UART Raspberry pi IoT (Windows IoT Core)

Question

UART data transmission Raspberry pi UART (RX TX) Arduino I know should avoid async void. They are only used for event handling. For other methods return Task. async and await Where can there be a mistake? Why the data does not come?

Who knows the link where it is shown how to receive data on the UART?

using Windows.Storage.Streams;
using Windows.Devices.Enumeration;
using Windows.Devices.SerialCommunication;

public async void Serial()
{
string aqs = SerialDevice.GetDeviceSelector("UART0");                   /* Find the selector string for the serial device   */
var dis = await DeviceInformation.FindAllAsync(aqs);                    /* Find the serial device with our selector string  */
SerialDevice SerialPort = await SerialDevice.FromIdAsync(dis[0].Id);    /* Create an serial device with our selected device */

/* Configure serial settings */
SerialPort.WriteTimeout = TimeSpan.FromMilliseconds(1000);
SerialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
SerialPort.BaudRate = 9600;                                             /* mini UART: only standard baudrates */
SerialPort.Parity = SerialParity.None;                                  /* mini UART: no parities */  
SerialPort.StopBits = SerialStopBitCount.One;                           /* mini UART: 1 stop bit */
SerialPort.DataBits = 8;

/* Write a string out over serial */
string txBuffer = "Hello Serial";
DataWriter dataWriter = new DataWriter();
dataWriter.WriteString(txBuffer);
uint bytesWritten = await SerialPort.OutputStream.WriteAsync(dataWriter.DetachBuffer());

/* Read data in from the serial port */
const uint maxReadLength = 1024;
DataReader dataReader = new DataReader(SerialPort.InputStream);
uint bytesToRead = await dataReader.LoadAsync(maxReadLength);
string rxBuffer = dataReader.ReadString(bytesToRead);
}

Answer 1

Working code for communication UART (RX TX) arduino and Raspberry pi It works through a voltage converter 5V -> 3.3V. RX TX do not forget to swap.

    public sealed partial class MainPage : Page
{
    private SerialDevice SerialPort;
    private DataWriter dataWriter;
    private DataReader dataReader;
    string rxBuffer;     
    CancellationTokenSource ReadCancellationTokenSource = new CancellationTokenSource();

    public MainPage()
    {
        this.InitializeComponent();
        InitSerial();   
    }

    private async void InitSerial()
    {
        string aqs = SerialDevice.GetDeviceSelector("UART0");
        var dis = await DeviceInformation.FindAllAsync(aqs);
        SerialPort = await SerialDevice.FromIdAsync(dis[0].Id);
        SerialPort.WriteTimeout = TimeSpan.FromMilliseconds(1000);
        SerialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
        SerialPort.BaudRate = 9600;
        SerialPort.Parity = SerialParity.None;
        SerialPort.StopBits = SerialStopBitCount.One;
        SerialPort.DataBits = 8;

        dataWriter = new DataWriter();
        //dataReader = new DataReader(SerialPort.InputStream);
        Listen();
    }

    public async void SerialSend(string txBuffer2)
    {
        /* Write a string out over serial */
        string txBuffer = txBuffer2;
        dataWriter.WriteString(txBuffer);
        uint bytesWritten = await SerialPort.OutputStream.WriteAsync(dataWriter.DetachBuffer());
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        SerialSend("Hello Serial");
    }

    private async void Listen()
    {
        try
        {
            if (SerialPort != null)
            {
                dataReader = new DataReader(SerialPort.InputStream);

                // keep reading the serial input
                while (true)
                {
                    await ReadAsync(ReadCancellationTokenSource.Token);
                }
            }
        }
        catch (Exception ex)
        {
            throw new Exception("Uart Error", ex);
        }
    }

    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
        dataReader.InputStreamOptions = InputStreamOptions.Partial;
        // Create a task object to wait for data on the serialPort.InputStream
        loadAsyncTask = dataReader.LoadAsync(ReadBufferLength).AsTask(cancellationToken);
        // Launch the task and wait
        UInt32 bytesRead = await loadAsyncTask;
        if (bytesRead > 0)
        {
            receivedData.Text = dataReader.ReadString(bytesRead);
        }
    }
}