Serial Port Packed Message Problem in VB.NET

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I have the Manual of Programming protocol, but when I write code vb.net returns error message.

The following is the table structure of bytes array

position     1       2         3         4        5         6            7      8

Name        SOH     LEN       SEQ       CMD      DATA    Post-amble     BCC     ETX

Lenth/bytes  1       1         1         1       0-200      1            4       1

Value      (01h) (20h-FFh) (20h-FFh) (20h-FFh) (20h-FFh)   (05h)     (30h-3Fh)  (03h)

Abbreviations:
“SOH”- (Start Of Heading) start of packed message
“LEN”- total number of bytes from position 2 to position 6, plus fixed offset of 20h.
“SEQ”- serial number of packet. SLAVE puts the same “SEQ” in the reply message. In case when SLAVE receives a message with the same “SEQ”and “CMD” like the last correctly received message, the device ignores the message and repeats the last packet sent to the HOST.
“CMD” – code of command
“DATA”- data, according to the command. If there is no data, the length field is zero.
“BCC” – control sum(0000h-FFFFh). Sum of data bytes from position 2 to position 6. The control sum is transferred in ASCІІ type (12АВ is transferred as 31h 32h 3Аh 3Вh).
“ETX” – (End of TeXt) end of packed message.
Codes sample:

VB

Public Class Form1

Private WithEvents sp As System.IO.Ports.SerialPort
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    For Each y As String In System.IO.Ports.SerialPort.GetPortNames
        Me.ComboBox1.Items.Add(y)
    Next
    sp = New IO.Ports.SerialPort("COM4")
    sp.StopBits = IO.Ports.StopBits.One
    sp.BaudRate = 9600
    sp.DataBits = 8
    sp.Parity = IO.Ports.Parity.None
    sp.Handshake = IO.Ports.Handshake.None
    sp.Open()
    Dim by As Byte = &H20
    ' MsgBox(&H20)
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Try
        Dim By(9) As Byte
        By(0) = 1
        By(1) = &H2 + &H20
        By(2) = &H58
        By(3) = &H45
        By(4) = &H5
        Dim S As String = Hex(&H58 Xor &H45)
        '  MsgBox(S)
        By(5) = &H30
        By(6) = &H30
        By(7) = &H31
        By(8) = &H3D
        By(9) = &H3
        sp.Write(By, 0, By.Length - 1)
       ' MsgBox(sp.ReadByte)
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End Sub
Private Sub sp_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles sp.DataReceived
    Dim rec As System.IO.Ports.SerialPort = sender
    MsgBox(Hex(rec.ReadByte))
End Sub
End Class

[edit]Code block added - OriginalGriff[/edit]

Posted 5-Jul-14 6:14am

Annael Samwel

Updated 5-Jul-14 6:18am

OriginalGriff

v3

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OriginalGriff 5-Jul-14 12:19pm

What error?
Where?

Annael Samwel 5-Jul-14 12:24pm

Return Decimal 21 which mean negative acknowledge. Please I real need to solve this problem. May be the calculation of BCC!!

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OriginalGriff · Answer 1 · 2014-07-05T06:36:00

"Return Decimal 21 which mean negative acknowledge. Please I real need to solve this problem. May be the calculation of BCC!!"

There are far too many possibilities to tell without examples, but I'd start by getting the length right...

"LEN"- total number of bytes from position 2 to position 6, plus fixed offset of 20h.

so "2" is probably going to be wrong.
Then there is the command, which should be in the range 0x20 to 0xFF, but you are supplying 0x05.

Get a working sample, and work it back to what you need to do.
Then write a method that takes a command byte and a byte array and works out teh rest - use the sample to work out if it's working.
And do note that the sequence number must be different each time!
(Hint: you can use BitConverter.GetBytes[^] to convert an integer to an array of bytes - that's your checksum sorted!)

