串行数据覆盖在visual basic上

Question

我是视觉基础的新手。我发送数据来自arduino evey 1s说当前。我想在文本框上打印。这是我在VB方面的代码。我面临的问题。我正在获取数据但不是ovwrwriting。只是一个接一个地打印。我正在使用VB2010。

VB代码

Imports System
Imports System.ComponentModel
Imports System.Threading
Imports System.IO.Ports
Public Class frmMain
    Dim myPort As Array  'COM Ports detected on the system will be stored here
    Delegate Sub SetTextCallback(ByVal [text] As String) 'Added to prevent threading errors during receiveing of data



    Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        myPort = IO.Ports.SerialPort.GetPortNames() 'Get all com ports available
        cmbBaud.Items.Add(9600)     'Populate the cmbBaud Combo box to common baud rates used
        cmbBaud.Items.Add(19200)
        cmbBaud.Items.Add(38400)
        cmbBaud.Items.Add(57600)
        cmbBaud.Items.Add(115200)

        For i = 0 To UBound(myPort)
            cmbPort.Items.Add(myPort(i))
        Next
        cmbPort.Text = cmbPort.Items.Item(0)    'Set cmbPort text to the first COM port detected
        cmbBaud.Text = cmbBaud.Items.Item(0)    'Set cmbBaud text to the first Baud rate on the list
        'SerialPort1.PortName = cmbPort.Text()
        'SerialPort1.BaudRate = cmbBaud.Text()
        btnDisconnect.Enabled = False           'Initially Disconnect Button is Disabled

    End Sub



    Private Sub btnConnect_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConnect.Click
        SerialPort1.PortName = cmbPort.Text()


        'Set SerialPort1 to the selected COM port at startup
        SerialPort1.BaudRate = cmbBaud.Text()
        'Set Baud rate to the selected value on

        'Other Serial Port Property
        SerialPort1.Parity = IO.Ports.Parity.None
        SerialPort1.StopBits = IO.Ports.StopBits.One
        SerialPort1.DataBits = 8            'Open our serial port
        SerialPort1.Open()

        btnConnect.Enabled = False          'Disable Connect button
        btnDisconnect.Enabled = True        'and Enable Disconnect button

    End Sub



    Private Sub btnDisconnect_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisconnect.Click
        SerialPort1.Close()             'Close our Serial Port

        btnConnect.Enabled = True
        btnDisconnect.Enabled = False
    End Sub






    Private Sub btnSend_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click
        SerialPort1.Write(txtTransmit.Text & vbCr) 'The text contained in the txtText will be sent to the serial port as ascii
        'plus the carriage return (Enter Key) the carriage return can be ommitted if the other end doe
    End Sub



    Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        ReceivedText(SerialPort1.ReadExisting())    'Automatically called every time a data is received at the serialPort
    End Sub
    Private Sub ReceivedText(ByVal [text] As String)
        'compares the ID of the creating Thread to the ID of the calling Thread
        If Me.Current_Read.InvokeRequired Then
            Dim x As New SetTextCallback(AddressOf ReceivedText)
            Me.Invoke(x, New Object() {(text)})
        Else
            Me.Current_Read.Text &= [text]
        End If
    End Sub





    Private Sub cmbPort_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
        If SerialPort1.IsOpen = False Then
            SerialPort1.PortName = cmbPort.Text         'pop a message box to user if he is changing ports
        Else                                                                               'without disconnecting first.
            MsgBox("Valid only if port is Closed", vbCritical)
        End If
    End Sub


    Private Sub cmbBaud_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
        If SerialPort1.IsOpen = False Then
            SerialPort1.BaudRate = cmbBaud.Text         'pop a message box to user if he is changing baud rate
        Else                                                                                'without disconnecting first.
            MsgBox("Valid only if port is Closed", vbCritical)
        End If
    End Sub




    Private Sub RELAY_ON_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RELAY_ON.Click

        SerialPort1.Write("1")

    End Sub




    Private Sub RELAY_OFF_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RELAY_OFF.Click

        SerialPort1.Write("0")

    End Sub


End Class

Arduino Code。

float   Output_Current ;
void TakeReading()
{
  newaverage = analogRead(A5);
  Output_Current = 0.0336666666667*newaverage - 17.17; 
}
void loop()
{
Serial.println(  Output_Current );
delay(1000);
    }