I am trying to use serial ports in a universal Windows application. I use the Microsoft Serial Sample application as a template, but I ran into a rather strange problem.
var dis = await DeviceInformation.FindAllAsync(SerialDevice.GetDeviceSelectorFromUsbVidPid(0x04D8, 0x000A)); var sp = await SerialDevice.FromIdAsync(dis[0].Id);
This is a fragment that does not work. It is slightly modified from the original sample when it connects to the first device with a specific vendor. Now, if I take this snippet and put it in a sample Microsoft application, the serial port opens, and everything is fine. However, when I port this code to my own project, it always returns null from the method.
Here is the full MainPage.xaml.cs from the Microsoft sample with my alerts: It works!
// Copyright (c) Microsoft. All rights reserved. using System; using System.Collections.ObjectModel; using System.Diagnostics; using System.Linq; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls; using Windows.Devices.Enumeration; using Windows.Devices.SerialCommunication; using Windows.Storage.Streams; using System.Threading; using System.Threading.Tasks; namespace SerialSample { public sealed partial class MainPage : Page { /// <summary> /// Private variables /// </summary> private SerialDevice serialPort = null; DataWriter dataWriteObject = null; DataReader dataReaderObject = null; private ObservableCollection<DeviceInformation> listOfDevices; private CancellationTokenSource ReadCancellationTokenSource; public MainPage() { this.InitializeComponent(); comPortInput.IsEnabled = false; sendTextButton.IsEnabled = false; listOfDevices = new ObservableCollection<DeviceInformation>(); ListAvailablePorts(); } /// <summary> /// ListAvailablePorts /// - Use SerialDevice.GetDeviceSelector to enumerate all serial devices /// - Attaches the DeviceInformation to the ListBox source so that DeviceIds are displayed /// </summary> private async void ListAvailablePorts() { try { string aqs = SerialDevice.GetDeviceSelector(); var dis = await DeviceInformation.FindAllAsync(SerialDevice.GetDeviceSelectorFromUsbVidPid(0x04D8, 0x000A)); serialPort = await SerialDevice.FromIdAsync(dis[0].Id); status.Text = "Select a device and connect"; for (int i = 0; i < dis.Count; i++) { listOfDevices.Add(dis[i]); } DeviceListSource.Source = listOfDevices; comPortInput.IsEnabled = true; ConnectDevices.SelectedIndex = -1; try { // Disable the 'Connect' button comPortInput.IsEnabled = false; // Configure serial settings 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; // Display configured settings status.Text = "Serial port configured successfully: "; status.Text += serialPort.BaudRate + "-"; status.Text += serialPort.DataBits + "-"; status.Text += serialPort.Parity.ToString() + "-"; status.Text += serialPort.StopBits; // Set the RcvdText field to invoke the TextChanged callback // The callback launches an async Read task to wait for data rcvdText.Text = "Waiting for data..."; // Create cancellation token object to close I/O operations when closing the device ReadCancellationTokenSource = new CancellationTokenSource(); // Enable 'WRITE' button to allow sending data sendTextButton.IsEnabled = true; Listen(); } catch (Exception ex) { status.Text = ex.Message; comPortInput.IsEnabled = true; sendTextButton.IsEnabled = false; } } catch (Exception ex) { status.Text = ex.Message; } } /// <summary> /// comPortInput_Click: Action to take when 'Connect' button is clicked /// - Get the selected device index and use Id to create the SerialDevice object /// - Configure default settings for the serial port /// - Create the ReadCancellationTokenSource token /// - Start listening on the serial port input /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private async void comPortInput_Click(object sender, RoutedEventArgs e) { var selection = ConnectDevices.SelectedItems; if (selection.Count <= 0) { status.Text = "Select a device and connect"; return; } DeviceInformation entry = (DeviceInformation)selection[0]; try { serialPort = await SerialDevice.FromIdAsync(entry.Id); // Disable the 'Connect' button comPortInput.IsEnabled = false; // Configure serial settings 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; // Display configured settings status.Text = "Serial port configured successfully: "; status.Text += serialPort.BaudRate + "-"; status.Text += serialPort.DataBits + "-"; status.Text += serialPort.Parity.ToString() + "-"; status.Text += serialPort.StopBits; // Set the RcvdText field to invoke the TextChanged callback // The callback launches an async Read task to wait for data rcvdText.Text = "Waiting for data..."; // Create cancellation token object to close I/O operations when closing the device ReadCancellationTokenSource = new CancellationTokenSource(); // Enable 'WRITE' button to allow sending data sendTextButton.IsEnabled = true; Listen(); } catch (Exception ex) { status.Text = ex.Message; comPortInput.IsEnabled = true; sendTextButton.IsEnabled = false; } } /// <summary> /// sendTextButton_Click: Action to take when 'WRITE' button is clicked /// - Create a DataWriter object with the OutputStream of the SerialDevice /// - Create an async task that performs the write operation /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private async void sendTextButton_Click(object sender, RoutedEventArgs e) { try { if (serialPort != null) { // Create the DataWriter object and attach to OutputStream dataWriteObject = new DataWriter(serialPort.OutputStream); //Launch the WriteAsync task to perform the write await WriteAsync(); } else { status.Text = "Select a device and connect"; } } catch (Exception ex) { status.Text = "sendTextButton_Click: " + ex.Message; } finally { // Cleanup once complete if (dataWriteObject != null) { dataWriteObject.DetachStream(); dataWriteObject = null; } } } /// <summary> /// WriteAsync: Task that asynchronously writes data from the input text box 'sendText' to the OutputStream /// </summary> /// <returns></returns> private async Task WriteAsync() { Task<UInt32> storeAsyncTask; if (sendText.Text.Length != 0) { // Load the text from the sendText input text box to the dataWriter object dataWriteObject.WriteString(sendText.Text); // Launch an async task to complete the write operation storeAsyncTask = dataWriteObject.StoreAsync().AsTask(); UInt32 bytesWritten = await storeAsyncTask; if (bytesWritten > 0) { status.Text = sendText.Text + ", "; status.Text += "bytes written successfully!"; } sendText.Text = ""; } else { status.Text = "Enter the text you want to write and then click on 'WRITE'"; } } /// <summary> /// - Create a DataReader object /// - Create an async task to read from the SerialDevice InputStream /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private async void Listen() { try { if (serialPort != null) { dataReaderObject = new DataReader(serialPort.InputStream); // keep reading the serial input while (true) { await ReadAsync(ReadCancellationTokenSource.Token); } } } catch (Exception ex) { if (ex.GetType().Name == "TaskCanceledException") { status.Text = "Reading task was cancelled, closing device and cleaning up"; CloseDevice(); } else { status.Text = ex.Message; } } finally { // Cleanup once complete if (dataReaderObject != null) { dataReaderObject.DetachStream(); dataReaderObject = null; } } } /// <summary> /// ReadAsync: Task that waits on data and reads asynchronously from the serial device InputStream /// </summary> /// <param name="cancellationToken"></param> /// <returns></returns> private async Task ReadAsync(CancellationToken cancellationToken) { Task<UInt32> loadAsyncTask; uint ReadBufferLength = 1024; // If task cancellation was requested, comply cancellationToken.ThrowIfCancellationRequested(); // Set InputStreamOptions to complete the asynchronous read operation when one or more bytes is available dataReaderObject.InputStreamOptions = InputStreamOptions.Partial; // Create a task object to wait for data on the serialPort.InputStream loadAsyncTask = dataReaderObject.LoadAsync(ReadBufferLength).AsTask(cancellationToken); // Launch the task and wait UInt32 bytesRead = await loadAsyncTask; if (bytesRead > 0) { rcvdText.Text = dataReaderObject.ReadString(bytesRead); status.Text = "bytes read successfully!"; } } /// <summary> /// CancelReadTask: /// - Uses the ReadCancellationTokenSource to cancel read operations /// </summary> private void CancelReadTask() { if (ReadCancellationTokenSource != null) { if (!ReadCancellationTokenSource.IsCancellationRequested) { ReadCancellationTokenSource.Cancel(); } } } /// <summary> /// CloseDevice: /// - Disposes SerialDevice object /// - Clears the enumerated device Id list /// </summary> private void CloseDevice() { if (serialPort != null) { serialPort.Dispose(); } serialPort = null; comPortInput.IsEnabled = true; sendTextButton.IsEnabled = false; rcvdText.Text = ""; listOfDevices.Clear(); } /// <summary> /// closeDevice_Click: Action to take when 'Disconnect and Refresh List' is clicked on /// - Cancel all read operations /// - Close and dispose the SerialDevice object /// - Enumerate connected devices /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void closeDevice_Click(object sender, RoutedEventArgs e) { try { status.Text = ""; CancelReadTask(); CloseDevice(); ListAvailablePorts(); } catch (Exception ex) { status.Text = ex.Message; } } } }
This next block, if from my code. These first 2 lines in ConnectToSerialPort() are the same as before for testing, however SerialDevice.FromIdAsync(dis[0].id); always null. This does not work!
using System; using System.Collections.Generic; using System.Diagnostics; using System.IO; using System.Linq; using Windows.Devices.Enumeration; using Windows.Devices.SerialCommunication; using Windows.Storage.Streams; using Windows.UI.Xaml.Controls; namespace OpenLab.Kitchen.Receiver { public sealed partial class MainPage : Page { private List<byte> Bytes { get; set; } public MainPage() { this.InitializeComponent(); Bytes = new List<byte>(); ConnectToSerialPort(); } private async void ConnectToSerialPort() { var dis = await DeviceInformation.FindAllAsync(SerialDevice.GetDeviceSelectorFromUsbVidPid(0x04D8, 0x000A)); var sp = await SerialDevice.FromIdAsync(dis[0].Id); Debug.WriteLine(sp.UsbVendorId); DeviceInformationCollection serialDevices; while ((serialDevices = await DeviceInformation.FindAllAsync(SerialDevice.GetDeviceSelectorFromUsbVidPid(0x04D8, 0x000A))).Count < 1) { Debug.WriteLine("Unable to locate..."); } SerialDevice serialPort; while ((serialPort = await SerialDevice.FromIdAsync(serialDevices[0].Id)) == null) { Debug.WriteLine("Failed to open serial port..."); } 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; var dataReader = new DataReader(serialPort.InputStream); var buffer = new byte[1024]; while (true) { var bytesRead = await dataReader.LoadAsync((uint)buffer.Length); dataReader.ReadBytes(buffer); Bytes.AddRange(buffer.Take((int)bytesRead)); byte[] slipPacket; while ((slipPacket = Slip.ExtractSlipPacket(Bytes)) != null) { var waxPacket = WaxPacketConverter.FromBinary(slipPacket, DateTime.Now); if (waxPacket != null) { Debug.WriteLine(waxPacket); } } } } } }
I checked all manifest permissions to match them, and checked things like reference versions of the DLL, and everything looks the same. Things have also been tested, such as starting VS as an administrator, and I don't have both applications at the same time, so I don’t need to keep the port open or anything else ...
Does anyone have any ideas?