothAvailable()
2. scan()
3. CentralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String: Any], rssi RSSI: NSNumber) (peripheral <CBPeripheral: 0xh6789a40, identifier = 98HG761CE-56C3-K767-26HJ-E51BA678Gh56, name = DeviceOne, state = disconnected)
4. scan()
5. CentralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String: Any], rssi RSSI: NSNumber) (peripheral <CBPeripheral: 0x678jhs0, identifier = H56KIL35-7835-7JKL-2B11-HJKLIYTAA400, name = ThirdDevice, state = disconnected)
6. CentralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String: Any], rssi RSSI: NSNumber)
7. stopScan()
8. connect(peripheral: CBPeripheral) currentPeripheral nil, currentPeripheral nil
9. CentralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral
10. centralManager(_:didConnect:) - didConnectPeripheral H56KIL35-7835-7JKL-2B11-HJKLIYTAA400
11. savedPeripheralString H56KIL35-7835-7JKL-2B11-HJKLIYTAA400
12. Bluetooth stop() - currentPeripheral Optional(<CBPeripheral: 0x78jkl680, identifier = H56KIL35-7835-7JKL-2B11-HJKLIYTAA400, name = ThirdDevice, state = connected>)
13. disableSleep()
14. peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?)
15. peripheral(_:didDiscoverServices:) - didDiscoverServices for peripheral H56KIL35-7835-7JKL-2B11-HJKLIYTAA400
16. **peripheral(_:didDiscoverServices:) - didDiscoverServices for peripheral.services Optional([<CBService: 0xlki8901c0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5 - same like for secondDevice>, <CBService: 0x281111180, isPrimary = YES, UUID = Device Information>]) services is [<CBService: 0x2827444c0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5 - same like for secondDevice>, <CBService: 0x282744580, isPrimary = YES, UUID = Device Information>], peripheral.services is Optional([<CBService: 0xlki8901c0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5 - same like for secondDevice>, <CBService: 0x281111180, isPrimary = YES, UUID = Device Information>])) service.uuid.uuidString is 59DE3994-6A63-4654-8FF0-F85C5163B2F5 - same like for secondDeviceand services is [<CBService: 0x27893kdc0, isPrimary = YES, UUID = 59DE3994-6A63-4654-8FF0-F85C5163B2F5 - same like for secondDevice>, <CBService: 0x679kh8580, isPrimary = YES, UUID = Device Information>]
17. peripheral(_:didDiscoverServices:) - didDiscoverServices ThirdDevice 59DE3994-6A63-4654-8FF0-F85C5163B2F5 - same like for secondDevice
18. peripheral(_:didDiscoverServices:) - didDiscoverServices for peripheral not found H56KIL35-7835-7JKL-2B11-HJKLIYTAA400**

Based on logs information for second device in 16th step app connected to my first service UUID and first characteristic UUID, that is wrong!

Do you have idea, Did I create UUIDs correct?

PS: Android app works fine with both devices.

Thanks a lot!

Answer 1

Receiving the same service and characteristic UUID for multiple BLE devices is perfectly normal and only means that all the devices offer exactly the same service.

For example : If you have two devices which measure the heart rate of a person, eg a smartwatch, both devices might offer the heart rate service with the same UUID.

If you want to differentiate between the device you can use the identifier which you received in step 3 of your provided log.