Merge branch 'master' of https://github.com/FrankBoesing/Audio

Audio.h

 #include "mixer.h"
 #include "output_dac.h"
 #include "output_i2s.h"
+#include "output_i2s_quad.h"
 #include "output_pwm.h"
 #include "output_spdif.h"
 #include "play_memory.h"

analyze_peak.cpp

 	max = max_sample;
 	do {
 		int16_t d=*p++;
+		// TODO: can we speed this up with SSUB16 and SEL
+		// http://www.m4-unleashed.com/parallel-comparison/
 		if (d<min) min=d;
 		if (d>max) max=d;
 	} while (p < end);

control_sgtl5000.cpp

 #define DAP_COEF_WR_A2_MSB		0x0138
 #define DAP_COEF_WR_A2_LSB		0x013A
 
-#define SGTL5000_I2C_ADDR  0x0A  // CTRL_ADR0_CS pin low (normal configuration)
-//#define SGTL5000_I2C_ADDR  0x2A // CTRL_ADR0_CS  pin high
+#define SGTL5000_I2C_ADDR_CS_LOW	0x0A  // CTRL_ADR0_CS pin low (normal configuration)
+#define SGTL5000_I2C_ADDR_CS_HIGH	0x2A // CTRL_ADR0_CS  pin high
 
 
+void AudioControlSGTL5000::setAddress(uint8_t level)
+{
+	if (level == LOW) {
+		i2c_addr = SGTL5000_I2C_ADDR_CS_LOW;
+	} else {
+		i2c_addr = SGTL5000_I2C_ADDR_CS_HIGH;
+	}
+}
 
 bool AudioControlSGTL5000::enable(void)
 {
 unsigned int AudioControlSGTL5000::read(unsigned int reg)
 {
 	unsigned int val;
-	Wire.beginTransmission(SGTL5000_I2C_ADDR);
+	Wire.beginTransmission(i2c_addr);
 	Wire.write(reg >> 8);
 	Wire.write(reg);
 	if (Wire.endTransmission(false) != 0) return 0;
-	if (Wire.requestFrom(SGTL5000_I2C_ADDR, 2) < 2) return 0;
+	if (Wire.requestFrom((int)i2c_addr, 2) < 2) return 0;
 	val = Wire.read() << 8;
 	val |= Wire.read();
 	return val;
 bool AudioControlSGTL5000::write(unsigned int reg, unsigned int val)
 {
 	if (reg == CHIP_ANA_CTRL) ana_ctrl = val;
-	Wire.beginTransmission(SGTL5000_I2C_ADDR);
+	Wire.beginTransmission(i2c_addr);
 	Wire.write(reg >> 8);
 	Wire.write(reg);
 	Wire.write(val >> 8);

control_sgtl5000.h

 class AudioControlSGTL5000 : public AudioControl
 {
 public:
+	AudioControlSGTL5000(void) : i2c_addr(0x0A) { }
+	void setAddress(uint8_t level);
 	bool enable(void);
 	bool disable(void) { return false; }
 	bool volume(float n) { return volumeInteger(n * 129 + 0.499); }
 	bool muted;
 	bool volumeInteger(unsigned int n); // range: 0x00 to 0x80
 	uint16_t ana_ctrl;
+	uint8_t i2c_addr;
 	unsigned char calcVol(float n, unsigned char range);
 	unsigned int read(unsigned int reg);
 	bool write(unsigned int reg, unsigned int val);

