[136] | 1 | /*
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| 2 | * Copyright (c) 2012 by Cristian Maglie <c.maglie@arduino.cc>
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| 3 | * Audio library for Arduino Due.
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| 4 | *
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| 5 | * This file is free software; you can redistribute it and/or modify
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| 6 | * it under the terms of either the GNU General Public License version 2
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| 7 | * or the GNU Lesser General Public License version 2.1, both as
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| 8 | * published by the Free Software Foundation.
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| 9 | */
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| 10 |
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| 11 | #include "Audio.h"
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| 12 |
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| 13 | void AudioClass::begin(uint32_t sampleRate, uint32_t msPreBuffer) {
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| 14 | // Allocate a buffer to keep msPreBuffer milliseconds of audio
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| 15 | bufferSize = msPreBuffer * sampleRate / 1000;
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| 16 | if (bufferSize < 1024)
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| 17 | bufferSize = 1024;
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| 18 | buffer = (uint32_t *) malloc(bufferSize * sizeof(uint32_t));
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| 19 | half = buffer + bufferSize / 2;
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| 20 | last = buffer + bufferSize;
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| 21 |
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| 22 | // Buffering starts from the beginning
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| 23 | running = buffer;
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| 24 | next = buffer;
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| 25 |
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| 26 | // Start DAC
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| 27 | dac->begin(VARIANT_MCK / sampleRate);
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| 28 | dac->setOnTransmitEnd_CB(onTransmitEnd, this);
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| 29 | }
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| 30 |
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| 31 | void AudioClass::end() {
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| 32 | dac->end();
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| 33 | free( buffer);
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| 34 | }
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| 35 |
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| 36 | void AudioClass::prepare(int16_t *buffer, int S, int volume){
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| 37 | uint16_t *ubuffer = (uint16_t*) buffer;
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| 38 | for (int i=0; i<S; i++) {
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| 39 | // set volume amplitude (signed multiply)
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| 40 | buffer[i] = buffer[i] * volume / 1024;
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| 41 | // convert from signed 16 bit to unsigned 12 bit for DAC.
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| 42 | ubuffer[i] += 0x8000;
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| 43 | ubuffer[i] >>= 4;
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| 44 | }
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| 45 | }
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| 46 |
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| 47 | size_t AudioClass::write(const uint32_t *data, size_t size) {
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| 48 | const uint32_t TAG = 0x10000000;
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| 49 | int i;
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| 50 | for (i = 0; i < size; i++) {
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| 51 | *next = data[i] | TAG;
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| 52 | next++;
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| 53 |
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| 54 | if (next == half || next == last) {
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| 55 | enqueue();
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| 56 | while (next == running)
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| 57 | ;
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| 58 | }
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| 59 | }
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| 60 |
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| 61 | return i;
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| 62 | }
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| 63 |
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| 64 | void AudioClass::enqueue() {
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| 65 | if (!dac->canQueue()) {
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| 66 | // DMA queue full
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| 67 | return;
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| 68 | }
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| 69 |
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| 70 | if (next == half) {
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| 71 | // Enqueue the first half
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| 72 | dac->queueBuffer(buffer, bufferSize / 2);
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| 73 | } else {
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| 74 | // Enqueue the second half
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| 75 | dac->queueBuffer(half, bufferSize / 2);
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| 76 | next = buffer; // wrap around
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| 77 | }
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| 78 | }
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| 79 |
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| 80 | void AudioClass::onTransmitEnd(void *_me) {
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| 81 | AudioClass *me = reinterpret_cast<AudioClass *> (_me);
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| 82 | if (me->running == me->buffer)
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| 83 | me->running = me->half;
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| 84 | else
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| 85 | me->running = me->buffer;
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| 86 | }
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| 87 |
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| 88 | AudioClass Audio(DAC);
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