Volume control with Bluetooth

Projects General Guidance
1

I have connected my phone to an ESP32 through bluetooth and added a speaker. I also have a HC-SR04 connected. I the volume on the speaker to be controlled by the outputs by the HC-SR04, but it seems like the volume on the phone is overruling the volume set by the HC-SR04.

I am using pschatzmann ESP32-A2DP library.

Is it possible to overwrite the volume set by the phone?

My code is:

#include "BluetoothA2DPSink.h"

BluetoothA2DPSink a2dp_sink;

int volume = 0;
const int trigPin = 5;
const int echoPin = 18;
const int numReadings = 10;
int readings[numReadings];
int readIndex = 0;
int total = 0;
int average = 0;
int minimum = 2;
int maximum = 400;

#define SOUND_SPEED 0.0343

long duration;
float distanceCm;
int power;
int invertPower;
long DSC = 3.1496

void volumeChanged(int newVolume) {
  Serial.println(newVolume);
  volume = newVolume;
}

void connection_state_changed(esp_a2d_connection_state_t state, void* ptr) {
  Serial.println(a2dp_sink.to_str(state));
}

void audio_state_changed(esp_a2d_audio_state_t state, void* ptr) {
  Serial.println(a2dp_sink.to_str(state));
}

void setup() {
  Serial.begin(115200);
  const i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_DAC_BUILT_IN),
    .sample_rate = 44100,
    .bits_per_sample = (i2s_bits_per_sample_t)16,
    .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
    .communication_format = (i2s_comm_format_t)I2S_COMM_FORMAT_STAND_MSB,
    .intr_alloc_flags = 0,
    .dma_buf_count = 8,
    .dma_buf_len = 64,
    .use_apll = false
  };
  
  a2dp_sink.set_i2s_config(i2s_config);
  a2dp_sink.set_on_volumechange(volumeChanged);
  a2dp_sink.set_on_connection_state_changed(connection_state_changed);
  a2dp_sink.set_on_audio_state_changed(audio_state_changed);
  a2dp_sink.start("Robert");

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(proxLED, OUTPUT);
  pinMode(alarmLED, OUTPUT);

  for (int thisReading = 0; thisReading < numReadings; thisReading++) {
    readings[thisReading] = 0;
  }
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  distanceCm = duration * SOUND_SPEED/2;
  distanceCm = constrain(distanceCm, minimum, maximum);

  total = total - readings[readIndex];
  readings[readIndex] = distanceCm;
  total = total + readings[readIndex];
  readIndex = readIndex + 1;

  if (readIndex >= numReadings) {
    readIndex = 0;
  }

  average = total / numReadings;
  power = average * 5;

  Serial.print("  Distance (cm): ");
  Serial.print(distanceCm);
  Serial.print("  │  Average (cm): ");
  Serial.print(average);
  Serial.print("  │  Voltage (mV): ");
  Serial.print(power);

  invertPower = map(power, 0, 2000, 2000, 0);

  volume = average / DSC;
  Serial.print("  │  Volume: ");
  Serial.println(volume);

  delay(500);
}
2

Do you see this being called?

What in your code is changing the volume of the speaker?

3

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