Add bt_music_sender_auto_reconnect.ino

[00kenno]

I wanted to enable auto reconnect.

Initially, I tried this:

void setup() {
  a2dp_source.set_auto_reconnect(true);
  a2dp_source.set_data_callback_in_frames(get_data_frames);
  a2dp_source.set_volume(30);
  a2dp_source.start("LEXON MINO L");
}

But it turns out set_auto_reconnect(true) should not be called before start().

Posting this here in case it helps someone else with the same problem.

[00kenno]

In the start() function, the following code exists:

void BluetoothA2DPSource::start(std::vector<const char *> names) {
  ESP_LOGD(BT_APP_TAG, "%s, ", __func__);
  this->bt_names = names;
  is_end = false;
  is_autoreconnect_allowed = (reconnect_status == AutoReconnect);

  init_nvs();
  if (is_autoreconnect_allowed) {
    // get last connection if not available
    if (!has_last_connection()) {
      get_last_connection();
    }
  }
  :
}

When set_auto_reconnect(true) is called earlier in the setup() function during the first startup, the code inside this if block is executed. As a result, get_last_connection() is called even though no previous connection information exists yet.

This behavior may cause an issue on the initial run, since there is no stored connection to retrieve.

[pschatzmann]

I don't see any issue here: The only thing is, that the very first time you get some error messages because no last address exsists.

In this case it is just connecting to the indicated name.

[00kenno]

Indeed, there seems to be nothing wrong with this source code. However, I couldn't get it to connect on my microcontroller no matter how many times I tried. What I'm looking for isn't an improvement to the source code. It's just a slightly overly detailed sample code. It reports that running set_auto_reconnect(true) before start() may result in a connection failure.

[00kenno]

This problem occurs especially when connecting to multiple devices.

[pschatzmann]

I agree, if you are not carefull with the parameters you try to reconnect (for a long time) to the last device which might not be available!

[00kenno]

I'm glad my intention was conveyed. I would really appreciate it if you could add a sample like the one I provided, or at least clearly state this in the comments of the sample.

[pschatzmann]

Here is my latest commit!

[00kenno]

Thank you for making the changes!

[00kenno]

I know this is a bit selfish, but I'd really appreciate it if you could also include this information in the A2DP Source documentation. That's where I encountered the problem.

[pschatzmann]

I extended the logic for the BluetoothA2DPSource set_auto_reconnect() to accept a retry count parameter to be consistent with the A2DP Sink implementation.

Here is the related commit.

[00kenno]

Thank you so much for making changes to this great library based on my feedback!!!