VB的DLL调用怎么“DLL调用约定错误”

[baiyongming]

"PrinterUsb.dll"里的数据类型及函数如下：
const int DEVNUM = 10;
const int PATHLEN = 200;

typedef struct
{
char strDevPath[PATHLEN];
}DEVPATH;

typedef struct
{
DEVPATH DevPath[DEVNUM];
int DevNum;
}DEVINFO;

int GetDevicePath(DEVINFO&);
bool Open(int PortNum);
bool Write(char *pBuf,DWORD nNumberOfBytesToWrite,DWORD &NumberOfBytesWritten);
void Close();


我在USB里调用DLL，作如下声明：


Public Const DevNum = 10
Public Const PATHLEN = 200
Public Type DEVPATH
strDevPath(0 To PATHLEN) As String
End Type

Public Type DEVINFO
iDevPath(0 To DevNum) As DEVPATH
DevNum As Integer
End Type

Public Declare Function GetDevicePath _
Lib "PrinterUsb.dll" _
(ByRef sDevInfo As DEVINFO) _
As Long

Public Declare Function OpenUSB _
Lib "PrinterUsb.dll" Alias "Open" _
(ByVal PortNum As Integer) _
As Boolean

Public Declare Function WriteUSB _
Lib "PrinterUsb.dll" Alias "Write" _
(ByVal pBuf As String, _
ByVal nNumberOfBytesToWrite As Long, _
ByVal nNumberOfBytesWritten As Long) _
As Boolean

Public Declare Sub CloseUSB _
Lib "PrinterUsb.dll" Alias "Close" ()


程序如下：
Private Sub cmdUSBTest_Click()
Dim MyDevInfo As DEVINFO
Dim ESC As String: ESC = Chr(27)
Dim strCmd As String
Dim nNumberOfBytesToWrite As Long: nNumberOfBytesToWrite = 0
Dim nNumberOfBytesWritten As Long: nNumberOfBytesWritten = 10

strCmd = "hello"


GetDevicePath MyDevInfo
If MyDevInfo.DevNum = 0 Then
MsgBox "未检测到USB设备！"
End
End If

If OpenUSB(0) = False Then
MsgBox "打开USB设备失败！"
End
End If

WriteUSB strCmd, nNumberOfBytesToWrite, nNumberOfBytesWritten

CloseUSB


End Sub



执行GetDevicePath MyDevInfo时就出现“实时错误49，DLL调用约定错误”
我把
Public Declare Function GetDevicePath _
Lib "PrinterUsb.dll" _
(ByRef sDevInfo As DEVINFO) _
As Long
改成
Public Declare Function GetDevicePath _
Lib "PrinterUsb.dll" _
(ByVal sDevInfo As DEVINFO) _
As Long
就出现“编译错误：用户类型不能用”。

现在怎么办，哪儿错了，要怎么改，原因是什么呢，谢谢！

[bob008]

另外个帖子里。。。。 AS DEVPATH这里估计是定长

[chenhui530]

int WINAPI GetDevicePath(DEVINFO&);
bool WINAPI Open(int PortNum);
bool WINAPI Write(char *pBuf,DWORD nNumberOfBytesToWrite,DWORD &NumberOfBytesWritten);
void WINAPI Close();