使用定時器從USB中讀取數據

我是使用USB的新手，我試圖弄清楚如何運行後臺定時器，然後在觸發時從USB設備讀取數據。這裏是我使用的是什麼，開始我的計時器，它到期時觸發該方法：）使用定時器從USB中讀取數據

void myTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e) 
{ 
    //ReadUSB(); 
} 

private void wndwMain_ContentRendered(object sender, EventArgs e) 
{ 
    USBInit(); 
    if (deviceFound) 
    { 
     System.Timers.Timer myTimer = new System.Timers.Timer(1000); 
     myTimer.Elapsed += new System.Timers.ElapsedEventHandler(myTimer_Elapsed); 
     myTimer.Start(); 
    } 
}

現在我想打電話給ReadUSB（，但我拋出EntryPointNotFound例外。我使用Jan Axelson的USB完整代碼中的USB代碼。我知道USB的延遲時間太長，我只是把它放在那裏用於測試，一旦我確認所有的東西都在工作，就會減少它。

在ReadUSB（）異常：

private void ReadUSB() 
    { 
     IntPtr eventObject = IntPtr.Zero; 
     NativeOverlapped HidOverlapped = new NativeOverlapped(); 
     Byte[] inputReportBuffer = null; 
     Int32 numberOfBytesRead = 0; 
     Int32 result = 0; 
     Boolean success = false; 
     IntPtr unManagedBuffer = IntPtr.Zero; 
     IntPtr unManagedOverlapped = IntPtr.Zero; 

     Array.Resize(ref inputReportBuffer, Capabilities.InputReportByteLength); 

     eventObject = CreateEvent 
      (IntPtr.Zero, 
      false, 
      false, 
      String.Empty); 

     HidOverlapped.OffsetLow = 0; 
     HidOverlapped.OffsetHigh = 0; 
     HidOverlapped.EventHandle = eventObject; 

     unManagedBuffer = Marshal.AllocHGlobal(inputReportBuffer.Length); 
     unManagedOverlapped = Marshal.AllocHGlobal(Marshal.SizeOf(HidOverlapped)); 
     Marshal.StructureToPtr(HidOverlapped, unManagedOverlapped, false); 

     readHandle = CreateFile 
      (devicePathName, 
      GENERIC_READ, 
      FILE_SHARE_READ | FILE_SHARE_WRITE, 
      IntPtr.Zero, 
      OPEN_EXISTING, 
      FILE_FLAG_OVERLAPPED, 
      0); 

     success = ReadFile 
      (readHandle, 
      unManagedBuffer, 
      inputReportBuffer.Length, 
      ref numberOfBytesRead, 
      unManagedOverlapped); 

     // If ReadFile returned true, report is available. Otherwise, check for completion 
     if (!success) 
     { 
      result = WaitForSingleObject 
       (eventObject, 3000); 

      switch (result) 
      { 
       case WAIT_OBJECT_0: 
        success = true; 
        GetOverlappedResult 
         (readHandle, 
         unManagedOverlapped, 
         ref numberOfBytesRead, 
         false); 
        break; 
       case WAIT_TIMEOUT: 
        Cancello(readHandle); <-- Exception thrown here. 
        break; 
       default: 
        Cancello(readHandle); 
        break; 
      } 
     }

來源

2012-01-05 Ian Oswald

該方法的名爲'CancelIo'，而不是'Cancello' – 2012-01-05 15:10:00

@RogerLipscombe，似乎是它。把它放在答案中，我會接受它。 – 2012-01-05 15:15:35

我很驚訝，沒有'生成編譯器錯誤？ – 2012-01-05 15:26:42

的方法的調用CancelIo（用大寫I），不Cancello（具有小寫l）。

來源

2012-01-05 16:45:40

使用定時器從USB中讀取數據

回答

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