Adding SimpleDrum synthesis object to audio library.

Adding CPP/H implementation files, plus example sketch and update to
HTML file.

examples/Synthesis/SimpleDrum/SimpleDrum.ino

+#include <Audio.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <SD.h>
+#include <SerialFlash.h>
+
+#include <synth_simple_drum.h>
+
+#include <Audio.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <SD.h>
+#include <SerialFlash.h>
+
+// GUItool: begin automatically generated code
+AudioSynthSimpleDrum     drum2;          //xy=399,244
+AudioSynthSimpleDrum     drum3;          //xy=424,310
+AudioSynthSimpleDrum     drum1;          //xy=431,197
+AudioSynthSimpleDrum     drum4;          //xy=464,374
+AudioMixer4              mixer1;         //xy=737,265
+AudioOutputI2S           i2s1;           //xy=979,214
+AudioConnection          patchCord1(drum2, 0, mixer1, 1);
+AudioConnection          patchCord2(drum3, 0, mixer1, 2);
+AudioConnection          patchCord3(drum1, 0, mixer1, 0);
+AudioConnection          patchCord4(drum4, 0, mixer1, 3);
+AudioConnection          patchCord5(mixer1, 0, i2s1, 0);
+AudioConnection          patchCord6(mixer1, 0, i2s1, 1);
+AudioControlSGTL5000     sgtl5000_1;     //xy=930,518
+// GUItool: end automatically generated code
+
+static uint32_t next;
+
+void setup() {
+  // put your setup code here, to run once:
+
+  Serial.begin(115200);
+
+  // audio library init
+  AudioMemory(15);
+
+  next = millis() + 1000;
+
+  AudioNoInterrupts();
+
+  drum1.frequency(60);
+  drum1.length(1500);
+  drum1.secondMix(0.0);
+  drum1.pitchMod(0.55);
+  
+  drum2.frequency(60);
+  drum2.length(300);
+  drum2.secondMix(0.0);
+  drum2.pitchMod(1.0);
+  
+  drum3.frequency(550);
+  drum3.length(400);
+  drum3.secondMix(1.0);
+  drum3.pitchMod(0.5);
+
+  drum4.frequency(1200);
+  drum4.length(150);
+  drum4.secondMix(0.0);
+  drum4.pitchMod(0.0);
+  
+  sgtl5000_1.enable();
+  sgtl5000_1.volume(0.5);
+
+  AudioInterrupts();
+
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+
+  static uint32_t num = 0;
+
+  if(millis() == next)
+  {
+    next = millis() + 1000;
+
+    switch(num % 4)
+    {
+      case 0:
+        drum1.noteOn();
+        break;
+      case 1:
+        drum2.noteOn();
+        break;
+      case 2:
+        drum3.noteOn();
+        break;
+      case 3:
+        drum4.noteOn();
+        break;
+    }
+    num++;
+
+    Serial.print("Diagnostics: ");
+    Serial.print(AudioProcessorUsageMax());
+    Serial.print(" ");
+    Serial.println(AudioMemoryUsageMax());
+    AudioProcessorUsageMaxReset();
+  }
+}

gui/index.html

 		{"type":"AudioPlaySerialflashRaw","data":{"defaults":{"name":{"value":"new"}},"shortName":"playFlashRaw","inputs":0,"outputs":1,"category":"play-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioPlayQueue","data":{"defaults":{"name":{"value":"new"}},"shortName":"queue","inputs":0,"outputs":1,"category":"play-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioRecordQueue","data":{"defaults":{"name":{"value":"new"}},"shortName":"queue","inputs":1,"outputs":0,"category":"record-function","color":"#E6E0F8","icon":"arrow-in.png"}},
+		{"type":"AudioSynthSimpleDrum","data":{"defaults":{"name":{"value":"new"}},"shortName":"drum","inputs":0,"outputs":1,"category":"synth-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioSynthWaveformSine","data":{"defaults":{"name":{"value":"new"}},"shortName":"sine","inputs":0,"outputs":1,"category":"synth-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioSynthWaveformSineHires","data":{"defaults":{"name":{"value":"new"}},"shortName":"sine_hires","inputs":0,"outputs":2,"category":"synth-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioSynthWaveformSineModulated","data":{"defaults":{"name":{"value":"new"}},"shortName":"sine_fm","inputs":1,"outputs":1,"category":"synth-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 	</div>
 </script>
 
