I'm experiencing a problem on Vista (UAC is enabled) with the cp2102 USB to UART com driver. Apparently, the port number for this is stored in a registry key under the hklm hive: [HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SerialComm]
"\\Device\\slabser0"="COM3"

My problem is that when my application attempts to open this key, but UAC is denying it access, so it cannot connect to the USB controller. Any idea why my app [ClearFit.exe] would do this instead of just doing a RegOpenReadOnly on the key? See process monitor log below:

http://img217.imageshack.us/img217/8995/picture20vk2.png

=> chapter 7. Discovering CP210x COM Port

Tsuneo

PS. The forum engine doesn't pass this message when "SP _DEVINFO_DATA" is written without blank.
The engine doesn't like "SP" with underscore...
Before compiling this code, please delete the blank from "SP _DEVINFO_DATA"
As usual, the formatted original post is retrieved from the Edit window of this post.

//
// CP210x_COM_port_lister.cpp
//      Snippet for console tool, coded on MS VC++ 2005
//      List up COM port and serial number of CP210x, currently connected to this PC
//
// Reference:
//  http://www.codeproject.com/KB/system/setupdi.aspx?df=100&forumid=4368&exp=0&select=479661
//  portlister.cpp : Defines the entry point for the console application.
//  by Christian B
//
#include "stdafx.h"
#include "atlstr.h"
#include "Windows.h"
#include "SetupAPI.h"
// Add "SetupAPI.Lib" to the Project -> Linker -> Input

int _tmain(int argc, _TCHAR* argv[])
{
                                                // device ID of CP210x VCP
                                                // default VID/PID: 10C4/EA60
                                                // for custom VID/PID, modify this string
    CString deviceID( _T("USB\\VID_10C4&PID_EA60\\") );
    CString instanceID;
    CString serialNumer;
    CString portName;
    DWORD requiredSize;
                                                // Get Class GUID for PORTS class
    GUID classGuid[1];
    if ( ! SetupDiClassGuidsFromName( _T("PORTS"), classGuid, 1, &requiredSize ) )
        return 0;
                                                // List up PORTS class devices in present
    HDEVINFO hDevInfoSet = SetupDiGetClassDevs( classGuid, NULL, NULL, DIGCF_PRESENT ); 
    if ( hDevInfoSet == INVALID_HANDLE_VALUE )
        return 0;
                                                // Enumerate devices in the list
    SP _DEVINFO_DATA devInfo;                        // <------------- please delete the blank
    devInfo.cbSize = sizeof( SP _DEVINFO_DATA );     // <------------- from "SP _DEVINFO_DATA"
    for (   DWORD deviceIndex = 0;
            SetupDiEnumDeviceInfo( hDevInfoSet, deviceIndex, &devInfo );
            deviceIndex++ )
    {
                                                // Get device instance ID
        SetupDiGetDeviceInstanceId(         hDevInfoSet, &devInfo, NULL, 0, &requiredSize );
        SetupDiGetDeviceInstanceId(         hDevInfoSet, &devInfo,
                                            instanceID.GetBuffer(requiredSize), requiredSize, NULL );
        instanceID.ReleaseBuffer();
                                                // Check device ID
        if( instanceID.Find( deviceID ) != 0 )
            continue;
                                                // Split serial number
        serialNumer = instanceID.Right( instanceID.GetLength() - deviceID.GetLength() );
                                                // Open device parameters reg key
        HKEY hkey = SetupDiOpenDevRegKey(   hDevInfoSet, &devInfo, DICS_FLAG_GLOBAL,
                                            0, DIREG_DEV, KEY_READ );
        if ( hkey == INVALID_HANDLE_VALUE )
            continue;
                                                // Qurey for portname
        RegQueryValueEx(                    hkey, _T("PortName"), NULL, NULL, NULL, &requiredSize );
        RegQueryValueEx(                    hkey, _T("PortName"), NULL, NULL,
                                            (LPBYTE)portName.GetBuffer(requiredSize), &requiredSize );
        portName.ReleaseBuffer();
                                                // Close reg key
        RegCloseKey( hkey );
                                                // Print result
        _tprintf( _T("Port: %s   Serial number: %s\n"), portName, serialNumer );
    }
                                                // Destroy device info list
    SetupDiDestroyDeviceInfoList( hDevInfoSet );
    return 0;
}