examples/HardwareTesting/SGTL5000/QuadChannelOutput/QuadChannelOutput.ino

+// Quad channel output test
+// Play two WAV files on two audio shields.
+//
+// TODO: add info about required hardware connections here....
+//
+// Data files to put on your SD card can be downloaded here:
+//   http://www.pjrc.com/teensy/td_libs_AudioDataFiles.html
+//
+// This example code is in the public domain.
+
+#include <Audio.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <SD.h>
+#include <SerialFlash.h>
+
+AudioPlaySdWav           playSdWav1;
+AudioPlaySdWav           playSdWav2;
+AudioOutputI2SQuad       audioOutput;
+AudioConnection          patchCord1(playSdWav1, 0, audioOutput, 0);
+AudioConnection          patchCord2(playSdWav1, 1, audioOutput, 1);
+AudioConnection          patchCord3(playSdWav2, 0, audioOutput, 2);
+AudioConnection          patchCord4(playSdWav2, 1, audioOutput, 3);
+AudioControlSGTL5000     sgtl5000_1;
+AudioControlSGTL5000     sgtl5000_2;
+
+// Use these with the audio adaptor board
+#define SDCARD_CS_PIN    10
+#define SDCARD_MOSI_PIN  7
+#define SDCARD_SCK_PIN   14
+
+void setup() {
+  Serial.begin(9600);
+  AudioMemory(10);
+  
+  sgtl5000_1.setAddress(LOW);
+  sgtl5000_1.enable();
+  sgtl5000_1.volume(0.5);
+
+  sgtl5000_2.setAddress(HIGH);
+  sgtl5000_2.enable();
+  sgtl5000_2.volume(0.5);
+
+  SPI.setMOSI(SDCARD_MOSI_PIN);
+  SPI.setSCK(SDCARD_SCK_PIN);
+  if (!(SD.begin(SDCARD_CS_PIN))) {
+    // stop here, but print a message repetitively
+    while (1) {
+      Serial.println("Unable to access the SD card");
+      delay(500);
+    }
+  }
+}
+
+void loop() {
+  if (playSdWav1.isPlaying() == false) {
+    Serial.println("Start playing 1");
+    playSdWav1.play("SDTEST2.WAV");
+    delay(10); // wait for library to parse WAV info
+  }
+  if (playSdWav2.isPlaying() == false) {
+    Serial.println("Start playing 2");
+    playSdWav2.play("SDTEST4.WAV");
+    delay(10); // wait for library to parse WAV info
+  }
+}
+

gui/index.html

 		{"type":"AudioInputAnalog","data":{"defaults":{"name":{"value":"new"}},"shortName":"adc","inputs":0,"outputs":1,"category":"input-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioInputI2Sslave","data":{"defaults":{"name":{"value":"new"}},"shortName":"i2ss","inputs":0,"outputs":2,"category":"input-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioOutputI2S","data":{"defaults":{"name":{"value":"new"}},"shortName":"i2s","inputs":2,"outputs":0,"category":"output-function","color":"#E6E0F8","icon":"arrow-in.png"}},
+		{"type":"AudioOutputI2SQuad","data":{"defaults":{"name":{"value":"new"}},"shortName":"i2s_quad","inputs":4,"outputs":0,"category":"output-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioOutputSPDIF","data":{"defaults":{"name":{"value":"new"}},"shortName":"spdif","inputs":2,"outputs":0,"category":"output-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioOutputAnalog","data":{"defaults":{"name":{"value":"new"}},"shortName":"dac","inputs":1,"outputs":0,"category":"output-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 		{"type":"AudioOutputPWM","data":{"defaults":{"name":{"value":"new"}},"shortName":"pwm","inputs":1,"outputs":0,"category":"output-function","color":"#E6E0F8","icon":"arrow-in.png"}},
 	</div>
 </script>
 
