ST STEVAL-BLUEMIC-1 User Manual

July 2017

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www.st.com

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User manual

Getting started with the STEVAL-BLUEMIC-1 evaluation board,

ultra-low power wireless microphone based on SPBTLE-1S module

Introduction

The STEVAL-BLUEMIC-1 evaluation board mounts the SPBTLE-1S Bluetooth® SMART application
processor compliant with BT specification v4.2. It supports multiple simultaneous roles and can act as a
Bluetooth Smart master and slave device at the same time.

This BLE wireless battery powered solution also embeds digital MEMS microphone MP34DT04-C1 and
3D accelerometer + 3D gyroscope, which render this evaluation board suitable for a wide range of
advanced smart application.

The evaluation board comes with a complete SW development kit that includes the Bluetooth low
energy stack, all the needed drivers for audio and inertial data acquisition, and button and LED
management. A ready-to-use BlueVoice library is included as middleware and a sample application is
provided to get you started with voice streaming over BLE to an Android or iOS device, running the ST
BlueMS apps.

Figure 1: STEVAL-BLUEMIC-1 evaluation board

Contents

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Contents

1 Getting started ................................................................................. 5

1.1 Hardware description ........................................................................ 5

1.1.1 Features ............................................................................................. 5

1.1.2 Evaluation kit ...................................................................................... 5

1.1.3 Evaluation board ................................................................................. 7

1.1.4 Schematic diagrams ........................................................................... 9

1.2 Software description ........................................................................ 11

1.2.1 Overview ........................................................................................... 11

1.2.2 Architecture ...................................................................................... 11

1.2.3 Folder structure ................................................................................ 12

1.2.4 APIs .................................................................................................. 12

1.2.5 BlueMic1 application ......................................................................... 12

1.2.6 Audio processing .............................................................................. 14

1.2.7 ADPCM compression ....................................................................... 15

1.2.8 Packetization .................................................................................... 16

1.2.9 STSW-BLUEMIC-1 application description ...................................... 17

1.3 BlueVoiceADPCM_BNRG1 library software description ................. 18

1.3.1 Initialization and configuration .......................................................... 18

1.3.2 Working mode setup ......................................................................... 18

1.3.3 Audio signal injection ........................................................................ 19

1.3.4 Compressed audio streaming .......................................................... 19

2 System setup ................................................................................. 21

2.1 Power supply ................................................................................... 21

2.2 STEVAL-BLUEMIC-1 evaluation board assembly in form factor
case 21

2.3 STEVAL-BLUEMIC-1 evaluation board programming interface ...... 22

2.4 STEVAL-BLUEMIC-1 evaluation board demos ............................... 23

2.4.1 Streaming to a mobile device ........................................................... 23

2.5 Streaming to an STM32 Nucleo board used as a receiver .............. 35

3 Revision history ............................................................................ 37

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List of tables

Table 1: STEVAL-BLUEMIC-1 evaluation board main component details ................................................. 8

Table 2: BlueMic1 UUID summary table ................................................................................................... 14

Table 3: Document revision history .......................................................................................................... 37

List of figures

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List of figures

Figure 1: STEVAL-BLUEMIC-1 evaluation board ....................................................................................... 1

Figure 2: STEVAL-BLUEMIC-1 evaluation kit ............................................................................................ 5

Figure 3: STEVAL-BLUEMIC-1 evaluation board: top and bottom ............................................................ 6

Figure 4: Battery ......................................................................................................................................... 6

Figure 5: Plastic case.................................................................................................................................. 6

Figure 6: SWD cable ................................................................................................................................... 6

Figure 7: STEVAL-BLUEMIC-1 evaluation board hardware architecture ................................................... 7

Figure 8: STEVAL-BLUEMIC-1 evaluation board main components ......................................................... 7

Figure 9: Power and SPBTLE-1S module .................................................................................................. 9

Figure 10: MEMS, button and LEDs ......................................................................................................... 10

Figure 11: STSW-BLUEMIC-1 software architecture ............................................................................... 11

Figure 12: STSW-BLUEMIC-1 folder structure ......................................................................................... 12

Figure 13: STSW-BLUEMIC-1 audio processing chain ............................................................................ 14

Figure 14: ADPCM encode-decode schema ............................................................................................ 15

Figure 15: ADPCM packet mechanism ..................................................................................................... 16

Figure 16: BLE packets for 16 Hz audio ................................................................................................... 17

Figure 17: STSW-BLUEMIC-1 software package architecture................................................................. 17

Figure 18: Battery connection and power switch ...................................................................................... 21

Figure 19: STEVAL-BLUEMIC-1 evaluation board in plastic case ........................................................... 22

Figure 20: STM32 Nucleo board and STEVAL-BLUEMIC-1 SWD connections with a 5-pin flat cable ... 23
Figure 21: Voice streaming from the STEVAL-BLUEMIC-1 evaluation board to an Android™ or iOS™

mobile device ............................................................................................................................................ 24

Figure 22: BlueMS (Android version) app device list ................................................................................ 24

Figure 23: BlueMS (Android version) BlueVoice demo ............................................................................ 25

Figure 24: BlueMS (Android version) ASR language selection ................................................................ 26

