using System;
using System.Runtime.InteropServices;
using System.Text;

namespace BaseStationPDA
{
 class GPS
 {

  public string PortNum;
  public int BaudRate;
  public byte ByteSize;
  public byte Parity; // 0-4=no,odd,even,mark,space
  public byte StopBits; // 0,1,2 = 1, 1.5, 2
  public int ReadTimeout;
  
  //comm port win32 file handle
  private int hComm = -1;
  
  public bool Opened = false;
  
  //win32 api constants
  private const uint GENERIC_READ = 0x80000000;
  private const uint GENERIC_WRITE = 0x40000000;
  private const int OPEN_EXISTING = 3;  
  private const int INVALID_HANDLE_VALUE = -1;
  
  [StructLayout(LayoutKind.Sequential)]
   public struct DCB
  {
   //taken from c struct in platform sdk
   public int DCBlength;           // sizeof(DCB)
   public int BaudRate;            // 指定当前波特率 current baud rate
   // these are the c struct bit fields, bit twiddle flag to set
   public int fBinary;          // 指定是否允许二进制模式,在windows95中必须主TRUE binary mode, no EOF check
   public int fParity;          // 指定是否允许奇偶校验 enable parity checking
   public int fOutxCtsFlow;      // 指定CTS是否用于检测发送控制，当为TRUE是CTS为OFF，发送将被挂起。 CTS output flow control
   public int fOutxDsrFlow;      // 指定CTS是否用于检测发送控制 DSR output flow control
   public int fDtrControl;       // DTR_CONTROL_DISABLE值将DTR置为OFF, DTR_CONTROL_ENABLE值将DTR置为ON, DTR_CONTROL_HANDSHAKE允许DTR"握手" DTR flow control type
   public int fDsrSensitivity;   // 当该值为TRUE时DSR为OFF时接收的字节被忽略 DSR sensitivity
   public int fTXContinueOnXoff; // 指定当接收缓冲区已满,并且驱动程序已经发送出XoffChar字符时发送是否停止。TRUE时，在接收缓冲区接收到缓冲区已满的字节XoffLim且驱动程序已经发送出XoffChar字符中止接收字节之后，发送继续进行。　FALSE时，在接收缓冲区接收到代表缓冲区已空的字节XonChar且驱动程序已经发送出恢复发送的XonChar之后，发送继续进行。XOFF continues Tx
   public int fOutX;          // TRUE时，接收到XoffChar之后便停止发送接收到XonChar之后将重新开始 XON/XOFF out flow control
   public int fInX;           // TRUE时，接收缓冲区接收到代表缓冲区满的XoffLim之后，XoffChar发送出去接收缓冲区接收到代表缓冲区空的XonLim之后，XonChar发送出去 XON/XOFF in flow control
   public int fErrorChar;     // 该值为TRUE且fParity为TRUE时，用ErrorChar 成员指定的字符代替奇偶校验错误的接收字符 enable error replacement
   public int fNull;          // eTRUE时，接收时去掉空（0值）字节 enable null stripping
   public int fRtsControl;     // RTS flow control
   /*RTS_CONTROL_DISABLE时,RTS置为OFF
   　        RTS_CONTROL_ENABLE时, RTS置为ON
　　          RTS_CONTROL_HANDSHAKE时,
　　          当接收缓冲区小于半满时RTS为ON
　   　        当接收缓冲区超过四分之三满时RTS为OFF
　　          RTS_CONTROL_TOGGLE时,
　　          当接收缓冲区仍有剩余字节时RTS为ON ,否则缺省为OFF*/

   public int fAbortOnError;   // TRUE时,有错误发生时中止读和写操作 abort on error
   public int fDummy2;        // 未使用 reserved
   
