Some experiments about Audio buffering. DAC class added.

hardware/arduino/sam/libraries/Audio/Audio.cpp

@@ -10,31 +10,126 @@
 
 #include "Audio.h"
 
-void AudioClass::begin(uint32_t sampleRate) {
-	const uint32_t T = VARIANT_MCK / sampleRate;
-	dac->begin(T);
+class LockDAC {
+public:
+	LockDAC(DACClass *_dac) : dac(_dac)
+	           { dac->disableInterrupts(); };
+	~LockDAC() { dac->enableInterrupts(); };
+	DACClass *dac;
+};
 
-	currentBuffer = 0;
+void AudioClass::begin(uint32_t sampleRate, uint32_t msPreBuffer) {
+	// Allocate a buffer to keep msPreBuffer milliseconds of audio
+	bufferSize = msPreBuffer * sampleRate / 1000;
+	if (bufferSize < 2048)
+		bufferSize = 2048;
+	buffer = (uint32_t *) malloc(bufferSize * sizeof(uint32_t));
+	last = buffer + bufferSize;
+
+	// Buffering starts from the beginning
+	running = last;
+	current = buffer;
+	next = buffer;
+
+	// Run DAC
+	dac->begin(VARIANT_MCK / sampleRate);
+	dac->setOnTransmitEnd_CB(onTransmitEnd, this);
 }
 
 void AudioClass::end() {
 	dac->end();
+	free(buffer);
 }
 
-uint32_t *AudioClass::cook(const uint32_t *buffer, size_t size) {
-	if (currentBuffer == 0) {
-		// Use buffer0
-		for (int i = 0; i < size; i++)
-			buffer0[i] = buffer[i] | 0x10000000;
-		currentBuffer = 1;
-		return buffer0;
+size_t AudioClass::write(const uint32_t *data, size_t size) {
+	LockDAC lock(dac);
+	//Serial1.print("WRI(");
+	const uint32_t TAG = 0x10000000;
+	int i;
+	for (i=0; i < size && next != running; i++) {
+		*next = data[i] | TAG;
+		next++;
+
+		// Wrap around circular buffer
+		if (next == last)
+			next = buffer;
+	}
+	debug();
+	if (dac->canQueue()) {
+		enqueue();
+		debug();
+	}
+	//Serial1.print(")");
+	return i;
+}
+
+void AudioClass::enqueue() {
+	if (!dac->canQueue())
+		// DMA queue full
+		return;
+
+	if (current == next)
+		// No data to enqueue
+		return;
+
+	// If wrapping happened
+	if (next < current) {
+
+		uint32_t size = last - current;
+
+		if (size < 1024) {
+			// enqueue the last part of the circular buffer
+			dac->queueBuffer(current, size);
+			current = buffer;
+			next = buffer;
 		} else {
-		// Use buffer1
-		for (int i = 0; i < size; i++)
-			buffer1[i] = buffer[i] | 0x10000000;
-		currentBuffer = 0;
-		return buffer1;
+			// Enqueue only a block of 512
+			dac->queueBuffer(current, 512);
+			current += 512;
+		}
+		return;
+	}
+
+	bool aboutToWrap = (last - next) < 512;
+	uint32_t size = next - current;
+
+	// If buffered data is less than 512 bytes
+	if (size < 512) {
+
+		// Enqueue all
+		dac->queueBuffer(current, size);
+
+		if (aboutToWrap)
+			next = buffer;
+		current = next;
+
+	} else {
+
+		if (aboutToWrap && size < 1024) {
+			// Enqueue all
+			dac->queueBuffer(current, size);
+			next = buffer;
+			current = buffer;
+		} else {
+			// Enqueue only a block of 512
+			dac->queueBuffer(current, 512);
+			current += 512;
+		}
+
 	}
 }
 
+void AudioClass::onTransmitEnd(void *me) {
+	AudioClass *audio = reinterpret_cast<AudioClass *>(me);
+
+	//Serial1.print("INT(");
+	audio->enqueue();
+
+	// Update running pointer
+	audio->running = audio->dac->getCurrentQueuePointer();
+
+	audio->debug();
+	//Serial1.print(")");
+}
+
 AudioClass Audio(DAC);

hardware/arduino/sam/libraries/Audio/Audio.h

@@ -18,19 +18,33 @@
 class AudioClass : public Print {
 public:
 	AudioClass(DACClass &_dac) : dac(&_dac) { };
-	void begin(uint32_t sampleRate);
+	void begin(uint32_t sampleRate, uint32_t msPreBuffer);
 	void end();
 