Annael Samwel · Answer 2 · 2014-07-06T08:22:00

The followin is the way worked

VB

Public Class PrinterControl
    Private Const SOH As Byte = &H1
    Private Const SEQ As Byte = 96
    Private Const POST_AMBLE As Byte = &H5
    Private Const ETX As Byte = &H3
    Private _SerialPort As System.IO.Ports.SerialPort

    Public Property SerialPort As System.IO.Ports.SerialPort
        Get
            Return _SerialPort
        End Get
        Set(ByVal value As System.IO.Ports.SerialPort)
            _SerialPort = value
        End Set
    End Property

    Public Function SendCommand(ByVal CMD As Byte, ByVal Data As String) As String
        If Not SerialPort.IsOpen Then
            SerialPort.Open()
        End If
        If Data = "" Then
            Dim by() As Byte = Write(CMD)


            SerialPort.Write(by, 0, by.Length)
        Else
            Dim FormASCII As Byte() = System.Text.ASCIIEncoding.ASCII.GetBytes(Data)
            Dim by() As Byte = Write(CMD, FormASCII)
            SerialPort.Write(by, 0, by.Length)
        End If
        If SerialPort.ReadByte = 21 Then
            Return "Error"
        End If

        Dim Baf(SerialPort.ReadBufferSize) As Byte
        SerialPort.Read(Baf, 0, Baf.Length)
        Dim lstB As New List(Of Byte)
        For px As Integer = 4 To 200 + 4
            If Baf(px) = &H4 Then Exit For
            lstB.Add(Baf(px))

        Next
        SerialPort.Close()
        Dim st As String = ""
        For Each bbb In lstB
            st = st & Chr(bbb)
        Next
        Return st
        Return "Error"
    End Function
    Public Function AddItem(ByVal ID As Integer, ByVal Description As String, ByVal Price As Double, ByVal VATGroup As String) As String
        Return Me.SendCommand(&H6B, "P" & VATGroup & ID & "," & Price & "," & Description)
    End Function

    Public Function Write(ByVal CMD As Byte, Optional ByVal DATA As Byte() = Nothing) As Byte()
        Dim LEN As Byte
        If DATA Is Nothing Then
            Len = (&H4 + &H20)
            Dim By(9) As Byte
            By(0) = SOH
            By(1) = LEN
            By(2) = SEQ
            By(3) = CMD
            By(4) = POST_AMBLE
            Dim V_Int As Integer = LEN + SEQ + POST_AMBLE
            V_Int = V_Int + CMD
            Dim strHex As String = Hex(V_Int)
            Dim reString As String = strHex
            If strHex.Length = 1 Then
                reString = "000" & strHex
            End If
            If strHex.Length = 2 Then
                reString = "00" & strHex
            End If

            If strHex.Length = 3 Then
                reString = "0" & strHex
            End If
            By(5) = "&H3" & reString(0)
            By(6) = "&H3" & reString(1)
            By(7) = "&H3" & reString(2)
            By(8) = "&H3" & reString(3)
            By(9) = ETX

            Return By
        Else
            LEN = (&H4 + &H20) + DATA.Length
            Dim By(9 + DATA.Length) As Byte
            By(0) = SOH
            By(1) = LEN
            By(2) = SEQ
            By(3) = CMD
            Dim II As Integer = 4
            Dim bCal As Integer = 0
            For Each bb As Byte In DATA
                By(II) = bb
                bCal += bb
                II += 1
            Next

            By(II) = POST_AMBLE
            II += 1

            Dim V_Int As Integer = LEN + SEQ + POST_AMBLE
            V_Int = V_Int + CMD
            V_Int = V_Int + bCal

            Dim strHex As String = Hex(V_Int)
            Dim reString As String = strHex
            If strHex.Length = 1 Then
                reString = "000" & strHex
            End If
            If strHex.Length = 2 Then
                reString = "00" & strHex
            End If

            If strHex.Length = 3 Then
                reString = "0" & strHex
            End If
            By(II) = "&H3" & reString(0)
            II += 1
            By(II) = "&H3" & reString(1)
            II += 1
            By(II) = "&H3" & reString(2)
            II += 1
            By(II) = "&H3" & reString(3)
            II += 1
            By(II) = ETX

            Return By
        End If



        Return Nothing
    End Function
End Class

Serial Port Packed Message Problem in VB.NET

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