🚀 go-pugleaf

Using information off the net about Direct Digital Synthesis 
(http://www.analog.com/library/analogDialogue/archives/38-08/dds.html) as an 
example, I have created a Direct Digital Synthesizer class  (TDDS) which can 
currently output square and sine waves (will upgrade to do triangle and 
sawtooth as well later).

You can produce your own arbitrary waveform at the desired frequency and 
sample rate on as well as the 4 built in wave types.

You would do this using your own TPhaseToAmplitude function 'event' to 
generate your own custom output.

I hope you guys find it useful

//*****  BEGINNING OF CODE *******
Unit direct_digital_synthensizer;

Interface

Type
{..............................................................................}
    TDDS = Class;
    TPhaseToAmplitude = Function(Const ADDS : TDDS) : Single;
    TNumberOfBits     = 2..31;
    TWaveType         = (wtSawtooth,wtSquare,wtTriangle,wtSine,wtCustom);
    TDefinedWaveType  = Low(TWaveType)..Pred(High(TWaveType));
    TDDS = Class
    Private
        FOnPhaseToAmplitude : TPhaseToAmplitude;
        FPhaseRegResolution : TNumberOfBits;
        FPhaseRegMaxPlus1   : LongWord;
        FPhaseRegMax        : LongWord;
        FPhaseRegHalfMax    : LongWord;
        FPhaseRegQuaterMax  : LongWord;
        FWaveType           : TWaveType;
        FSampleRate         : LongWord;
        FFrequency          : Single;
        FPhase              : LongWord;
        FPhaseReg           : LongWord;
        FPhaseRegIncrement  : LongWord;
        FAmplitude          : Single;
        Procedure FSetOnPhaseToAmplitude(Const AValue : TPhaseToAmplitude);
        Procedure SetPhaseRegIncrement;
    Public
        Constructor Create(Const APhaseRegResolution : TNumberOfBits);
        Procedure SetWaveType  (Const AValue : TDefinedWaveType);
        Procedure SetSampleRate(Const AValue : LongWord);
        Procedure SetFrequency (Const AValue : Single);
        Procedure Reset;
        Procedure Synthesize;
        Property  PhaseRegResolution : TNumberOfBits     Read 
FPhaseRegResolution;
        Property  PhaseRegMaxPlus1   : LongWord          Read 
FPhaseRegMaxPlus1;
        Property  PhaseRegMax        : LongWord          Read  FPhaseRegMax;
        Property  PhaseRegHalfMax    : LongWord          Read 
FPhaseRegHalfMax;
        Property  PhaseRegQuaterMax  : LongWord          Read 
FPhaseRegQuaterMax;
        Property  WaveType           : TWaveType         Read  FWaveType;
        Property  SampeRate          : LongWord          Read  FSampleRate;
        Property  Frequency          : Single            Read  FFrequency;
        Property  Phase              : LongWord          Read  FPhase;
        Property  Amplitude          : Single            Read  FAmplitude;
        Property  OnPhaseToAmplitude : TPhaseToAmplitude Read 
FOnPhaseToAmplitude
                                                         Write 
FSetOnPhaseToAmplitude;
    End;
{..............................................................................}

Implementation

{..............................................................................}

{..............................................................................}
Function PhaseToAmplitude_Sawtooth(Const ADDS : TDDS) : Single;
Begin
    Result := 0;
End;
{..............................................................................}

{..............................................................................}
Function PhaseToAmplitude_Square(Const ADDS : TDDS) : Single;
Begin
    If ADDS.Phase <= ADDS.PhaseRegHalfMax Then
        Result := -1
    Else
        Result := +1;
End;
{..............................................................................}

{..............................................................................}
Function PhaseToAmplitude_Triangle(Const ADDS : TDDS) : Single;
Begin
    Result := 0;
End;
{..............................................................................}

{..............................................................................}
Function PhaseToAmplitude_Sine(Const ADDS : TDDS) : Single;
Begin
    Result := Sin(2 * PI * ADDS.Phase/ADDS.PhaseRegMaxPlus1);
End;
{..............................................................................}

{..............................................................................}
Constructor TDDS.Create(Const APhaseRegResolution : TNumberOfBits);
Begin
    Inherited Create;
    FOnPhaseToAmplitude := Nil;
    FPhaseRegResolution := APhaseRegResolution;
    FPhaseRegMaxPlus1   := LongWord((1 Shl FPhaseRegResolution));
    FPhaseRegMax        := LongWord((1 Shl FPhaseRegResolution) - 1);
    FPhaseRegHalfMax    := LongWord(FPhaseRegMaxPlus1 Shr 1);
    FPhaseRegQuaterMax  := LongWord(FPhaseRegMaxPlus1 Shr 2);
    FSampleRate         := 44100;
    FFrequency          := 100;
    SetPhaseRegIncrement;
    SetWaveType(wtSine);
    Reset;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.FSetOnPhaseToAmplitude(Const AValue : TPhaseToAmplitude);
Begin
    If Not Assigned(AValue) Then Exit;
    FOnPhaseToAmplitude := AValue;
    FWaveType           := wtCustom;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.SetWaveType(Const AValue : TDefinedWaveType);
Begin
    FWaveType := AValue;
    Case FWaveType Of
        wtSawtooth : FOnPhaseToAmplitude := PhaseToAmplitude_Sawtooth;
        wtSquare   : FOnPhaseToAmplitude := PhaseToAmplitude_Square;
        wtTriangle : FOnPhaseToAmplitude := PhaseToAmplitude_Triangle;
        wtSine     : FOnPhaseToAmplitude := PhaseToAmplitude_Sine;
    End;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.SetPhaseRegIncrement;
Begin
    FPhaseRegIncrement  := LongWord(Trunc(FPhaseRegMax * FFrequency / 
FSampleRate)) And FPhaseRegMax;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.SetSampleRate(Const AValue : LongWord);
Begin
    FSampleRate := AValue;
    SetPhaseRegIncrement;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.SetFrequency(Const AValue : Single);
Begin
    FFrequency := AValue;
    SetPhaseRegIncrement;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.Reset;
Begin
    FPhase    := 0;
    FPhaseReg := 0;
End;
{..............................................................................}

{..............................................................................}
Procedure TDDS.Synthesize;
Begin
    FPhase     := FPhaseReg;
    FAmplitude := FOnPhaseToAmplitude(Self);
    {$R-}
    FPhaseReg  := LongWord(FPhaseReg + FPhaseRegIncrement) And FPhaseRegMax;
    {$R+}
End;
{..............................................................................}

{..............................................................................}
End.

//*****  END OF CODE *******

You set up the desired parameters in the class, call the Reset method once, 
and each time you need a sample, just call the Synthesize method to generate 
a value you can then read using the Amplitude or Phase properties.

cheers,
Paul