从串行端口Visual Basic中读取字符串

Question

Imports System.IO.Ports 
Imports System.Text

Public Class Form4
    Dim myStringBuilder As String
    Dim insert As New OleDb.OleDbCommand
    Dim cnn As New OleDb.OleDbConnection
    Public user As String

Private Sub Serialport2_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort2.DataReceived
    myStringBuilder = SerialPort2.ReadExisting()
    Me.Invoke(New EventHandler(AddressOf UpdateControls))
End Sub

Private Sub UpdateControls(ByVal sender As Object, ByVal e As EventArgs)
    Dim A As String = myStringBuilder
    Dim Sqql As String

    If Not cnn.State = ConnectionState.Open Then
        cnn.Open()
    End If

    insert.Connection = cnn


    Dim dt As New DataTable
    Sqql = "SELECT * FROM `FileInfo` WHERE `File ID`='" & A & "'"
    Dim cmd As New OleDb.OleDbDataAdapter(Sqql, cnn)
    cmd.Fill(dt)
    Dim i As Integer = dt.Rows.Count
    Dim todaysdate As String = String.Format("{0:dd/MM/yyyy}", DateTime.Now)
    If i = 1 Then
            insert.CommandText = "INSERT INTO `File Log`(File ID,Name,Information,Time,Date) " & _
                " VALUES('" & A & "','" & dt.Rows(0).Item("Name") & "','" & user & " telah" & dt.Rows(0).Item("Status") & "File" & "','" &
_
                TimeOfDay & "','" & todaysdate & "')"
            textBox1.Text += dt.Rows(0).Item("Name") & "   " & TimeOfDay & "   " & todaysdate & 

Environment.NewLine
            textBox1.Select(textBox1.TextLength, 0)
            textBox1.ScrollToCaret()
            insert.ExecuteNonQuery()
            myStringBuilder = ""
        Else
            myStringBuilder = ""
            textBox1.Text += A & Environment.NewLine
        End If


End Sub


Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    cnn = New OleDb.OleDbConnection
    cnn.ConnectionString = "Provider=Microsoft.Jet.Oledb.4.0; Data Source=" & Application.StartupPath & "\data.mdb"

    If SerialPort2 IsNot Nothing Then
        SerialPort2.Close()
    End If

    SerialPort2 = My.Computer.Ports.OpenSerialPort("COM27", 9600, Parity.None, 8, StopBits.One)
    textBox1.Text = "-- Door Have Open -- " & Environment.NewLine & Environment.NewLine


End Sub

Private Sub textBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles textBox1.TextChanged

End Sub End Class

in my serial monitor view it will appear correctly but in visual basic it will auto break line and not display the string in one line. I Tried other method like serialport.readline() but nothing happen.

Answer 1

If you are having issues with extracting data from your serial port you could try this:

Sub SerialPort_DataReceived(sender As Object, e As SerialDataReceivedEventArgs)

    Dim currentSP As SerialPort = Convert.ChangeType(sender, GetType(SerialPort))
    Dim strBuilder As System.Text.StringBuilder = New System.Text.StringBuilder()

    For index = 1 To currentSP.BytesToRead        
        strBuilder.Append(Convert.ChangeType(currentSP.ReadByte(), GetType(Char)))
    Next

    ' Have a global string to allow the threads to have a shared resource
    myString = strBuilder.ToString()

    Me.Invoke(New EventHandler(AddressOf UpdateControls))

End Sub

It should work the same way as the SerialPort.ReadLine() , this approach also lets you manipulate the data however you want. Instead of working with a string you could always work the data like this:

Dim buffer As Byte() = New Byte(currentSP.BytesToRead) {}
buffer(index) = Convert.ChangeType(currentSP.ReadByte(), GetType(Byte))

So instead of appending the Char to the String you can add the Byte to the buffer