+<script type="text/x-red" data-help-name="AudioOutputI2SQuad">
+	<h3>Summary</h3>
+	<div class=tooltipinfo>
+	<p>Transmit quad (4) channel 16 bit audio, using I2S master mode.</p>
+	</div>
+	<h3>Audio Connections</h3>
+	<table class=doc align=center cellpadding=3>
+		<tr class=top><th>Port</th><th>Purpose</th></tr>
+		<tr class=odd><td align=center>In 0</td><td>Channel #1</td></tr>
+		<tr class=odd><td align=center>In 1</td><td>Channel #2</td></tr>
+		<tr class=odd><td align=center>In 2</td><td>Channel #3</td></tr>
+		<tr class=odd><td align=center>In 3</td><td>Channel #4</td></tr>
+	</table>
+	<h3>Functions</h3>
+	<p>This object has no functions to call from the Arduino sketch.  It
+		simply streams data from its 4 input ports to the I2S hardware.</p>
+	<h3>Hardware</h3>
+	<p>TODO: <a href="https://forum.pjrc.com/threads/29373-Bit-bang-multiple-I2S-inputs-simultaneously?p=79606#post79606" target="_blank">details</a> for how to connect 2 Teensy audio shields</p>
+	<p>The I2S signals are used in "master" mode, where Teensy creates
+		all 3 clock signals and controls all data timing.</p>
+	<table class=doc align=center cellpadding=3>
+		<tr class=top><th>Pin</th><th>Signal</th><th>Direction</th></tr>
+		<tr class=odd><td align=center>9</td><td>BCLK</td><td>Output</td></tr>
+		<tr class=odd><td align=center>11</td><td>MCLK</td><td>Output</td></tr>
+		<tr class=odd><td align=center>22</td><td>TX (ch 1+2)</td><td>Output</td></tr>
+		<tr class=odd><td align=center>15</td><td>TX (ch 3+4)</td><td>Output</td></tr>
+		<tr class=odd><td align=center>23</td><td>LRCLK</td><td>Output</td></tr>
+	</table>
+	<p>Audio from
+		master mode I2S may be used in the same project as ADC, DAC and
+		PWM signals, because all remain in sync to Teensy's timing</p>
+	<h3>Examples</h3>
+	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; SGTL5000 &gt; QuadChannelOutput
+	</p>
+	<h3>Notes</h3>
+	<p>Normally, this object is used with two Audio Shields, which
+		are controlled separately by a pair of "sgtl5000" objects.</p>
+</script>
+<script type="text/x-red" data-template-name="AudioOutputI2SQuad">
+	<div class="form-row">
+		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
+		<input type="text" id="node-input-name" placeholder="Name">
+	</div>
+</script>
+
+
+
+
+
+
 <script type="text/x-red" data-help-name="AudioOutputSPDIF">
 	<h3>Summary</h3>
 	<div class=tooltipinfo>

keywords.txt

 AudioInputI2S	KEYWORD2
 AudioInputI2Sslave	KEYWORD2
 AudioOutputI2S	KEYWORD2
+AudioOutputI2SQuad	KEYWORD2
 AudioOutputI2Sslave	KEYWORD2
 AudioOutputSPDIF	KEYWORD2
 AudioOutputPWM	KEYWORD2
 trigger	KEYWORD2
 length	KEYWORD2
 threshold	KEYWORD2
+setAddress	KEYWORD2
 enable	KEYWORD2
 enableIn	KEYWORD2
 enableOut	KEYWORD2

memcpy_audio.S

 	BX lr
 
 
+
+/* void memcpy_tointerleaveQuad(int16_t *dst, const int16_t *src1, const int16_t *src2, const int16_t *src3, const int16_t *src4) */
+ .global	memcpy_tointerleaveQuad
+.thumb_func
+	memcpy_tointerleaveQuad:
+
+	@ r0: dst
+	@ r1: src1
+	@ r2: src2
+	@ r3: src3
+	@ r4: src4
+
+	push	{r4-r11}
+	ldr r4, [sp, #(0+32)] //4th parameter is saved on the stack
+	add r11,r0,#512		// TODO: 512 = AUDIO_BLOCK_SAMPLES*4
+	.align 2
+.loopQuad:
+
+	.irp offset, 1,2
+
+	ldr r5, [r1],4
+	ldr r6, [r3],4
+	pkhbt r7,r5,r6,LSL #16
+	pkhtb r9,r6,r5,ASR #16
+	ldr r5, [r2],4
+	ldr r6, [r4],4
+	pkhbt r8,r5,r6,LSL #16
+	pkhtb r10,r6,r5,ASR #16
+
+	stmia r0!, {r7-r10}
+
+	.endr
+
+	cmp r11, r0
+	bne .loopQuad
+
+	pop	{r4-r11}
+
+	BX lr
+
+
 .END
 
