This repository contains the ST BVLINK_rbpi3 app source code for Linux OS. The application has been tested on Raspberry Pi 3 Model B but could be easily ported to other Linux platform provided that they support ALSA drivers and BlueZ.

The BVLINK_rbpi3 application can receive an audio stream over Bluetooth Low Energy link using the "BlueVoice" vendor-specific profile. The received audio stream is then exported as a it was a standard microphone peripheral taking advantage of the ALSA aloop device.

The transmitter (or BLE microphone) can be any ST platform that supports the BlueVoice protocol. The following table states the list of compatible firmware and the supported hardware platform that can be programmed as "BlueVoice" transmitting device.

SensorTile Development kit --> www.st.com/sensortile BlueCoin Starter Kit --> www.st.com/bluecoin STEVAL-BLUEMIC-1 --> www.st.com/en/evaluation-tools/steval-bluemic-1.html

FP-AUD-BVLINK1 --> www.st.com/en/embedded-software/fp-aud-bvlink1.html FP-SNS-ALLMEMS1 --> www.st.com/en/embedded-software/fp-sns-allmems1.html STSW-BLUEMIC-1 --> www.st.com/en/embedded-software/stsw-bluemic-1.html

The chosen firmware must be configured to stream BlueVoice at either 8KHz or 16KHz with a connection interval set to 8. FP-AUD-BVLINK1 or FP-SNS-ALLMEMS1

BV_ADPCM_Config.sampling_frequency = FR_8000; /* FR_16000; */

#define AUDIO_IN_SAMPLING_FREQUENCY   SAMPLING_FREQ_8000 /* SAMPLING_FREQ_16000 */

aci_l2cap_connection_parameter_update_request(handle,
                                              8 /* interval_min*/,
                                              8 /* interval_max */,
                                              0   /* slave_latency */,
                                              400 /*timeout_multiplier*/);

STSW-BLUEMIC-1

#define AUDIO_SAMPLING_FREQUENCY     (uint16_t)(SAMPLING_FREQ_8000) /* SAMPLING_FREQ_16000 */ 

aci_l2cap_connection_parameter_update_request(handle,
                                              8   /* interval_min*/,
                                              8   /* interval_max */,
                                              0   /* slave_latency */,
                                              400 /*timeout_multiplier*/);

Once the firmware code has been modified according to the above hints it must be recompiled and flashed on the microcontroller, STM32 or BlueNRG-1 depending on the chosen platform.

• Linux based system (Tested on Raspberry Pi 3 Model B)
• Linux OS (Tested on Raspbian)
• ALSA kernel drivers
• BlueZ kernel modules
• Python 3

Type the following commands to the console to install required packages

 sudo apt-get update
 sudo apt-get install build-essential libssl-dev libffi-dev python-dev python-cffi libglib2.0-dev
 sudo pip3 install sounddevice
 sudo pip3 install bluepy

Type the following commands to the console to load required module

 sudo modprobe snd-aloop 
 sudo bash -c "echo snd-aloop >> /etc/modules"
 sudo bash -c "echo options snd_bcm2835 index=0 >> /etc/modprobe.d/alsa-base.conf"
 sudo bash -c "echo options snd_aloop index=-2 >> /etc/modprobe.d/alsa-base.conf"

Clone the repository

git clone https://github.com/STMicroelectronics-CentralLabs/BlueVoice-for-Linux.git

Go to the proper directory

cd BlueVoice-for-Linux/BVLINK_rbpi3

 sudo python3 main.py [mode] [frequency]

• mode
  • alsa_playback: to playback directly the audio acquired from ST platform to the speaker
  • stl_capture: to create a standard microphone named STL_capture for audio acquisition by audacity or arecord
• frequency
  • 16000: for a 16KHz audio frequency
  • 8000: for a 8KHz audio frequency

Running example: To create a 16KHz microphone peripheral named STL_capture.

 sudo python3 main.py stl_capture 16000

Acquisition example: Create a 16Khz file audio called "record1.wav" by arecord.

 arecord -D STL_capture -f S16_LE -r 16000 -c 1 record1.wav

Prevent audio out garbling because of audio out peripheral of raspberry

sudo bash -c "echo disable_audio_dither=1 >> /boot/config.txt"
sudo bash -c "echo audio_pwm_mode=2 >> /boot/config.txt"

• Central Lab - STMicroelectronics -

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