Список портов пуст, не идёт построение графика

Imports System.IO.Ports
 
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ComboBox1.DataSource = SerialPort.GetPortNames()
        SerialPort1.Open()
    End Sub
 
    Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        SerialPort1.PortName = ComboBox1.Text
        SerialPort2.PortName = ComboBox1.Text
    End Sub
 
    Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
        SerialPort1.BaudRate = ComboBox2.Text
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Timer1.Enabled = True
    End Sub
 
 
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Static Dim x As Decimal = 0
        Static Dim y As Decimal = 0
        x = Timer1.Interval
        x = x + 1
        y = Math.Cos(x)
        Chart1.Series("Series1").Points.AddXY(x, y)
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Form2.ShowDialog()
    End Sub
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Timer1.Stop()
    End Sub
End Class