USB HID通讯中,在CreatFile返回总是-1是什么问题呀?
Private Sub GetHidGuid_Click()
Dim Result As Long
Dim MemberIndex As Long
'/* Get GUID for all System HIDs */
Result = HidD_GetHidGuid(HidGuid)
'/* Get Device Information for all present devices */
DeviceInfoSet = SetupDiGetClassDevs( _
HidGuid, _
vbNullString, _
0, _
(DIGCF_PRESENT Or DIGCF_DEVICEINTERFACE))
'/* Scan all Devices */ 查找设备
MemberIndex = 0
ADevice.Total = 0
Do
MyDeviceInterfaceData.cbSize = LenB(MyDeviceInterfaceData)
'/* Device Interface Element of a Device Information set */
Result = SetupDiEnumDeviceInterfaces( _
DeviceInfoSet, _
0, _
HidGuid, _
MemberIndex, _
MyDeviceInterfaceData)
MemberIndex = MemberIndex + 1
If Result = 0 Then Exit Do
'/* Get Device Interface Details - Get Length */
'第一次调用函数DeviceInfoSet,MyDeviceInterfaceData是传回结构
'Needed包含要传给下一个调用的缓冲区大小
Result = SetupDiGetDeviceInterfaceDetail( _
DeviceInfoSet, _
MyDeviceInterfaceData, _
0, _
0, _
Needed, _
0)
'要传给下一个调用的 DetailData=Needed
DetailData = Needed
MyDeviceInterfaceDetailData.cbSize = Len(MyDeviceInterfaceDetailData)
'Use a byte array to allocate memory for
'the MyDeviceInterfaceDetailData structure
ReDim DetailDataBuffer(Needed)
'字节数组的前4个字节是数组的大小
Call RtlMoveMemory(DetailDataBuffer(0), MyDeviceInterfaceDetailData, 4)
'VarPtr(DetailDataBuffer(0))是包含MyDeviceInterfaceDetailData的字节数组的开始地址
'DetailData储存上一个调用所传回的大小
Result = SetupDiGetDeviceInterfaceDetail( _
DeviceInfoSet, _
MyDeviceInterfaceData, _
VarPtr(DetailDataBuffer(0)), _
DetailData, _
Needed, _
0)
If Result = 0 Then GoTo DO_Next
DevicePathName = CStr(DetailDataBuffer())
'Convert to Unicode.
DevicePathName = StrConv(DevicePathName, vbUnicode)
'Strip cbSize (4 bytes) from the beginning.
DevicePathName = Right$(DevicePathName, Len(DevicePathName) - 4)
HidDevice = CreateFile( _
DevicePathName, _
GENERIC_READ Or GENERIC_WRITE, _
(FILE_SHARE_READ Or FILE_SHARE_WRITE), _
0, _
OPEN_EXISTING, _
0, _
0)
这里总是失败什么问题呀?
If HidDevice = INVALID_HANDLE_VALUE Then GoTo DO_Next
Result = HidD_GetPreparsedData( _
HidDevice, _
PreparsedData)
If Result = 0 Then GoTo DO_Next
Result = HidP_GetCaps( _
PreparsedData, _
Capabilities)
If (Capabilities.UsagePage = &HFF00) And (Capabilities.Usage = &H1) Then
ADevice.DevicePath(ADevice.Total) = DevicePathName
ADevice.Total = ADevice.Total + 1
End If
DO_Next:
Loop Until NumMax < ADevice.Total
End Sub
[解决办法]
请注意第四个函数原型:Public Declare Function CreateFile _
Lib "kernel32 " _
Alias "CreateFileA " _
(ByVal lpFileName As String, _
ByVal dwDesiredAccess As Long, _
ByVal dwShareMode As Long, _
ByRef lpSecurityAttributes As Security_Attributes, _
ByVal dwCreationDisposition As Long, _
ByVal dwFlagsAndAttributes As Long, _
ByVal hTemplateFile As Long) _
As Long
