Add Synthesis Guitar example

examples/Synthesis/Guitar/Guitar.ino

+#include <Audio.h>
+#include <Wire.h>
+#include <SD.h>
+#include <SPI.h>
+#include <SerialFlash.h>
+
+#include "chords.h"
+
+// Special thanks to Matthew Rahtz - http://amid.fish/karplus-strong/
+
+AudioSynthKarplusStrong  string1;
+AudioSynthKarplusStrong  string2;
+AudioSynthKarplusStrong  string3;
+AudioSynthKarplusStrong  string4;
+AudioSynthKarplusStrong  string5;
+AudioSynthKarplusStrong  string6;
+AudioMixer4              mixer1;
+AudioMixer4              mixer2;
+AudioOutputI2S           i2s1;
+AudioConnection          patchCord1(string1, 0, mixer1, 0);
+AudioConnection          patchCord2(string2, 0, mixer1, 1);
+AudioConnection          patchCord3(string3, 0, mixer1, 2);
+AudioConnection          patchCord4(string4, 0, mixer1, 3);
+AudioConnection          patchCord5(mixer1, 0, mixer2, 0);
+AudioConnection          patchCord6(string5, 0, mixer2, 1);
+AudioConnection          patchCord7(string6, 0, mixer2, 2);
+AudioConnection          patchCord8(mixer2, 0, i2s1, 0);
+AudioConnection          patchCord9(mixer2, 0, i2s1, 1);
+AudioControlSGTL5000     sgtl5000_1;
+
+const int finger_delay = 5;
+const int hand_delay = 220;
+
+int chordnum=0;
+
+void setup() {
+  AudioMemory(15);
+  sgtl5000_1.enable();
+  sgtl5000_1.volume(0.6);
+  mixer1.gain(0, 0.15);
+  mixer1.gain(1, 0.15);
+  mixer1.gain(2, 0.15);
+  mixer1.gain(3, 0.15);
+  mixer2.gain(1, 0.15);
+  mixer2.gain(2, 0.15);
+  delay(700);
+}
+
+void strum_up(const float *chord, float velocity);
+void strum_dn(const float *chord, float velocity);
+
+void loop() {
+  const float *chord;
+
+  // each time through the loop, play a different chord
+  if (chordnum == 0) {
+    chord = Cmajor;
+    Serial.println("C major");
+    chordnum = 1;
+  } else if (chordnum == 1) {
+    chord = Gmajor;
+    Serial.println("G major");
+    chordnum = 2;
+  } else if (chordnum == 2) {
+    chord = Aminor;
+    Serial.println("A minor");
+    chordnum = 3;
+  } else {
+    chord = Eminor;
+    Serial.println("E minor");
+    chordnum = 0;
+  }
+
+  // then strum the 6 string several times
+  strum_up(chord, 1.0);
+  delay(hand_delay);
+  delay(hand_delay);
+  strum_up(chord, 1.0);
+  delay(hand_delay);
+  strum_dn(chord, 0.8);
+  delay(hand_delay);
+  delay(hand_delay);
+  strum_dn(chord, 0.8);
+  delay(hand_delay);
+  strum_up(chord, 1.0);
+  delay(hand_delay);
+  strum_dn(chord, 0.8);
+  delay(hand_delay);
+  strum_up(chord, 1.0);
+  delay(hand_delay);
+  delay(hand_delay);
+  strum_up(chord, 1.0);
+  delay(hand_delay);
+  strum_dn(chord, 0.7);
+  delay(hand_delay);
+  delay(hand_delay);
+  strum_dn(chord, 0.7);
+  delay(hand_delay);
+  strum_up(chord, 1.0);
+  delay(hand_delay);
+  strum_dn(chord, 0.7);
+  delay(hand_delay);
+}
+
+void strum_up(const float *chord, float velocity)
+{
+  if (chord[0] > 20.0) string1.noteOn(chord[0], velocity);
+  delay(finger_delay);
+  if (chord[1] > 20.0) string2.noteOn(chord[1], velocity);
+  delay(finger_delay);
+  if (chord[2] > 20.0) string3.noteOn(chord[2], velocity);
+  delay(finger_delay);
+  if (chord[3] > 20.0) string4.noteOn(chord[3], velocity);
+  delay(finger_delay);
+  if (chord[4] > 20.0) string5.noteOn(chord[4], velocity);
+  delay(finger_delay);
+  if (chord[5] > 20.0) string6.noteOn(chord[5], velocity);
+  delay(finger_delay);
+}
+
+void strum_dn(const float *chord, float velocity)
+{
+  if (chord[5] > 20.0) string1.noteOn(chord[5], velocity);
+  delay(finger_delay);
+  if (chord[4] > 20.0) string2.noteOn(chord[4], velocity);
+  delay(finger_delay);
+  if (chord[3] > 20.0) string3.noteOn(chord[3], velocity);
+  delay(finger_delay);
+  if (chord[2] > 20.0) string4.noteOn(chord[2], velocity);
+  delay(finger_delay);
+  if (chord[1] > 20.0) string5.noteOn(chord[1], velocity);
+  delay(finger_delay);
+  if (chord[0] > 20.0) string6.noteOn(chord[0], velocity);
+  delay(finger_delay);
+}
+
+
+