Figure 25: BlueMS (Android version) Chinese ASR, iFlytek technology .................................................. 27

Figure 26: BlueMS (Android version) popup API key window .................................................................. 27

Figure 27: BlueMS (Android version) ASR service enabled ..................................................................... 28

Figure 28: BlueMS (Android version) voice recording .............................................................................. 29

Figure 29: BlueMS (Android version) recognised voice text ..................................................................... 30

Figure 30: Google Chromium-dev: search group ..................................................................................... 31

Figure 31: Google Chromium-dev: join group to post ............................................................................... 31

Figure 32: Google Chromium-dev: join the group .................................................................................... 31

Figure 33: Google Chromium-dev: create project .................................................................................... 32

Figure 34: Google Developers Console: new project ............................................................................... 32

Figure 35: Google Developers Console: ASRProject ............................................................................... 32

Figure 36: Google Developers Console: select API ................................................................................. 32

Figure 37: Google API Manager: enable API ........................................................................................... 33

Figure 38: Google API Manager: create API key ..................................................................................... 33

Figure 39: Google API Manager: Android API key ................................................................................... 33

Figure 40: BlueMS (Android version) plot data page ................................................................................ 34

Figure 41: Voice streaming from a STEVAL-BLUEMIC-1 evaluation board to an STM32 Nucleo board 35

Figure 42: Receiver recognized as USB microphone ............................................................................... 36

Figure 43: Audacity recording voice streamed by the peripheral ............................................................. 36

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1 Getting started

1.1 Hardware description

1.1.1 Features

 Bluetooth® SMART small form factor board based on the SPBTLE-1S module,

Bluetooth v4.2 compliant

 On-board SPBTLE-1S module, based on BlueNRG-1, Bluetooth low energy

application processor system on chip embedding an high performance:

 ultra-low power ARM® Cortex®-M0 32-bit core architecture
 Programmable embedded 160 KB Flash

 24 KB embedded RAM with data retention
 On-board MP34DT04-C1 digital MEMS microphone
 On-board LSM6DSL: MEMS 3D accelerometer (±2 / ±4 / ±8 / ±16 g) + 3D gyroscope

(±125 / ±245 / ±500 / ±1000 / ±2000 dps)

 Voltage supply: 1V8 or 3V3
 Battery or USB powered
 On-board STBC08 linear Li-Ion battery charger
 SWD connector
 Included in the development kit package:

 STEVAL-BLUEMIC-1

 Plastic box for housing STEVAL-BLUEMIC-1

 100 mAh Li-Ion battery

 SWD programming cable
 SW development kit for audio and inertial MEMS data streaming over BLE
 ST BlueMS: Android and iOS demo App available in the respective stores

1.1.2 Evaluation kit

The STEVAL-BLUEMIC-1 evaluation kit helps you to start prototyping a very low power
solution to stream audio and inertial data over BLE, exploiting the single-mode system-on­chip BlueNRG-1.

Figure 2: STEVAL-BLUEMIC-1 evaluation kit

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The evaluation kit contains:
 an STEVAL-BLUEMIC-1 evaluation board

Figure 3: STEVAL-BLUEMIC-1 evaluation board: top and bottom

 a 100 mAh LiPO battery to be connected to the evaluation board as power supply

Figure 4: Battery

 a plastic case to house the evaluation board connected to the battery

Figure 5: Plastic case

 an ST-LINK SWD programming cable to program the evaluation board connected to

ST-LINK

Figure 6: SWD cable

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1.1.3 Evaluation board

The STEVAL-BLUEMIC-1 evaluation board is a highly integrated reference design that
enables a fast prototyping of very low power solutions for audio and inertial streaming.

Figure 7: STEVAL-BLUEMIC-1 evaluation board hardware architecture

Figure 8: STEVAL-BLUEMIC-1 evaluation board main components

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Table 1: STEVAL-BLUEMIC-1 evaluation board main component details

Reference

Device

Description

A

SPBTLE-1S

Bluetooth Low Energy application processor compliant with BT
specification v4.2, based on BlueNRG-1 system-on-chip

B

LSM6DSL

iNEMO inertial module: low-power 3D accelerometer and 3D
gyroscope

C

MP34DT04-C1

MEMS audio sensor digital microphone

D

Button

User button

E

LED

A blue LED and a green LED for visual feedback

F

USB

Micro USB connector for power supply and battery charging

G

Battery

connector

Connector to plug the LiPO battery contained in the kit

H

Switch

ON-OFF switch to power the board

I

SWD

connector

5-pin SWD connector for programming and debugging

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1.1.4 Schematic diagrams

Figure 9: Power and SPBTLE-1S module

Battery Charge

r

BlueNRG-1 Module Footprint

USB, SWD, Battery monitor

Max 200mA

Vout=3V3

R1=147K R2=47K

Vout=1V8

R1=150K R2=120K

Battery monitor

(4.2V -> 1.8V)

