March 2013

DocID023502 Rev 2

1/30

AN4146

Application note

STSmartVoice demonstration board STEVAL-MKI126Vx

Introduction

This application note describes the STSmartVoice demonstration board STEVAL-

MKI126Vx. The connections and setup of the programming and interface boards are also

detailed as well as other versions of the main board hosting the different microphones.

The STA321MP/MPL (package option respectively VFQFPN56 and TQFP64) has been

designed to decode the pulse-density modulation (PDM) signal coming from the

also able to provide pulse-width modulation (PWM) outputs, one per channel, suitable to

support an analog interface. The processor also includes a digital block, the hardware

accelerator, composed of a chain of biquads (see Figure 1).

The STEVAL-MKI126Vx board can connect up to six microphones using the sockets

provided or through a dedicated six-microphone array. The digital interface of the device

allows interfacing the MIC output to the most widely used audio receivers and digital

amplifiers or simply evaluating the MIC using generic audio measurement equipment. The

filtered PWM signals allow the connection of a headset to listen to the audio received

through the microphones.

The fully digital path ensures a high level of processing with sound preconditioning, filtering

and voice enhancement. The pre- and post-mixing of the signals coming from the

microphones, in combination with the frequency equalization block, allow the

implementation of acoustic algorithms such as beam forming.

Figure 1. Microphone processor

Audio

Matrix

( Muxing/

Mixing )

PDM

Interface

STA321MP/MPL

MEMS Digital

Microphone 6

SDA

Clock management

I2C

Serial Data

Output

SCL

PLL

1

6

LRCK

BICK

SDAT 1/2/3

MEMS Digital

Microphone 1

OUTxA

OUTxB

Scalable

Microphone

Processor TM

Hardware

Accelerator

PWM

www.st.com