vfo.cpp

00001 #include "signal_processing.h"
00002 
00003 
00004 VFO::VFO( int32_t block_size )
00005 {
00006         // initial parameter setting.
00007     this->block_size = block_size;
00008     
00009     this->form = triangle;
00010     this->Fs = 48000;
00011     this->frequency = 440;
00012     this->duty_cycle = 0.5;
00013     
00014     this->update_parameters();
00015 }   // End of constructor()
00016 
00017 VFO::~VFO( void )
00018 {
00019     // do nothing
00020 }
00021     
00022     
00023 
00024 void VFO::run(           
00025             float out_buffer[]         // vfo output buffer
00026            )
00027 {
00028         
00029         // place the signal processing coce here
00030     for ( int i= 0; i< this->block_size; i++ )
00031     {
00032             // 1 : if phase < half_way; 0 : others.
00033         if ( this->form == square ) 
00034         {
00035             if ( this->current_phase < this->half_way )
00036                 out_buffer[i] = 1.0;
00037             else
00038                 out_buffer[i] = 0.0;
00039         }
00040         else    // form == triangle
00041         {
00042             if ( this->current_phase < this->half_way )
00043                 out_buffer[i] = this->rising_rate * this->current_phase;
00044             else
00045                 out_buffer[i] = 1 + this->falling_rate * ( this->current_phase - this->half_way );
00046         }
00047         
00048             // update phase
00049         this->current_phase += this->frequency;
00050             // limit the range of the phase.
00051         if ( this->current_phase >= this->Fs )
00052             this->current_phase -= this->Fs;
00053     }
00054 }   // End of run()
00055     
00056 
00057 void VFO::set_Fs( int Fs )
00058 {
00059         // regulate the Fs.
00060     if ( Fs != 32000 && Fs != 44100 && Fs != 96000 && Fs != 48000 )
00061         Fs = 48000;
00062     this->Fs = Fs;
00063     
00064     this->update_parameters();
00065 }
00066 
00067 void VFO::set_frequency( float freq )
00068 {
00069     if ( freq > this->Fs / 4 )
00070         freq = Fs / 4;
00071     this->frequency = freq;
00072     
00073     this->update_parameters();
00074 }
00075 
00076 void VFO::set_duty_cycle( float duty )
00077 {
00078     if ( duty > 0.5f )   // high limit
00079         duty = 0.5f;
00080     if ( duty < 0.0f )  // low limit
00081         duty = 0.0f;
00082     this->duty_cycle = duty;
00083     
00084     this->update_parameters();
00085 }
00086 
00087 void VFO::set_wave_form( wave_form form )
00088 {
00089     this->form = form;
00090 }
00091 
00092 
00093     // update the internal parameter by given parameters
00094 void VFO::update_parameters(void)
00095 {
00096         // calc the half_way;
00097     this-> half_way = this->Fs * this-> duty_cycle;
00098     
00099         // make it integer multiple of frequency
00100     this->half_way = (int)(this->half_way/this->frequency);
00101     this->half_way *= this->frequency;
00102 
00103         // forbid to be zero.
00104     if ( this-> half_way < this->frequency )
00105         this->half_way = this->frequency;              
00106         
00107         // for triangle wave;
00108     this->rising_rate = 1.0 / this->half_way;
00109     
00110     this->falling_rate = - 1.0 / ( this->Fs - this->half_way ); 
00111 }
00112