Tsuneo

//
// CP210x_COM_port_lister.cs
//      Snippet for C# console tool, coded on MSVS 2008
//      List up COM port, Product ID (just for XP) and serial number of CP210x, currently connected to this PC
//
using System;
using System.Runtime.InteropServices;
using System.Text;
namespace CP210x_COM_port_lister
{    
    class Program
    {
        private readonly static IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);
        // constants for SetupDiGetClassDevs( flags )
        internal const UInt32 DIGCF_PRESENT = 0x00000002;
        internal const UInt32 DIGCF_DEVICEINTERFACE = 0x00000010;
        // constants for SetupDiOpenDevRegKey( scope,,parameterRegistryValueKind,samDesired )
        internal const UInt32 DICS_FLAG_GLOBAL = 0x00000001;
        internal const UInt32 DIREG_DEV = 0x00000001;
        internal const UInt32 KEY_READ =  0x00020019;
        // constants for SetupDiGetDeviceRegistryProperty( Property )
        internal const UInt32 SPDRP_DEVICEDESC = 0x00000000;
        internal const UInt32 SPDRP_MFG = 0x0000000B;
        internal const UInt32 SPDRP_FRIENDLYNAME = 0x0000000C;
        internal const UInt32 SPDRP_LOCATION_INFORMATION = 0x0000000D;
        [StructLayout(LayoutKind.Sequential)]
        public struct DEVINFO_DATA
        {
            internal Int32  cbSize;
            internal Guid   ClassGuid;
            internal UInt32 DevInst;
            internal IntPtr Reserved;
        }
        [DllImport("setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern Boolean SetupDiClassGuidsFromName(
            String     className,
            ref Guid   classGuidArray1stItem,
            UInt32     classGuidArraySize,
            out Int32  RequiredSize
        );
        [DllImport("setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern IntPtr SetupDiGetClassDevs(
            ref Guid   classGuid,
            IntPtr     enumerator,
            IntPtr     hwndParent,
            UInt32     flags
        );
        [DllImport("setupapi.dll", SetLastError = true)]
        static extern Boolean SetupDiDestroyDeviceInfoList(
            IntPtr     hDevInfo
        );
        [DllImport("setupapi.dll", SetLastError = true)]
        static extern Boolean SetupDiEnumDeviceInfo(
            IntPtr     DeviceInfoSet,
            UInt32     MemberIndex,
            out DEVINFO_DATA DeviceInfoData
        );
        [DllImport("setupapi.dll", EntryPoint = "SetupDiGetDeviceInstanceId", CharSet = CharSet.Auto, SetLastError = true)]
        static extern Boolean SetupDiGetDeviceInstanceId_getSize(
            IntPtr     DeviceInfoSet,
            ref DEVINFO_DATA DeviceInfoData,
            IntPtr     DeviceInstanceId,
            Int32      DeviceInstanceIdSize,
            out Int32  RequiredSize
        );
        [DllImport("setupapi.dll", EntryPoint = "SetupDiGetDeviceInstanceId", CharSet = CharSet.Auto, SetLastError = true)]
        static extern Boolean SetupDiGetDeviceInstanceId_getString(
            IntPtr     DeviceInfoSet,
            ref DEVINFO_DATA DeviceInfoData,
            StringBuilder DeviceInstanceId,
            Int32      DeviceInstanceIdSize,
            IntPtr     RequiredSize
        );
        [DllImport("setupapi.dll", EntryPoint = "SetupDiGetDeviceRegistryProperty", CharSet = CharSet.Auto, SetLastError = true)]
        static extern Boolean SetupDiGetDeviceRegistryProperty_getSize(
            IntPtr     DeviceInfoSet,
            ref DEVINFO_DATA DeviceInfoData,
            UInt32     Property,
            IntPtr     PropertyRegDataType,
            IntPtr     PropertyBuffer,
            Int32      PropertyBufferSize,
            out Int32  RequiredSize
        );
        [DllImport("setupapi.dll", EntryPoint = "SetupDiGetDeviceRegistryProperty", CharSet = CharSet.Auto, SetLastError = true)]
        static extern Boolean SetupDiGetDeviceRegistryProperty_getString(
            IntPtr     DeviceInfoSet,
            ref DEVINFO_DATA DeviceInfoData,
            UInt32     Property,
            IntPtr     PropertyRegDataType,
            StringBuilder PropertyBuffer,
            Int32      PropertyBufferSize,
            IntPtr     RequiredSize
        );
        [DllImport("Setupapi", SetLastError = true)]
        public static extern IntPtr SetupDiOpenDevRegKey(
            IntPtr hDeviceInfoSet,
            ref DEVINFO_DATA deviceInfoData,
            UInt32     scope,
            UInt32     hwProfile,
            UInt32     parameterRegistryValueKind,
            UInt32     samDesired
        );
        [DllImport("advapi32.dll", EntryPoint = "RegQueryValueEx", CharSet = CharSet.Auto, SetLastError = true)]
        static extern int RegQueryValueEx_getSize(
            IntPtr     hKey,
            String     lpValueName,
            IntPtr     lpReserved,
            IntPtr     lpType,
            IntPtr     lpData,