   public uint flags;
   public ushort wReserved;          // 未使用,必须为0 not currently used
   public ushort XonLim;             // 指定在XON字符发送这前接收缓冲区中可允许的最小字节数 transmit XON threshold
   public ushort XoffLim;            // 指定在XOFF字符发送这前接收缓冲区中可允许的最小字节数 transmit XOFF threshold
   public byte ByteSize;           // 指定端口当前使用的数据位 number of bits/byte, 4-8
   public byte Parity;             // 指定端口当前使用的奇偶校验方法,可能为:EVENPARITY,MARKPARITY,NOPARITY,ODDPARITY  0-4=no,odd,even,mark,space
   public byte StopBits;           // 指定端口当前使用的停止位数,可能为:ONESTOPBIT,ONE5STOPBITS,TWOSTOPBITS  0,1,2 = 1, 1.5, 2
   public char XonChar;            // 指定用于发送和接收字符XON的值 Tx and Rx XON character
   public char XoffChar;           // 指定用于发送和接收字符XOFF值 Tx and Rx XOFF character
   public char ErrorChar;          // 本字符用来代替接收到的奇偶校验发生错误时的值 error replacement character
   public char EofChar;            // 当没有使用二进制模式时,本字符可用来指示数据的结束 end of input character
   public char EvtChar;            // 当接收到此字符时,会产生一个事件 received event character
   public ushort wReserved1;         // 未使用 reserved; do not use
  }

  [StructLayout(LayoutKind.Sequential)]
   private struct COMMTIMEOUTS
  { 
   public int ReadIntervalTimeout;
   public int ReadTotalTimeoutMultiplier;
   public int ReadTotalTimeoutConstant;
   public int WriteTotalTimeoutMultiplier;
   public int WriteTotalTimeoutConstant;
  }  

  [StructLayout(LayoutKind.Sequential)] 
   private struct OVERLAPPED
  {
   public int  Internal;
   public int  InternalHigh;
   public int  Offset;
   public int  OffsetHigh;
   public int hEvent;
  } 
  
  [DllImport("coredll.dll")]
  private static extern int CreateFile(
   string lpFileName,                         // 要打开的串口名称
   uint dwDesiredAccess,                      // 指定串口的访问方式，一般设置为可读可写方式
   int dwShareMode,                          // 指定串口的共享模式，串口不能共享，所以设置为0
   int lpSecurityAttributes, // 设置串口的安全属性，WIN9X下不支持，应设为NULL
   int dwCreationDisposition,                // 对于串口通信，创建方式只能为OPEN_EXISTING
   int dwFlagsAndAttributes,                 // 指定串口属性与标志，设置为FILE_FLAG_OVERLAPPED(重叠I/O操作)，指定串口以异步方式通信
   int hTemplateFile                        // 对于串口通信必须设置为NULL
   );
  [DllImport("coredll.dll")]
  private static extern bool GetCommState(
   int hFile,  //通信设备句柄
   ref DCB lpDCB    // 设备控制块DCB
   ); 
  [DllImport("coredll.dll")]
  private static extern bool BuildCommDCB(
   string lpDef,  // 设备控制字符串
   ref DCB lpDCB     // 设备控制块
   );
  [DllImport("coredll.dll")]
  private static extern bool SetCommState(
   int hFile,  // 通信设备句柄
   ref DCB lpDCB    // 设备控制块
   );
  [DllImport("coredll.dll")]
  private static extern bool GetCommTimeouts(
   int hFile,                  // 通信设备句柄 handle to comm device
   ref COMMTIMEOUTS lpCommTimeouts  // 超时时间 time-out values
   ); 
  [DllImport("coredll.dll")] 
  private static extern bool SetCommTimeouts(
   int hFile,                  // 通信设备句柄 handle to comm device
   ref COMMTIMEOUTS lpCommTimeouts  // 超时时间 time-out values
   );
  [DllImport("coredll.dll")]
  private static extern bool ReadFile(
   int hFile,                // 通信设备句柄 handle to file
   byte[] lpBuffer,             // 数据缓冲区 data buffer
   int nNumberOfBytesToRead,  // 多少字节等待读取 number of bytes to read
   ref int lpNumberOfBytesRead, // 读取多少字节 number of bytes read
   ref OVERLAPPED lpOverlapped    // 溢出缓冲区 overlapped buffer
   );
  [DllImport("coredll.dll")] 
  private static extern bool WriteFile(
   int hFile,                    // 通信设备句柄 handle to file
   byte[] lpBuffer,                // 数据缓冲区 data buffer
   int nNumberOfBytesToWrite,     // 多少字节等待写入 number of bytes to write
   ref int lpNumberOfBytesWritten,  // 已经写入多少字节 number of bytes written
   ref OVERLAPPED lpOverlapped        // 溢出缓冲区 overlapped buffer
   );
  [DllImport("coredll.dll")]
  private static extern bool CloseHandle(
   int hObject   // handle to object
   );
  [DllImport("coredll.dll")]
  private static extern uint GetLastError();
  