 #endif

memcpy_audio.h

 void memcpy_tointerleaveLR(int16_t *dst, const int16_t *srcL, const int16_t *srcR);
 void memcpy_tointerleaveL(int16_t *dst, const int16_t *srcL);
 void memcpy_tointerleaveR(int16_t *dst, const int16_t *srcR);
+void memcpy_tointerleaveQuad(int16_t *dst, const int16_t *src1, const int16_t *src2,
+	const int16_t *src3, const int16_t *src4);
 #ifdef __cplusplus
 }
 #endif

output_i2s_quad.cpp

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2014, 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 "output_i2s_quad.h"
+#include "memcpy_audio.h"
+
+#if defined(__MK20DX256__)
+
+audio_block_t * AudioOutputI2SQuad::block_ch1_1st = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch2_1st = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch3_1st = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch4_1st = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch1_2nd = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch2_2nd = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch3_2nd = NULL;
+audio_block_t * AudioOutputI2SQuad::block_ch4_2nd = NULL;
+uint16_t  AudioOutputI2SQuad::ch1_offset = 0;
+uint16_t  AudioOutputI2SQuad::ch2_offset = 0;
+uint16_t  AudioOutputI2SQuad::ch3_offset = 0;
+uint16_t  AudioOutputI2SQuad::ch4_offset = 0;
+//audio_block_t * AudioOutputI2SQuad::inputQueueArray[4];
+bool AudioOutputI2SQuad::update_responsibility = false;
+DMAMEM static uint32_t i2s_tx_buffer[AUDIO_BLOCK_SAMPLES*2];
+DMAChannel AudioOutputI2SQuad::dma(false);
+
+static const uint32_t zerodata[AUDIO_BLOCK_SAMPLES/4] = {0};
+
+void AudioOutputI2SQuad::begin(void)
+{
+#if 1
+	dma.begin(true); // Allocate the DMA channel first
+
+	block_ch1_1st = NULL;
+	block_ch2_1st = NULL;
+	block_ch3_1st = NULL;
+	block_ch4_1st = NULL;
+
+	// TODO: can we call normal config_i2s, and then just enable the extra output?
+	config_i2s();
+	CORE_PIN22_CONFIG = PORT_PCR_MUX(6); // pin 22, PTC1, I2S0_TXD0 -> ch1 & ch2
+	CORE_PIN15_CONFIG = PORT_PCR_MUX(6); // pin 15, PTC0, I2S0_TXD1 -> ch3 & ch4
+
+	dma.TCD->SADDR = i2s_tx_buffer;
+	dma.TCD->SOFF = 2;
+	dma.TCD->ATTR = DMA_TCD_ATTR_SSIZE(1) | DMA_TCD_ATTR_DSIZE(1) | DMA_TCD_ATTR_DMOD(3);
+	dma.TCD->NBYTES_MLNO = 4;
+	dma.TCD->SLAST = -sizeof(i2s_tx_buffer);
+	dma.TCD->DADDR = &I2S0_TDR0;
+	dma.TCD->DOFF = 4;
+	dma.TCD->CITER_ELINKNO = sizeof(i2s_tx_buffer) / 4;
+	dma.TCD->DLASTSGA = 0;
+	dma.TCD->BITER_ELINKNO = sizeof(i2s_tx_buffer) / 4;
+	dma.TCD->CSR = DMA_TCD_CSR_INTHALF | DMA_TCD_CSR_INTMAJOR;
+	dma.triggerAtHardwareEvent(DMAMUX_SOURCE_I2S0_TX);