            out Int32  lpcbData
        );
        [DllImport("advapi32.dll", EntryPoint = "RegQueryValueEx", CharSet = CharSet.Auto, SetLastError = true)]
        static extern int RegQueryValueEx_getString(
            IntPtr     hKey,
            String     lpValueName,
            IntPtr     lpReserved,
            IntPtr     lpType,
            StringBuilder lpData,
            ref Int32  lpcbData
        );
        [DllImport("advapi32.dll", SetLastError = true)]
        public static extern int RegCloseKey(
            IntPtr hKey
        );
        static void Main(string[] args)
        {
                                                            // device ID of CP210x VCP
                                                            // default VID/PID: 10C4/EA60
                                                            // for custom VID/PID, modify this string
            String deviceID = @"USB\VID_10C4&PID_EA60\";
            StringBuilder instanceID = new StringBuilder();
            StringBuilder locationInfo = new StringBuilder();
            StringBuilder portName = new StringBuilder();
            String serialNumer;
            Int32 requiredSize;
                                                            // Get Class GUID for PORTS class
            Guid[] classGuidArray = new Guid[1];
            if ( !SetupDiClassGuidsFromName( "PORTS", ref classGuidArray[0], 1, out requiredSize ) )
                return;
                                                            // List up PORTS class devices in present
            IntPtr hDevInfoSet = SetupDiGetClassDevs( ref classGuidArray[0], IntPtr.Zero, IntPtr.Zero, DIGCF_PRESENT );
            if (hDevInfoSet == INVALID_HANDLE_VALUE)
                return;
                                                            // Enumerate devices in the list
            DEVINFO_DATA devInfo = new DEVINFO_DATA();
            devInfo.cbSize = Marshal.SizeOf(devInfo);
            for (   UInt32 deviceIndex = 0;
                    SetupDiEnumDeviceInfo( hDevInfoSet, deviceIndex, out devInfo );
                    deviceIndex++ )
            {
                                                            // Get device instance ID
                SetupDiGetDeviceInstanceId_getSize(  hDevInfoSet, ref devInfo, IntPtr.Zero, 0, out requiredSize);
                instanceID.EnsureCapacity( requiredSize );
                SetupDiGetDeviceInstanceId_getString(hDevInfoSet, ref devInfo, instanceID, requiredSize, IntPtr.Zero);
                                                            // Check device ID
                if ( !instanceID.ToString().StartsWith(deviceID, StringComparison.OrdinalIgnoreCase) )
                    continue;
                                                            // Split serial number
                serialNumer = instanceID.ToString().Substring(deviceID.Length);
                                                            // Get location information
                                                            // For XP, LocationInformation value on registry hardware key holds
                                                            // iProduct string on the device
                SetupDiGetDeviceRegistryProperty_getSize(hDevInfoSet, ref devInfo, SPDRP_LOCATION_INFORMATION, IntPtr.Zero,
                                                            IntPtr.Zero, 0, out requiredSize);
                locationInfo.EnsureCapacity(requiredSize);
                SetupDiGetDeviceRegistryProperty_getString(hDevInfoSet, ref devInfo, SPDRP_LOCATION_INFORMATION, IntPtr.Zero,
                                                            locationInfo, requiredSize, IntPtr.Zero);
                
                                                            // Open device parameters reg key
                IntPtr hkey = SetupDiOpenDevRegKey(hDevInfoSet, ref devInfo, DICS_FLAG_GLOBAL,
                                                    0, DIREG_DEV, KEY_READ );
                if (hkey == INVALID_HANDLE_VALUE)
                    continue;
                                                            // Qurey for portname
                RegQueryValueEx_getSize(  hkey, "PortName", IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, out requiredSize);
                portName.EnsureCapacity( requiredSize );
                RegQueryValueEx_getString(hkey, "PortName", IntPtr.Zero, IntPtr.Zero, portName, ref requiredSize);
                                                            // Close reg key
                RegCloseKey( hkey );
                Console.WriteLine("Port: " + portName + "   Product ID: " + locationInfo + "   Serial number: " + serialNumer);
            }
                                                            // Destroy device info list
            SetupDiDestroyDeviceInfoList( hDevInfoSet );
        }
    }
}