USB转串口通过windows消息检测拨出,为什么检测不到?
正如题,我需要通过USB转串口线向外传送数据,在网上找了很久才找到了一个用例,修改了下只能检测到插入消息,怎么也检测不到拨出消息,但换成U盘就可以,通过将消息弹出拨出时只检测到了消息为“7” 我的是笔记本电脑。请高手指点下是什么原因?
完代码如下:
// usb消息定义
public const int WM_DEVICE_CHANGE = 0x219;
public const int DBT_DEVICEARRIVAL = 0x8000;
public const int DBT_DEVICE_REMOVE_COMPLETE = 0x8004;
public const UInt32 DBT_DEVTYP_PORT = 0x00000003;
[StructLayout(LayoutKind.Sequential)]
public struct DEV_BROADCAST_HDR
{
public Int32 dbch_size;
public Int32 dbch_devicetype;
public Int32 dbch_reserved;
}
[StructLayout(LayoutKind.Sequential)]
protected struct DEV_BROADCAST_PORT_Fixed
{
public uint dbcp_size;
public uint dbcp_devicetype;
public uint dbcp_reserved;
}
protected override void WndProc(ref Message m)
{
// 捕获USB设备的拔出消息 WM_DEVICECHANGE
if (m.Msg == WM_DEVICE_CHANGE)
{
switch (m.WParam.ToInt32())
{
case DBT_DEVICEARRIVAL: //串口插入
try
{
if (!IsCopy)
{
DEV_BROADCAST_HDR dbhdr = (DEV_BROADCAST_HDR)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));
if (dbhdr.dbch_devicetype == DBT_DEVTYP_PORT)
{
IsCopy = true;
log.Info(DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss") + "捕获到USB转串口接入");
string portName = Marshal.PtrToStringUni((IntPtr)(m.LParam.ToInt32() + Marshal.SizeOf(typeof(DEV_BROADCAST_PORT_Fixed))));
comboBox.Items.Add(portName); //将串口名添加到下拉框中
comboBox.SelectedItem = portName; //选中当前串口
serialPort.PortName = portName; //设置串口名为当前串口
txtBaudRate.Text = Convert.ToString(serialPort.BaudRate); //显示波特率
OpenCom_but.Enabled = true;
}
}
}
catch (Exception ex)
{
log.Error(DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss") + "USB串口捕获失败" + ex.Message);
}
break;
case DBT_DEVICE_REMOVE_COMPLETE: // 串口拔出
DEV_BROADCAST_HDR dbhd = (DEV_BROADCAST_HDR)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));
if (dbhd.dbch_devicetype == DBT_DEVTYP_PORT)
{
string portName = Marshal.PtrToStringUni((IntPtr)(m.LParam.ToInt32() + Marshal.SizeOf(typeof(DEV_BROADCAST_PORT_Fixed))));
//Thread.CurrentThread.Abort();
if (portName == serialPort.PortName)
{
IsCopy = false;
CloseSerialPort(); //关闭串口
//将控件清空
this.comboBox.Items.Remove(portName);
this.txtBaudRate.Text = String.Empty;
}
//this.Close();
//Process.GetCurrentProcess().Kill();
}
break;
}
}
base.WndProc(ref m);
}