High speed screen updates for oscilloscope

'zeit2=DateTime.Now

zeit1=DateTime.Now

Sub Process_Globals
   Dim zeit1,zeit2 As Long
   
End Sub
Sub Globals

   Dim volts As Double
   Dim Timer1 As Timer
   Dim Canvas1 As Canvas
   Dim x,y,hx(),hy() As Int
   
   Dim btnLED As ToggleButton
   Dim Label1 As Label
   Dim i As Int
   Dim d As Int
   Dim lastvalue As Double
   Dim SeekBar1 As SeekBar
   Dim Label2 As Label
      
   Dim Panel1 As Panel
   Dim Rect1 As Rect
        
        Dim factor as Int
      
End Sub

Sub Activity_Create(FirstTime As Boolean)
 
      Activity.LoadLayout("Main")
      Canvas1.Initialize(Panel1)
       
      d=1000
      Timer1.Initialize("Timer1", d)
      lastvalue=240
      Timer1.Enabled=True
      i=0
      Rect1.Initialize(0dip, 0dip, 800dip, 480dip)'clear display
    
End Sub

Sub Activity_Resume
End Sub

Sub Activity_Pause (UserClosed As Boolean)
End Sub


Sub Timer1_Tick
      label1.Text=DateTime.Now - zeit1 
      zeit1=DateTime.Now
      draw_Oscillator
End Sub   

Sub draw_Oscillator
   
      Canvas1.DrawRect(Rect1, Colors.Black, True, 5dip)
      
      For x=0 To 800 Step 5
          volts=Sin(x/800*3*2*3.14159)
         y = 180-(volts*factor)'scale for scope display   scale factor=variable 
         canvas1.DrawLine(x-5,lastvalue,x,y,Colors.Yellow,5dip)
         lastvalue=y
      Next   
                factor=factor+1

                if factor>150 then factor=1  ' limit scale factor to 150 .... and restart with 1

         canvas1.DrawLine(0,180,800,180,Colors.green,5dip)
      
    panel1.Invalidate 
End Sub

Sub SeekBar1_ValueChanged (Value As Int, UserChanged As Boolean)
   d=Value
   Timer1.Interval=d
   Label2.Text=d
End Sub