VPROG = 1V

IBAT=(VPROG/RPROG)x1000

RPROG=1000*VPROG/IBAT

V_USB

VBlue

VBat

VBlue

VBlue

VBlue

V_USB

V_USB

VBat

VBat

VBat

VBat

V_USB

VBat

I2C_SDA

I2C_SCL

INT1_AG

INT2_AG

PDM_CL

K

PDM_DAT

A

LED1

LED2

BUTTON1

R8

0R

SW1

PWR

R16

0R

R1

147K

R13

20K

C9

4.7µF

U2

LDK120

M-R

EN

3

GND

2

IN

1

ADJ

4

OUT

5

U1 STBC08PMR

PROG

5

CHRG

3

PAD

7

BAT

1

Vcc

6

GND

4

PWR_ON

2

R15

NC

BATT1

Battery Connector

123

CHRG

2

1

C1

4.7µF

SWD

12345

R14

2K

R12

105K

VBAT

VBAT

1

U3

SPBTLE

-1S

DIO14

/ANATEST

0

6

VBLUE5DIO5/I2C_SDA4DIO4/I2C_CLK3ADC IN12ADC IN2

1

DIO6/UAR

T_RTS

9

DIO7/BOOT

/UART_CT

S

7

DIO8/UAR

T_TXD

10

DIO11

/UAR

T_RX

D

11

DIO9/TCK

/SWTCK

12

DIO10

/TMS/SWTDI

13

ANATEST

1

14

DIO0/SPI_CLK

15

DIO2/SPI_MOSI

16

DIO1/SPI_CS

18

BT_RESE

T

19

DIOA12

20

DIO3/SPI_MISO

17

GND

8

R5

4K7

C8

100nF

C7

4.7µF

USB

USB-MICRO

123

4

SH1
SH2

5

R11

140K

R2

47K

C2

4.7µF

GND

GND

1

SWDIO

RESET

SWDCLK

SWDCLK

RESET

SWDIO

ADC_IN2

ADC_IN2

CHRG

CHRG

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Figure 10: MEMS, button and LEDs

VBlue

VBlue

VBlue

VBlue

VBlue

VBlue

VBlue

PDM_CL K

I2C_SC

L

I2C_SD

A

INT1_AG

INT2_AG

PDM_DA TA

I2C_SC

L

I2C_SD

A

BUTTON1

LED1

LED2

R7

100K

C4

100nF

R9 1K

LED2

LED Blue

2

1

R3

4K7

R10

100

Button1

1

2

3

4

5

6

R6

4K7

C5

100nF

C6

10nF

M1

MP34D T04

DOUT

4

LR

2

GND

5A

VDD

1

CLK

3

GND

5B

GND

5D

GND

5C

U4

LSM6DS L

GND 1

6

VDD

IO

5

INT1

4

SCx3SDx

2

SDO/SA0

1

VDD

8

INT2

9

OCS_A ux

10

SDO_Aux

11

CS

12

SCL

13

GND 2

7

SDA

14

R4 1K

LED1

LED Gree n

2

1

C3

100nF

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1.2 Software description

1.2.1 Overview

The STSW-BLUEMIC-1 is an evaluation software package that allows development of
smart and innovative solution using the SPBTLE-1S module.

The software package includes the entire Bluetooth® low energy stack and protocols,
complaint with the STSW-BLUENRG1-DK. It also contains a Board Support Package that
offers a complete set of APIs for digital MEMS microphone, 3-axis accelerometer and
gyroscope, button and LED management.

The latter is based on BlueNRG-1, a very low power Bluetooth low energy single mode
system-on-chip embedding a high performance, ultra-low power 32-bit ARM® Cortex®-M0,
with 160 kB of Flash memory and 24 kB of RAM.

The BlueVoiceADPCM_BNRG1 binary library (available as middleware) provides a vendor
specific profile for voice streaming over Bluetooth® low energy; it includes all APIs needed
for audio compression using the ITU-T G.726 ADPCM standard, packetization and
streaming.

The STSW-BLUEMIC-1 allows an STEVAL-BLUEMIC-1 evaluation board to act as a
peripheral in a point-to-point connection with a mobile device running the ST BlueMS app,
available for Android™ and iOS™. In this configuration, the evaluation board streams the
audio acquired from the on-board digital MEMS microphone (MP34DT04-C1) or motion
data acquired from the 3-axis accelerometer and gyroscope (LSM6DSL).

1.2.2 Architecture

The STSW-BLUEMIC-1 software is organized in different layers.

Figure 11: STSW-BLUEMIC-1 software architecture

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The application layer manages the complete software chain from the audio and inertial data
acquisition to the streaming.

A complete set of drivers is available to interact with the on-board sensors and to manage
the BlueNRG-1 peripheral.

A middleware layer, between the application and the hardware abstraction layer, includes:
 the Bluetooth® Low Energy stack library that allows communication between the

central and the peripheral device;
 the BlueVoiceADPCM_BNRG1 library that provides all the APIs needed to implement

a voice-over-Bluetooth® Low Energy profile.

