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

#ifdef __cplusplusextern "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 classDEFINE_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[1024];    // 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, 0, 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 = 0;                // 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, 0, &dwSize, NULL);            // Allocate memory for the DeviceInterfaceDetail struct. Don‘t forget to            // deallocate it later!            DevIntfDetailData =http://www.mamicode.com/ 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,                                0,                                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(), 0, DevIntfDetailData);            // Continue looping            SetupDiEnumDeviceInterfaces(                hDevInfo, NULL, &GUID_DEVINTERFACE_USB_DEVICE, ++dwMemberIdx, &DevIntfData);        }        SetupDiDestroyDeviceInfoList(hDevInfo);    }    return 0;}