Full Synth Demo

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Four Oscillator Synthesizer

This final example will give you an idea of how to patch a more complex synthesizer that uses four waveform nodes, each initialized to a different waveform type.

These will each flow through a different envelope, and in some cases their own effects nodes.

Finally, we'll use multiple mixers to combine the sounds together.

To begin, replicate the patch shown above.

Most of it is pretty straightforward, with four waveforms each running through a respective envelope.

mixer1 is used to combine the four waveforms, with some of them running through effects first.

We then use a pair of mixers, mixerLeft and mixerRight to mix in the multiple taps of the delay, and then combine everything for stereo audioOut.

These are the relevant settings used to make this sounds come alive. (You can experiment with them once you've got it running later.)

Waveforms

We're setting up the four waveform nodes as sine, square, sawtooth, and triangle waves respectively.

wave0.begin(0.85, 50, WAVEFORM_SINE);
wave1.begin(0.4, 50, WAVEFORM_SQUARE);
wave2.begin(0.6, 50, WAVEFORM_SAWTOOTH);
wave3.begin(0.4, 50, WAVEFORM_TRIANGLE);

Envelopes

The envelopes are defined with the attack, hold, decay, sustain, and release settings. Our first row has a very soft attack and a long release:

env0.attack(300);
env0.hold(2);
env0.decay(30);
env0.sustain(0.6);
env0.release(1200);

The second oscillator has a quick attack and a moderate release:

env1.attack(10);
env1.hold(2);
env1.decay(30);
env1.sustain(0.6);
env1.release(400);

The third oscillator is similar to the second with a longer release:

env2.attack(10);
env2.hold(20);
env2.decay(30);
env2.sustain(0.6);
env2.release(1000);

The fourth oscillator has a quick attack and moderately long release:

env3.attack(10);
env3.hold(2);
env3.decay(30);
env3.sustain(0.6);
env3.release(600);

Arduino Code

This is the code you'll copy and paste into a new Arduino sketch.

Download File
Copy Code 
/* Audio library demonstration - pocket synth with C major scale and 4 wave types */
//each row is a different waveform, envelope, and effect set in major scale
// row 0 sine, soft attack, long release ADSR
// row 1 square, hard attack, moderate release, flanger effect
// row 2 sawtooth, hard attack, soft release, chorus effect
// row 3 triangle, medium attack, long release ADSR, multi tap delay

#include <Audio.h>
#include <Adafruit_NeoTrellisM4.h>

Adafruit_NeoTrellisM4 trellis = Adafruit_NeoTrellisM4();
// Paste your Audio System Design Tool code below this line:




//




AudioSynthWaveform *waves[4] = {
&wave0, &wave1, &wave2, &wave3,
};
short wave_type[4] = {
  WAVEFORM_SINE,
  WAVEFORM_SQUARE,
  WAVEFORM_SAWTOOTH,
  WAVEFORM_TRIANGLE,
};
float cmaj_low[8] = { 130.81, 146.83, 164.81, 174.61, 196.00, 220.00, 246.94, 261.63 };
float cmaj_high[8] = { 261.6, 293.7, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3 };
AudioEffectEnvelope *envs[4] = {
  &env0, &env1, &env2, &env3,
};
int n_chorus = 5;
#define CHORUS_DELAY_LENGTH (400*AUDIO_BLOCK_SAMPLES)
short chorusDelayline[CHORUS_DELAY_LENGTH];

#define FLANGER_DELAY_LENGTH (6*AUDIO_BLOCK_SAMPLES)
short flangerDelayline[FLANGER_DELAY_LENGTH];

void setup(){
  Serial.begin(115200);
  //while (!Serial);

  trellis.begin();
  trellis.setBrightness(255);

  AudioMemory(120);

  //Initialize the waveform nodes
  wave0.begin(0.85, 50, WAVEFORM_SINE);
  wave1.begin(0.4, 50, WAVEFORM_SQUARE);
  wave2.begin(0.6, 50, WAVEFORM_SAWTOOTH);
  wave3.begin(0.4, 50, WAVEFORM_TRIANGLE);