1.2.3 Folder structure

Figure 12: STSW-BLUEMIC-1 folder structure

The following folders are included in the software package:
 Binary: contains ready-to-use firmware binary to be flashed on the STEVAL-

BLUEMIC-1 evaluation board
 Documentation: contains a compiled HTML file generated from the source code

detailing the software components and APIs

 Drivers: contains the board specific drivers including the on-board components
 Library: contains the Bluetooth low energy stack binary library, the CMSIS vendor-

independent hardware abstraction layer for the ARM®Cortex®-M processor series, and

BlueNRG-1 peripheral drivers

 Middlewares: contains the BlueVoice over BlueNRG-1 library
 Projects: contains demo applications for voice transmission over Bluetooth Low

Energy. The projects support IAR Embedded Workbench for ARM, RealView

Microcontroller Development Kit (MDK-ARM) and Atollic-True Studio for ARM

development environments

1.2.4 APIs

Fully detailed user-API function and parameter descriptions are compiled in an HTML file
located in the software Documentation folder.

1.2.5 BlueMic1 application

The BlueMic1 application has been designed and built on the Bluetooth low energy
architecture.

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1.2.5.1 BlueMic1 profile description

The BlueMic1 application deploys a connection-based communication paradigm by
providing a permanent point-to-point link between two devices, one acting as peripheral
and one as central (Generic Access Profile or GAP).

The STEVAL-BLUEMIC-1 evaluation board acts as a peripheral device supporting a single
connection and low complexity. This device only requires a controller that supports the
slave role.

The central module can be an Android™ and iOS™ device running the ST BlueMS app

(v3.0.0 or higher) or a FP-AUD-BVLINK1 receiver node.
The central and peripheral role assignment reflects the asymmetric design concept of

Bluetooth Low Energy, where the device with a lower energy source works less: a slave
cannot initiate complex procedures, whereas a master manages communication timing,
adaptive frequency hopping, encryption setup, etc. A portable device provided with a coin­size battery is usually suitable as slave device.

Data sent through a Bluetooth Low Energy connection is organized through an additional
protocol layer, the Generic Attribute Profile (GATT). It provides standard profiles to ensure
interoperability between devices from different vendors that implement features like
Proximity Profile, Glucose Profile and Health Thermometer Profile. The Bluetooth
specification also lets you add custom profiles.

GATT defines client and server roles for interacting devices independent of the GAP
master/central and slave/peripheral roles:

 Client performs service discovery about the presence and nature of server attributes;

it sends requests to a server and accepts responses and server-initiated updates.
 Server accepts requests, commands and confirmations from a client and sends

responses and server-initiated updates; it arranges and stores data according to the

attribute (ATT) protocol.
In a mono-directional audio streaming asymmetric system, the device with voice data is the

one with a microphone and is therefore considered the server. The client device sends
requests to the server and accepts server-initiated updates containing audio data.

Audio data transmission is based on periodic server-to-client notifications which do not
require a request or response from the receiving device. Server-initiated updates are sent
as asynchronous notification packets which include the handle of a characteristic along
with its current value.

According to the Bluetooth specification, the peripheral enters advertising mode at start-up
and sends advertisement packets at relatively long intervals. The central unit enters
discovery mode and sends a connection request on reception of an advertisement packet
from a slave device. After connection, notifications carrying audio data are periodically sent
from the server to the client.

1.2.5.2 BlueMic1 service

The Attribute Protocol (ATT) is used by GATT as a transport protocol for exchanging data
between devices. The smallest entities defined by ATT (named attributes) are addressable
pieces of information that may contain user data or meta-information on the attribute
architecture, stored in the server and exchanged between client and server.

GATT server attributes are organized as a sequence of services, each one starting with a
service declaration attribute marking its beginning. Each service groups one or more
characteristics and each characteristic can include zero or more descriptors.

Since audio streaming is not part of the predefined set of profiles, the STSW-BLUEMIC-1
application defines a vendor-specific service named BlueMic1 Service based on an Audio

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characteristic to expose actual compressed audio data and a Sync characteristic to expose
collateral information to implement a synchronization mechanism and an inertial
characteristic to expose 3-axis accelerometer and gyroscope raw data.

Table 2: BlueMic1 UUID summary table

UUID name

UUID

bluemic1_service_uuid

00000000-0001-11e1-9ab4-0002a5d5c51b

audio_adpcm_char_uuid

08000000-0001-11e1-ac36-0002a5d5c51b

audio_adpcm_sync_char_uuid

40000000-0001-11e1-ac36-0002a5d5c51b

acc_gyr_char_uuid

00E00000-0001-11e1-ac36-0002a5d5c51b

Given the service hierarchical architecture, further characteristics may be added to the
BlueMic1 service, such as configuration of parameters like volume, enabling/disabling of
processing algorithms, etc.

1.2.6 Audio processing

The audio processing component of the STSW-BLUEMIC-1 application is designed to
achieve an audio sampling frequency of 8 or 16 kHz at the receiver side, with a trade-off
between audio quality and bandwidth occupation for voice signals. The audio signal
transmitted is compressed via ADPCM (adaptive differential pulse code modulation) to fit in
the available data rate while minimizing radio transmission time and power consumption.

The figure below shows the speech processing chain in a complete communication system
with Tx and Rx.

On the Tx side, the library receives an audio signal which is typically acquired by a digital
MEMS microphone as a 1-bit PDM signal and converted by a PDM to PCM conversion
filter, integrated in the ADC peripheral of the BlueNRG-1 SoC, into 16-bit PCM samples at
8 or 16 kHz.