+	update_responsibility = update_setup();
+	dma.enable();
+
+	I2S0_TCSR |= I2S_TCSR_TE | I2S_TCSR_BCE | I2S_TCSR_FRDE | I2S_TCSR_FR;
+	dma.attachInterrupt(isr);
+#endif
+}
+
+void AudioOutputI2SQuad::isr(void)
+{
+	uint32_t saddr;
+	const int16_t *src1, *src2, *src3, *src4;
+	const int16_t *zeros = (const int16_t *)zerodata;
+	int16_t *dest;
+
+	saddr = (uint32_t)(dma.TCD->SADDR);
+	dma.clearInterrupt();
+	if (saddr < (uint32_t)i2s_tx_buffer + sizeof(i2s_tx_buffer) / 2) {
+		// DMA is transmitting the first half of the buffer
+		// so we must fill the second half
+		dest = (int16_t *)&i2s_tx_buffer[AUDIO_BLOCK_SAMPLES];
+		if (update_responsibility) update_all();
+	} else {
+		dest = (int16_t *)i2s_tx_buffer;
+	}
+
+	src1 = (block_ch1_1st) ? block_ch1_1st->data + ch1_offset : zeros;
+	src2 = (block_ch2_1st) ? block_ch2_1st->data + ch2_offset : zeros;
+	src3 = (block_ch3_1st) ? block_ch3_1st->data + ch3_offset : zeros;
+	src4 = (block_ch4_1st) ? block_ch4_1st->data + ch4_offset : zeros;
+
+	// TODO: fast 4-way interleaved memcpy...
+#if 1
+	memcpy_tointerleaveQuad(dest, src1, src2, src3, src4);
+#else
+	for (int i=0; i < AUDIO_BLOCK_SAMPLES/2; i++) {
+		*dest++ = *src1++;
+		*dest++ = *src3++;
+		*dest++ = *src2++;
+		*dest++ = *src4++;
+	}
+#endif
+
+	if (block_ch1_1st) {
+		if (ch1_offset == 0) {
+			ch1_offset = AUDIO_BLOCK_SAMPLES/2;
+		} else {
+			ch1_offset = 0;
+			release(block_ch1_1st);
+			block_ch1_1st = block_ch1_2nd;
+			block_ch1_2nd = NULL;
+		}
+	}
+	if (block_ch2_1st) {
+		if (ch2_offset == 0) {
+			ch2_offset = AUDIO_BLOCK_SAMPLES/2;
+		} else {
+			ch2_offset = 0;
+			release(block_ch2_1st);
+			block_ch2_1st = block_ch2_2nd;
+			block_ch2_2nd = NULL;
+		}
+	}
+	if (block_ch3_1st) {
+		if (ch3_offset == 0) {
+			ch3_offset = AUDIO_BLOCK_SAMPLES/2;
+		} else {
+			ch3_offset = 0;
+			release(block_ch3_1st);
+			block_ch3_1st = block_ch3_2nd;
+			block_ch3_2nd = NULL;
+		}
+	}
+	if (block_ch4_1st) {
+		if (ch4_offset == 0) {
+			ch4_offset = AUDIO_BLOCK_SAMPLES/2;
+		} else {
+			ch4_offset = 0;
+			release(block_ch4_1st);
+			block_ch4_1st = block_ch4_2nd;
+			block_ch4_2nd = NULL;
+		}
+	}
+}
+
+
+void AudioOutputI2SQuad::update(void)
+{
+	audio_block_t *block, *tmp;
+
+	block = receiveReadOnly(0); // channel 1
+	if (block) {
+		__disable_irq();
+		if (block_ch1_1st == NULL) {
+			block_ch1_1st = block;
+			ch1_offset = 0;
+			__enable_irq();
+		} else if (block_ch1_2nd == NULL) {
+			block_ch1_2nd = block;
+			__enable_irq();
+		} else {
+			tmp = block_ch1_1st;
+			block_ch1_1st = block_ch1_2nd;
+			block_ch1_2nd = block;
