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libraries/audio-tools/examples/examples-dsp/examples-maximilian/09-Envelopes/09-Envelopes.ino

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+//Envelopes allow you to shape the sound. The basic idea is that a sound has the following shape
+// Attack: This is how long it takes to fade up to maximum volume
+// Decay: This is how long it takes to reach the sustain level.
+// Sustain: This is the sustain level
+// Release: This is how long it takes to fade out.
+
+#include "AudioTools.h"
+#include "AudioTools/AudioLibs/MaximilianDSP.h"
+
+// Define Arduino output
+I2SStream out;
+Maximilian maximilian(out);
+
+// Maximilian
+maxiOsc myCounter,mySwitchableOsc;//
+int CurrentCount;//
+double myOscOutput,myCurrentVolume;//
+maxiEnv myEnvelope;
+
+
+void setup() {//some inits
+    // setup logging
+    Serial.begin(115200);
+    AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Info);
+
+    // setup audio output
+    auto cfg = out.defaultConfig(TX_MODE);
+    out.begin(cfg);
+    maximilian.begin(cfg);
+
+    
+    //Timing is in ms    
+    myEnvelope.setAttack(0);
+    myEnvelope.setDecay(1);  // Needs to be at least 1
+    myEnvelope.setSustain(1);
+    myEnvelope.setRelease(1000);
+    
+}
+
+void play(float *output) {
+    
+    //notice that we feed in a value of 1. to create an envelope shape we can apply later.
+    myCurrentVolume=myEnvelope.adsr(1.,myEnvelope.trigger);
+    
+    CurrentCount=myCounter.phasorBetween(1, 1, 9);//phasor can take three arguments; frequency, start value and end value.
+    
+    // You'll notice that these 'if' statements don't require curly braces "{}".
+    // This is because there is only one outcome if the statement is true.
+    
+    if (CurrentCount==1) myEnvelope.trigger=1; //trigger the envelope
+    
+    else myEnvelope.trigger=0;//release the envelope to make it fade out only if it's been triggered
+    
+    if (CurrentCount<5)
+        
+        myOscOutput=mySwitchableOsc.sawn(CurrentCount*100);
+    
+    else if (CurrentCount>=5)//and the 'else' bit.
+        
+        myOscOutput=mySwitchableOsc.sinewave(CurrentCount*50);//one osc object can produce whichever waveform you want.
+    
+    
+    output[0]=myOscOutput*myCurrentVolume;//left speaker
+    output[1]=output[0];
+    
+}
+
+// Arduino loop
+void loop() {
+    maximilian.copy();
+}