The library can be provided with 1, 2, 5 or 10 ms of audio data. When the compressed
output buffer is ready, a flag is set and audio data is streamed via Bluetooth Low Energy
together with collateral ADPCM information. The resulting communication bandwidth is 32
kbps (with 8 kHz audio sampling frequency) or 64 kbps (with 16 kHz audio sampling
frequency) of audio data plus 300 bps of collateral information.

Figure 13: STSW-BLUEMIC-1 audio processing chain

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1.2.7 ADPCM compression

The ITU-T G.726 adaptive differential pulse code modulation (ADPCM) standard is applied
to save bandwidth. This audio algorithm for lossy waveform coding predicts the current
signal value from previous values, and transmits the difference between the real and the
predicted value, quantized with an adaptive quantization step.

The ADPCM algorithm used in this application compresses digital voice signals encoded
as:

 Audio format: PCM
 Audio sample size: 16 bits
 Channels: 1 (mono)
 Audio sample rate: 8-16 kHz

Figure 14: ADPCM encode-decode schema

BlueVoiceADPCM implements a modified version of the compression algorithm with
improved communication robustness through an additional low data rate channel with
collateral information added to the ADPCM quantized values; slightly increasing the overall
bit-rate to an average 64.3 Kbps.

The internal buffering required by ADPCM compression is shown in the figure below. 16-bit
input PCM samples are encoded in 8-bit temporary samples with 4-bit actual data (u8
ADPCM_app buffer) and then encapsulated in 8-bit samples containing information of two
PCM samples (u8 ADPCM buffer).

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Figure 15: ADPCM packet mechanism

ADCPM decoding on the Rx side is performed in a symmetric fashion.

1.2.8 Packetization

The Tx data rate for streaming data is obtained from:

 the connection interval
 the number of packets per connection interval and user data payload for each packet

The STSW-BLUEMIC-1 application implements:

 a constant bitrate allocated to audio data through the chosen ADPCM compression
 a small connection interval to minimize the overall audio latency

The following connection intervals are set for Android™ and iOS™ compliance:

 conn_min_int=10 ms
 conn_max_int=21.25 ms

If the streaming is performed between two ST modules, the selected connection interval is
the minimum value (10 ms). The target 64 kbps constant data rate is achieved by sending
80 bytes of ADPCM data (640 bits) at each connection event. Consistent with maxPayload
= 20 bytes per packet (160 bit), four packets (two if an audio sampling frequency of 8 kHz
is set) of 20 bytes are sent per average connection event. In addition, ADPCM collateral
information is sent at a lower frequency via an additional smaller packet sent at regular
intervals.

The following figure shows a 16 kHz compressed audio streaming example, where four
data packets of 20 bytes are sent at each connection interval of 10 ms, while ADPCM
collateral information is sent as an additional packet once every 160 ms.

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Figure 16: BLE packets for 16 Hz audio

1.2.9 STSW-BLUEMIC-1 application description

The STSW-BLUEMIC-1 software package is a complete example of audio and inertial data
streaming over Bluetooth® Low Energy to an Android™ and iOS™ mobile device running
the ST BlueMS app or to an STM32 platform.

Figure 17: STSW-BLUEMIC-1 software package architecture

The main loop continuously calls the BTLE_StackTick function needed for the RF
management and the APP_Tick that contains all the functions implemented by the user.

As soon as the application starts, the APP_STATUS_ADVERTISEMENT state is set,
BlueNRG-1 acts as a peripheral and sends advertisement messages until a central node
requests a connection.

When the connection is estabilished, the app status is set to APP_STATUS_CONNECTED
and two different demos can be activated from the ST BlueMS app running on the central
node.

If BlueVoice is enabled (firmware status set to APP_BLUEVOICE_ENABLED) audio
acquisition from the on-board digital microphone starts and drives the voice streaming.
PCM samples are compressed and sent.

The audio streaming can be stopped or restarted by pressing the STEVAL-BLUEMIC-1
evaluation board button.

The user can switch to the inertial demo (firmware status set to APP_INERTIAL_ENABLE)
via the BlueMS app.

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A timer is set and every 30 ms raw data are acquired from the 3-axis accelerometer and
gyroscope and sent to the mobile device together with a timestamp increased by one every
10 ms.

1.3 BlueVoiceADPCM_BNRG1 library software description

1.3.1 Initialization and configuration

To initialize the library call the BluevoiceADPCM_BNRG1_Initialize API. Then,
configure the library on the basis of the audio acquisition implemented in the application.

A configuration structure must be filled by setting the audio sampling frequency (FR_8000
or FR_16000), the total number of channels given as the input to the library and which
channel (between 1 and channel_tot) is used for the voice streaming:

BV_ADPCM_BNRG1_Config_t BV_ADPCM_BNRG1_Config;
BV_ADPCM_BNRG1_Config.sampling_frequency = FR_8000;
BV_ADPCM_BNRG1_Config.channel_in = 1;
BV_ADPCM_BNRG1_Config.channel_tot = 1;
BluevoiceADPCM_BNRG1_SetConfig(&BV_ADPCM_BNRG1_Config);

If the return value is BV_ADPCM_BNRG1_SUCCESS, the library has been correctly
configured.

