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Code for write and read com port on Visual Basic?

  • 29-09-2011 8:37pm
    #1
    ciaramkm
    Registered Users, Registered Users 2 Posts: 33 ✭


    I'm writing a VB code at the moment but I seem to keep getting problems. What I need to do is to read from and write to a com port. What I have in the code so far is just for open and close. Anyone have an idea what code should I use for read and write please?? Also the com port number is 2 hence why it's com2.

    Code I have so far is:

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click

    Dim com2 As IO.Ports.SerialPort = Nothing
    com2 = My.Computer.Ports.OpenSerialPort("Com2")

    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click

    Dim com2 As IO.Ports.SerialPort = Nothing

    If com2 IsNot Nothing Then com2.Close()

    End Sub

    End Class


Comments

  • #2
    ciaramkm
    Registered Users, Registered Users 2 Posts: 33 ✭ciaramkm


    Can anyone help me out on this one please :) ??


  • #3
    Beano
    Closed Accounts Posts: 3,357 ✭✭✭Beano


    The first link i found on google was this http://www.codeworks.it/net/VBNetRs232.htm

    seems to cover what you want to do.


  • #4
    FSL
    Registered Users, Registered Users 2 Posts: 1,456 ✭✭✭FSL


    Why are you defining your com port twice.

    Where are you going to initialise the settings, assuming they are not the defaults.


    Below is an extract from a VB6 programme which communicated with devices which didn't support handshaking the input was always a fixed length string smaller that the buffer size allocated to the port the output was sent one character at a time the speed of which was controlled by a timer the timer only being enabled when there was anything to output str2 contained the output string, i was initialised as 1 and j set to the length of the string before enabling the timer.

    If handshaking is supported then in VB6 you simply used:-
    stringvariable = comsdevice.Input
    comsdevice.Outpit = stringvariable

    There must be similar commands in VB Net

    Sub setPorts()

    Me.MSComm1.Settings = "9600,n,8,1"
    Me.MSComm1.Handshaking = comNone
    Me.MSComm1.RTSEnable = True
    Me.MSComm1.RThreshold = 1
    Me.MSComm1.SThreshold = 1
    Me.MSComm1.CommPort = 4
    Me.MSComm1.PortOpen = True
    Me.MSComm1.DTREnable = True
    Me.MSComm2.Settings = "9600,n,8,1"
    Me.MSComm2.Handshaking = comNone
    Me.MSComm2.RTSEnable = True
    Me.MSComm2.RThreshold = 372
    Me.MSComm2.InputMode = comInputModeBinary
    Me.MSComm2.InBufferSize = 2048
    Me.MSComm2.SThreshold = 1
    Me.MSComm2.CommPort = 5
    Me.MSComm2.PortOpen = True
    Me.MSComm2.DTREnable = True
    End Sub

    Private Sub MSComm2_OnComm()

    If Me.MSComm2.CommEvent = comEvReceive Then
    buf = MSComm2.Input


    rest of code to process input

    End Sub

    Private Sub Timer1_Timer()


    Me.MSComm1.Output = Mid(str2, i, 1)
    i = i + 1
    If i > j Then
    Me.Timer1.Enabled = False
    str2 = ""
    End If
    End Sub


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