+			ch1_offset = 0;
+			__enable_irq();
+			release(tmp);
+		}
+	}
+	block = receiveReadOnly(1); // channel 2
+	if (block) {
+		__disable_irq();
+		if (block_ch2_1st == NULL) {
+			block_ch2_1st = block;
+			ch2_offset = 0;
+			__enable_irq();
+		} else if (block_ch2_2nd == NULL) {
+			block_ch2_2nd = block;
+			__enable_irq();
+		} else {
+			tmp = block_ch2_1st;
+			block_ch2_1st = block_ch2_2nd;
+			block_ch2_2nd = block;
+			ch2_offset = 0;
+			__enable_irq();
+			release(tmp);
+		}
+	}
+	block = receiveReadOnly(2); // channel 3
+	if (block) {
+		__disable_irq();
+		if (block_ch3_1st == NULL) {
+			block_ch3_1st = block;
+			ch3_offset = 0;
+			__enable_irq();
+		} else if (block_ch3_2nd == NULL) {
+			block_ch3_2nd = block;
+			__enable_irq();
+		} else {
+			tmp = block_ch3_1st;
+			block_ch3_1st = block_ch3_2nd;
+			block_ch3_2nd = block;
+			ch3_offset = 0;
+			__enable_irq();
+			release(tmp);
+		}
+	}
+	block = receiveReadOnly(3); // channel 4
+	if (block) {
+		__disable_irq();
+		if (block_ch4_1st == NULL) {
+			block_ch4_1st = block;
+			ch4_offset = 0;
+			__enable_irq();
+		} else if (block_ch4_2nd == NULL) {
+			block_ch4_2nd = block;
+			__enable_irq();
+		} else {
+			tmp = block_ch4_1st;
+			block_ch4_1st = block_ch4_2nd;
+			block_ch4_2nd = block;
+			ch4_offset = 0;
+			__enable_irq();
+			release(tmp);
+		}
+	}
+}
+
+
+// MCLK needs to be 48e6 / 1088 * 256 = 11.29411765 MHz -> 44.117647 kHz sample rate
+//
+#if F_CPU == 96000000 || F_CPU == 48000000 || F_CPU == 24000000
+  // PLL is at 96 MHz in these modes
+  #define MCLK_MULT 2
+  #define MCLK_DIV  17
+#elif F_CPU == 72000000
+  #define MCLK_MULT 8
+  #define MCLK_DIV  51
+#elif F_CPU == 120000000
+  #define MCLK_MULT 8
+  #define MCLK_DIV  85
+#elif F_CPU == 144000000
+  #define MCLK_MULT 4
+  #define MCLK_DIV  51
+#elif F_CPU == 168000000
+  #define MCLK_MULT 8
+  #define MCLK_DIV  119
+#elif F_CPU == 16000000
+  #define MCLK_MULT 12
+  #define MCLK_DIV  17
+#else
+  #error "This CPU Clock Speed is not supported by the Audio library";
+#endif
+
+#if F_CPU >= 20000000
+  #define MCLK_SRC  3  // the PLL
+#else
+  #define MCLK_SRC  0  // system clock
+#endif
+
+void AudioOutputI2SQuad::config_i2s(void)
+{
+	SIM_SCGC6 |= SIM_SCGC6_I2S;
+	SIM_SCGC7 |= SIM_SCGC7_DMA;
+	SIM_SCGC6 |= SIM_SCGC6_DMAMUX;
+
+	// if either transmitter or receiver is enabled, do nothing
+	if (I2S0_TCSR & I2S_TCSR_TE) return;
+	if (I2S0_RCSR & I2S_RCSR_RE) return;
+
+	// enable MCLK output
+	I2S0_MCR = I2S_MCR_MICS(MCLK_SRC) | I2S_MCR_MOE;
+	I2S0_MDR = I2S_MDR_FRACT((MCLK_MULT-1)) | I2S_MDR_DIVIDE((MCLK_DIV-1));
