Hi Geoff,
 
  I write my code in Visual Basic, and also have another FFT routine  written 
in QBasic. The code listing below is what I use in my FFTDemo program,  which 
you can access from _http://www.jclahr.com/science/psn/mcclure/index.html_ 
(http://www.jclahr.com/science/psn/mcclure/index.html)  
 
Cheers,
 
Bob
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
Private Sub FFT(Z() As Single)
Inv = 0
Call  FT(Inv, Npwr, Z())
End Sub
 

Private Sub IFT(Z() As Single)
Inv =  1
Call FT(Inv, Npwr, Z())
End Sub
 

Private Sub FT(Inv As Long, Npwr As Long, Z()  As Single)
Dim PI As Single, Isi As Long, ex As Single
Dim I As Long, n As  Long, J As Long, m As Long, Mmax As Long
Dim Ang As Single, wr As Single, wi  As Single, tr As Single
Dim ti As Single, istep As Long
PI = 4# *  Atn(1#)
Isi = -1
If Inv > 0 Then Isi = 1
n =  1
For I = 1 To Npwr
n = 2 * n
Next I
J =  0
For I = 0 To n - 2
If I < J Then
ex =  Z(0, I)
Z(0, I) = Z(0, J)
Z(0, J) =  ex
ex = Z(1, I)
Z(1, I) = Z(1,  J)
Z(1, J) = ex
End If
m = n / 2
While m <= J
J = J - m
m = m / 2
Wend
J = J + m
Next I
Mmax = 1
While Mmax  <> n
istep = 2 * Mmax
For m = 0 To Mmax -  1
Ang = PI * Isi * m / Mmax
wr =  Cos(Ang)
wi = Sin(Ang)
For I = m To  n - 1 Step istep
J = I +  Mmax
tr = wr * Z(0, J) - wi * Z(1,  J)
ti = wi * Z(0, J) + wr * Z(1,  J)
Z(0, J) = Z(0, I) -  tr
Z(1, J) = Z(1, I) -  ti
Z(0, I) = Z(0, I) +  tr
Z(1, I) = Z(1, I) + ti
Next  I
Next m
Mmax = istep
Wend
If Isi  > 0 Then
For I = 0 To n - 1
Z(0, I) =  (1 / n) * Z(0, I)
Z(1, I) = (1 / n) * Z(1,  I)
Next I
End If
End Sub
 
 



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Hi Geoff,
 
  I write my code in Visual Basic, and also have another FFT routi=
ne=20
written in QBasic. The code listing below is what I use in my FFTDemo progra=
m,=20
which you can access from http://www.jcl=
ahr.com/science/psn/mcclure/index.html=20

 
Cheers,
 
Bob
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
Private Sub FFT(Z() As Single)
Inv =3D 0<=
BR>Call=20
FT(Inv, Npwr, Z())
End Sub
 

Private Sub IFT(Z() As Single)
Inv=20=
=3D=20
1
Call FT(Inv, Npwr, Z())
End Sub
 

Private Sub FT(Inv As Long, Npwr As Long=
, Z()=20
As Single)
Dim PI As Single, Isi As Long, ex As Single
Dim I As Long,=20=
n As=20
Long, J As Long, m As Long, Mmax As Long
Dim Ang As Single, wr As Single,=
 wi=20
As Single, tr As Single
Dim ti As Single, istep As Long
 PI =3D 4=
# *=20
Atn(1#)
 Isi =3D -1
 If Inv > 0 Then Isi =3D 1
 n=
 =3D=20
1
 For I =3D 1 To Npwr
  n =3D 2 * n
 Next I
&nbs=
p;J =3D=20
0
 For I =3D 0 To n - 2
  If I < J Then
   e=
x =3D=20
Z(0, I)
   Z(0, I) =3D Z(0, J)
   Z(0, J) =3D=20
ex
   ex =3D Z(1, I)
   Z(1, I) =3D Z(1,=20
J)
   Z(1, J) =3D ex
  End If
  m =3D n / 2
=
 =20
While m <=3D J
   J =3D J - m
   m =3D m / 2 =20
Wend
  J =3D J + m
  Next I
  Mmax =3D 1
 Wh=
ile Mmax=20
<> n
   istep =3D 2 * Mmax
   For m =3D 0 To=
 Mmax -=20
1
    Ang =3D PI * Isi * m / Mmax
    wr=
 =3D=20
Cos(Ang)
    wi =3D Sin(Ang)
    For I=20=
=3D m To=20
n - 1 Step istep
     J =3D I +=20
Mmax
     tr =3D wr * Z(0, J) - wi * Z(1,=20
J)
     ti =3D wi * Z(0, J) + wr * Z(1,=20
J)
     Z(0, J) =3D Z(0, I) -=20
tr
     Z(1, J) =3D Z(1, I) -=20
ti
     Z(0, I) =3D Z(0, I) +=20
tr
     Z(1, I) =3D Z(1, I) + ti
   =
; Next=20
I
   Next m
   Mmax =3D istep
  Wend
If=
 Isi=20
> 0 Then
   For I =3D 0 To n - 1
    Z(0,=20=
I) =3D=20
(1 / n) * Z(0, I)
    Z(1, I) =3D (1 / n) * Z(1,=20
I)
   Next I
  End If
 End Sub
 
 


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