rpi-i2s-audio's Introduction

I2S Microphone Overlay

Testing Paul's rpi-i2s-audio device tree overlay on Pi Zero2W (Bookworm OS - 6.6.21) 03/17/24

rpi-i2s-mic.dts

This is the overlay for a MEMs microphone, specifically the SPH0645 I2C MIC.

Clone and Compile

Clone repo without history

cd ~
git clone --depth=1 https://github.com/JayIke/rpi-i2s-audio.git

Compile device tree into device tree blob overlay

git clone --depth=1 https://github.com/JayIke/rpi-i2s-audio.git
dtc  -I dts -O dtb -o rpi-i2s-mic.dtbo  rpi-i2s-mic.dts 
sudo cp rpi-i2s-mic.dtbo /boot/firmware/overlays/.
# just to be safe:
sudo cp rpi-i2s-mic.dtbo /boot/overlays/.

Enable overlay in config.txt

echo "dtoverlay=rpi-i2s-mic" | sudo tee -a /boot/firmware/config.txt
sudo reboot

Install Hardware and Test

Check if sound card is available in alsa

arecord -l && arecord -L

Try recording a file and saving it as .wav

arecord -D mic -c 2 -r 48000 -f S32_LE -V stereo -v -t wav test.wav

ADAFRUIT SPH0645 - Stereo Hardware Configuration

LEFT MIC

3.3V Connector Pin 1
GND Connector Pin 39
LRCL Connector Pin 35 GPIO 19
DOUT Connector Pin 37 GPIO 20
BCLK Connector Pin 12 GPIO 18
SEL Connector Pin 3.3V

RIGHT MIC

3.3V Connector Pin 1
GND Connector Pin 5?
LRCL Connector Pin 35 GPIO 19
DOUT Connector Pin 37 GPIO 20
BCLK Connector Pin 12 GPIO 18
SEL Connector Pin GND

i2s_audio_read_test.py

Simple demo application for recording audio from I2S mems mic

Warning

After looking at the raw data via python using the sounddevice module, it seems there is a dc offset in the output data. Subtracting the mean or high pass filtering can be used to remove this offset. During playback you will hear a pop or click when audio playback starts or finishes.

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