BT Audio click

Bluetooth class 2 radio and DSP processor combined

Microchip’s RN52 Bluetooth audio module delivers high quality audio in small form factor (26.0 mm x 13.5 mm x 2.7 mm). The module combines a class 2 Bluetooth radio and an embedded DSP processor, controlled and configured by simple ASCII commands.

Learn more from the vendor’s datasheet.

BT Audio Click can stream audio files

DSP, or digital signal processor, is what makes this module special, because it can actually stream audio – it converts and compresses the radio waves sent from your phone or computer into digital data, and then sends it to your speakers or headphones.

As a use case example, we built a multimedia station project. Read about it in this tutorial.

Quality of sound over Bluetooth

The module supports aptX, audio codec for high quality stereo audio streaming over a Bluetooth connection. So the quality of the sound is not something you will have to compromise on, as aptX encodes a CD-quality (16-bit / 44.1kHz) audio stream.

The RN52 module supports HSP/HFP, A2DP, AVRCP and SPP, as well as digital I/O, stereo speaker output, stereo microphone input. The module also supports iAP profile discovery for connecting the BT Audio click to Apple devices like, iPods, iPhones or MAC computers.

HSP/HFP stands for Hands-Free Profile and Headset Profile for an audio connection between Bluetooth on your phone and the headset.

Bluetooth range

BT Audio click has a 10m range in open space. The range is smaller indoors, but still enough to cover a few rooms.

BT Audio click communicates with the target board MCU through the mikroBUS™ UART interfaces, with few additional pins. The board uses a 3.3V power supply only.

Specifications

Pinout diagram

This table shows how the pinout on BT Audio click corresponds to the pinout on the mikroBUS™ socket.

Notes	Pin					Pin	Notes
Defines baud rate of module	BAUD	1	AN	PWM	16	CMD	Puts module in command/data operation
	NC	2	RST	INT	15	FIRST	Factory reset
Powers up the module	POWER_EN	3	CS	TX	14	RX	UART receive
	NC	4	SCK	RX	13	TX	UART transmit
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
+3.3V power input	+3.3V	7	+3.3V	+5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Connectivity to Apple devices

The module also supports iAP profile discovery for connecting BT Audio click to Apple devices like iPods, iPhones or MAC computers.

• The RN52 supports HSP/HFP, A2DP, AVRCP and SPP, as well as digital I/O, stereo speaker output, stereo microphone input,up to 11 General Purpose I/O’s, and 2 LED status outputs.
• The HSP/HFP stands for Hands-Free Profile and Headset Profile for an audio connection between Bluetooth on your phone and the headset.

The module is fully Bluetooth qualified and provides global modular approval. The ADC can sample up to 200 kHz using different inputs as sample triggers and it supports 8/10/12 bit resolution. Any of the 8 analog inputs can be used both as single-ended inputs and as differential pairs for measuring the voltage across them. The ADC supports full 0 V to VCC input range.

The BT Audio click runs on 3.3V power supply only.

Programming

The demo is a GUI application made for the mikromedia+ for STM32F7 with a shield. The Application uses BT Audio library to interface between the touch screen and click board to play music and make phone calls.

The complete project is available on Libstock

Code snippet

 1 void play_btnOnClick()
2 {
3     connection_status_t connection;
4
5     bt_audio_query_connection_status( &connection );
6     if( !connection.A2DP_connection )
7         return;
8     if( music_state_t == PAUSED )
9     {
10         bt_audio_pause_play_track();
11         music_state_t = PLAYING;
12         if( first_song )
13         {
14             get_track_data();
15             first_song = false;
16         }
17     }
18 }