A USB Library to Detect USB Devices

Introduction

This article is about a USB library which enables you to manage Attach and Detach events of USB devices and detect your own device. I was not able to find a working code written in C# and which runs under both Windows XP and Windows 7 x64. I therefore decided to write my own code. I read various articles about USB Attach and Detach detection, and got some help from both the Microsoft website and the PINVOKE.NET website (http://www.pinvoke.net).

This code is a separate module that you can link to your own project. The code explains how to add additional properties.

Using the Code

Updating your Code

Add a reference to your project.
Add the using directive in your code:
```
using USBClassLibrary;
```

Declare an instance of USBClass.

private USBClassLibrary.USBClass USBPort;

Declare an instance of the DeviceProperties class if you want to read the properties of your devices.
```
private USBClassLibrary.USBClass.DeviceProperties USBDeviceProperties;
```
Create an instance of the USBClass class.
```
USBPort = new USBClass();
```

Create an instance of the DeviceProperties class.

USBDeviceProperties = new USBClass.DeviceProperties();

Add handlers for the events exposed by the USBClass class.

USBPort.USBDeviceAttached += 
  new USBClass.USBDeviceEventHandler(USBPort_USBDeviceAttached);
USBPort.USBDeviceRemoved += 
  new USBClass.USBDeviceEventHandler(USBPort_USBDeviceRemoved);

Register your form to receive Windows messages when devices are added or removed.
```
USBPort.RegisterForDeviceChange(true, this);
```

Then, check if your device is not already connected:

if (USBClass.GetUSBDevice(MyDeviceVID, MyDevicePID, 
             ref USBDeviceProperties, false))
{
   //My Device is connected
   MyUSBDeviceConnected = true;
}

Implement Attach and Detach handlers:

private void USBPort_USBDeviceAttached(object sender, 
             USBClass.USBDeviceEventArgs e)
{
   if (!MyUSBDeviceConnected)
   {
      if (USBClass.GetUSBDevice(MyDeviceVID, MyDevicePID, 
                                ref USBDeviceProperties, false))
      {
         //My Device is connected
         MyUSBDeviceConnected = true;
      }
   }
}

private void USBPort_USBDeviceRemoved(object sender, 
             USBClass.USBDeviceEventArgs e)
{
   if (!USBClass.GetUSBDevice(MyDeviceVID, MyDevicePID, 
                              ref USBDeviceProperties, false))
   {
      //My Device is removed
      MyUSBDeviceConnected = false;
   }
}

Handle Windows message in your form to pass them to the USBClass class:

protected override void WndProc(ref Message m)
{
   USBPort.ProcessWindowsMessage(ref m);

   base.WndProc(ref m);
}

Getting the COM Port Associated to a USB Device

If your device emulates a Serial Port, then you can retrieve its COM Port.

The GetUSBDevice function has a fourth parameter GetCOMPort:

public static bool GetUSBDevice
	(UInt32 VID, UInt32 PID, ref DeviceProperties DP, bool GetCOMPort)

Set its value to True in your connection code and retrieve the COM Port from the DeviceProperties structure:

if (USBClass.GetUSBDevice(MyDeviceVID, MyDevicePID, 
             ref USBDeviceProperties, true))
{
   String COMPort;

   //My Device is connected
   MyUSBDeviceConnected = true;
   COMPort = DP.COMPort;
}

Compiling

In the project properties, Build tab, do not select Any CPU in the "Platform target" drop down list, pick up x86 or x64.

Updating the Code

If you need to read other device properties, simply update the code as follows:

Look up the SetupDiGetDeviceRegistryProperty function in MSDN and find the property you want to get.

Add a new variable to the DeviceProperties matching the characteristics of your property:

public struct DeviceProperties
{
   public string FriendlyName;
   public string DeviceDescription;
   public string DeviceType;
   public string DeviceManufacturer;
   public string DeviceClass;
   public string DeviceLocation;
   public string DevicePath;
   public string DevicePhysicalObjectName;
   public string COMPort;
}

Update the GetUSBDevice function:

public static bool GetUSBDevice(UInt32 VID, UInt32 PID, 
		ref DeviceProperties DP, bool GetCOMPort)
{
   ...
   if (Win32Wrapper.SetupDiGetDeviceRegistryProperty(h, ref DevInfoData, 
      (UInt32)Win32Wrapper.SPDRP.SPDRP_PHYSICAL_DEVICE_OBJECT_NAME, 
      ref RegType, intptrBuffer, BUFFER_SIZE, ref RequiredSize))
   {
      DP.DevicePhysicalObjectName = Marshal.PtrToStringAuto(intptrBuffer);
   }
...
}

History

Feb 22, 2010
- Article first published
Feb 26, 2010
- Added code to retrieve the COM Port associated to USB Devices emulating a serial port
- Updated documentation accordingly