Python i2s experiments on Raspberry PI 4B board.

The following 5 tests are included: ( see below for tests summary )
1. speech_recog.py
2. sound_recorder.py
3. i2s_wavefile.py
4. i2s_lcd.py
5. i2s_servo.py

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To compile and flash to sd card:

cd rpi4b-python-i2smic
Download OS:
wget https://downloads.raspberrypi.org/raspios_lite_armhf/images/raspios_lite_armhf-2020-12-04/2020-12-02-raspios-buster-armhf-lite.zip
unzip 2020-12-02-raspios-buster-armhf-lite.zip
Use balenaEtcher to burn img to sd card.
eject sd card.
Plugin sd card to PC.
To enable I2S add dtparam=i2s=on in /boot/config.txt
sudo cp config.txt /media/$USER/boot
sync
sudo umount /media/$USER/boot
eject sd card.
Plugin the sd card to Raspberry PI 4B board.
Connect gpio Pin 8 to serial USB cable TX.
Connect gpio pin 10 to serial USB cable RX. 
Connect gpio pin 39 to serial USB cable ground. 
Type "script ~/outputfile.txt" on PC.
Plugin serial USB cable to PC.
Type "sudo screen /dev/ttyUSB0 115200" on PC.
Power on Raspberry PI 4B board.
It should prompt login message.
user pi
password raspberry
sudo raspi-config
set password, wifi, locale, timezone, peripheral etc.
vi nosleep.sh ( add following line to disable sleep feature )
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.ta
rget
./nosleep.sh
sudo dmesg -n 1
sudo vi /etc/rc.local ( add sudo dmesg -n 1 )
sudo ifconfig
sudo apt-get update
sudo apt-get upgrade
sync
sudo reboot
./nosleep.sh
sudo apt-get install python-dev python-pip python-setuptools python3-dev python3-pip python3-setuptools dnsutils apache2 vsftpd ftp pavucontrol libportaudio0 libportaudio2 libportaudiocpp0 portaudio19-dev libasound2-dev flac python-smbus
sync
sudo apt-get remove --purge pulseaudio
sudo apt autoremove
sudo pip install pyaudio
sudo pip install SpeechRecognition
sudo pip3 install --upgrade adafruit-python-shell
wget https://raw.githubusercontent.com/adafruit/Raspberry-Pi-Installer-Scripts/master/i2smic.py
sudo python3 i2smic.py
./nosleep.sh
lsmod
git clone https://github.com/chenphilip888/rpi4b-python-i2smic.git
cp ~/rpi4b-python-i2smic/asoundrc ~/.asoundrc
sudo cp ~/.asoundrc /etc/asound.conf
sudo /etc/init.d/alsa-utils restart

sudo cat /proc/device-tree/soc/i2c@7e804000/status
sudo cat /proc/device-tree/soc/pwm@7e20c000/status
ls /sys/class/pwm
sudo apt-get install i2c-tools
sudo i2cdetect -y 1

Download gpio library on Raspberry PI 4B board:
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
gpio -v      ( make sure it's v2.52 or above )
gpio readall

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Here are the summary of the tests: 

See GPIO-Pinout-rpi4b.png and https://www.raspberrypi.org/documentation/usage/gpio
These tests used Seeed Grove-LCD RGB Backlight V3.0 JHD1313M2, Analog Servo and Adafruit SPH0645 I2S Mic.
To use Adafruit SPH0645 I2S Mic see https://learn.adafruit.com/adafruit-i2s-mems-microphone-breakout/overview

I2S_Mic:
   Connect LRCL to pin 35
   Connect DOUT to pin 38
   Connect BCLK to pin 12
   Connect GND  to pin 9
   Connect 3V   to pin 1
I2C_LCD:
   Connect gpio pin 3 to lcd display SDA.
   Connect gpio pin 5 to lcd display SCL.
   Connect gpio pin 2 to lcd display 5V.
   Connect gpio pin 6 to lcd display ground.
Servo:
   Connect gpio pin 33 to servo control.
   Connect gpio pin 4 to servo 5V.
   Connect gpio pin 14 to servo ground.

1. speech_recog.py
   Speak to Microphone for 3 seconds. It will print what you said.

2. sound_recorder.py
   Speak to Microphone for 3 seconds. It will save sound to 'file.wav'.

3. i2s_wavefile.py
   It will read 'file.wav' and print what you said in 'file.wav'.

4. i2s_lcd.py
   Speak to Microphone for colors of your choice. It will display colors of your choice to LCD background color.

5. i2s_servo.py
   You can command servo to turn right, left or stay in the middle by speaking to Microphone.

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Here are the procedure to test the above 5 tests:

cat /proc/asound/cards
arecord -l
arecord -D dmic_sv -c2 -r 44100 -f S32_LE -t wav -V mono -v file.wav
alsamixer  ( adjust volume to 66% )

arecord -D dmic_sv -c2 -r 44100 -f S32_LE -t wav -V mono -v file.wav
arecord -c2 -r 44100 -f S32_LE -t wav -V mono -v file.wav

\rm .config/pulse/*
sudo \rm /etc/alsa/conf.d/*
sudo vi /usr/share/alsa/alsa.conf  ( commented out pcm.cards and 21 lines below it )

cd ~/rpi4b-python-i2smic
./speech_recog.py
./sound_recorder.py
./i2s_wavefile.py
./i2s_lcd.py
./i2s_servo.py

When done all tests:
sudo shutdown -h now
Power off Raspberry PI 4B board.
Unplug serial USB cable from PC.
Type "exit" on PC.

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