Providing Audio Data

The A2DP Source sends the audio data that you provide to a Bluetooth speaker or headphones. The data is PCM: 44.1 kHz, two channels, 16 bits per sample.

Callback with Bytes

#include "BluetoothA2DPSource.h"

BluetoothA2DPSource a2dp_source;

int32_t get_sound_data(uint8_t *data, int32_t byteCount) {
  // fill data with your sound data
  // and return the effective length in bytes
  return byteCount;
}

void setup() {
  a2dp_source.set_data_callback(get_sound_data);
  a2dp_source.start("MyMusic");
}

void loop() {
  delay(1000);
}

Callback with Frames

A Frame contains the 16 bit samples of the two channels (channel1, channel2), which is often more convenient. Here is an example that generates a sine tone:

#include "BluetoothA2DPSource.h"
#include <math.h>

const float deltaAngle = 2.0 * PI * 440.0 / 44100.0;
BluetoothA2DPSource a2dp_source;

int32_t get_data_frames(Frame *frame, int32_t frame_count) {
  static float angle = 0.0;
  for (int j = 0; j < frame_count; j++) {
    frame[j].channel1 = 10000.0 * sin(angle);
    frame[j].channel2 = frame[j].channel1;
    angle += deltaAngle;
    if (angle > 2.0 * PI) angle -= 2.0 * PI;
  }
  return frame_count;
}

void setup() {
  a2dp_source.set_data_callback_in_frames(get_data_frames);
  a2dp_source.set_volume(30);
  a2dp_source.start("MyMusic");
}

void loop() {
  delay(1000);
}

Arduino Streams

In Arduino you can also provide a Stream (e.g. a File) that contains the PCM data:

• set_data_source(Stream&): a single Stream
• set_data_source_callback(Stream& (*next_stream)()): a callback that provides the next Stream when the current one has ended

Notes

• The callbacks are called from a separate task, so keep them fast and avoid any blocking operations.
• set_volume() adjusts the volume of the data before it is sent. See Volume Control.
• To use AAC or your own SBC encoder, see Custom Codecs.
• To select the device you connect to, see Device Discovery & Selection.