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'******************************************************************************
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'* ToneGenerator *
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'* *
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'* This class implements a custom control to generate a sinusoidal tone. *
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'* The user can modify the frequency and output power in real time. *
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'* *
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'* We calculate the minimum samples of the tone that we need to generate a *
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'* continous signal with the given sampling and output frequency. *
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'* Then, each time the caller want to have a new fragment of the tone, we *
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'* repeat the calculated samples as many times as we need to fill the output *
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'* buffer. *
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'* *
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'* EQUITEL - C.V. February 2007 ALMDI *
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'******************************************************************************
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Imports System.ComponentModel
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Imports System.Math
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Public Class ToneGenerator
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Private mInternalBuffer As Short()
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Private mBufSize As Integer
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Private mSampligFrequency As Integer = 8000
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Private mFrequency As Integer = 1000
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Private mPower As Double = -0
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Private mSignalIsCalculated As Boolean = False
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#Region "Properties"
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<Category("Signal"), DefaultValue(GetType(Integer), "8000"), _
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Description("Samplinf frequency of the generated signal")> _
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Public Property SamplingFrequency() As Integer
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Get
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Return mSampligFrequency
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End Get
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Set(ByVal value As Integer)
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If value >= 8000 AndAlso value <= 96000 Then
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mSampligFrequency = value
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End If
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End Set
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End Property
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<Category("Signal"), DefaultValue(GetType(Integer), "1000"), _
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Description("Frequency of the tone")> _
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Public Property Frequency() As Integer
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Get
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Return mFrequency
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End Get
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Set(ByVal value As Integer)
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If value >= 100 AndAlso value <= mSampligFrequency / 2 Then
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mFrequency = value
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CtrlFrequency.Value = value
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lblFrequency.Text = Format(mFrequency / 1000, "0.0 kHz")
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ToneCalculation()
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End If
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End Set
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End Property
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<Category("Signal"), DefaultValue(GetType(Integer), "-100"), _
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Description("Relative output power in decibels")> _
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Public Property Power() As Double
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Get
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Return mPower
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End Get
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Set(ByVal value As Double)
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If value >= -100 AndAlso value <= 0 Then
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mPower = value
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CtrlPower.Value = value
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lblPower.Text = Format(value, "0 dB")
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ToneCalculation()
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End If
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End Set
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End Property
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<Category("Signal"), _
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Description("Indicates if the tone is calculated")> _
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Public ReadOnly Property SignalIsCalculated() As Boolean
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Get
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Return mSignalIsCalculated
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End Get
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End Property
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<Category("Signal"), _
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Description("Number of samples calculated")> _
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Public ReadOnly Property NumCalculatedSamples() As Integer
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Get
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Return mBufSize
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End Get
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End Property
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#End Region
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Public Event OnCalculatedTone()
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Private Sub ToneCalculation()
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Dim i As Integer
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Dim t As Double
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Dim W As Double
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Dim Factor As Double
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Dim Vmax As Integer
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Dim M As Integer
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Dim NecessaryCycles As Integer
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Dim NecessarySamples As Integer
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'We calculate the maximum common divider ot the two frequencies
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'and the number of cycles and samples that we need to create a
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'buffer that can be repeated to generate the tone.
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M = MCD(mSampligFrequency, mFrequency)
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NecessaryCycles = mFrequency / M
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NecessarySamples = mSampligFrequency / M
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'.. and do the calculation
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ReDim mInternalBuffer(NecessarySamples - 1)
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mBufSize = NecessarySamples
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W = 2 * 3.141592659 * mFrequency
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Factor = 20 ^ (mPower / (10 * 3))
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Vmax = Int(32767 * Factor)
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For i = 0 To NecessarySamples - 1
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t = i * (1 / mSampligFrequency)
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mInternalBuffer(i) = Vmax * Sin(W * t)
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Next
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mSignalIsCalculated = True
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RaiseEvent OnCalculatedTone()
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End Sub
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Private Function MCD(ByVal F1 As Integer, ByVal F2 As Integer) As Integer
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'Maximum common divider of two integers calculated with the
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'Euclide algorithm
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'We assume that F1>F2
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Dim X1 As Integer, X2 As Integer, X3 As Integer
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X1 = F1
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X2 = F2
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Do
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X3 = X1 Mod X2
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If X3 = 0 Then Exit Do
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X1 = X2
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X2 = X3
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Loop
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Return X2
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End Function
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Private Sub Power_Scroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CtrlPower.Scroll
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Power = CtrlPower.Value
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End Sub
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Private Sub Frequency_Scroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CtrlFrequency.Scroll
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CtrlFrequency.Value = Int(CtrlFrequency.Value / 100) * 100
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Frequency = CtrlFrequency.Value
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End Sub
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Public Sub OutputPacket(ByRef Buffer As Short(), ByVal NumSamples As Integer)
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'Returns a packet of the tone calculated
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Dim i As Integer
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Static mInternalBufferPointer As Integer = 0
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If Not mSignalIsCalculated Then ToneCalculation()
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For i = 0 To NumSamples - 1
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Buffer(i) = mInternalBuffer(mInternalBufferPointer)
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mInternalBufferPointer += 1
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If mInternalBufferPointer = mBufSize Then
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mInternalBufferPointer = 0
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End If
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Next
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End Sub
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End Class
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