September 2012

Doc ID 022706 Rev 2

1/14

AN4041

Application note

APWLink+ microphone USB demonstration boards based on the

MP34DT01, MP45DT02, or MP34DB01

Introduction

The purpose of this application note is to give a brief description of the APWLink+

microphone USB demonstration boards from STMicroelectronics. These boards host the

microcontroller STM32F107RC and either the MP45DT02, MP34DT01 (top-port digital

microphones) or the MP34DB01 (bottom-port digital microphone). Figure 1 shows the

capability of the board to host these microphones.

These microphones are analog-to-digital transducers, in other words, they are able to sense

sound pressure and convert this signal to a digital signal using the pulse-density modulation

(PDM) technique. The STM32 microcontroller decodes the PDM signal coming from the

microphones and streams the audio via the USB.

This document will provide a brief description of the software that decodes the PDM signal

and also information about the hardware as well as simple steps to use the boards. Ordering

information for these boards can be found in Appendix C on page 12.

Figure 1.

APWLink+ demonstration board

www.st.com