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Table of Contents
Audio Injector Installation
Audio Injector is a audio hat for the Raspberry Pi. This sound card comes with two inputs and two outputs, plus a build in microphone.
Installation
This manual is made for an Raspberry Pi 4 running Raspian Buster on it.
After connecting the Audio Injector to the Raspberry Pi change some configurations, in:
$ sudo nano /boot/config.txt
Comment out:
# dtparam=audio=on
And type in:
dtoverlay=audioinjector-wm8731-audio
ctl + o for saving, press return and ctl + x to leave.
Reboot your Raspberry Pi:
$ sudo reboot
After the reboot download:
$ wget https://github.com/Audio-Injector/stereo-and-zero/archive/master.zip
Unpack it:
$ unzip master.zip
go into the folder:
$ cd stereo-and-zero-master/
and run:
$ alsactl --file asound.state.MIC.thru.test restore $ alsactl --file asound.state.RCA.thru.test restore
Test
For the 10 kHz test follow the instructions on https://github.com/Audio-Injector/stereo-and-zero.
Then install sox:
$ sudo apt install sox
In /home/pi/stereo-and-zero-master/ run:
$ sudo chmod 755 audioInjector-test.sh $ ./audioInjector-test.sh
Simple Play and Record
Recording:
$ arecord -r 48000 -f S16_LE -c 2 -d 20 test.wav
Playing back:
$ aplay test.wav
I2S Pins
Beside the power and ground the I2S bus needs the following pins:
GPIO 18 (Pin12) BITCLOCK; GPIO 19 (Pin 35) LRCLOCK; GPIO 20 (Pin 38) DATA IN; GPIO 21 (Pin 40) DATA OUT;
And the I2C bus needs these pins:
GPIO 02 (pin 02) SDIN GPIO 03 (pin 03) SCLK
graphic from:
https://hifiduino.wordpress.com/2014/11/13/raspberry-pi-b-digital-audio/