Application examples

AN4207

22/28

Doc ID 023945 Rev 1

4.3

Wave recorder

This application shows how to use the 16-bit Sigma-Delta Analog-to-Digital converter to

record the human voice using the electric condenser microphone installed on the

STM32373C-EVAL evaluation board.

The application source code is available in the

Project\STM32373C-EVAL\src\waverecorder.c

file in the STM32373C-EVAL demonstration firmware package stm32373c-eval_fw

A microphone is connected to SDADC1 channel 6 (PB0) through an audio amplifier/filter.

The SDADC is configured in Single-Ended Zero Reference mode and voice recording is

triggered by TIM13 at a sampling rate of 8 KHz.

The wave recorder application uses a ping-pong buffer: one buffer is actively being written in

the MicroSD memory card while the second buffer is filled with the new samples.

Writing access to the MicroSD memeory card uses the open source file system FatFS.

Figure 12 shows the block diagram of the voice recorder application.

Figure 12.

Block diagram of voice recorder

The flowchart of this application is given in Figure 13.

MSv31139V1

1st buffer

2nd buffer

16-bit

ΣΔ

SDADC

TIM13

Audio

AOP

SRAM

SPI

Cortex M4

CPU wth FPU/

MPU

72 MHz

STM32F37x