examples/Synthesis/Guitar/chords.h

+
+#define NOTE_E2 82.41
+#define NOTE_F2 87.31
+#define NOTE_G2 98.00
+#define NOTE_A2 110.0
+#define NOTE_B2 123.5
+#define NOTE_C3 130.8
+#define NOTE_D3 146.8
+#define NOTE_E3 164.8
+#define NOTE_F3 174.6
+#define NOTE_G3 196.0
+#define NOTE_A3 220.0
+#define NOTE_B3 246.9
+#define NOTE_C4 261.6
+#define NOTE_D4 293.7
+#define NOTE_E4 329.6
+#define NOTE_F4 349.2
+#define NOTE_G4 392.0
+#define NOTE_A4 440.0
+#define NOTE_B4 493.9
+
+// according to http://www.guitar-chords.org.uk/
+              // open =  NOTE_E2  NOTE_A2  NOTE_D3  NOTE_G3  NOTE_B3  NOTE_E4
+const float Cmajor[6] = {      0, NOTE_C3, NOTE_E3, NOTE_G3, NOTE_C4, NOTE_E4};  // C - E - G
+const float Gmajor[6] = {NOTE_G2, NOTE_B2, NOTE_D3, NOTE_G3, NOTE_B3, NOTE_E4};  // G - B - D
+const float Aminor[6] = {      0, NOTE_A2, NOTE_E3, NOTE_A3, NOTE_C4, NOTE_E4};  // A - C - E
+const float Eminor[6] = {NOTE_E2, NOTE_B2, NOTE_E3, NOTE_G3, NOTE_B3, NOTE_E4};  // E - G - B
+
+//                   E2, F2, F2#, G2, G2#, A2, A2#, B2
+// C3, C3#, D3, D3#, E3, F3, F3#, G3, G3#, A3, A3#, B3
+// C4, C4#, D4, D4#, E4, F4, F4#, G4, G4#, A4, A4#, B4
+

keywords.txt

 AudioSynthWaveformDc	KEYWORD2
 AudioSynthNoiseWhite	KEYWORD2
 AudioSynthNoisePink	KEYWORD2
+AudioSynthKarplusStrong	KEYWORD2
 isPlaying	KEYWORD2
 positionMillis	KEYWORD2
 lengthMillis	KEYWORD2

synth_karplusstrong.h

 		}
 		magnitude = velocity * 65535.0f;
 		int len = (AUDIO_SAMPLE_RATE_EXACT / frequency) + 0.5f;
-		if (len > 400) len = 400;
+		if (len > 536) len = 536;
 		bufferLen = len;
 		bufferIndex = 0;
 		state = 1;
 	}
 	virtual void update(void);
 private:
-	uint8_t  state;     // 0=steady output, 1=transitioning
+	uint8_t  state;     // 0=steady output, 1=begin on next update, 2=playing
 	uint16_t bufferLen;
 	uint16_t bufferIndex;
 	int32_t  magnitude; // current output
 	static uint32_t seed;  // must start at 1
-	int16_t buffer[400];
+	int16_t buffer[536]; // TODO: dynamically use audio memory blocks
 };
 
 #endif