C#中USB转串口的拔插捕获_C

2012-11-28 23:15:44| 分类：项目心得 | 标签：@H_403_10@c# usb转串口 |举报|字号订阅

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C#中USB转串口的拔插捕获

最近一个C#项目用户要求能够实现插入USB接口，自动识别所接入的串口，而无需人工去选择插入的是那个串口。通过一阵子的资料搜罗，总算找到一个最佳的实现方案。以前是通过线程循环逐个打开串口，发送握手包来确认接入的是那个串口，这么做能实现，不过会产生通信的数据包信息。现在，采用windows的消息机制来捕获插入的usb状态，然后，获取对应的串口名称。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)]
        struct DEV_broADCAST_HDR
        {
            public UInt32 dbch_size;
            public UInt32 dbch_devicetype;
            public UInt32 dbch_reserved;
        }

       [StructLayout(LayoutKind.Sequential)]
        protected struct DEV_broADCAST_PORT_Fixed
        {
            public uint dbcp_size;
            public uint dbcp_devicetype;
            public uint dbcp_reserved;
            // Variable?length fIEld dbcp_name is declared here in the C header file.
        }

        /// <summary>
        /// 检测USB串口的拔插
        /// </summary>
        /// <param name="m"></param>
        protected overrIDe voID WndProc(ref Message m)
        {
            if (m.Msg == WM_DEVICE_CHANGE)        // 捕获USB设备的拔出消息WM_DEVICECHANGE
            {
                switch (m.WParam.ToInt32())
                {
                   case DBT_DEVICE_REMOVE_COMPLETE:    // USB拔出
                            break;
                    case DBT_DEVICEARRIVAL:             // USB插入获取对应串口名称
                            DEV_broADCAST_HDR dbhdr = (DEV_broADCAST_HDR)Marshal.PtrToStructure(m.LParam,typeof(DEV_broADCAST_HDR));
                        if (dbhdr.dbch_devicetype == DBT_DEVTYP_PORT) {
                            string portname = Marshal.PtrToStringUni((IntPtr)(m.LParam.ToInt32() +Marshal.SizeOf(typeof(DEV_broADCAST_PORT_Fixed))));
                            Console.Writeline("Port '" + portname + "' arrived.");
                        }
                    break;
                }
            }
            base.WndProc(ref m);
        }