Serial port data plotting on ZedGraph

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Visual-Studio

Hello,
I have a ZedGraph on Form1 along with a button and a label. I'm reading serialinput data(data format:startbit data stopbit checksum checksum)Serial Input data is the values of pressure sensor.I want to plot Pressure(in cmH2o) on X axis and time on y axis(in milliseconds). i read serial input data in a thread and display it in label as well as plot it on graph.. i can display data in label but cant plot the graph.

Imports ZedGraph
Imports System.IO.Ports
Imports System.Threading

Public Class Form1
  
    Public data As Double
    Public count As Integer
    Public data_buffer(4) As Integer
    Public data_available As Integer = 0
    Public p As Double
    
    Private Sub cmd_open_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd_open.Click
        Try
            If SerialPort1.IsOpen = False Then
                SerialPort1.Open()
                Console.WriteLine("PORT OPEN SUCCEEDED.")
            End If
                data_available = 1
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
   
    
    Private Sub DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived

        Do
            Try
                data = SerialPort1.ReadByte ' read first byte and check if it is 64
            Catch ex As Exception
                MessageBox.Show(ex.Message)
            End Try

        Loop While (data <> 64) 'if data is 64 (new frame starts) , so come out of the loop and start reading and storing data in an array

        data_buffer(0) = data ' 64=startbit is stored inside the databuffer


        data = SerialPort1.ReadByte  'data is read from serialport 
        data_buffer(1) = data ' push data to buffer

       

        data = SerialPort1.ReadByte  '  *=stop bit data 
        data_buffer(2) = data ' push to buffer

        Me.Invoke(New EventHandler(AddressOf UpdateControls_label))
        Me.Invoke(New EventHandler(AddressOf UpdateControls_graph))
        data = SerialPort1.ReadByte  ' read checksum CHECKSUM 
        data_buffer(3) = data ' push to buffer


        data = SerialPort1.ReadByte ' CHECKSUM 
        data_buffer(4) = data ' push to buffer

        For i = 0 To 4
            Console.WriteLine(data_buffer(i))
        Next


    End Sub

    Public Sub UpdateControls_label(ByVal sender As Object, ByVal e As EventArgs)

     
        Me.Label1.Text = data_buffer(1)
     
    End Sub

    Private Sub UpdateControls_graph(ByVal sender As Object, ByVal e As EventArgs)
        Dim zgc = New ZedGraphControl
        Dim myPane As GraphPane = zgc.GraphPane
        Dim list = New PointPairList()
        Dim x As Double, y As Double
        For x = 0 To 36 ' considering some points for trial
            y = data_buffer(1)
            list.Add(x, y)
        Next x

        ' Generate a blue curve with circle symbols, and "My Curve 2" in the legend
        Dim myCurve As LineItem = myPane.AddCurve("My Curve", list, Color.Blue, SymbolType.Circle)
        ' Fill the area under the curve with a white-red gradient at 45 degrees
        myCurve.Line.Fill = New Fill(Color.White, Color.Red, 45.0F)
        ' Make the symbols opaque by filling them with white
        myCurve.Symbol.Fill = New Fill(Color.White)

        ' Fill the axis background with a color gradient
        myPane.Chart.Fill = New Fill(Color.White, Color.LightGoldenrodYellow, 45.0F)

        ' Fill the pane background with a color gradient
        myPane.Fill = New Fill(Color.White, Color.FromArgb(220, 220, 255), 45.0F)

        ' Calculate the Axis Scale Ranges
        zgc.AxisChange()
    End Sub

   
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.CenterToScreen()
    End Sub
End Class

Your help will be much appreciated.
Thanks and Regards,
Kadhambari K