  public void Open()
  {
  
   DCB dcbCommPort = new DCB();
   COMMTIMEOUTS ctoCommPort = new COMMTIMEOUTS(); 
    
   // 打开串口 OPEN THE COMM PORT.
   hComm = CreateFile(PortNum ,GENERIC_READ | GENERIC_WRITE,0, 0,OPEN_EXISTING,0,0);
   // 如果串口没有打开，就打开 IF THE PORT CANNOT BE OPENED, BAIL OUT.
   if(hComm == INVALID_HANDLE_VALUE)
   {
    throw(new ApplicationException("非法操作，不能打开串口！"));
   }
  
   // 设置通信超时时间 SET THE COMM TIMEOUTS.
   GetCommTimeouts(hComm,ref ctoCommPort);
   ctoCommPort.ReadTotalTimeoutConstant = ReadTimeout;
   ctoCommPort.ReadTotalTimeoutMultiplier = 0;
   ctoCommPort.WriteTotalTimeoutMultiplier = 0;
   ctoCommPort.WriteTotalTimeoutConstant = 0; 
   SetCommTimeouts(hComm,ref ctoCommPort);
  
   // 设置串口 SET BAUD RATE, PARITY, WORD SIZE, AND STOP BITS.
   GetCommState(hComm, ref dcbCommPort);
   dcbCommPort.BaudRate=BaudRate;
   dcbCommPort.flags=0;
   //dcb.fBinary=1;
   dcbCommPort.flags|=1;
   if (Parity>0)
   {
    //dcb.fParity=1
    dcbCommPort.flags|=2;
   }
   dcbCommPort.Parity=Parity;
   dcbCommPort.ByteSize=ByteSize;
   dcbCommPort.StopBits=StopBits;
   if (!SetCommState(hComm, ref dcbCommPort))
   {
    //uint ErrorNum=GetLastError();
    throw(new ApplicationException("非法操作，不能打开串口！"));
   }
   //unremark to see if setting took correctly
   //DCB dcbCommPort2 = new DCB();
   //GetCommState(hComm, ref dcbCommPort2);
   Opened = true;
  }
  
  public void Close()
  {
   if (hComm!=INVALID_HANDLE_VALUE)
   {
    CloseHandle(hComm);
   }
  }
  
  public byte[] Read(int NumBytes)
  {
   byte[] BufBytes;
   byte[] OutBytes;
   BufBytes = new byte[NumBytes];
   if (hComm!=INVALID_HANDLE_VALUE)
   {
    OVERLAPPED ovlCommPort = new OVERLAPPED();
    int BytesRead=0;
    ReadFile(hComm,BufBytes,NumBytes,ref BytesRead,ref ovlCommPort);
    try
    {
     OutBytes = new byte[BytesRead];
     Array.Copy(BufBytes,0,OutBytes,0,BytesRead);
    }
    catch
    {
     return BufBytes;
    }
    
