Add simple pulse waveform

pulse plus example

examples/Synthesis/pulse/pulse.ino

+// demonstrate pulse with slow changes in width
+
+#include <Audio.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <SD.h>
+
+// GUItool: begin automatically generated code
+AudioSynthWaveform       waveform1;      //xy=188,240
+AudioEffectEnvelope      envelope1;      //xy=371,237
+AudioOutputI2S           i2s1;           //xy=565,241
+AudioConnection          patchCord1(waveform1, envelope1);
+AudioConnection          patchCord2(envelope1, 0, i2s1, 0);
+AudioConnection          patchCord3(envelope1, 0, i2s1, 1);
+AudioControlSGTL5000     audioShield;     //xy=586,175
+// GUItool: end automatically generated code
+
+
+void setup(void)
+{
+
+  // Set up
+  AudioMemory(8);
+  audioShield.enable();
+  audioShield.volume(0.45);
+
+  waveform1.width(0.5);
+  waveform1.begin(0.4, 220, WAVEFORM_PULSE);
+
+  envelope1.attack(50);
+  envelope1.decay(50);
+  envelope1.release(250);
+
+}
+
+void loop() {
+  
+  float w;
+  for (uint32_t i =1; i<20; i++) {
+    w = i / 20.0;
+    waveform1.width(w);
+    envelope1.noteOn();
+    delay(800);
+    envelope1.noteOff();
+    delay(600);
+  }
+}
+
+

synth_waveform.cpp

         tone_phase += 2*tone_incr;
       }
       break;
+      
+    case WAVEFORM_PULSE:
+      for(int i = 0;i < AUDIO_BLOCK_SAMPLES;i++) {
+        if(tone_phase < tone_width)*bp++ = -tone_amp;
+        else *bp++ = tone_amp;
+        tone_phase += tone_incr;
+      }
+      break;
+      
     }
     if (tone_offset) {
 	bp = block->data;

synth_waveform.h

 #define WAVEFORM_SQUARE    2
 #define WAVEFORM_TRIANGLE  3
 #define WAVEFORM_ARBITRARY 4
+#define WAVEFORM_PULSE     5
 
 // todo: remove these...
 #define TONE_TYPE_SINE     0
   AudioSynthWaveform(void) : 
   AudioStream(0,NULL), 
   tone_phase(0), tone_incr(0), tone_type(0),
-  tone_offset(0), arbdata(NULL)
+  tone_offset(0), tone_width(0.25), arbdata(NULL)
   { 
   }
   
     else if (n > 1.0) n = 1.0;
     tone_offset = n * 32767.0;
   }
+  void width(float n) {          // 0.0 to 1.0
+    if (n < 0) n = 0;
+    else if (n > 1.0) n = 1.0;
+    tone_width = n * 0x7fffffffLL; 
+    // width is stored as the equivalent phase
+  }
   void begin(short t_type) {
 	tone_phase = 0;
 	tone_type = t_type;
   short    tone_amp;
   short    tone_freq;
   uint32_t tone_phase;
+  uint32_t tone_width;
   // volatile prevents the compiler optimizing out the frequency function
   volatile uint32_t tone_incr;
   short    tone_type;