/* Example of amplitude modulation (as tremelo),
using Mozzi sonification library.
Demonstrates audio and control rate updates.
The tremelo oscillator is updated at control rate,
and a Line is used to interpolate the control updates
at audio rate, to remove zipper noise.
A bit contrived and probably less efficient than just
using an audio-rate tremelo oscillator, but hey it's a demo!
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
Copyright 2012-2024 Tim Barrass and the Mozzi Team
Mozzi is licensed under the GNU Lesser General Public Licence (LGPL) Version 2.1 or later.
*/
#define MOZZI_CONTROL_RATE 64 // Hz, powers of 2 are most reliable
#include <Mozzi.h>
#include <Oscil.h>
#include <tables/triangle_valve_2048_int8.h>
#include <tables/sin2048_int8.h>
#include <Line.h>
#include <mozzi_midi.h>
// audio oscillator
Oscil<TRIANGLE_VALVE_2048_NUM_CELLS, MOZZI_AUDIO_RATE> aSig(TRIANGLE_VALVE_2048_DATA);
// control oscillator for tremelo
Oscil<SIN2048_NUM_CELLS, MOZZI_CONTROL_RATE> kTremelo(SIN2048_DATA);
// a line to interpolate control tremolo at audio rate
Line <unsigned int> aGain;
void setup(){
aSig.setFreq(mtof(65.f));
kTremelo.setFreq(5.5f);
startMozzi();
}
void updateControl(){
// gain shifted up to give enough range for line's internal steps
unsigned int gain = (128u+kTremelo.next())<<8;
aGain.set(gain, MOZZI_AUDIO_RATE / MOZZI_CONTROL_RATE); // divide of literals should get optimised away
}
AudioOutput updateAudio(){
// cast to long before multiply to give room for intermediate result,
// and also before shift,
// to give consistent results for both 8 and 32 bit processors.
return MonoOutput::fromNBit(24, (int32_t) aSig.next() * aGain.next()); // shifted back to audio range after multiply
}
void loop(){
audioHook();
}