   }
   else
   {
    throw(new ApplicationException("串口未打开！"));
   }
   return OutBytes;
   //   return BufBytes;
  }
  
  public void Write(byte[] WriteBytes)
  {
   if (hComm!=INVALID_HANDLE_VALUE)
   {
    OVERLAPPED ovlCommPort = new OVERLAPPED();
    int BytesWritten = 0;
    WriteFile(hComm,WriteBytes,WriteBytes.Length,ref BytesWritten,ref ovlCommPort);
   }
   else
   {
    throw(new ApplicationException("串口未打开！"));
   }  
  }

  public string GetGPS(string strGPS,string strFind)
  {
   ///从GPS中读取的数据中,找出想要的数据
   ///GPSstring原始字符串，
   ///strFind要查找的内容,X:经度，Y：纬度，T：时间，V：速度，是数字从1开始，即以“，”分隔的位置
   ///返回查找到指定位置的字符串
   string handerStr="$GPRMC";//GPS串头
   int findHander=strGPS.IndexOf(handerStr);//看是否含有GPS串头
   if (findHander<0)
   {
    return "-1";
   }
   else
   {
    strGPS=strGPS.Substring(findHander,strGPS.Length-findHander);
    string[] ArryTmp=strGPS.Split(",".ToCharArray());
    try
    {
     if(ArryTmp[2]=="V")
     {
      return "V";//没有信号
     }
     else
     {
      switch(strFind)
      {
       case "X":
        return DM2DD(ArryTmp[5]);
        
       case "Y":
        return DM2DD(ArryTmp[3]);
        
       case "T":
        return T2Time(ArryTmp[9],ArryTmp[1]);
        
       case "V":
        return Convert.ToString(Convert.ToDouble(ArryTmp[7])* 1.852);
        
       default:
        return "V";
        
      }
     }
    }
    catch
    {
     return "V";
    }
   }
  }

  public string T2Time(string strDate,string strTime)
  {
   string dT="20"+strDate.Substring(4,2)+"-"+strDate.Substring(2,2)+"-"+strDate.Substring(0,2);
   string TT=Convert.ToString(Convert.ToInt32(strTime.Substring(0,2)))+":"+strTime.Substring(2,2)+":"+strTime.Substring(4,2);
   DateTime T=Convert.ToDateTime(dT+" "+TT);
   T=T.AddHours(8);
   return T.ToString();
  }

  public string DM2DD(string DegreeMinutes)
  {
   //转换NMEA协议的“度分”格式为十进制“度度”格式
   string sDegree;
   string sMinute;
   string sReturn="";
   if(DegreeMinutes.IndexOf(".")==4)
   {
    //DegreeMinutes = Replace(DegreeMinutes, ".", "")
    //DM2DD = CDbl(Left(DegreeMinutes, 2)) + CDbl(Left(CStr(CDbl(Right(DegreeMinutes, Len(DegreeMinutes) – 2)) / 60), 8)) / 10000
    DegreeMinutes=DegreeMinutes.Replace(".","");
    double sDegree1=Convert.ToDouble(DegreeMinutes.Substring(0,2));
    double sDegree2=Convert.ToDouble(DegreeMinutes.Substring(2,DegreeMinutes.Length-2));
    string sTmp=Convert.ToString(sDegree2/60);
    sDegree2=Convert.ToDouble(sTmp.Substring(0,sTmp.Length));
    sDegree2=sDegree2/10000;
    sDegree=Convert.ToString(sDegree1+sDegree2);
    if(sDegree.Length>11)
     sDegree=sDegree.Substring(0,11);
    sReturn=sDegree;
   }
   else if(DegreeMinutes.IndexOf(".")==5)
   {
    //DegreeMinutes = Replace(DegreeMinutes, ".", "")
    //DM2DD = CDbl(Left(DegreeMinutes, 2)) + CDbl(Left(CStr(CDbl(Right(DegreeMinutes, Len(DegreeMinutes) – 2)) / 60), 8)) / 10000
    DegreeMinutes=DegreeMinutes.Replace(".","");
    double sMinute1=Convert.ToDouble(DegreeMinutes.Substring(0,3));
    double sMinute2=Convert.ToDouble(DegreeMinutes.Substring(3,DegreeMinutes.Length-2));
    string sTmp=Convert.ToString(sMinute2/60);
    sMinute2=Convert.ToDouble(sTmp.Substring(0,sTmp.Length));
    sMinute2=sMinute2/10000;
    sMinute=Convert.ToString(sMinute1+sMinute2);
    if(sMinute.Length>10)
     sMinute=sMinute.Substring(0,10);
    sReturn=sMinute;
   }
   return sReturn;
  }

  public bool ScanPort()
  {
   
   try
   {
    if (Opened)
    {
     Close();
     Open();
    }
    else
    {
     Open();//打开串口
     
