I'm facing problems with reading data from serial port.
Im sending out a command to the spectrum analyzer, and start reading. characters appears continously but i still cant read as its in ascii.
this is what i wrote:

Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click

SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13) & vbCrLf)

End Sub

Private Sub DataReceived( _
ByVal sender As Object, _
ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _
Handles SerialPort1.DataReceived

TextBox3.Invoke(New _
myDelegate(AddressOf updateTextBox3), _
New Object() {})
End Sub

Public Delegate Sub myDelegate()

Public Sub updateTextBox3()
With TextBox3
.Font = New Font("Garamond", 12.0!, FontStyle.Bold)
.AppendText(SerialPort1.ReadExisting & vbCrLf)
End With
End Sub

here're my questions:
1)how to convert my data read from port which is in ascii into decimal?
2)the incoming data is running such as in an overflow state,
it goes on...

but i want it to appears as a continuously changing figure.
like XX.XX (keeps changing)

How to write this command?

3) How to write the data read from the serial port into a txt file inside certain folder?