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libraries/audio-tools/examples/examples-dsp/examples-mozzi/control_gain-a2dp/control_gain-a2dp.ino

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+/**
+ * Demo how to use the Mozzi API to provide a stream of int16_t data.
+ * Inspired by https://sensorium.github.io/Mozzi/examples/#01.Basics
+ * The result is published to a bluetooth speaker. We use the more efficient
+ * A2DP base API with a callback
+ */
+#include "AudioTools.h"
+#include "AudioTools/Communication/A2DPStream.h"
+#include "AudioTools/AudioLibs/MozziStream.h"
+#include <Oscil.h>                // oscillator template
+#include <tables/sin2048_int8.h>  // sine table for oscillator
+
+const int sample_rate = 44100;
+AudioInfo info(sample_rate, 2, 16);  // bluetooth requires 44100, stereo, 16 bits
+BluetoothA2DPSource a2dp_source;
+MozziStream mozzi;  // audio source
+const int16_t BYTES_PER_FRAME = 4;
+// use: Oscil <table_size, update_rate> oscilName (wavetable), look in .h file
+// of table #included above
+Oscil<SIN2048_NUM_CELLS, sample_rate> aSin(SIN2048_DATA);
+// control variable, use the smallest data size you can for anything used in
+// audio
+byte gain = 255;
+
+// callback used by A2DP to provide the sound data - usually len is 128 2 channel int16 frames
+int32_t get_sound_data(uint8_t* data, int32_t size) {
+  int32_t result = mozzi.readBytes(data, size);
+  //LOGI("get_sound_data %d->%d",size, result);
+  return result;
+}
+
+// Arduino Setup
+void setup(void) {
+  Serial.begin(115200);
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Info);
+
+  // setup mozzi
+  auto cfg = mozzi.defaultConfig();
+  cfg.control_rate = CONTROL_RATE;
+  cfg.copyFrom(info);
+  mozzi.begin(cfg);
+
+  aSin.setFreq(3320);  // set the frequency
+
+  // start the bluetooth
+  Serial.println("starting A2DP...");
+  a2dp_source.set_data_callback(get_sound_data);
+  a2dp_source.start("LEXON MINO L");
+  //a2dp_source.set_volume(100);
+}
+
+void updateControl() {
+  // as byte, this will automatically roll around to 255 when it passes 0
+  gain = gain - 3;
+}
+
+AudioOutputMozzi updateAudio() {
+  // shift back to STANDARD audio range, like /256 but faster
+  return (aSin.next() * gain) >> 8;
+}
+
+// Arduino loop - repeated processing
+void loop() {
+  delay(1000);
+}