UWP应用无法从心率监测器获取数据，收到协议错误

Question

我正在尝试制作一个简单的UWP应用，该应用显示从心率监测器（Wahoo TICKR FIT）读取的值。我能够连接到显示器，但是无法访问HeartRateMeasurement特征的值。 GattReadResult的状态为ProtocolError，值为null。如何修复ProtocolError？

这一切都在使用Visual Studio 2017模板的普通UWP应用程序中完成。然后计划将工作代码转移到HoloLens项目中。

代码如下：

            string btAddr = "F013C3B15603";
            System.UInt64 addrInt = Convert.ToUInt64(btAddr, 16);

            BluetoothLEDevice device = await BluetoothLEDevice.FromBluetoothAddressAsync(addrInt);

            string guidString = "0000180d-0000-1000-8000-00805f9b34fb"; // Armband HeartRate uuid
            Guid guid = new Guid(guidString);
            GattDeviceService gattService = device.GetGattService(guid);

            // Try to access the characteristic we want
            DeviceAccessStatus serviceAccessStatus = await gattService.RequestAccessAsync(); // allowed
            GattOpenStatus openStatus = await gattService.OpenAsync(GattSharingMode.SharedReadAndWrite); // success
            GattCharacteristicsResult results = await gattService.GetCharacteristicsAsync();
            IReadOnlyList<GattCharacteristic> charList = results.Characteristics;
            Debug.WriteLine(charList.Count); // should be 2
            GattCharacteristic heartRateChar = charList[0];
            Debug.WriteLine(heartRateChar.AttributeHandle); // should be 15

            // Try to pull the heart rate data
            GattCommunicationStatus commStatus = await heartRateChar.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify); // This works
            GattReadResult heartRateResult = await heartRateChar.ReadValueAsync(BluetoothCacheMode.Uncached); // Status is ProtocolError (2)

问题最终出现在ReadValueAsync调用中。

Answer 1

迈克·彼得里申科的评论就是解决方案。该特征不可读，我需要为ValueChanged事件创建一个事件处理程序方法，以接收传入的数据。