I2S Audio Interface for Raspberry Pi Zero
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.
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.
| Component type | Reference | Description | Quantity | Possible sources and notes |
|---|---|---|---|---|
| PCB | I2S Audio pHAT PCB - Version 3.0 | 1 | Order from OSH Park | |
| Integrated Circuit | U1 | WM8731, I2S audio codec, SSOP28 | 1 | Mouser 238-WM8731SEDS/V |
| Integrated Circuit | U2 | TPS79333DBVR, LDO, SOT23-5 | 1 | Mouser 595-TPS79333DBVR |
| Integrated Circuit | U3 | CAT24C32WI-GT3, I2C EEPROM, SOIC8 | 1 | Mouser 698-CAT24C32WI-GT3 |
| Crystal | X1 | 12.288MHz, 3 mm x 5.3 mm | 1 | Mouser 717-7A-12.288MAAJ-T |
| Microphone | MK1 | 9.7 mm, electret condenser microphone | 1 | Mouser 490-CMA-4544PF-W |
| Connector | P1 | 3.5 mm audio jack, blue | 1 | Mouser 806-STX-31205B284C |
| Connector | P2 | 3.5 mm audio jack, green | 1 | Mouser 806-STX-31205B577C |
| Connector | P3 | 3.5 mm audio jack, black | 1 | Mouser 806-STX-3120-5B |
| Connector | P4 | 20x2, 2.54 mm, socket | 1 | Mouser 517-929852-01-20-RB |
| Header | JP1 | 2x1, 2.54mm, header | 1 | (optional) Mouser 855-M20-9990245 |
| Capacitor | C1, C2 | 22pF, 0603 | 2 | Mouser 77-VJ0603A220JXACBC |
| Capacitor | C3-C5 | 220pF, 0603 | 3 | Mouser 77-VJ0603A221GXAPBC |
| Capacitor | C6 | 0.01uF, 0603 | 1 | Mouser 77-VJ0603Y103KXACBC |
| Capacitor | C7-C12 | 0.1uF, 0603 | 6 | Mouser 77-VJ0603Y104JXJPBC |
| Capacitor | C13-C15 | 1uF, 5 mm, radial | 3 | Mouser 647-USW1H010MDD |
| Capacitor | C16, C17 | 10uF, 5 mm, radial | 2 | Mouser 647-USW1H100MDD |
| Capacitor | C18-C21 | 10uF, 0603 | 4 | Mouser 81-GRM188R61A106KE9D |
| Capacitor | C22, C23 | 220uF, 6.3 mm, radial | 2 | Mouser 647-USW0J221MDD |
| Resistor | R1-R6 | 33 ohm, 0603 | 6 | Mouser 603-RC0603FR-0733RL |
| Resistor | R7, R8 | 100 ohm, 0603 | 2 | Mouser 603-RC0603FR-07100RL |
| Resistor | R9 | 330 ohm, 0603 | 1 | Mouser 603-RC0603FR-07330RL |
| Resistor | R10 | 680 ohm, 0603 | 1 | Mouser 603-RC0603FR-07680RL |
| Resistor | R11 | 1 kohm, 0603 | 1 | Mouser 603-RC0603FR-071KL |
| Resistor | R12, R13 | 3.9 kohm, 0603 | 2 | Mouser 603-RC0603FR-073K9L |
| Resistor | R14-R18 | 5.6 kohm, 0603 | 5 | Mouser 603-RC0603FR-075K6L |
| Resistor | R19-R22 | 47 kohm, 0603 | 4 | Mouser 603-RC0603FR-0747KL |
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
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 Raspbian 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.
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/skiselev/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