| Mozzi version v1.1.0 sound synthesis library for Arduino |

06.Synthesis/WaveShaper/WaveShaper.ino

This is an example of how to use the WaveShaper class.

/* Example using waveshaping to modify the spectrum of an audio signal
using Mozzi sonification library.
Demonstrates the use of WaveShaper(), EventDelay(), Smooth(),
rand(), and fixed-point numbers.
Circuit: Audio output on digital pin 9 on a Uno or similar, or
DAC/A14 on Teensy 3.1, or
check the README or http://sensorium.github.io/Mozzi/
Mozzi documentation/API
https://sensorium.github.io/Mozzi/doc/html/index.html
Mozzi help/discussion/announcements:
https://groups.google.com/forum/#!forum/mozzi-users
Tim Barrass 2012, CC by-nc-sa.
*/
#include <MozziGuts.h>
#include <Oscil.h>
#include <WaveShaper.h>
#include <EventDelay.h>
#include <mozzi_rand.h>
#include <mozzi_midi.h>
#include <Smooth.h>
#include <tables/sin2048_int8.h>
#include <tables/waveshape_chebyshev_3rd_256_int8.h>
#include <tables/waveshape_chebyshev_6th_256_int8.h>
#include <tables/waveshape_compress_512_to_488_int16.h>
// use: Oscil <table_size, update_rate> oscilName (wavetable), look in .h file of table #included above
Oscil <SIN2048_NUM_CELLS, AUDIO_RATE> aSin(SIN2048_DATA); // sine wave sound source
Oscil <SIN2048_NUM_CELLS, AUDIO_RATE> aGain1(SIN2048_DATA); // to fade sine wave in and out before waveshaping
Oscil <SIN2048_NUM_CELLS, AUDIO_RATE> aGain2(SIN2048_DATA); // to fade sine wave in and out before waveshaping
// Chebyshev polynomial curves, The nth curve produces the n+2th harmonic component.
WaveShaper <char> aCheby3rd(CHEBYSHEV_3RD_256_DATA); // 5th harmonic
WaveShaper <char> aCheby6th(CHEBYSHEV_6TH_256_DATA); // 8th harmonic
WaveShaper <int> aCompress(WAVESHAPE_COMPRESS_512_TO_488_DATA); // to compress instead of dividing by 2 after adding signals
// for scheduling note changes
EventDelay kChangeNoteDelay;
// for random notes
Q8n0 octave_start_note = 42;
Q24n8 carrier_freq; // unsigned long with 24 integer bits and 8 fractional bits
// smooth transitions between notes
Smooth <unsigned int> kSmoothFreq(0.85f);
int target_freq, smoothed_freq;
void setup(){
startMozzi(); // :)
randSeed(); // reseed the random generator for different results each time the sketch runs
aSin.setFreq(110); // set the frequency
aGain1.setFreq(2.f); // use a float for low frequencies, in setup it doesn't need to be fast
aGain2.setFreq(.4f);
kChangeNoteDelay.set(4000); // note duration ms, within resolution of CONTROL_RATE
}
byte rndPentatonic(){
byte note = rand((byte)5);
switch(note){
case 0:
note = 0;
break;
case 1:
note = 3;
break;
case 2:
note = 5;
break;
case 3:
note = 7;
break;
case 4:
note = 10;
break;
}
return note;
}
void updateControl(){
if(kChangeNoteDelay.ready()){
if(rand((byte)5)==0){ // about 1 in 5 or so
// change octave to midi 24 or any of 3 octaves above
octave_start_note = (rand((byte)4)*12)+36;
}
Q16n16 midi_note = Q8n0_to_Q16n16(octave_start_note+rndPentatonic());
target_freq = Q16n16_to_Q16n0(Q16n16_mtof(midi_note)); // has to be 16 bits for Smooth
kChangeNoteDelay.start();
}
smoothed_freq = kSmoothFreq.next(target_freq*4); // temporarily scale up target_freq to get better int smoothing at low values
aSin.setFreq(smoothed_freq/4); // then scale it back down after it's smoothed
}
AudioOutput_t updateAudio(){
char asig0 = aSin.next(); // sine wave source
// make 2 signals fading in and out to show effect of amplitude when waveshaping with Chebyshev polynomial curves
// offset the signals by 128 to fit in the 0-255 range for the waveshaping table lookups
byte asig1 = (byte)128+((asig0*((byte)128+aGain1.next()))>>8);
byte asig2 = (byte)128+((asig0*((byte)128+aGain2.next()))>>8);
// get the waveshaped signals
char awaveshaped1 = aCheby3rd.next(asig1);
char awaveshaped2 = aCheby6th.next(asig2);
// use a waveshaping table to squeeze 2 summed 8 bit signals into the range -244 to 243
int awaveshaped3 = aCompress.next(256u + awaveshaped1 + awaveshaped2);
return MonoOutput::fromAlmostNBit(9, awaveshaped3);
}
void loop(){
audioHook(); // required here
}