AN4227 Datasheet, PDF (1/13 Pages) STMicroelectronics – Audio hub demonstration kit supporting the MP45DT02

AN4227
Application note
Audio hub demonstration kit supporting the MP45DT02,
MP34DB01, and MP34DT01 microphones
Introduction
This document provides a brief description of the audio hub demonstration board STEVAL-
MKI138V1 available from www.st.com along with simple steps to use the board with the
APWorkbench software tool.
The purpose of this board is twofold:
1. It can be used as an STSmartVoice interface. In combination with this board
(STEVAL-MKI126Vx), it manages the signal coming from the onboard microphones.
The STSmartVoice board hosts up to six microphones and the STA321MPL
microphone processor converts the PDM signals from them into the common I²S audio
format. (For additional details, please refer to AN4146 “STSmartVoice demonstration
board STEVAL-MKI126Vx” available from www.st.com). Basically the audio hub, using
the STM32F107RC microcontroller, is able to program the STA321MPL device via the
I²C and decodes the I²S into a USB stream in order for the PC to manage the sound
captured by the microphones. Multiple features for using the microphones on the
STSmartVoice demonstration board are listed and accessible thanks to the
APWorkbench software tool.
2. It can be used as a USB sound card. As shown in Figure 1, the audio hub board hosts
either the MP45DT02 or MP34DT01 (top-port digital microphones) and the MP34DB01
which is a bottom-port digital microphone. The board is able to host both types of
microphones as shown below. The task of the STM32 microcontroller is to decode the
PDM signals coming from the microphones and stream the audio via the USB.
Figure 1. STEVAL-MKI138V1
March 2013
MP45DT02
Entire board (top and bottom views)
MP34DB01
MP34DT01
Microphone section (zoom)
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