10.Audio_Filters/ResonantFilter/ResonantFilter.ino

This example demonstrates the ResonantFilter specification of this class.

/*  Example of filtering a wave,
    using Mozzi sonification library.

    Demonstrates ResonantFilter<uint8_t, FILTER_TYPE>>.
    
    Note that, on 8bits platforms (Arduino) this filter cannot work
    on samples of more than 8bits. Use LowPassFilter16() if you need
    more than that.

    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 <tables/chum9_int8.h> // recorded audio wavetable
#include <tables/cos2048_int8.h> // for filter modulation
#include <ResonantFilter.h>
#include <mozzi_rand.h>

Oscil<CHUM9_NUM_CELLS, AUDIO_RATE> aCrunchySound(CHUM9_DATA);
Oscil<COS2048_NUM_CELLS, CONTROL_RATE> kFilterMod(COS2048_DATA);

//Different types of filters available
LowPassFilter rf; // Equivalent to ResonantFilter<LOWPASS>
//ResonantFilter<HIGHPASS> rf; // HighPass filter
//ResonantFilter<BANDPASS> rf; // BandPass filter
//ResonantFilter<NOTCH> rf; // Notch filter

uint8_t resonance = 200; // range 0-255, 255 is most resonant

void setup(){
  startMozzi();
  aCrunchySound.setFreq(2.f);
  kFilterMod.setFreq(1.3f);
}

void loop(){
  audioHook();
}

void updateControl(){
  if (rand(CONTROL_RATE/2) == 0){ // about once every half second
    kFilterMod.setFreq((float)rand(255)/64);  // choose a new modulation frequency
  }
  // map the modulation into the filter range (0-255), corresponds with 0-AUDIO_RATE/(sqrt(2)*pi) Hz
  byte cutoff_freq = 100 + kFilterMod.next()/2;
  rf.setCutoffFreqAndResonance(cutoff_freq, resonance);
}

AudioOutput_t updateAudio(){
  char asig = rf.next(aCrunchySound.next());
  return MonoOutput::from8Bit(asig);
}