  // reduce the gain on some channels, so half of the channels
  // are "positioned" to the left, half to the right, but all
  // are heard at least partially on both ears
  mixerLeft.gain(0, 0.3);
  mixerLeft.gain(1, 0.1);
  mixerLeft.gain(2, 0.5);

  mixerRight.gain(0, 0.3);
  mixerRight.gain(1, 0.5);
  mixerRight.gain(2, 0.1);


  // set envelope parameters, for pleasing sound :-)
  env0.attack(300);
  env0.hold(2);
  env0.decay(30);
  env0.sustain(0.6);
  env0.release(1200);

  env1.attack(10);
  env1.hold(2);
  env1.decay(30);
  env1.sustain(0.6);
  env1.release(400);

  env2.attack(10);
  env2.hold(20);
  env2.decay(30);
  env2.sustain(0.6);
  env2.release(1000);

  env3.attack(10);
  env3.hold(2);
  env3.decay(30);
  env3.sustain(0.6);
  env3.release(600);

  // set delay parameters
  delay1.delay(0, 110);
  delay1.delay(1, 660);
  delay1.delay(2, 220);
  delay1.delay(3, 1220);

  // set effects parameters
  chorus1.begin(chorusDelayline, CHORUS_DELAY_LENGTH, n_chorus);
  flange1.begin(flangerDelayline, FLANGER_DELAY_LENGTH, FLANGER_DELAY_LENGTH/4, FLANGER_DELAY_LENGTH/4, .5);


  Serial.println("setup done");

  // Initialize processor and memory measurements
  AudioProcessorUsageMaxReset();
  AudioMemoryUsageMaxReset();
}

void noteOn(int num){
  int voice = num/8;
  float *scale;
  if(voice == 0 || voice == 1) scale = cmaj_low;
  else scale = cmaj_high;
  AudioNoInterrupts();
  //waves[voice]->begin(.5, scale[num%8], wave_type[voice]);
  waves[voice]->frequency(scale[num%8]);
  envs[voice]->noteOn();
  AudioInterrupts();
}

void noteOff(int num){
  int voice = num/8;
  envs[voice]->noteOff();
}

void loop() {
  trellis.tick();

  while(trellis.available())
  {
    keypadEvent e = trellis.read();
    int keyindex = e.bit.KEY;
    if(e.bit.EVENT == KEY_JUST_PRESSED){
        //trellis.setPixelColor(keyindex, 0xFFFFFF); // plain white
        trellis.setPixelColor(keyindex, Wheel(keyindex * 255 / 32)); // rainbow!
        noteOn(keyindex);
      }
    else if(e.bit.EVENT == KEY_JUST_RELEASED){
        noteOff(keyindex);
        trellis.setPixelColor(keyindex, 0);
      }
   }
  delay(10);
}


// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  WheelPos = 255 - WheelPos;
  if(WheelPos < 85) {
    return Adafruit_NeoPixel::Color(255 - WheelPos * 3, 0, WheelPos * 3);
  }
  if(WheelPos < 170) {
    WheelPos -= 85;
    return Adafruit_NeoPixel::Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
  WheelPos -= 170;
  return Adafruit_NeoPixel::Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}

Now, export the source code snippet from the Audio System Design Tool and paste it into the section indicated in the Arduino sketch.

Save this code as Synth_Design_Tool_Demo_TrellisM4.ino and then upload it to the board.

This is what the final code looks like with the Audio System Design Tool GUI code added.

