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89 lines
2.1 KiB
C++
89 lines
2.1 KiB
C++
/*
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* Copyright (c) 2012 by Cristian Maglie <c.maglie@bug.st>
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* Audio library for Arduino Due.
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of either the GNU General Public License version 2
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* or the GNU Lesser General Public License version 2.1, both as
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* published by the Free Software Foundation.
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*/
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#include "Audio.h"
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void AudioClass::begin(uint32_t sampleRate, uint32_t msPreBuffer) {
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// Allocate a buffer to keep msPreBuffer milliseconds of audio
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bufferSize = msPreBuffer * sampleRate / 1000;
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if (bufferSize < 1024)
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bufferSize = 1024;
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buffer = (uint32_t *) malloc(bufferSize * sizeof(uint32_t));
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half = buffer + bufferSize / 2;
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last = buffer + bufferSize;
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// Buffering starts from the beginning
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running = buffer;
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next = buffer;
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// Start DAC
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dac->begin(VARIANT_MCK / sampleRate);
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dac->setOnTransmitEnd_CB(onTransmitEnd, this);
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}
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void AudioClass::end() {
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dac->end();
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free( buffer);
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}
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void AudioClass::prepare(int16_t *buffer, int S, int volume){
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uint16_t *ubuffer = (uint16_t*) buffer;
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for (int i=0; i<S; i++) {
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// set volume amplitude (signed multiply)
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buffer[i] = buffer[i] * volume / 1024;
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// convert from signed 16 bit to unsigned 12 bit for DAC.
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ubuffer[i] += 0x8000;
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ubuffer[i] >>= 4;
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}
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}
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size_t AudioClass::write(const uint32_t *data, size_t size) {
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const uint32_t TAG = 0x10000000;
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int i;
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for (i = 0; i < size; i++) {
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*next = data[i] | TAG;
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next++;
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if (next == half || next == last) {
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enqueue();
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while (next == running)
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;
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}
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}
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return i;
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}
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void AudioClass::enqueue() {
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if (!dac->canQueue()) {
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// DMA queue full
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return;
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}
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if (next == half) {
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// Enqueue the first half
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dac->queueBuffer(buffer, bufferSize / 2);
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} else {
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// Enqueue the second half
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dac->queueBuffer(half, bufferSize / 2);
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next = buffer; // wrap around
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}
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}
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void AudioClass::onTransmitEnd(void *_me) {
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AudioClass *me = reinterpret_cast<AudioClass *> (_me);
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if (me->running == me->buffer)
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me->running = me->half;
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else
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me->running = me->buffer;
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}
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AudioClass Audio(DAC);
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