The BlueVoiceADPCM_BNRG1 library can be reset by recalling
BluevoiceADPCM_BNRG1_SetConfig.

The library includes three callbacks that must be called when the corresponding BlueNRG
event occurs:

 BluevoiceADPCM_BNRG1_ConnectionComplete_CB sets the connection handle

when an EVT_LE_CONN_COMPLETE event occurs;
 BluevoiceADPCM_BNRG1_DisconnectionComplete_CB resets internal

parameters when an EVT_DISCONN_COMPLETE event occurs;
 BluevoiceADPCM_BNRG1_AttributeModified_CB sets the working mode

according to the enable notification received when an

EVT_BLUE_GATT_ATTRIBUTE_MODIFIED event occurs.
A timeout has been included for correct management of the BlueVoice profile status; when

the module is no longer streaming or receiving, the profile status switches to
BV_ADPCM_BNRG1_STATUS_READY as soon as the timer expires. The timeout duration (in
ms) is defined by BV_ADPCM_BNRG1_TIMEOUT_STATUS.

To increase this timer, call the BluevoiceADPCM_BNRG1_IncTick function every 1 ms
from the SysTick_Handler.

1.3.2 Working mode setup

The library working mode can be configured as NOT_READY (initial setting),
TRANSMITTER, RECEIVER or HALF-DUPLEX.

The service and characteristics for the BlueVoice profile can be created by calling the
BluevoiceADPCM_BNRG1_AddService and BluevoiceADPCM_BNRG1_AddChar
functions.

Both APIs require the UUIDs (chosen by the user) as parameters and they return the
relevant handle.

The handle of the service must be passed to the BluevoiceADPCM_AddChar API.

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Alternately, BlueVoice characteristics can be added to a pre-existing service created in
your own application by calling BluevoiceADPCM_BNRG1_AddChar and passing the
handle of that particular service as a parameter.

If both the functions return BV_ADPCM_BNRG1_SUCCESS, the library is set to
TRANSMITTER mode and can stream audio over Bluetooth Low Energy.

You can also create the characteristics out of the library and pass the relevant handles
using a structure of the type BV_ADPCM_BNRG1_ProfileHandle_t to the
BluevoiceADPCM_BNRG1_SetTxHandle API. In the latter case, the following
characteristics must be created:

 related to the compressed audio data

aci_gatt_add_char(ServiceHandle,

UUID_TYPE_128, CharAudioUUID, 20,

CHAR_PROP_NOTIFY, ATTR_PERMISSION_NONE,

GATT_DONT_NOTIFY_EVENTS, 16, 1,

CharAudioHandle);
 to send collateral information for synchronization mechanism implementation

aci_gatt_add_char(ServiceHandle,

UUID_TYPE_128, CharAudioSyncUUID, 6,

CHAR_PROP_NOTIFY, ATTR_PERMISSION_NONE,

GATT_DONT_NOTIFY_EVENTS, 16, 1,

CharAudioSyncHandle);
You can choose to not create the BlueVoice Service and the module is not able to transmit

audio.
This node can still function as a RECEIVER; however, if the connected module exports the

BlueVoice profile; you must set the handle of the BlueVoice service and characteristics
exported by the transmitter module through the BluevoiceADPCM_BNRG1_SetRxHandle
API and enable notifications on the other node by calling the
BluevoiceADPCM_BNRG1_EnableNotification function.

If both the TRANSMITTER and RECEIVER procedures are performed, the module acts as
transmitter and receiver and the working mode is set to HALF-DUPLEX, creating a half­duplex link over Bluetooth Low Energy.

1.3.3 Audio signal injection

The BlueVoiceADPCM_BNRG1 library receives audio PCM input samples.
The BluevoiceADPCM_BNRG1_AudioIn function accepts parameters from a PCM buffer,

containing all the acquired audio channels (channel_tot according to the previous library
configuration) and the number of PCM samples (for each channel) given as input. An
amount of data equal to 1, 2, 5 or 10 ms is accepted, otherwise an
BV_ADPCM_BNRG1_PCM_SAMPLES_ERR is returned.

The library compresses received PCM input samples; when 10 ms of audio is compressed,
the BluevoiceADPCM_BNRG1_AudioIn API returns
BV_ADPCM_BNRG1_OUT_BUF_READY.

1.3.4 Compressed audio streaming

On the transmitter side, the BlueVoiceADPCM_BNRG1 library gathers compressed data in
an internal double buffer. For every 10 ms of audio, the

BluevoiceADPCM_BNRG1_AudioIn function returns
BV_ADPCM_BNRG1_OUT_BUF_READY to signal output data can be send via Bluetooth Low
Energy by calling the BluevoiceADPCM_BNRG1_SendData API.

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If the audio sampling frequency is set to 8 kHz, two 20-byte packets are sent every 10 ms
(according to the connection interval); if the frequency is 16 kHz, four 20-byte packets are
sent.

On the receiver side, compressed audio is received from a notification through a
EVT_BLUE_GATT_NOTIFICATION event and passed to the
BluevoiceADPCM_BNRG1_ParseData function that decompresses the data and returns
a PCM buffer. This API is used to parse both audio and collateral information data.

