1  #include "Adafruit_MP3.h"
 2  #include "sine.h"
 3  
 4  Adafruit_MP3 player;
 5  
 6  void writeDacs(int16_t l, int16_t r){
 7    uint16_t val = map(l, -32768, 32767, 0, 4095);
 8  #if defined(__SAMD51__) // feather/metro m4
 9    analogWrite(A0, val);
10  #elif defined(__MK66FX1M0__) || defined(__MK20DX256__) // teensy 3.6
11    analogWrite(A21, val);
12  #endif
13  }
14  
15  uint8_t *currentPtr;
16  uint32_t thisManyBytesLeft;
17  
18  int getMoreData(uint8_t *writeHere, int thisManyBytes){
19    int toWrite = min(thisManyBytesLeft, thisManyBytes);
20    memcpy(writeHere, currentPtr, toWrite);
21    currentPtr += toWrite;
22    thisManyBytesLeft -= toWrite;
23    return toWrite;
24  }
25  
26  // the setup routine runs once when you press reset:
27  void setup() {
28  
29  #if defined(__SAMD51__)
30    //set the DAC to the center of the range
31    analogWrite(A0, 2048);
32  #endif
33  
34    currentPtr = (uint8_t*)sine_mp3;
35    thisManyBytesLeft = sizeof(sine_mp3);
36  
37    player.begin();
38  
39    //do this when there are samples ready
40    player.setSampleReadyCallback(writeDacs);
41  
42    //do this when more data is required
43    player.setBufferCallback(getMoreData);
44  
45    player.play();
46  }
47  
48  // the loop routine runs over and over again forever:
49  void loop() {
50    player.tick();
51  }