LibUsbDotNet 2.2.8
Async Read/Write
LibUsbDotNet on SourceForge

This example only works with custom usb hardware. Using this example on a usb device it was not designed for could be catastrophic! To meet the requirements, your usb hardware must implement loopback functionality in Config 1, Interface 0, Endpoints 0x01 and 0x81.

Async Read/Write: Console Application Description
  1. Opens a USB device by vendor and product id.

  2. Opens a UsbEndpointReader class for reading.

  3. Opens a UsbEndpointWriter class for writing.

  4. Creates and submits an asynchronous read transfer to Ep01.

  5. Creates and submits an asynchronous write transfer to Ep01.

  6. Displays the transfer results.

  7. Steps 4,5 and 6 are repeated 5 times.

Example
CopyC#
using System;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using LibUsbDotNet;
using LibUsbDotNet.Internal;
using LibUsbDotNet.Main;
using LibUsbDotNet.LudnMonoLibUsb;

namespace Examples
{
    internal class ReadWriteAsync
    {
        public static UsbDevice MyUsbDevice;

        #region SET YOUR USB Vendor and Product ID!

        public static UsbDeviceFinder MyUsbFinder = new UsbDeviceFinder(1234, 1);

        #endregion

        public static void Main(string[] args)
        {
            ErrorCode ec = ErrorCode.None;
            try
            {
                // Find and open the usb device.
                MyUsbDevice = UsbDevice.OpenUsbDevice(MyUsbFinder);

                // If the device is open and ready
                if (MyUsbDevice == null) throw new Exception("Device Not Found.");

                // If this is a "whole" usb device (libusb-win32, linux libusb)
                // it will have an IUsbDevice interface. If not (WinUSB) the 
                // variable will be null indicating this is an interface of a 
                // device.
                IUsbDevice wholeUsbDevice = MyUsbDevice as IUsbDevice;
                if (!ReferenceEquals(wholeUsbDevice, null))
                {
                    // This is a "whole" USB device. Before it can be used, 
                    // the desired configuration and interface must be selected.

                    // Select config #1
                    wholeUsbDevice.SetConfiguration(1);

                    // Claim interface #0.
                    wholeUsbDevice.ClaimInterface(0);
                }

                // open read endpoint 1.
                UsbEndpointReader reader = MyUsbDevice.OpenEndpointReader(ReadEndpointID.Ep01);

                // open write endpoint 1.
                UsbEndpointWriter writer = MyUsbDevice.OpenEndpointWriter(WriteEndpointID.Ep01);

                // the write test data.
                string testWriteString = "ABCDEFGH";

                ErrorCode ecWrite;
                ErrorCode ecRead;
                int transferredOut;
                int transferredIn;
                UsbTransfer usbWriteTransfer;
                UsbTransfer usbReadTransfer;
                byte[] bytesToSend = Encoding.Default.GetBytes(testWriteString);
                byte[] readBuffer = new byte[1024];
                int testCount = 0;
                do
                {
                    // Create and submit transfer
                    ecRead = reader.SubmitAsyncTransfer(readBuffer, 0, readBuffer.Length, 100, out usbReadTransfer);
                    if (ecRead != ErrorCode.None) throw new Exception("Submit Async Read Failed.");

                    ecWrite = writer.SubmitAsyncTransfer(bytesToSend, 0, bytesToSend.Length, 100, out usbWriteTransfer);
                    if (ecWrite != ErrorCode.None)
                    {
                        usbReadTransfer.Dispose();
                        throw new Exception("Submit Async Write Failed.");
                    }

                    WaitHandle.WaitAll(new WaitHandle[] { usbWriteTransfer.AsyncWaitHandle, usbReadTransfer.AsyncWaitHandle },200,false);
                    if (!usbWriteTransfer.IsCompleted) usbWriteTransfer.Cancel();
                    if (!usbReadTransfer.IsCompleted) usbReadTransfer.Cancel();

                    ecWrite = usbWriteTransfer.Wait(out transferredOut);
                    ecRead = usbReadTransfer.Wait(out transferredIn);

                    usbWriteTransfer.Dispose();
                    usbReadTransfer.Dispose();

                    Console.WriteLine("Read  :{0} ErrorCode:{1}", transferredIn, ecRead);
                    Console.WriteLine("Write :{0} ErrorCode:{1}", transferredOut, ecWrite);
                    Console.WriteLine("Data  :" + Encoding.Default.GetString(readBuffer, 0, transferredIn));
                    testCount++;
                } while (testCount < 5);
                Console.WriteLine("\r\nDone!\r\n");
            }
            catch (Exception ex)
            {
                Console.WriteLine();
                Console.WriteLine((ec != ErrorCode.None ? ec + ":" : String.Empty) + ex.Message);
            }
            finally
            {
                if (MyUsbDevice != null)
                {
                    if (MyUsbDevice.IsOpen)
                    {
                        // If this is a "whole" usb device (libusb-win32, linux libusb-1.0)
                        // it exposes an IUsbDevice interface. If not (WinUSB) the 
                        // 'wholeUsbDevice' variable will be null indicating this is 
                        // an interface of a device; it does not require or support 
                        // configuration and interface selection.
                        IUsbDevice wholeUsbDevice = MyUsbDevice as IUsbDevice;
                        if (!ReferenceEquals(wholeUsbDevice, null))
                        {
                            // Release interface #0.
                            wholeUsbDevice.ReleaseInterface(0);
                        }

                        MyUsbDevice.Close();
                    }
                    MyUsbDevice = null;

                    // Free usb resources
                    UsbDevice.Exit();
                }

                // Wait for user input..
                Console.ReadKey();
            }
        }
    }
}
Example
CopyVB.NET
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports System.Text.RegularExpressions
Imports System.Threading
Imports LibUsbDotNet
Imports LibUsbDotNet.Internal
Imports LibUsbDotNet.Main
Imports LibUsbDotNet.LudnMonoLibUsb

Namespace Examples
    Friend Class ReadWriteAsync
        Public Shared MyUsbDevice As UsbDevice

        #Region "SET YOUR USB Vendor and Product ID!"