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2 System setup

Two types of demos can be set up using an STEVAL-BLUEMIC-1 evaluation board:

1. unidirectional streaming of inertial data and audio at a sampling frequency of 8 kHz

from the STEVAL-BLUEMIC-1 to an Android™ or iOS™ device running the ST

BlueMS app (v3.0.0 or higher);

2. unidirectional audio streaming at a sampling frequency of 8 or 16 kHz from the

STEVAL-BLUEMIC-1 to the receiver node of the FP-AUD-BVLINK1 application

available on www.st.com.

2.1 Power supply

The main board power supply is the 100 mAh lithium-Ion polymer battery plugged to the
connector on the PCB.

Figure 18: Battery connection and power switch

Use SW1 switch to power the STEVAL-BLUEMIC-1 evaluation board on or off.
The battery can be recharged via USB connected to a PC or any micro-USB battery

charger. A red LED indicates the charging status:

 steady ON: the board is charging
 steady OFF: charge complete

The on-board voltage regulator provides a 3.3 V power supply that can be changed to 1.8
V by replacing R1 and R2 according to the board schematic diagram (see Section 1.1.4:

"Schematic diagrams").

The STEVAL-BLUEMIC-1 can be powered using only the USB connector; the battery must
be unplugged and the battery charger must be bypassed by removing R8 e by soldering
the R15 0 Ohm resistor.

2.2 STEVAL-BLUEMIC-1 evaluation board assembly in form
factor case

The STEVAL-BLUEMIC-1 evaluation board connected to the battery can be housed in the
plastic box included in the evaluation kit as shown below.

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Figure 19: STEVAL-BLUEMIC-1 evaluation board in plastic case

2.3 STEVAL-BLUEMIC-1 evaluation board programming
interface

To program the board, connect an external ST-LINK to the SWD connector on the
STEVAL-BLUEMIC-1 evaluation board; a 5-pin flat cable is provided in the evaluation kit.

The easiest way to obtain an ST-LINK device is to get an STM32 Nucleo board, which
bundles an ST-LINK V2.1 debugger and programmer.

1

Ensure that CN2 jumpers are OFF and connect your STM32 Nucleo board to the

STEVAL-BLUEMIC-1 evaluation board via the cable provided, paying attention to the
polarity of the connectors.

Pin 1 is identified by:

 a small dot on the PCB silkscreen on the STM32 Nucleo board
 the square shape of the soldering pad on the STEVAL-BLUEMIC-1 evaluation

board

2

Download from ST website the "BlueNRG-1 ST-LINK utility", a full-featured software
interface to program the BlueNRG-1 microcontroller.

3

Follow the installation procedure

4

Program the STEVAL-BLUEMIC-1 evaluation board with the demo binary available in
the software package.

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Figure 20: STM32 Nucleo board and STEVAL-BLUEMIC-1 SWD connections with a 5-pin

flat cable

2.4 STEVAL-BLUEMIC-1 evaluation board demos

2.4.1 Streaming to a mobile device

One of the possible demos to be performed using a STEVAL-BLUEMIC-1 evaluation board

is the unidirectional streaming from the board to an Android™ or iOS™ device running the

ST BlueMS app (v3.0.0 or higher).
Set up the STEVAL-BLUEMIC-1 evaluation board as explained in the previous sections

and program it with the relevant binary file (STSW-BLUEMIC1_8kHz.bin) included in the
software package.

In this configuration, a point-to-point connection is created between the STEVAL­BLUEMIC-1 evaluation board acting as a peripheral and a mobile device acting as a central
device: as soon as the two systems are connected, the evaluation board streams audio
(acquired from the on-board microphone at 8 kHz of sampling frequency) or inertial raw
data (acquired from the 3-axis accelerometer and gyroscope).

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Figure 21: Voice streaming from the STEVAL-BLUEMIC-1 evaluation board to an Android™ or

iOS™ mobile device

2.4.1.1 ST BlueMS app

To run this demo:

1

Turn the STEVAL-BLUEMIC-1 evaluation board on via SW1 switch

2

Open the ST BlueMS app on your smartphone or tablet.

a

3

Start the scanning procedure when the app is ready

4

Wait until BVBNRG1 appears in the device list
If it does not appear, clear the device cache from the upper right corner menu.

5

When the scan finishes, select the device to be connect to.
The application switches to the demo view and starts the connection procedure.

Figure 22: BlueMS (Android version) app device list

a

Android app screenshots are used to show how the app works, but the procedure is the same for the iOS app.

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2.4.1.2 BlueVoice page

When the STEVAL-BLUEMIC-1 evaluation board is connected to a mobile device the on­board green LED turns on and the board starts streaming audio to the mobile device (in
this phase the blue LED starts blinking fast).

In a different version of the evaluation board the color of the LED can be inverted.

You can stop and restart the streaming by pressing the button on the evaluation board.
The volume can be adjusted (via the slider on the BlueVoice page) or muted (by clicking on

the speaker icon).

Figure 23: BlueMS (Android version) BlueVoice demo

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2.4.1.2.1 ASR language selection

Opening the ASR language menu, located in the demo main menu, the application displays
a popup window that allows the ASR language selection.

