缓冲来自GPS串行的消息

Question

我使用串口从GPS读取一条线。一段时间后，似乎消息正在排队。为了进行测试，我做了一个事件，将GPS时​​间与计算机时间进行比较。起初他们是平等的，但几分钟后，他们跳了长达4秒钟。好像消息正在缓冲。

在下面输入我的代码。

Imports System.IO.Ports
Imports System.Threading    
Public Class gps_serial
   Public _serialPort As SerialPort
   Public coordN As String
   Public coordE As String
   Public gpsString As String
   Public time As String
   Public Event newTime()

Sub newTimeRaise()
    RaiseEvent newTime()
End Sub

Public Property open() As Boolean
    Get
        Return m_Open
    End Get
    Set(value As Boolean)
        m_Open = value
    End Set
End Property
Private m_Open As Boolean

Public Function connect(com As String, baud As Integer) As Boolean
    Try
        _serialPort = New SerialPort()
        _serialPort.PortName = com
        _serialPort.BaudRate = baud

        _serialPort.Encoding = System.Text.Encoding.GetEncoding(1252)
        AddHandler _serialPort.DataReceived, AddressOf DataReceivedHandler
        _serialPort.Open()

        If _serialPort.IsOpen Then
            open = True
            Return True
        Else
            open = False
            Return False
        End If
    Catch
        Return False
    End Try
End Function
Public Function disconnect()
    open = False
    _serialPort.Close()
    Return True
End Function
Private Sub DataReceivedHandler(sender As Object, e As SerialDataReceivedEventArgs)

    If _serialPort.IsOpen = True Then
        Dim sp As SerialPort = CType(sender, SerialPort)
        Try
            Dim GPSdata As String = sp.ReadLine()
            Dim split_GPSdata As String() = GPSdata.Split(New Char() {","c})

            If split_GPSdata(0) = "$GPGGA" Then
                gpsString = GPSdata
                coordN = split_GPSdata(2)
                coordE = split_GPSdata(4)
                If split_GPSdata(1) <> time Then
                    time = split_GPSdata(1)
                    newTimeRaise()
                End If
            End If
        Catch
        End Try
    End If


End Sub
End Class