+
+	// configure transmitter
+	I2S0_TMR = 0;
+	I2S0_TCR1 = I2S_TCR1_TFW(1);  // watermark at half fifo size
+	I2S0_TCR2 = I2S_TCR2_SYNC(0) | I2S_TCR2_BCP | I2S_TCR2_MSEL(1)
+		| I2S_TCR2_BCD | I2S_TCR2_DIV(3);
+	I2S0_TCR3 = I2S_TCR3_TCE_2CH;
+	I2S0_TCR4 = I2S_TCR4_FRSZ(1) | I2S_TCR4_SYWD(15) | I2S_TCR4_MF
+		| I2S_TCR4_FSE | I2S_TCR4_FSP | I2S_TCR4_FSD;
+	I2S0_TCR5 = I2S_TCR5_WNW(15) | I2S_TCR5_W0W(15) | I2S_TCR5_FBT(15);
+
+	// configure receiver (sync'd to transmitter clocks)
+	I2S0_RMR = 0;
+	I2S0_RCR1 = I2S_RCR1_RFW(1);
+	I2S0_RCR2 = I2S_RCR2_SYNC(1) | I2S_TCR2_BCP | I2S_RCR2_MSEL(1)
+		| I2S_RCR2_BCD | I2S_RCR2_DIV(3);
+	I2S0_RCR3 = I2S_RCR3_RCE_2CH;
+	I2S0_RCR4 = I2S_RCR4_FRSZ(1) | I2S_RCR4_SYWD(15) | I2S_RCR4_MF
+		| I2S_RCR4_FSE | I2S_RCR4_FSP | I2S_RCR4_FSD;
+	I2S0_RCR5 = I2S_RCR5_WNW(15) | I2S_RCR5_W0W(15) | I2S_RCR5_FBT(15);
+
+	// configure pin mux for 3 clock signals
+	CORE_PIN23_CONFIG = PORT_PCR_MUX(6); // pin 23, PTC2, I2S0_TX_FS (LRCLK)
+	CORE_PIN9_CONFIG  = PORT_PCR_MUX(6); // pin  9, PTC3, I2S0_TX_BCLK
+	CORE_PIN11_CONFIG = PORT_PCR_MUX(6); // pin 11, PTC6, I2S0_MCLK
+}
+
+
+#else // not __MK20DX256__
+
+
+void AudioOutputI2SQuad::begin(void)
+{
+}
+
+void AudioOutputI2SQuad::update(void)
+{
+	audio_block_t *block;
+
+	block = receiveReadOnly(0);
+	if (block) release(block);
+	block = receiveReadOnly(1);
+	if (block) release(block);
+	block = receiveReadOnly(2);
+	if (block) release(block);
+	block = receiveReadOnly(3);
+	if (block) release(block);
+}
+
+#endif

output_i2s_quad.h

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2014, 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 output_i2s_quad_h_
+#define output_i2s_quad_h_
+
+#include "AudioStream.h"
+#include "DMAChannel.h"
+
+class AudioOutputI2SQuad : public AudioStream
+{
+public:
+	AudioOutputI2SQuad(void) : AudioStream(4, inputQueueArray) { begin(); }
+	virtual void update(void);
+	void begin(void);
+private:
+	static void config_i2s(void);
+	static audio_block_t *block_ch1_1st;
+	static audio_block_t *block_ch2_1st;
+	static audio_block_t *block_ch3_1st;
+	static audio_block_t *block_ch4_1st;
+	static bool update_responsibility;
+	static DMAChannel dma;
+	static void isr(void);
+	static audio_block_t *block_ch1_2nd;
+	static audio_block_t *block_ch2_2nd;
+	static audio_block_t *block_ch3_2nd;
+	static audio_block_t *block_ch4_2nd;
+	static uint16_t ch1_offset;
+	static uint16_t ch2_offset;
+	static uint16_t ch3_offset;
+	static uint16_t ch4_offset;
+	audio_block_t *inputQueueArray[4];
+};
+
+#endif