USB Device Finder

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[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 = 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;
}