+<script type="text/x-red" data-help-name="AudioSynthSimpleDrum">
+	<h3>Summary</h3>
+	<div class=tooltipinfo>
+	<p>Generate a synthesised drum sound.  Also useful for laser pistol and bursting 
+  bubble sound effects.</p>
+	</div>
+	<h3>Audio Connections</h3>
+	<table class=doc align=center cellpadding=3>
+		<tr class=top><th>Port</th><th>Purpose</th></tr>
+		<tr class=odd><td align=center>Out 0</td><td>Drum Tone Output</td></tr>
+	</table>
+	<h3>Functions</h3>
+  <p class=func><span class=keyword>noteOn</span>();</p>
+	<p class=desc>Trigger the drum.
+	</p>
+  <p class=func><span class=keyword>frequency</span>(frequency);</p>
+	<p class=desc>Set the base frequency of the drum.
+	</p>
+  <p class=func><span class=keyword>length</span>(milliseconds);</p>
+	<p class=desc>Set the duration of the envelope, in milliseconds.
+	</p>
+  <p class=func><span class=keyword>secondMix</span>(level);</p>
+	<p class=desc>Emulates a two-headed tom, by adding a second sine wave that is
+  harmonized a perfect fifth above 
+  the base frequency.  Using this involves a slight CPU penalty.
+	</p>
+  <p class=func><span class=keyword>pitchMod</span>(depth);</p>
+	<p class=desc>Set the depth of envelope of the pitch, by a maximum of two octaves.
+  Default is 0.5, with no modulation.  Values above 0.5 cause the pitch to sweep 
+  downwards, values lower than 0.5 cause the pitch to sweep upwards.
+	</p>
+  
+	<h3>Examples</h3>
+	<p class=exam>File &gt; Examples &gt; Synthesis &gt; SimpleDrumm
+	</p>
+	<h3>Notes</h3>
+	<p></p>
+</script>
+<script type="text/x-red" data-template-name="AudioSynthSimpleDrum">
+	<div class="form-row">
+		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
+		<input type="text" id="node-input-name" placeholder="Name">
+	</div>
+</script>
+
 <script type="text/x-red" data-help-name="AudioSynthWaveformSineHires">
 	<h3>Summary</h3>
 	<div class=tooltipinfo>

synth_simple_drum.cpp

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2016, Byron Jacquot, SparkFun Electronics
+ *
+ * Development of this audio library was funded by PJRC.COM, LLC by sales of
+ * Teensy and Audio Adaptor boards.  Please support PJRC's efforts to develop
+ * open source software by purchasing Teensy or other PJRC products.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice, development funding notice, and this permission
+ * notice shall be included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "synth_simple_drum.h"
+
+extern "C" {
+extern const int16_t AudioWaveformSine[257];
+}
+
+void AudioSynthSimpleDrum::noteOn(void)
+{
+  __disable_irq();
+
+  wav_phasor = 0;
+  wav_phasor2 = 0;
+
+  env_lin_current = 0x7fff0000;
+  
+  __enable_irq();
+}
+
+void AudioSynthSimpleDrum::secondMix(float level)
+{
+  // As level goes from 0.0 to 1.0,
+  // second goes from 0 to 1/2 scale
+  // first goes from full scale to half scale. 
+
+  if(level < 0)
+  {
+    level = 0;
+  }
+  else if(level > 1.0)
+  {
+    level = 1.0;
+  }
+
+  __disable_irq();
+  wav_amplitude2 = level * 0x3fff;
+  wav_amplitude1 = 0x7fff - wav_amplitude2;
+  __enable_irq();
+}
+
+
+void AudioSynthSimpleDrum::pitchMod(float depth)
+{
+  int32_t intdepth, calc;
+
+  // Validate parameter
+  if(depth < 0)
+  {
+    depth = 0;
+  }
+  else if(depth > 1.0)
+  {
+    depth = 1.0;
+  }
+
+  // Depth is float, 0.0..1.0
+  // turn 0.0 to 1.0 into
+  // 0x0 to 0x3fff;
+  intdepth = depth * 0x7fff;
+
+  // Lets turn it into 2.14, in range between -0.75 and 2.9999, woth 0 at 0.5
+  // It becomes the scalar for the modulation component of the phasor increment.
+  if(intdepth < 0x4000)
+  {
+    // 0 to 0.5 becomes
+    // -0x3000 (0xffffCfff) to 0 ()
+    calc = ((0x4000 - intdepth) * 0x3000 )>> 14;
+    calc = -calc;
+  }
+  else
+  {
+    // 0.5 to 1.0 becomes
+    // 0x00 to 0xbfa0
+    calc = ((intdepth - 0x4000) * 0xc000)>> 14;
+  }
+
+  // Call result 2.14 format (max of ~3.99...approx 4)
+  // See note in update().
+  wav_pitch_mod = calc;
+}
+
+
+
+void AudioSynthSimpleDrum::update(void)
+{
+  audio_block_t *block_wav;
+  int16_t *p_wave, *end;
+  int32_t sin_l, sin_r, interp, mod, mod2, delta;
+  int32_t interp2;
+  int32_t index, scale;
+  bool do_second;
+
+  int32_t env_sqr_current; // the square of the linear value - inexpensive quasi exponential decay.
+
+  block_wav = allocate();
+  if (!block_wav) return;
+  p_wave = (block_wav->data);
+  end = p_wave + AUDIO_BLOCK_SAMPLES;
+
+  // 50 is arbitrary threshold...
+  // low values of second are inaudible, and we can save CPU cycles
+  // by not calculating second when it's really quiet.
+  do_second = (wav_amplitude2 > 50);
+
+  while(p_wave < end)
+  {
+    // Do envelope first
+    if(env_lin_current < 0x0000ffff)
+    {
+      // If envelope has expired, then stuff zeros into output buffer.
+      *p_wave = 0;
+      p_wave++; 
+    }
+    else
+    {
+      env_lin_current -= env_decrement;
+      env_sqr_current = multiply_16tx16t(env_lin_current, env_lin_current) ;
+
+      // do wave second;
+      wav_phasor  += wav_increment;
+
+      // modulation changes how we use the increment
+      // the increment will be scaled by the modulation amount.
+      //
+      // Pitch mod is in range [-0.75 .. 3.99999] in 2.14 format
+      // Current envelope value gets scaled by mod depth.
+      // Then phasor increment gets scaled by that.
+      mod = signed_multiply_32x16b((env_sqr_current), (wav_pitch_mod>>1)) >> 13;      
+      mod2 = signed_multiply_32x16b(wav_increment<<3, mod>>1);
+
+      wav_phasor += (mod2);
+      wav_phasor &= 0x7fffffff;
+
+      if(do_second)
+      {
+        // A perfect fifth uses increment of 1.5 times regular increment
+        wav_phasor2 += wav_increment;
+        wav_phasor2 += (wav_increment >> 1);
+        wav_phasor2 += mod2;
+        wav_phasor2 += (mod2 >> 1);
+        wav_phasor2 &= 0x7fffffff;
+      }
+    
+      // Phase to Sine lookup * interp:
+      index = wav_phasor >> 23; // take top valid 8 bits
+      sin_l = AudioWaveformSine[index];
+      sin_r = AudioWaveformSine[index+1];
+
+      // The fraction of the phasor in time we are between L and R
+      // is the same as the fraction of the ampliture of that interval we should add 
+      // to L.
+      delta = sin_r-sin_l;
+      scale = (wav_phasor >> 7) & 0xfFFF;
+      delta = (delta * scale)>> 16;
+      interp = sin_l + delta;
+      
+      if(do_second)
+      {
+        index = wav_phasor2 >> 23; // take top valid 8 bits
+        sin_l = AudioWaveformSine[index];
+        sin_r = AudioWaveformSine[index+1];
+
+        delta = sin_r-sin_l;
+        scale = (wav_phasor2 >> 7) & 0xFFFF;
+        delta = (delta * scale)>> 16;
+        interp2 = sin_l + delta;
+
+        // Then scale and add the two waves
+        interp2 = (interp2 * wav_amplitude2 ) >> 15;
+        interp = (interp * wav_amplitude1) >> 15;
+        interp = interp + interp2;
+      }
+
+      *p_wave = signed_multiply_32x16b(env_sqr_current, interp ) >> 15 ;
+      p_wave++; 
+    }
+  }
+
+  transmit(block_wav, 0);
+  release(block_wav);
+
+}
+