Download File
Copy Code 
// SPDX-FileCopyrightText: 2018 John Park for Adafruit Industries
//
// SPDX-License-Identifier: MIT

/* Audio library demonstration - pocket synth with C major scale and 4 wave types */
//each row is a different waveform, envelope, and effect set in major scale
// row 0 sine, soft attack, long release ADSR
// row 1 square, hard attack, moderate release, flanger effect
// row 2 sawtooth, hard attack, soft release, chorus effect
// row 3 triangle, medium attack, long release ADSR, multi tap delay

#include <Audio.h>
#include <Adafruit_NeoTrellisM4.h>

Adafruit_NeoTrellisM4 trellis = Adafruit_NeoTrellisM4();
// Paste your Audio System Design Tool code below this line:
// GUItool: begin automatically generated code
AudioSynthWaveform       wave0;          //xy=453.84613037109375,254.61540985107422
AudioSynthWaveform       wave1;          //xy=453.84613037109375,294.6154098510742
AudioSynthWaveform       wave2;          //xy=453.84613037109375,354.6154098510742
AudioSynthWaveform       wave3;          //xy=453.84613037109375,404.6154098510742
AudioEffectEnvelope      env0;           //xy=602.8461303710938,254.61540985107422
AudioEffectEnvelope      env1;           //xy=602.8461303710938,294.6154098510742
AudioEffectEnvelope      env2;           //xy=602.8461303710938,354.6154098510742
AudioEffectEnvelope      env3;           //xy=602.8461303710938,404.6154098510742
AudioEffectChorus        chorus1;        //xy=734.6796264648438,333.14093017578125
AudioEffectFlange        flange1;        //xy=737.7564392089844,284.6794891357422
AudioEffectDelay         delay1;         //xy=880.7692260742188,582.3077392578125
AudioMixer4              mixer1;         //xy=882.3076171875,284.6154327392578
AudioMixer4              mixerLeft;      //xy=1041.9999389648438,293.84617614746094
AudioMixer4              mixerRight;     //xy=1045.0768432617188,394.6153869628906
AudioOutputAnalogStereo  audioOut;       //xy=1212.8461303710938,354.6154098510742
AudioConnection          patchCord1(wave0, env0);
AudioConnection          patchCord2(wave1, env1);
AudioConnection          patchCord3(wave2, env2);
AudioConnection          patchCord4(wave3, env3);
AudioConnection          patchCord5(env0, 0, mixer1, 0);
AudioConnection          patchCord6(env1, flange1);
AudioConnection          patchCord7(env2, chorus1);
AudioConnection          patchCord8(env3, delay1);
AudioConnection          patchCord9(env3, 0, mixer1, 3);
AudioConnection          patchCord10(chorus1, 0, mixer1, 2);
AudioConnection          patchCord11(flange1, 0, mixer1, 1);
AudioConnection          patchCord12(delay1, 0, mixerLeft, 1);
AudioConnection          patchCord13(delay1, 1, mixerLeft, 2);
AudioConnection          patchCord14(delay1, 2, mixerRight, 1);
AudioConnection          patchCord15(delay1, 3, mixerRight, 2);
AudioConnection          patchCord16(mixer1, 0, mixerLeft, 0);
AudioConnection          patchCord17(mixer1, 0, mixerRight, 0);
AudioConnection          patchCord18(mixerLeft, 0, audioOut, 0);
AudioConnection          patchCord19(mixerRight, 0, audioOut, 1);
// GUItool: end automatically generated code

AudioSynthWaveform *waves[4] = {
&wave0, &wave1, &wave2, &wave3,
};
short wave_type[4] = {
  WAVEFORM_SINE,
  WAVEFORM_SQUARE,
  WAVEFORM_SAWTOOTH,
  WAVEFORM_TRIANGLE,
};
float cmaj_low[8] = { 130.81, 146.83, 164.81, 174.61, 196.00, 220.00, 246.94, 261.63 };
float cmaj_high[8] = { 261.6, 293.7, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3 };
AudioEffectEnvelope *envs[4] = {
  &env0, &env1, &env2, &env3,
};
int n_chorus = 5;
#define CHORUS_DELAY_LENGTH (400*AUDIO_BLOCK_SAMPLES)
short chorusDelayline[CHORUS_DELAY_LENGTH];