According to the language selected, a specific ASR service is configured which determines
the application behavior.

Figure 24: BlueMS (Android version) ASR language selection

2.4.1.2.2 Chinese ASR: iFlyTek MSC service

When Chinese is selected, the ASR service provided by iFlyTek is enabled.
Pushing the button on the bottom right hand of the screen, it becomes green and the

speech-to-text service starts.
The recognition is continuous and every sentence is recorded as shown below.

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Figure 25: BlueMS (Android version) Chinese ASR, iFlytek technology

2.4.1.2.3 Alternative languages: Google Speech API

The ADD button allows the insertion of the key (see Section 2.4.1.2.4: "Google speech

ASR Key generation") to enable the ASR feature: a popup window prompts the insertion of

a valid API key, followed by the ASR service activation key.

Figure 26: BlueMS (Android version) popup API key window

Once the key is correctly inserted, the start screen changes.

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Figure 27: BlueMS (Android version) ASR service enabled

Hold the recording button to record your voice for subsequent recognition. While the button
is pressed, a bar progressively indicates the elapsed recording time. When you release the
button a “Sending request…” message appears.

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Figure 28: BlueMS (Android version) voice recording

The speech recognized by the ASR service appears below the volume bar.

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Figure 29: BlueMS (Android version) recognised voice text

If the recording cannot be recognized, a “Token not recognized’ message appears

instead of the text.

2.4.1.2.4 Google speech ASR Key generation

The Google Speech APIs require a key to access the web-based service. You need a
Google account to complete the procedure and access the service.

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To generate a key:

1

Login with your own Google account.

2

Subscribe to Chromium-dev at

https://groups.google.com/a/chromium.org/forum/?fromgroups#!forum/chromium-dev.

3

Write “Chromium-dev” in the search box, and select the appropriate group.

Figure 30: Google Chromium-dev: search group

4

Click on “Join group to post” button

Figure 31: Google Chromium-dev: join group to post

5

Click on “Join this group” button to join the Chromium-dev group.

Figure 32: Google Chromium-dev: join the group

6

Go to https://console.developers.google.com/project

7

Click on “Create a project…”

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Figure 33: Google Chromium-dev: create project

8

Choose the Project name.

9

Click on “Create” button.

Figure 34: Google Developers Console: new project

10

Make sure you have selected the newly created project.

Figure 35: Google Developers Console: ASRProject

11

Write "Speech API" in the search box, and select correct result.

Figure 36: Google Developers Console: select API

12

Enable the Speech API clicking on the blue button.

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Figure 37: Google API Manager: enable API

13

Move from the “Dashboard” tab to “Credentials” tab.

14

Open the “Create credentials” menu and select “API key”.

Figure 38: Google API Manager: create API key

15

Your API key is created. Click on Close to return to the Credentials section. Here you
can see your API Key.

Figure 39: Google API Manager: Android API key

2.4.1.3 Inertial data plot page

The STEVAL-BLUEMIC-1 evaluation board also streams inertial data acquired from the on­board 3-axis accelerometer and gyroscope.

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Swipe from the right to open a new page that allows a real-time plot of inertial raw data
received from the evaluation board. Gyroscope or accelerometer can be selected from the
menu on the top; the plot starts as soon as the "Play button" on the right is pressed.

By clicking on the Plot Length menu item, you can set the time scale in seconds to be
displayed.

Figure 40: BlueMS (Android version) plot data page

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2.5 Streaming to an STM32 Nucleo board used as a receiver

Another possible demo to be performed using a STEVAL-BLUEMIC-1 evaluation board is
the unidirectional voice streaming from the evaluation board to an STM32Nucleo stack
running the FP-AUD-BVLINK1 central application.

The audio can be acquired at 8 or 16 kHz of sampling frequency: the transmitter and the
receiver must be configured accordingly.a

Figure 41: Voice streaming from a STEVAL-BLUEMIC-1 evaluation board to an STM32 Nucleo

board

1

Power the STEVAL-BLUEMIC-1 evaluation board on using the on-board switch SW1

2

Connect the receiver to a PC via the mini USB on the X-NUCLEO-CCA02M1
expansion board (the jumper JP5 on the STM32 Nucleo must be E5V).

When the green LED on the STEVAL-BLUEMIC-1 evaluation board turns on, the
connection is established and the voice streaming from the peripheral to central device
starts.

In a different version of the evaluation board the color of the LED can
be inverted.

3

As soon as the central unit is recognized as a standard USB microphone, select the
correct option in Microphone Properties (8 or 16 kHz) as shown below.

a

Refer to the relevant page on www.st.com to set up the central module to be used as a receiver.

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Figure 42: Receiver recognized as USB microphone

4

Use any freeware or commercial audio recording software to interface with the system,
for example Audacity (http://audacity.sourceforge.net/).

5

Open it and press the Record button to record the audio streamed from the STEVAL­BLUEMIC-1 evaluation board.

Figure 43: Audacity recording voice streamed by the peripheral

6

Stop or restart the streaming by pressing the user button on the evaluation board.

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3 Revision history

Table 3: Document revision history

Date

Version

Changes

17-Jul-2017

1

Initial release

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