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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