EventHandler 传递连续的异步 I2C 数据以供 ViewModel 使用

Question

我正在使用连接到 Raspberry Pi 的 I2C 传感器，需要从该总线收集和报告连续数据并将其传递，以便我可以处理数据并使用传感器读数更新 GUI .我正在使用 .NET Core，这样我就可以在 linux 上跨平台，并且无法在 Pi 上的 Async I2C 集合上找到资源。

我目前可以从 I2C 总线正确提取数据并且知道如何 implement/update ViewModel，我只是不知道如何在新线程上连续提取数据。

我有在 Windows 中使用 using System.IO.Ports 做类似工作的经验，它已经内置了 DataReceivedEventHandlers，但是当我从头开始盯着看时，我遇到了一些困难堵塞。这是我第一次深入研究异步任务和事件处理程序，它们本身可能有点令人困惑。

2 到目前为止的主要问题：如何以异步方式或在新线程上收集 I2C 数据？如何将它传递给不同线程上的同步方法？

下面的代码是我目前的代码。

I2CInitialize.cs

public class I2CInitialize
{
    public event EventHandler<I2CDataEventArgs> NewI2CDataRecieved;
        
    ///Need to call readingi2c in new thread and pass continuous i2c sensor data
    public static string readingi2c()
        {
            int i = 0
            while (true)
                {
                     ///Taking advantage of using's dispose feature so that memory isn't consumed on loop
                     using (var i2cBus = new I2CBus(bus))
                        {
                            ///Driver to get I2C bytes from bus sits here. Returns bytes and converts to string
                            string result;
                            result = "I2CDataString";
                            return result;
                         }
                 }
        }

///Calls readingi2c() and passes continuous string "data" to subscribers            
public void I2C_DataRecieved()
    {
        string data = readingi2c();

         if (NewI2CDataRecieved != null)
             NewI2CDataRecieved(this, new I2CDataEventArgs(data));          
    }


public class I2CDataEventArgs : EventArgs
    {
        public I2CDataEventArgs(string dataInByteArray)
        {
            Data = dataInByteArray;
        }
        public string Data;
    }
}

MainWindow.cs

public class MainWindow : Window
{
    public void _NewI2CDataRecieved(object sender, I2CDataEventArgs e)
        {
            string RawStr = e.ToString();
            ///Update MainWindowViewModel with continuously passed I2C sensor data string "RawStr"
        }

    public MainWindow()
        {
            var _i2cInitialize = new I2CInitialize();
            _i2cInitialize.NewI2CDataRecieved += new EventHandler<I2CDataEventArgs>(_NewI2CDataRecieved);

            _i2cInitialize.I2C_DataRecieved();
        }
}

Answer 1

我会这样做：

I2CInitialize.cs

public event EventHandler<I2CDataEventArgs> NewI2CDataRecieved;
private Thread i2cThread;

// changed to public void
public void readingi2c()
{
    while (true)
    {
        using (var i2cBus = new I2CBus(bus))
        {
            string result;
            result = "I2CDataString";
            //With the question mark you can omit the if-statement.
            EventHandler<I2CDataEventArgs> handler = NewI2CDataRecieved;
            handler?.Invoke(this, new I2CDataEventArgs(result));                    
        }
    }
}

// Starts the thread
public void I2C_StartReceiveData()
{
    if (i2cThread == null || !i2cThread.IsAlive)
    {
        ThreadStart ts = new ThreadStart(() => readingi2c());
        i2cThread = new Thread(ts);
        i2cThread.Start();
    }
}

// Stops the thread
public void I2C_StopReceiveData()
{
    if (i2cThread != null || i2cThread.IsAlive)
    {
        i2cThread.Abort();
    }
}

public class I2CDataEventArgs : EventArgs
{
    public I2CDataEventArgs(string dataInByteArray)
    {
        Data = dataInByteArray;
    }
    public string Data;
}

