#144: Add the reverse sawtooth and sample-and-hold waveforms.

keywords.txt

@@ -162,6 +162,8 @@ WAVEFORM_SQUARE	LITERAL1
 WAVEFORM_TRIANGLE	LITERAL1
 WAVEFORM_ARBITRARY	LITERAL1
 WAVEFORM_PULSE	LITERAL1
+WAVEFORM_SAWTOOTH_REVERSE	LITERAL1
+WAVEFORM_SAMPLE_HOLD	LITERAL1
 
 AUDIO_MEMORY_23LC1024	LITERAL1
 AUDIO_MEMORY_MEMORYBOARD	LITERAL1

synth_waveform.cpp

@@ -108,6 +108,14 @@ void AudioSynthWaveform::update(void)
       }
       break;
 
+    case WAVEFORM_SAWTOOTH_REVERSE:
+      for(int i = 0;i < AUDIO_BLOCK_SAMPLES;i++) {
+        *bp++ = ((short)(tone_phase>>15)*tone_amp) >> 15;
+         // phase and incr are both unsigned 32-bit fractions
+         tone_phase -= tone_incr;
+      }
+      break;
+
     case WAVEFORM_TRIANGLE:
       for(int i = 0;i < AUDIO_BLOCK_SAMPLES;i++) {
         if(tone_phase & 0x80000000) {
@@ -137,6 +145,15 @@ void AudioSynthWaveform::update(void)
       }
       break;
       
+    case WAVEFORM_SAMPLE_HOLD:
+      for(int i = 0;i < AUDIO_BLOCK_SAMPLES;i++) {
+        if(tone_phase < tone_incr) {
+          sample = random(-tone_amp, tone_amp);
+        }
+        *bp++ = sample;
+        tone_phase += tone_incr;
+      }
+      break;
     }
     if (tone_offset) {
 	bp = block->data;

synth_waveform.h

@@ -45,6 +45,8 @@ extern const int16_t AudioWaveformSine[257];
 #define WAVEFORM_TRIANGLE  3
 #define WAVEFORM_ARBITRARY 4
 #define WAVEFORM_PULSE     5
+#define WAVEFORM_SAWTOOTH_REVERSE 6
+#define WAVEFORM_SAMPLE_HOLD 7
 
 // todo: remove these...
 #define TONE_TYPE_SINE     0
@@ -117,6 +119,8 @@ private:
   short    tone_freq;
   uint32_t tone_phase;
   uint32_t tone_width;
+  // sample for SAMPLE_HOLD
+  short sample;
   // volatile prevents the compiler optimizing out the frequency function
   volatile uint32_t tone_incr;
   short    tone_type;