Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
SerialPort1.Open()
Dim mBuffer As Byte() = New Byte(0) {}
mBuffer(0) = &H74 'ASCII letra "t".
SerialPort1.Write(mBuffer, 0, mBuffer.Length)
SerialPort1.Close()
End Sub