CODEWITHSUNDEEP
vb.netserial-portserial-communication
Shrey Gupta
Shrey Gupta

Reputation: 31

Communication with Serial Device on COM port gives unreadable characters in VB

I am trying to communicate with a CBC Autoanaylyser machine which sends data across RS232 serial port. These are the device settings

enter image description here

I am connecting it to com4 port using a serial to usb adapter

ON COM4 port I am using the following VB code to read the data coming through.

Imports System
Imports System.Threading
Imports System.IO.Ports
Imports System.ComponentModel


Public Class ComReadWrite
    Dim myPorts As Array
    Dim txtline As String
    Dim txtchar As String
    Dim txtbyte As String
    Dim txtexisting As String
    Delegate Sub setTextCallBack(ByVal txt As String)


    Private Sub ComReadWrite_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        myPorts = IO.Ports.SerialPort.GetPortNames()
        portnamecombo.Items.AddRange(myPorts)
        WriteButton.Enabled = False
        CloseButton.Enabled = False

    End Sub

    Private Sub Start_Click(sender As Object, e As EventArgs) Handles Start.Click
        SerialPort1.PortName = portnamecombo.Text
        SerialPort1.BaudRate = BaudRateBox.Text
        SerialPort1.ReadTimeout = 500

        SerialPort1.Parity = Parity.None
        SerialPort1.DataBits = 8
        SerialPort1.StopBits = StopBits.One

        SerialPort1.Open()

        Start.Enabled = False
        WriteButton.Enabled = True
        CloseButton.Enabled = True


    End Sub

    Private Sub WriteButton_Click(sender As Object, e As EventArgs) Handles WriteButton.Click
        SerialPort1.Write(WriteBox.Text)
    End Sub

    Private Sub CloseButton_Click(sender As Object, e As EventArgs) Handles CloseButton.Click
        SerialPort1.Close()
        Start.Enabled = True
        WriteButton.Enabled = False
        CloseButton.Enabled = False
    End Sub

    Private Sub SerialPort1_DataReceived(sender As Object, e As SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        RecievedText(SerialPort1.ReadExisting())

    End Sub

    Private Sub RecievedText(ByVal txt As String)
        If Me.ReadBox.InvokeRequired Then
            Dim x As New setTextCallBack(AddressOf RecievedText)
            Me.Invoke(x, New Object() {(txt)})
        Else

            Me.ReadBox.Text &= txt

        End If
    End Sub


    Private Sub portnamecombo_SelectedIndexChanged(sender As Object, e As EventArgs) Handles portnamecombo.SelectedIndexChanged

    End Sub

    Private Sub Label5_Click(sender As Object, e As EventArgs)

    End Sub

    Private Sub BindingSource1_CurrentChanged(sender As Object, e As EventArgs) Handles BindingSource1.CurrentChanged

    End Sub
End Class

On running the program the form only reads weird unreadable characters like OOOOOOOO but not any thing readable as shown in pic

only shows weird characters

The documentation which came with the device has the following pages which seem to be relevant.

page1

page2

Upvotes: 1

Views: 1582

Answers (1)

Shrey Gupta
Shrey Gupta

Reputation: 31

We need to communicate the commands in ASCII code. Enq is Chr(5) ack is Chr(6). These were the unreadable characters.

Hey Thanks to the Stack overflow community for the help. I found the solution it is as follows

The machine is supposed to say enq to which host is supposed to reply ack. But when I read the serial port machine seems to be sending an unreadable character.

Well the enq is equal to ASCII code 5 which does not have any character associated with it so it's unreadable character. So if instead of serialport1.readexisting() I write serialport1.readchar() I get that the machine is saying 5. That is machine is actually sending the enq.

Now we need to send the whose ASCII value is 6

If I say serialport1.write('6') it's not get to work. What will work is serialport1.write(Chr(6))

And using this I got the machine to send the data.

Upvotes: 1

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