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libraries/audio-tools/examples/examples-communication/a2dp/basic-a2dp-mixer-i2s/basic-a2dp-mixer-i2s.ino

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+/**
+ * @file basic-a2dp-mixer-i2s.ino
+ * @brief A2DP Sink with output to mixer: I think this is the most efficient way
+ * of mixing a signal that is coming from A2DP which requires only 160 byte of additional RAM.
+ *
+ * @author Phil Schatzmann
+ * @copyright GPLv3
+ */
+
+#include "AudioTools.h"
+#include "BluetoothA2DPSink.h"
+
+AudioInfo info(44100, 2, 16);
+BluetoothA2DPSink a2dp_sink;
+I2SStream i2s;
+SineWaveGenerator<int16_t> sineWave(10000);  // subclass of SoundGenerator with max amplitude of 10000
+GeneratedSoundStream<int16_t> sound(sineWave); // Stream generated from sine wave
+OutputMixer<int16_t> mixer(i2s, 2);  // output mixer with 2 outputs
+const int buffer_size = 80;  // split up the output into small chunks
+uint8_t sound_buffer[buffer_size];
+
+// Write data to mixer
+void read_data_stream(const uint8_t *data, uint32_t length) {
+  // To keep the mixing buffer small we split up the output into small chunks
+  int count = length / buffer_size + 1;
+  for (int j = 0; j < count; j++) {
+    const uint8_t *start = data + (j * buffer_size);
+    const uint8_t *end = min(data + length, start + buffer_size);
+    int len = end - start;
+    if (len > 0) {
+      // write a2dp
+      mixer.write(start, len);
+
+      // write sine tone with identical length
+      sound.readBytes(sound_buffer, len);
+      mixer.write(sound_buffer, len);
+
+      // We could flush to force the output but this is not necessary because we
+      // were already writing all 2 streams mixer.flushMixer();
+    }
+  }
+}
+
+void setup() {
+  Serial.begin(115200);
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);
+
+  // setup Output mixer with min necessary memory
+  mixer.begin(buffer_size);
+
+  // Register data callback
+  a2dp_sink.set_stream_reader(read_data_stream, false);
+
+  // Start Bluetooth Audio Receiver
+  a2dp_sink.set_auto_reconnect(false);
+  a2dp_sink.start("a2dp-i2s");
+
+  // Update sample rate
+  info.sample_rate = a2dp_sink.sample_rate();
+
+  // start sine wave
+  sineWave.begin(info, N_B4);
+
+  // setup output
+  auto cfg = i2s.defaultConfig();
+  cfg.copyFrom(info);
+  // cfg.pin_data = 23;
+  cfg.buffer_count = 8;
+  cfg.buffer_size = 256;
+  i2s.begin(cfg);
+}
+
+void loop() { delay(100); }