 	virtual size_t write(uint8_t c)                         { /* not implemented */ };
-	virtual size_t write(const uint8_t *buffer, size_t size)  { return write((uint32_t*) buffer, size/4) * 4; };
-	virtual size_t write(const uint16_t *buffer, size_t size) { return write((uint32_t*) buffer, size/2) * 2; };
-	virtual size_t write(const int16_t *buffer, size_t size)  { return write((uint32_t*) buffer, size/2) * 2; };
-	virtual size_t write(const uint32_t *buffer, size_t size) { return dac->queueBuffer(cook(buffer,size), size); };
+	virtual size_t write(const uint8_t *data, size_t size)  { return write(reinterpret_cast<const uint32_t*>(data), size/4) * 4; };
+	virtual size_t write(const uint16_t *data, size_t size) { return write(reinterpret_cast<const uint32_t*>(data), size/2) * 2; };
+	virtual size_t write(const int16_t *data, size_t size)  { return write(reinterpret_cast<const uint32_t*>(data), size/2) * 2; };
+	virtual size_t write(const uint32_t *data, size_t size);
 
+	void debug() {
+//		Serial1.print(running-buffer, DEC);
+//		Serial1.print(" ");
+//		Serial1.print(current-buffer, DEC);
+//		Serial1.print(" ");
+//		Serial1.print(next-buffer, DEC);
+//		Serial1.print(" ");
+//		Serial1.println(last-buffer, DEC);
+	}
 private:
-	uint32_t buffer0[1024];
-	uint32_t buffer1[1024];
-	int currentBuffer;
+	void enqueue();
+	static void onTransmitEnd(void *me);
+	uint32_t bufferSize;
+	uint32_t *buffer;
+	uint32_t *last;
+	uint32_t * volatile running;
+	uint32_t * volatile current;
+	uint32_t * volatile next;
 
 	uint32_t *cook(const uint32_t *buffer, size_t size);
 

hardware/arduino/sam/libraries/Audio/DAC.cpp

@@ -1,3 +1,12 @@
+/*
+ * Copyright (c) 2012 by Cristian Maglie <c.maglie@bug.st>
+ * DAC library for Arduino Due.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
 
 #include <DAC.h>
 
@@ -108,21 +117,25 @@ size_t DACClass::queueBuffer(const uint32_t *buffer, size_t size) {
 	return 0;
 }
 
-void DACClass::setOnQueueFree_CB(OnQueueFree_CB _cb) {
+uint32_t *DACClass::getCurrentQueuePointer() {
+	return reinterpret_cast<uint32_t *>(dac->DACC_TPR);
+}
+
+void DACClass::setOnTransmitEnd_CB(OnTransmitEnd_CB _cb, void *_data) {
 	cb = _cb;
-	if (cb) {
-		dacc_enable_interrupt(dac, DACC_IER_ENDTX);
-	} else {
+	cbData = _data;
+	if (!cb)
 		dacc_disable_interrupt(dac, DACC_IDR_ENDTX);
-	}
 }
 
 void DACClass::onService() {
 	uint32_t sr = dac->DACC_ISR;
-	if (sr & DACC_ISR_ENDTX) {
+//	if (sr & DACC_ISR_ENDTX) {
+		// There is a free slot, enqueue data
 		dacc_disable_interrupt(dac, DACC_IDR_ENDTX);
-		if (cb) cb();
-	}
+		if (cb)
+			cb(cbData);
+//	}
 }
 
 DACClass DAC(DACC_INTERFACE, DACC_INTERFACE_ID, DACC_ISR_ID);

hardware/arduino/sam/libraries/Audio/DAC.h

@@ -1,10 +1,19 @@
+/*
+ * Copyright (c) 2012 by Cristian Maglie <c.maglie@bug.st>
+ * DAC library for Arduino Due.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
 
 #ifndef DAC_INCLUDED
 #define DAC_INCLUDED
 
 #include "Arduino.h"
 
-typedef void (*OnQueueFree_CB)(void);
+typedef void (*OnTransmitEnd_CB)(void *data);
 
 class DACClass
 {
@@ -15,14 +24,19 @@ public:
 	void end();
 	bool canQueue();
 	size_t queueBuffer(const uint32_t *buffer, size_t size);
-	void setOnQueueFree_CB(OnQueueFree_CB _cb);
+	uint32_t *getCurrentQueuePointer();
+	void setOnTransmitEnd_CB(OnTransmitEnd_CB _cb, void *data);
 	void onService();
 
+	void enableInterrupts()  { NVIC_EnableIRQ(isrId); };
+	void disableInterrupts() { NVIC_DisableIRQ(isrId); };
+
 private:
 	Dacc *dac;
 	uint32_t dacId;
 	IRQn_Type isrId;
-	OnQueueFree_CB cb;
+	OnTransmitEnd_CB cb;
+	void *cbData;
 };
 
 extern DACClass DAC;