IAsyncOperation<SerialDevice> FromIdAsync(string deviceId) returns 空

Question

我有 Windows IoT Core 10 17744 运行超过 Raspberry Pi 3.
我尝试使用以下代码从 UWP 应用程序初始化 COM 端口：

string aqs = SerialDevice.GetDeviceSelector();
DeviceInformationCollection devices = await DeviceInformation.FindAllAsync(aqs);
List<DeviceInformation> list = devices.ToList();
DeviceInformation di = list.First();
_serial_port = await SerialDevice.FromIdAsync(di.Id);

我有 di.Id -> \?\ACPI#BCM2836#0#{86e0d1e0-8089-11d0-9ce4-08003e301f73}
di 变量的完整表示如下：

-       di  {Windows.Devices.Enumeration.DeviceInformation} Windows.Devices.Enumeration.DeviceInformation
        EnclosureLocation   null    Windows.Devices.Enumeration.EnclosureLocation
        Id  "\\?\ACPI#BCM2836#0#{86e0d1e0-8089-11d0-9ce4-08003e301f73}"  string
        IsDefault   false   bool
        IsEnabled   true    bool
        Kind    DeviceInterface Windows.Devices.Enumeration.DeviceInformationKind
        Name    "MINWINPC"  string
-       Pairing {Windows.Devices.Enumeration.DeviceInformationPairing}  Windows.Devices.Enumeration.DeviceInformationPairing
        CanPair false   bool
+       Custom  {Windows.Devices.Enumeration.DeviceInformationCustomPairing}    Windows.Devices.Enumeration.DeviceInformationCustomPairing
        IsPaired    false   bool
        ProtectionLevel None    Windows.Devices.Enumeration.DevicePairingProtectionLevel
        Native View To inspect the native object, enable native code debugging. 
+       Properties  {System.__ComObject}    System.Collections.Generic.IReadOnlyDictionary<string, object> {System.__ComObject}
        Native View To inspect the native object, enable native code debugging.

但是在 await 操作后我在 _serial_port.

中有 null

更新

即使我将Raspberry UART接口连接到工作节点也是null:
第 8 个引脚作为 TX 到配对的 RX 线。
第 10 个引脚作为 RX 到配对的 TX 线。

更新

我在清单中有 DeviceCapability：

<DeviceCapability Name="serialcommunication">
  <Device Id="any">
    <Function Type="name:serialPort" />
  </Device>
</DeviceCapability>

Answer 1

您需要在Package.appxmanifest中添加串行设备功能：

<DeviceCapability Name="serialcommunication">
  <Device Id="any">
    <Function Type="name:serialPort" />
  </Device>
</DeviceCapability>

It is null even if I connect Raspberry UART interface to working node: 8th pin as TX to paired RX line. 10th pin as RX to paired TX line.

这不是 SerialDevice.FromIdAsync() 成功所必需的。即使您不连接这些引脚，如果代码和设置正确，SerialDevice.FromIdAsync() 也可以获得有效设备。可以参考Serial UART Sample.

IAsyncOperation<SerialDevice> FromIdAsync(string deviceId) returns 空

IAsyncOperation<SerialDevice> FromIdAsync(string deviceId) returns null

raspberry-pi3

uart

windows-iot-core-10