Chapter 29 Bluetooth Media by Audio Module

In the previous section, ESP32’s own DAC was used to output the audio signal, and obviously there was some distortion in the sound quality. In this section, with the help of PCM5102A chip, you will enjoy higher-quality music.

Project 29.1 Playing Bluetooth Music through Audio Converter & Amplifier

In this project, we will use Audio Converter & Amplifier to transcode audio data into stereo and output it.

Component List

ESP32-WROVER x1	GPIO Extension Board x1
Micro USB Wire x1	Speaker
Audio Converter & Amplifier	Jumper F/M x4 Jumper F/F x2

Component knowledge

The front and reverse view of Audio Converter & Amplifier module.

front view	reverse view	schematic diagram

Interface description for Audio Converter & Amplifier module

Pin	Name	Introductions
1	SCK	System clock input
2	BCK	Audio data bit clock input
3	DIN	Audio data input
4	LCK	Audio data word clock input
5	VCC	Power input, 3.3V~5.0V
6	GND	Power Ground
7	L	External audio left channel input
8	G	Power Ground
9	R	External audio right channel input
10	G	Power Ground
11	R+	Positive pole of right channel horn
12	R-	Negative pole of right channel horn
13	L+	Positive pole of left channel horn
14	L-	Negative pole of left channel horn

Speaker interface: Connect left channel speaker and right channel speaker. Group L: L+ & L-; Group R: R+& R-. The two interfaces of the speaker can be connected to the interfaces of group L or group R. But when one interface is connected to group L, the other cannot be connected to group R. Doing so may cause the module to malfunction.

Headphone interface: the interface to connect the headphones.

I2S input interface: connect to the device with I2S. Used to transcode audio data into DAC audio signals.

External audio input interface: connect to external audio equipment. Used to amplify externally input audio signals.

Power interface: connect to external power supply. External power supply selection range: 3.3V-5.0V.

Circuit

Schematic diagram

Hardware connection

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Sketch

If you are using ESP32 Core 2.x.x, please see Sketch_29.1_Bluetooth_Music_by_Audio_Converter(2.x.x)

If you are using ESP32 Core 3.x.x, please see Sketch_29.1_Bluetooth_Music_by_Audio_Converter(3.x.x)

Sketch_29.1_Bluetooth_Music_by_Audio_Converter(2.x.x)

Compile and upload the code to the ESP32-WROVER and open the serial monitor. ESP32 takes a few seconds to initialize the program.

When you see the prompt as shown in the figure below, it means that the Bluetooth function of ESP32 is ready and waiting for the connection of other Bluetooth devices.

Please use your mobile phone to search and connect a Bluetooth device named “ESP32”. After the connection is successful, you can use ESP32 to play the audio files in your mobile phone.

Code

The following is the program code:

Code Explanation

Define an I2S configuration class and initialize it; define an I2S pin configuration class and associate I2S signals with these pins.

In this chapter, the procedure is very similar to the previous section. The difference only lies in the I2S configuration. The audio quality of the DAC output from the PCM5102 chip after decoding is significantly higher than that of the ESP32’s own 8-bit precision DAC.

Sketch_29.1_Bluetooth_Music_by_Audio_Converter(3.x.x)

Code

The following is the program code:

Code Explanation

Introduce the necessary libraries.

Define the required pins

Create instances of I2S and Bluetooth A2DP Sink

Configure the specific pins used for I2S

Initialize the I2S interface

Start the Bluetooth sink with the name “ESP32 A2DP”