Add AudioSynthWaveformPWM

Audio.h

 #include "synth_pinknoise.h"
 #include "synth_karplusstrong.h"
 #include "synth_simple_drum.h"
+#include "synth_pwm.h"
 
 #endif

keywords.txt

 AudioSynthWaveformSineHires	KEYWORD2
 AudioSynthWaveformSineModulated	KEYWORD2
 AudioSynthWaveformDc	KEYWORD2
+AudioSynthWaveformPWM	KEYWORD2
 AudioSynthNoiseWhite	KEYWORD2
 AudioSynthNoisePink	KEYWORD2
 AudioSynthKarplusStrong	KEYWORD2

synth_pwm.cpp

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2017, Paul Stoffregen, paul@pjrc.com
+ *
+ * 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_pwm.h"
+#include "utility/dspinst.h"
+
+
+#if defined(KINETISK)
+
+void AudioSynthWaveformPWM::update(void)
+{
+	audio_block_t *block, *modinput;
+	uint32_t i;
+	int32_t out;
+
+	modinput = receiveReadOnly();
+	if (magnitude == 0) {
+		if (modinput) release(modinput);
+		return;
+	}
+	block = allocate();
+	if (!block) {
+		// unable to allocate memory, so we'll send nothing
+		if (modinput) release(modinput);
+		return;
+	}
+	if (modinput) {
+		for (i=0; i < AUDIO_BLOCK_SAMPLES; i++) {
+			elapsed += 65536;
+			int32_t in = modinput->data[i];
+			if (magnitude < 0) in = -in;
+			uint32_t dur = ((uint64_t)(in + 32768) * duration) >> 15;
+			if (elapsed < dur) {
+				out = magnitude;
+			} else {
+				int32_t e = elapsed - dur;
+				if (e < 0) e = 0;
+				else if (e > 65535) e = 65535;
+				elapsed = e;
+				// elapsed must be 0 to 65535
+				// magnitude must be -32767 to +32767
+				out = magnitude - ((magnitude * elapsed * 2) >> 16);
+				magnitude = -magnitude;
+			}
+			block->data[i] = out;
+		}
+		release(modinput);
+	} else {
+		for (i=0; i < AUDIO_BLOCK_SAMPLES; i++) {
+			elapsed += 65536;
+			if (elapsed < duration) {
+				out = magnitude;
+			} else {
+				elapsed -= duration;
+				// elapsed must be 0 to 65535
+				// magnitude must be -32767 to +32767
+				out = magnitude - ((magnitude * elapsed * 2) >> 16);
+				magnitude = -magnitude;
+			}
+			block->data[i] = out;
+		}
+	}
+	transmit(block);
+	release(block);
+}
+
+#elif defined(KINETISL)
+
+void AudioSynthWaveformPWM::update(void)
+{
+	audio_block_t *block = receiveReadOnly();
+	if (block) release(block);
+}
+
+#endif
+

synth_pwm.h

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2017, Paul Stoffregen, paul@pjrc.com
+ *
+ * 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.
+ */
+
+#ifndef synth_pwm_h_
+#define synth_pwm_h_
+
+#include "Arduino.h"
+#include "AudioStream.h"
+#include "arm_math.h"
+
+class AudioSynthWaveformPWM : public AudioStream
+{
+public:
+	AudioSynthWaveformPWM() : AudioStream(1, inputQueueArray), magnitude(0), elapsed(0) {}
+	void frequency(float freq) {
+		if (freq < 1.0) freq = 1.0;
+		else if (freq > AUDIO_SAMPLE_RATE_EXACT/4) freq = AUDIO_SAMPLE_RATE_EXACT/4;
+		//phase_increment = freq * (4294967296.0 / AUDIO_SAMPLE_RATE_EXACT);
+		duration = (AUDIO_SAMPLE_RATE_EXACT * 65536.0 + freq) / (freq * 2.0);
+	}
+	void amplitude(float n) {
+		if (n < 0) n = 0;
+		else if (n > 1.0) n = 1.0;
+		magnitude = n * 32767.0;
+	}
+	virtual void update(void);
+private:
+	uint32_t duration; // samples per half cycle (when 50% duty) * 65536
+	audio_block_t *inputQueueArray[1];
+	int32_t magnitude;
+	uint32_t elapsed;
+};
+
+
+#endif