Displaying data graphically (Ultrasonic radar)

[Alex83UK]

dglienna: Thanks for your reply! I figured out what was wrong.
I have done some progress since my last post but now I have another problem.
The Visual Basic program is not fast enough to display the real-time data. My motor takes about 4.5 seconds to complete a full rotation (which is 250 steps) but in my Visual Basic display it takes about 10 seconds to complete the full rotation.
I have already changed the Baud rate from my microcontroller but it doesn't improve a lot.
I am planning to do the sweep and display the data at same time (is that possible?) Because I aiming to build a real-time data 'radar'.

And this is how I am receiving the data, splitting it into angle and distance, and plotting the angle (snapshots):

'from mySerialPort subroutine
inputData = mySerialPort.ReadChar

'from data handling subroutine
Dim data As String
        data = Chr(inputData)
        If data = " " Then
            Temp = ""

        Else
            Temp &= data
        End If

        If Temp.Length = 6 Then
            angle = Val(Mid(Temp, 1, 3))
            radius = Val(Mid(Temp, 4, 3))
            PictureBox1.Invalidate()

        End If

'from PictureBox1_Paint subroutine
 e.Graphics.RotateTransform(angle * 360 / 250, Drawing2D.MatrixOrder.Append)

***EDIT: I am using If data = " " Then Temp = "" and If Temp.Length = 6 because every string has 6 numbers (3: step angle + 3: distance of object detected) and the strings are separated by a " " (space) as I explained in my first post.