Add AudioInputPDM

Audio.h

 #include "input_i2s.h"
 #include "input_i2s_quad.h"
 #include "input_tdm.h"
+#include "input_pdm.h"
 #include "mixer.h"
 #include "output_dac.h"
 #include "output_dacs.h"

input_pdm.h

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2018, 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 _input_pdm_h_
+#define _input_pdm_h_
+
+#include "Arduino.h"
+#include "AudioStream.h"
+#include "DMAChannel.h"
+
+class AudioInputPDM : public AudioStream
+{
+public:
+	AudioInputPDM(void) : AudioStream(0, NULL) { begin(); }
+	virtual void update(void);
+	void begin(void);
+protected:	
+	static bool update_responsibility;
+	static DMAChannel dma;
+	static void isr(void);
+private:
+	static audio_block_t *block_left;
+};
+
+#endif

keywords.txt

 AudioInputI2SQuad	KEYWORD2
 AudioInputI2Sslave	KEYWORD2
 AudioInputTDM	KEYWORD2
+AudioInputPDM	KEYWORD2
 AudioInputUSB	KEYWORD2
 AudioOutputI2S	KEYWORD2
 AudioOutputI2SQuad	KEYWORD2