For the I2S codec, pick whatever chip or board works for you; this code was written using a PCM5102 chip, but other I2S boards and chips will probably work as well. The default I2S connections are shown below, but these can be changed in menuconfig:
+-----------+--------------+
| ESP pin | I2S signal |
+===========+==============+
| GPIO22 | LRCK |
+-----------+--------------+
| GPIO25 | DATA |
+-----------+--------------+
| GPIO26 | BCK |
+-----------+--------------+
If the internal DAC is selected, analog audio will be available on GPIO25 and GPIO26. The output resolution on these pins will always be limited to 8 bit because of the internal structure of the DACs.
After the program started, other bluetooth devices such as smart phones can discover this device named "ESP_SPEAKER", and after connection is established, audio data can be transmitted and there will occur a count of audio data packets printed.