        Public Shared MyUsbFinder As New UsbDeviceFinder(1234, 1)

        #End Region

        Public Shared Sub Main(args As String())
            Dim ec As ErrorCode = ErrorCode.None
            Try
                ' Find and open the usb device.
                MyUsbDevice = UsbDevice.OpenUsbDevice(MyUsbFinder)

                ' If the device is open and ready
                If MyUsbDevice Is Nothing Then
                    Throw New Exception("Device Not Found.")
                End If

                ' If this is a "whole" usb device (libusb-win32, linux libusb)
                ' it will have an IUsbDevice interface. If not (WinUSB) the 
                ' variable will be null indicating this is an interface of a 
                ' device.
                Dim wholeUsbDevice As IUsbDevice = TryCast(MyUsbDevice, IUsbDevice)
                If Not ReferenceEquals(wholeUsbDevice, Nothing) Then
                    ' This is a "whole" USB device. Before it can be used, 
                    ' the desired configuration and interface must be selected.


                    ' Select config #1
                    wholeUsbDevice.SetConfiguration(1)

                    ' Claim interface #0.
                    wholeUsbDevice.ClaimInterface(0)
                End If

                ' open read endpoint 1.
                Dim reader As UsbEndpointReader = MyUsbDevice.OpenEndpointReader(ReadEndpointID.Ep01)

                ' open write endpoint 1.
                Dim writer As UsbEndpointWriter = MyUsbDevice.OpenEndpointWriter(WriteEndpointID.Ep01)

                ' the write test data.
                Dim testWriteString As String = "ABCDEFGH"

                Dim ecWrite As ErrorCode
                Dim ecRead As ErrorCode
                Dim transferredOut As Integer
                Dim transferredIn As Integer
                Dim usbWriteTransfer As UsbTransfer
                Dim usbReadTransfer As UsbTransfer
                Dim bytesToSend As Byte() = Encoding.[Default].GetBytes(testWriteString)
                Dim readBuffer As Byte() = New Byte(1023) {}
                Dim testCount As Integer = 0
                Do
                    ' Create and submit transfer
                    ecRead = reader.SubmitAsyncTransfer(readBuffer, 0, readBuffer.Length, 100, usbReadTransfer)
                    If ecRead <> ErrorCode.None Then
                        Throw New Exception("Submit Async Read Failed.")
                    End If

                    ecWrite = writer.SubmitAsyncTransfer(bytesToSend, 0, bytesToSend.Length, 100, usbWriteTransfer)
                    If ecWrite <> ErrorCode.None Then
                        usbReadTransfer.Dispose()
                        Throw New Exception("Submit Async Write Failed.")
                    End If

                    WaitHandle.WaitAll(New WaitHandle() {usbWriteTransfer.AsyncWaitHandle, usbReadTransfer.AsyncWaitHandle}, 200, False)
                    If Not usbWriteTransfer.IsCompleted Then
                        usbWriteTransfer.Cancel()
                    End If
                    If Not usbReadTransfer.IsCompleted Then
                        usbReadTransfer.Cancel()
                    End If

                    ecWrite = usbWriteTransfer.Wait(transferredOut)
                    ecRead = usbReadTransfer.Wait(transferredIn)

                    usbWriteTransfer.Dispose()
                    usbReadTransfer.Dispose()

                    Console.WriteLine("Read  :{0} ErrorCode:{1}", transferredIn, ecRead)
                    Console.WriteLine("Write :{0} ErrorCode:{1}", transferredOut, ecWrite)
                    Console.WriteLine("Data  :" & Encoding.[Default].GetString(readBuffer, 0, transferredIn))
                    testCount += 1
                Loop While testCount < 5
                Console.WriteLine(vbCr & vbLf & "Done!" & vbCr & vbLf)
            Catch ex As Exception
                Console.WriteLine()
                Console.WriteLine((If(ec <> ErrorCode.None, ec & ":", [String].Empty)) & ex.Message)
            Finally
                If MyUsbDevice IsNot Nothing Then
                    If MyUsbDevice.IsOpen Then
                        ' If this is a "whole" usb device (libusb-win32, linux libusb-1.0)
                        ' it exposes an IUsbDevice interface. If not (WinUSB) the 
                        ' 'wholeUsbDevice' variable will be null indicating this is 
                        ' an interface of a device; it does not require or support 
                        ' configuration and interface selection.
                        Dim wholeUsbDevice As IUsbDevice = TryCast(MyUsbDevice, IUsbDevice)
                        If Not ReferenceEquals(wholeUsbDevice, Nothing) Then
                            ' Release interface #0.
                            wholeUsbDevice.ReleaseInterface(0)
                        End If

                        MyUsbDevice.Close()
                    End If
                    MyUsbDevice = Nothing

                    ' Free usb resources
                    UsbDevice.[Exit]()
                End If

                ' Wait for user input..
                Console.ReadKey()
            End Try
        End Sub
    End Class
End Namespace
Compiling the Code
  1. Create a new console application in your favorite designer.

  2. Verify your project references:

    • System.dll

    • LibUsbDotNet.dll

  3. Add/edit the main class. Copy/Paste code from one of the examples above.

Note: Example usb device firmware is located in the [InstallDirectory]\Benchmark\Firmware\[Manufacturer] directory.