SerialDevice.FromIdAsync() returns 空

Question

我在尝试通过串口 (usb) 将我的 raspberry pi 连接到我的 Arduino Uno 时遇到了一个非常奇怪的问题。

serialPort = await SerialDevice.FromIdAsync(myDevices[0].Id);

始终returns 为空。我尝试了很多东西，直到我把它放在一个循环中，然后它第二次工作，它才会成功。所以我删除了循环并将其运行 2 次。

这是我的输出

begintest
testrange
\?\USB#VID_2341&PID_0001#55639313633351210252#{86e0d1e0-8089-11d0-9ce4-08003e301f73}
test1
null
begintest
ok
ok2
debugtest2
gelukt
Opened device for communication.
test
test2

这是我的代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Http;
using Windows.ApplicationModel.Background;
using Windows.Devices.Enumeration;
using Windows.Devices.SerialCommunication;
using System.Diagnostics;

namespace BackgroundApplication2
{
    public sealed class StartupTask : IBackgroundTask
    {
        private SerialDevice serialPort = null;
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            FindDevice();
            Debug.WriteLine("test1");

            if (serialPort == null)
            {
                Debug.WriteLine("null");
            }
            FindDevice();
        }


        private async void FindDevice()
        {
            Debug.WriteLine("begintest");
            UInt16 vid = 0x2341;
            UInt16 pid = 0x0001;

            string aqs = SerialDevice.GetDeviceSelectorFromUsbVidPid(vid, pid);

            var myDevices = await DeviceInformation.FindAllAsync(aqs);

            if (myDevices.Count == 0)
            {
                Debug.WriteLine("Device not found!");
                return;
            }

            try
            {
                Debug.WriteLine("testrange");
                Debug.WriteLine(myDevices[0].Id);
                serialPort = await SerialDevice.FromIdAsync(myDevices[0].Id);
                if (serialPort == null)
                {
                    Debug.WriteLine("null2");
                    return;
                }
                Debug.WriteLine("ok");
                serialPort.WriteTimeout = TimeSpan.FromMilliseconds(1000);
                serialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
                serialPort.BaudRate = 9600;
                serialPort.Parity = SerialParity.None;
                serialPort.StopBits = SerialStopBitCount.One;
                serialPort.DataBits = 8;
                serialPort.Handshake = SerialHandshake.None;
                Debug.WriteLine("ok2");
                /*String debugtest = "Serial port configured successfully: ";
                debugtest += serialPort.BaudRate + "-";
                debugtest += serialPort.DataBits + "-";
                debugtest += serialPort.Parity.ToString() + "-";
                debugtest += serialPort.StopBits;
                debugtest += (DeviceInformation)myDevices[0];

                Debug.WriteLine("debugtest1");
                Debug.WriteLine(debugtest);*/
                Debug.WriteLine("debugtest2");
                Listen();
            }
            catch (Exception exception)
            {
                Debug.WriteLine(exception.Message.ToString());
                Debug.WriteLine("error");
            }
            finally
            {
                Debug.WriteLine("Opened device for communication.");
            }
            Debug.WriteLine("test2");
        }
        private async void Listen()
        {
            Debug.WriteLine("gelukt");
        }
    }
}

由于某种原因，这部分卡住了。它就停在那里...

String debugtest = "Serial port configured successfully: ";
debugtest += serialPort.BaudRate + "-";
debugtest += serialPort.DataBits + "-";
debugtest += serialPort.Parity.ToString() + "-";
debugtest += serialPort.StopBits;
debugtest += (DeviceInformation)myDevices[0];

Debug.WriteLine("debugtest1");
Debug.WriteLine(debugtest);

这是输出：

begintest
testrange
\?\USB#VID_2341&PID_0001#55639313633351210252#{86e0d1e0-8089-11d0-9ce4-08003e301f73}
test1
null
begintest
ok
ok2
The thread 0x508 has exited with code 0 (0x0).
The program '[2308] serialsample.exe' has exited with code -1 (0xffffffff).

还有我的最后一个问题，为什么它会自动停止运行ning？我的调试总是以此（或上面看到的代码 -1）退出：

The program '[240] backgroundTaskHost.exe' has exited with code 1 (0x1).

抱歉，如果我的代码中到处都是荷兰语单词。

Answer 1

您使用 IBackgroundTask 不正确，您必须注册您的延期并在完成时通知。这是通过将 async void 函数更改为 async task 并使 Run 成为 async void

来完成的

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Http;
using Windows.ApplicationModel.Background;
using Windows.Devices.Enumeration;
using Windows.Devices.SerialCommunication;
using System.Diagnostics;
using System.Threading.Tasks;

namespace BackgroundApplication2
{
    public sealed class StartupTask : IBackgroundTask
    {
        private SerialDevice serialPort = null;
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            //This tells IBackgroundTask you will be doing some extra work in the background and it should not shut down.
            var deferral = taskInstance.GetDeferral();
            try
            {
                await FindDevice();
                Debug.WriteLine("test1");

                if (serialPort == null)
                {
                    Debug.WriteLine("null");
                }
                await FindDevice();
            }
            finally
            {
                //This tells IBackgroundTask that you are done with the last await.
                deferral.Complete();
            }
        }


        private async Task FindDevice()
        {
            Debug.WriteLine("begintest");
            UInt16 vid = 0x2341;
            UInt16 pid = 0x0001;

            string aqs = SerialDevice.GetDeviceSelectorFromUsbVidPid(vid, pid);

            var myDevices = await DeviceInformation.FindAllAsync(aqs);

            if (myDevices.Count == 0)
            {
                Debug.WriteLine("Device not found!");
                return;
            }

            try
            {
                Debug.WriteLine("testrange");
                Debug.WriteLine(myDevices[0].Id);
                serialPort = await SerialDevice.FromIdAsync(myDevices[0].Id);
                if (serialPort == null)
                {
                    Debug.WriteLine("null2");
                    return;
                }
                Debug.WriteLine("ok");
                serialPort.WriteTimeout = TimeSpan.FromMilliseconds(1000);
                serialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
                serialPort.BaudRate = 9600;
                serialPort.Parity = SerialParity.None;
                serialPort.StopBits = SerialStopBitCount.One;
                serialPort.DataBits = 8;
                serialPort.Handshake = SerialHandshake.None;
                Debug.WriteLine("ok2");
                /*String debugtest = "Serial port configured successfully: ";
                debugtest += serialPort.BaudRate + "-";
                debugtest += serialPort.DataBits + "-";
                debugtest += serialPort.Parity.ToString() + "-";
                debugtest += serialPort.StopBits;
                debugtest += (DeviceInformation)myDevices[0];

                Debug.WriteLine("debugtest1");
                Debug.WriteLine(debugtest);*/
                Debug.WriteLine("debugtest2");
                await Listen();
            }
            catch (Exception exception)
            {
                Debug.WriteLine(exception.Message.ToString());
                Debug.WriteLine("error");
            }
            finally
            {
                Debug.WriteLine("Opened device for communication.");
            }
            Debug.WriteLine("test2");
        }
        private async Task Listen()
        {
            Debug.WriteLine("gelukt");
        }
    }
}

SerialDevice.FromIdAsync() returns 空

SerialDevice.FromIdAsync() returns null

c#

serial-port

uwp

raspberry-pi3

windows-iot-core-10