    }
    byte[] bytRead=Read(512);
    Close();
    if(Encoding.ASCII.GetString(bytRead,0,bytRead.Length).IndexOf("$GP")>=0)
     return true;
    else
     return false;
   }
   catch
   {
    return false;
   }

  }
 }

 class HexCon
 {
  // 把十六进制字符串转换成字节型和把字节型转换成十六进制字符串 converter hex string to byte and byte to hex string
  public static string ByteToString(byte[] InBytes)
  {
   string StringOut="";
   foreach (byte InByte in InBytes)
   {
    StringOut=StringOut + String.Format("{0:X2} ",InByte);
   }
   return StringOut;
  }
  public static byte[] StringToByte(string InString)
  {
   string[] ByteStrings;
   ByteStrings = InString.Split(" ".ToCharArray());
   byte[] ByteOut;
   ByteOut = new byte[ByteStrings.Length-1];
   for (int i = 0;i==ByteStrings.Length-1;i++)
   {
    ByteOut[i] = Convert.ToByte(("0x" + ByteStrings[i]));
   }
   return ByteOut;
  }
 }
}

在别的class中调用时如Frmlogoin(是通过一个时间控件来循环的)

public class Frmlogin : System.Windows.Forms.Form
 {

private GPS ss_port=new GPS();

}

#region 读取GPS
  private void opengps(string ComPoint)
  {
   ss_port.PortNum = ComPoint;
   ss_port.BaudRate = 4800;
   ss_port.ByteSize = 8;
   ss_port.Parity = 0;
   ss_port.StopBits = 1;
   ss_port.ReadTimeout = 1000;

   try
   {
    if (ss_port.Opened)
    {
     ss_port.Close();
     ss_port.Open();
     timer1.Enabled=true;
    }
    else
    {
     ss_port.Open();//打开串口
     timer1.Enabled=true;
    }
    
   }
   catch
    
   {
//    MessageBox.Show("读取GPS错误!" ,"系统提示");
    
   }
  }
  private void timer1_Tick(object sender, System.EventArgs e)
  {
   
   if (ss_port.Opened)
    gpsread();
   else
    ss_port.Open();//打开串口
  }
  
  private void gpsread()
  {
   byte[] aa=ss_port.Read(512);
   string gpsinfo =System.Text.Encoding.ASCII.GetString(aa,0,aa.Length);
   GetParam.GpsLongitude=ss_port.GetGPS(gpsinfo,"X");
   GetParam.GpsLatitude=ss_port.GetGPS(gpsinfo,"Y");
   GetParam.GpsSpeed=ss_port.GetGPS(gpsinfo,"V");
   GetParam.GpsTime=ss_port.GetGPS(gpsinfo,"T");
   if(GetParam.GpsLongitude=="-1")
    GetParam.GpsState="0";
   if(GetParam.GpsLongitude=="V" && GetParam.GpsLatitude=="V")
    GetParam.GpsState="0";
   if(GetParam.GpsLongitude!="-1" && GetParam.GpsLongitude!="V")
    GetParam.GpsState="1";

    GetParam.GpsLongitude=(GetParam.GpsLongitude=="V") ? "0" : GetParam.GpsLongitude;
    GetParam.GpsLatitude=(GetParam.GpsLatitude=="V") ? "0" : GetParam.GpsLatitude;
    GetParam.GpsSpeed=(GetParam.GpsSpeed=="V") ? "0" : GetParam.GpsSpeed;
    GetParam.GpsTime=(GetParam.GpsTime=="V") ? "0" :GetParam.GpsTime;
   
  }
  private void GpsClose()
  {
   timer1.Enabled=false;
   if (ss_port.Opened)
    ss_port.Close();
  }
  #endregion