synth_simple_drum.h

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2016, Byron Jacquot, SparkFun Electronics
+ *
+ * Development of this audio library was funded by PJRC.COM, LLC by sales of
+ * Teensy and Audio Adaptor boards.  Please support PJRC's efforts to develop
+ * open source software by purchasing Teensy or other PJRC products.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice, development funding notice, and this permission
+ * notice shall be included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#pragma once
+
+#ifndef _SYNTH_SIMPLE_DRUM_H_
+#define _SYNTH_SIMPLE_DRUM_H_
+#include "AudioStream.h"
+#include "utility/dspinst.h"
+
+class AudioSynthSimpleDrum : public AudioStream
+{
+public:
+
+  AudioSynthSimpleDrum() : AudioStream(1, inputQueueArray) 
+  {
+    length(600);
+    frequency(60);
+    pitchMod(0x200);
+    wav_amplitude1 = 0x7fff;
+    wav_amplitude2 = 0;
+  }
+  void noteOn();
+
+  void frequency(float freq)
+  {
+    if(freq < 0.0)
+      freq = 0;
+    else if(freq > (AUDIO_SAMPLE_RATE_EXACT/2))
+      freq = AUDIO_SAMPLE_RATE_EXACT/2;
+
+    wav_increment = (freq * (0x7fffffffLL/AUDIO_SAMPLE_RATE_EXACT)) + 0.5;
+  }
+
+  void length(int32_t milliseconds)
+  {
+    if(milliseconds < 0)
+      return;
+    if(milliseconds > 5000)
+      milliseconds = 5000;
+
+    int32_t len_samples = milliseconds*(AUDIO_SAMPLE_RATE_EXACT/1000.0);
+
+    env_decrement = (0x7fff0000/len_samples);
+  };
+
+  void secondMix(float level);
+  void pitchMod(float depth);
+
+  using AudioStream::release;
+  virtual void update(void);
+
+private:
+  audio_block_t *inputQueueArray[1];
+
+  // Envelope params
+  int32_t env_lin_current; // present value of linear slope.
+  int32_t env_decrement;   // how each sample deviates from previous.
+
+  // Waveform params
+  uint32_t wav_phasor;      
+  uint32_t wav_phasor2;     
+  
+  int16_t wav_amplitude1;
+  int16_t wav_amplitude2;
+  
+  uint32_t wav_increment;
+  int32_t  wav_pitch_mod;
+};
+
+#endif
+