#define FLANGER_DELAY_LENGTH (6*AUDIO_BLOCK_SAMPLES)
short flangerDelayline[FLANGER_DELAY_LENGTH];

void setup(){
  Serial.begin(115200);
  //while (!Serial);

  trellis.begin();
  trellis.setBrightness(255);

  AudioMemory(120);

  //Initialize the waveform nodes
  wave0.begin(0.85, 50, WAVEFORM_SINE);
  wave1.begin(0.4, 50, WAVEFORM_SQUARE);
  wave2.begin(0.6, 50, WAVEFORM_SAWTOOTH);
  wave3.begin(0.4, 50, WAVEFORM_TRIANGLE);

  // reduce the gain on some channels, so half of the channels
  // are "positioned" to the left, half to the right, but all
  // are heard at least partially on both ears
  mixerLeft.gain(0, 0.3);
  mixerLeft.gain(1, 0.1);
  mixerLeft.gain(2, 0.5);

  mixerRight.gain(0, 0.3);
  mixerRight.gain(1, 0.5);
  mixerRight.gain(2, 0.1);


  // set envelope parameters, for pleasing sound :-)
  env0.attack(300);
  env0.hold(2);
  env0.decay(30);
  env0.sustain(0.6);
  env0.release(1200);

  env1.attack(10);
  env1.hold(2);
  env1.decay(30);
  env1.sustain(0.6);
  env1.release(400);

  env2.attack(10);
  env2.hold(20);
  env2.decay(30);
  env2.sustain(0.6);
  env2.release(1000);

  env3.attack(10);
  env3.hold(2);
  env3.decay(30);
  env3.sustain(0.6);
  env3.release(600);

  // set delay parameters
  delay1.delay(0, 110);
  delay1.delay(1, 660);
  delay1.delay(2, 220);
  delay1.delay(3, 1220);

  // set effects parameters
  chorus1.begin(chorusDelayline, CHORUS_DELAY_LENGTH, n_chorus);
  flange1.begin(flangerDelayline, FLANGER_DELAY_LENGTH, FLANGER_DELAY_LENGTH/4, FLANGER_DELAY_LENGTH/4, .5);


  Serial.println("setup done");

  // Initialize processor and memory measurements
  AudioProcessorUsageMaxReset();
  AudioMemoryUsageMaxReset();
}

void noteOn(int num){
  int voice = num/8;
  float *scale;
  if(voice == 0 || voice == 1) scale = cmaj_low;
  else scale = cmaj_high;
  AudioNoInterrupts();
  waves[voice]->frequency(scale[num%8]);
  envs[voice]->noteOn();
  AudioInterrupts();
}

void noteOff(int num){
  int voice = num/8;
  envs[voice]->noteOff();
}

void loop() {
  trellis.tick();

  while(trellis.available())
  {
    keypadEvent e = trellis.read();
    int keyindex = e.bit.KEY;
    if(e.bit.EVENT == KEY_JUST_PRESSED){
        trellis.setPixelColor(keyindex, Wheel(keyindex * 255 / 32)); // rainbow!
        noteOn(keyindex);
      }
    else if(e.bit.EVENT == KEY_JUST_RELEASED){
        noteOff(keyindex);
        trellis.setPixelColor(keyindex, 0);
      }
   }
  delay(10);
}


// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  WheelPos = 255 - WheelPos;
  if(WheelPos < 85) {
    return Adafruit_NeoPixel::Color(255 - WheelPos * 3, 0, WheelPos * 3);
  }
  if(WheelPos < 170) {
    WheelPos -= 85;
    return Adafruit_NeoPixel::Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
  WheelPos -= 170;
  return Adafruit_NeoPixel::Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}
View on GitHub

Now, you can play the synth! Each row plays a C major scale using a different oscillator waveform type or mix. Try playing notes on multiple rows to create chords.

 Audio Library Examples on Trellis M4

This guide was first published on Dec 18, 2018. It was last updated on Dec 18, 2018.

This page (Full Synth Demo) was last updated on Jan 09, 2023.

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