VB6如何操控USB串行端口

在 VB6 中，可以使用 Win32 API 函数来操控 USB 串行端口。以下是一个简单的示例代码，演示如何打开、读取和写入 USB 串行端口。

首先，需要在代码模块的顶部添加以下声明：

Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, ByVal lpSecurityAttributes As Long, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long

Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long

Private Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, ByRef lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, ByVal lpOverlapped As Any) As Long

Private Declare Function WriteFile Lib "kernel32" (ByVal hFile As Long, ByRef lpBuffer As Any, ByVal nNumberOfBytesToWrite As Long, lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Any) As Long

接下来，可以使用以下代码来打开 USB 串行端口：

Dim hPort As Long
hPort = CreateFile("COM1", GENERIC_READ Or GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0)
If hPort <> INVALID_HANDLE_VALUE Then
    ' 打开成功，可以进行读取和写入操作
    ' ...
Else
    MsgBox "无法打开串行端口！", vbExclamation
End If

在打开端口成功后，可以使用 `ReadFile` 函数来读取数据，使用 `WriteFile` 函数来写入数据。例如：

Dim buffer(255) As Byte
Dim bytesRead As Long

' 读取数据
If ReadFile(hPort, buffer(0), Len(buffer), bytesRead, 0) <> 0 Then
    ' 读取成功，可以处理读取到的数据
    ' ...
Else
    MsgBox "读取串行端口失败！", vbExclamation
End If

' 写入数据
Dim bufferToSend() As Byte
bufferToSend = "Hello, World!" ' 要发送的数据
Dim bytesWritten As Long

If WriteFile(hPort, bufferToSend(0), Len(bufferToSend), bytesWritten, 0) <> 0 Then
    ' 写入成功
Else
    MsgBox "写入串行端口失败！", vbExclamation
End If

需要注意的是，上述代码中的串行端口名称为 "COM1"，你需要根据实际的串行端口名称进行修改。

此外，还可以使用其他的 Win32 API 函数来设置串行端口的参数，如波特率、数据位、停止位等。具体的设置方法可以参考相关文档或资料。

希望以上信息对你有帮助！如果还有其他问题，请随时提问。