然后你可以在MainWindow中调用I2C_StartReceiveData()，比如：

public class MainWindow : Window
{
    // Helpful in main class so that we don't have to make a new instance every time we need it
    I2CInitialize _i2cInitialize = new I2CInitialize();

    public void _NewI2CDataRecieved(object sender, I2CDataEventArgs e)
    {
        // You must use e.Data and not e.ToSting().
        string RawStr = e.Data;
    }

    public MainWindow()
    {
        //var _i2cInitialize = new I2CInitialize();
        _i2cInitialize.NewI2CDataRecieved += _NewI2CDataRecieved;

        _i2cInitialize.I2C_StartReceiveData();
    }
}

顺便说一句，您不需要指定 EventHandler 来注册事件。

要停止线程，可以注册关闭事件并调用I2C_StopReceiveData()。

Answer 2

我能够采用上述方法并应用的建议来避免 Thread.Abort。似乎这种方法暂时不是推荐的终止线程的方法。我当前的方法添加了一个布尔值来结束线程。这是解决此问题的一种备受争议的方法，因为线程必须完全完成而不是立即终止。对于我的应用程序，它只需要完成从 I2C 传感器获取 16 个字节，这基本上是瞬时的，并且对计算周期 and/or 最终用户体验没有现实世界的影响。我还将 I2CInitialize 制作成单例，以便可以从应用程序中任何位置的同一实例启动和停止线程。

I2CInitialize.cs

public sealed class I2CInitialize
{
    //Start Singleton instance
    public static I2CInitialize Instance { get; private set; }

    private I2CInitialize() { }

    static I2CInitialize() { Instance = new I2CInitialize(); }
        
    public event EventHandler<I2CDataEventArgs> NewI2CDataRecieved;
    private Thread i2cThread;    

    //Set this bool to true or false to run new thread
    public bool i2cReadBool;
 
    public void readingi2c()
       {
          //If bool is true run continuously and send data
          while (i2cReadBool)
          {
             //Keep this using keyword for disposing of continuous data
             using (var i2cBus = new I2CBus(bus))
                {
                   //Get data from I2C Bus here
                   string result;
                   result = "I2CDataString";
                   //With the question mark you can omit the if-statement.
                   EventHandler<I2CDataEventArgs> handler = NewI2CDataRecieved;
                   handler?.Invoke(this, new I2CDataEventArgs(result));                    
                }
           }
       } 

    //Starts the thread
    public void I2C_StartReceiveData()
    {
        if (i2cThread == null || !i2cThread.IsAlive)
        {
                i2cReadBool = true;
                ThreadStart ts = new ThreadStart(() => readingi2c());
                i2cThread = new Thread(ts);
                i2cThread.Start();
        }
    }

    //Stops the thread
    //After adding 'using' reference to this namespace you can call this 
    //function to stop the thread from anywhere:
    //I2CInitialize.Instance.I2C_StopReceiveData();
    public void I2C_StopReceiveData()
    {
        if (i2cReadBool)
        {
            i2cReadBool = false;
        }
    }
}

MainWindow.cs

public class MainWindow : Window
{
    public void _NewI2CDataRecieved(object sender, I2CDataEventArgs e)
    {
        string RawStr = e.Data;
        //Update UI from RawStr string here
    }

    public MainWindow()
    {
        //Call I2CInitialize with Sinleton allows us to call from anywhere
        //using I2CInitialize.Instance

        I2CInitialize.Instance.NewI2CDataRecieved += _NewI2CDataRecieved;

        I2CInitialize.Instance.I2C_StartReceiveData();
    }
}

到stop/end你只需要调用线程I2CInitialize.Instance.I2C_StopReceiveData(); 确保将此添加到您的应用程序 window 的关闭事件中，以便线程在主应用程序 window 关闭后不会继续运行。

EventHandler 传递连续的异步 I2C 数据以供 ViewModel 使用

EventHandler to pass continuous asynchronous I2C data for use in ViewModel

c#

asp.net-core

asynchronous

raspberry-pi

i2c