http://www.velleman.eu/images/tmp/usbfind.c

#ifdef __cplusplus

extern "C" {

#endif

#include <windows.h>

#include <tchar.h>

#include <setupapi.h>

#include <initguid.h>

#include <stdio.h>

// This is the GUID for the USB device class

DEFINE_GUID(GUID_DEVINTERFACE_USB_DEVICE,

            0xA5DCBF10L, 0x6530, 0x11D2, 0x90, 0x1F, 0x00, 0xC0, 0x4F, 0xB9, 0x51, 0xED);

// (A5DCBF10-6530-11D2-901F-00C04FB951ED)

int main()

{

    HDEVINFO                         hDevInfo;

    SP_DEVICE_INTERFACE_DATA         DevIntfData;

    PSP_DEVICE_INTERFACE_DETAIL_DATA DevIntfDetailData;

    SP_DEVINFO_DATA                  DevData;

    DWORD dwSize, dwType, dwMemberIdx;

    HKEY hKey;

    BYTE lpData[];

    // We will try to get device information set for all USB devices that have a

    // device interface and are currently present on the system (plugged in).

    hDevInfo = SetupDiGetClassDevs(

        &GUID_DEVINTERFACE_USB_DEVICE, NULL, , DIGCF_DEVICEINTERFACE | DIGCF_PRESENT);

    if (hDevInfo != INVALID_HANDLE_VALUE)

    {

        // Prepare to enumerate all device interfaces for the device information

        // set that we retrieved with SetupDiGetClassDevs(..)

        DevIntfData.cbSize = sizeof(SP_DEVICE_INTERFACE_DATA);

        dwMemberIdx = ;

        // Next, we will keep calling this SetupDiEnumDeviceInterfaces(..) until this

        // function causes GetLastError() to return  ERROR_NO_MORE_ITEMS. With each

        // call the dwMemberIdx value needs to be incremented to retrieve the next

        // device interface information.

        SetupDiEnumDeviceInterfaces(hDevInfo, NULL, &GUID_DEVINTERFACE_USB_DEVICE,

            dwMemberIdx, &DevIntfData);

        while(GetLastError() != ERROR_NO_MORE_ITEMS)

        {

            // As a last step we will need to get some more details for each

            // of device interface information we are able to retrieve. This

            // device interface detail gives us the information we need to identify

            // the device (VID/PID), and decide if it's useful to us. It will also

            // provide a DEVINFO_DATA structure which we can use to know the serial

            // port name for a virtual com port.

            DevData.cbSize = sizeof(DevData);

            // Get the required buffer size. Call SetupDiGetDeviceInterfaceDetail with

            // a NULL DevIntfDetailData pointer, a DevIntfDetailDataSize

            // of zero, and a valid RequiredSize variable. In response to such a call,

            // this function returns the required buffer size at dwSize.

            SetupDiGetDeviceInterfaceDetail(

                  hDevInfo, &DevIntfData, NULL, , &dwSize, NULL);

            // Allocate memory for the DeviceInterfaceDetail struct. Don't forget to

            // deallocate it later!

            DevIntfDetailData = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, dwSize);

            DevIntfDetailData->cbSize = sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA);

            if (SetupDiGetDeviceInterfaceDetail(hDevInfo, &DevIntfData,

                DevIntfDetailData, dwSize, &dwSize, &DevData))

            {

                // Finally we can start checking if we've found a useable device,

                // by inspecting the DevIntfDetailData->DevicePath variable.

                // The DevicePath looks something like this:

                //

                // \\?\usb#vid_04d8&pid_0033#5&19f2438f&0&2#{a5dcbf10-6530-11d2-901f-00c04fb951ed}

                //

                // The VID for Velleman Projects is always 10cf. The PID is variable

                // for each device:

                //

                //    -------------------

                //    | Device   | PID  |

                //    -------------------

                //    | K8090    | 8090 |

                //    | VMB1USB  | 0b1b |

                //    -------------------

                //

                // As you can see it contains the VID/PID for the device, so we can check

                // for the right VID/PID with string handling routines.

                if (NULL != _tcsstr((TCHAR*)DevIntfDetailData->DevicePath, _T("vid_10cf&pid_8090")))

                {

                    // To find out the serial port for our K8090 device,

                    // we'll need to check the registry:

                    hKey = SetupDiOpenDevRegKey(

                                hDevInfo,

                                &DevData,

                                DICS_FLAG_GLOBAL,

                                ,

                                DIREG_DEV,

                                KEY_READ

                            );

                    dwType = REG_SZ;

                    dwSize = sizeof(lpData);

                    RegQueryValueEx(hKey, _T("PortName"), NULL, &dwType, lpData, &dwSize);

                    RegCloseKey(hKey);

                    // Eureka!

                    wprintf(_T("Found a device on port '%s'\n"), lpData);

                }

            }

            HeapFree(GetProcessHeap(), , DevIntfDetailData);

            // Continue looping

            SetupDiEnumDeviceInterfaces(

                hDevInfo, NULL, &GUID_DEVINTERFACE_USB_DEVICE, ++dwMemberIdx, &DevIntfData);

        }

        SetupDiDestroyDeviceInfoList(hDevInfo);

    }

    return ;

}