I2S Audio Interface for Raspberry Pi Zero -- by Sergey Kiselev

This is a Raspberry Pi Zero pHAT form-factor I2S audio interface board based on a Cirrus Logic (Wolfson) WM8731 audio codec. It provides line input, line output, headphones output, and includes an on-board microphone.

Schematic - Version 3.0

PCB Layout - Version 3.0

I2S Audio pHAT project on Mouser.com - View and order all components except of the PCB.

I2S Audio pHAT project on OSH Park - View and order the PCB.

Open /boot/config.txt in your favorite editor (nano, vi) as root, for example:

sudo nano /boot/config.txt

Comment out the dtparam=audio=on line:

# Enable audio (loads snd_bcm2835)
#dtparam=audio=on

When using I2S Audio pHAT without ID EEPROM (see Raspberry Pi HAT ID EEPROM Programming section below), add the following lines:

# Enable WM8731 codec
# enable I2C bus for HAT (i2c0)
dtoverlay=i2c0
dtparam=i2c_arm=on
dtparam=i2s=on
dtoverlay=i2s-mmap
dtoverlay=rpi-proto

Save the file and reboot the system.

Start alsamixer. If the I2S Audio pHAT is detected properly, it should show Card: snd_rpi_proto on the top left. Also use this opportunity to unmute Output Mixer HiFi control, otherwise the codec will not play any sound. To do so, use cursor keys to highlight that control, and then press the M key to unmute it.

When recording the sound, switch to Capture controls in alsamixer by pressing the F4 key. Next select the capture source: Line or Mic, and unmute it by pressing the Space key.

Now you can use your favorite application to play music or record sound. Enjoy!

The I2S Audio pHAT includes an ID EEPROM as specified by HAT requirements. This ID EEPROM allows Raspberry OS to automatically detect the I2S Audio pHAT, add it to the device tree, and load approprate overlays and kernel modules. Follow the instructions below to program the EEPROM. Install dependencies software, if needed:

sudo apt-get install -y i2c-tools device-tree-compiler

Check to see if EEPROM is on i2c bus 0:

(Note - to enable bus 0 you need to add 'dtparam=i2c_vc=on' in your /boot/config.txt)

pi@raspberrypi:~ $ i2cdetect -y 0

Check to see if WM8731 shows on i2c bus 1:

(Note  - 'UU' means a driver has been loaded for the chip already, otherwise 1A address will show)

pi@raspberrypi:~ $ i2cdetect -y 1

Clone the Raspberry Pi hats repostory from GitHub:

git clone https://github.com/raspberrypi/hats

Clone the I2S Audio pHAT repository from GitHub:

git clone https://github.com/cghercoias/i2s_audio_phat

Build the eepromutils in the hats repository:

cd hats/eepromutils
make

Create the i2s_audio_phat.eep ID EEPROM image, using the eeprom_settings_i2s_audio_phat.txt file provided in the i2s_audio_phat repository:

./eepmake ../../i2s_audio_phat/eeprom_settings_i2s_audio_phat.txt i2s_audio_phat.eep /boot/overlays/rpi-proto.dtbo

Finally, flash the i2s_audio_phat.eep ID EEPROM image to the EEPROM. Make sure to close the JP1 jumper on the I2S Audio pHAT before writing the EEPROM, for example using male to male jumper wire, or otherwise the write will fail.

sudo ./eepflash.sh -w -f=i2s_audio_phat.eep -t=24c32

Disable built-in RaspberryPi audio. Open /boot/config.txt in your favorite editor (nano or vi) as root:

sudo nano /boot/config.txt

Comment out the dtparam=audio=on line:

# Enable audio (loads snd_bcm2835)
# dtparam=audio=on

Install MOC-- (Music On Console) is a console audio player for LINUX/UNIX designed to be powerful and easy to use. MOC plays smoothly, regardless of system or I/O load because it uses the output buffer in a separate thread. It provides gapless playback because the next file to be played is precached while the current file is playing.

pi@raspberrypi:~ $ sudo apt install -y moc

Place your music in a directory (i.e. /home/pi/Music/), then launch mocp

pi@raspberrypi:~ $ mocp

ENTER          Start playing at this file or go to this directory
DOWN           Move down in the menu
UP             Move up in the menu
<              Decrease volume by 1%
>              Increase volume by 1%
,              Decrease volume by 5%
.              Increase volume by 5%
RIGHT          Seek forward by n-s
LEFT           Seek backward by n-s