Add some easy-listenin' tunes to your Raspberry Pi using this basic audio bonnet. It'll give you stereo line out from a digital I2S converter for a good price, and sounds nice to boot! This bonnet features the UDA1334A I2S Stereo DAC, a perfect match for any I2S-output audio interface. It's affordable but sounds great - music to our ears.

It's the exact same size as a Raspberry Pi Zero but works with any and all Raspberry Pi computers with a 2x20 connector - A+, B+, Zero, Pi 2, Pi 3, etc. We've tested it out with Raspbian (the official operating system) and Retropie.

This Bonnet uses I2S a digital sound standard, so you get really crisp audio. The digital data goes right into the amplifier so there's no static like you hear from the onboard headphone jack. And it's super easy to get started. Just plug in any line level output into powered speakers or audio system. You can plug in headphones but you'll get some distortion - so its best used into something that is expecting line level out

Each order comes as a fully tested and assembled PCB with a 2x20 socket connector. No soldering required! Plug it right onto your pi, install the script and reboot. Pow!


I2S Audio Pins

The UDA1334A is an I2S amplifier - it does not use analog inputs, it only has digital audio input support! Don't confuse I2S with I2C, I2S is a sound protocol whereas I2C is for small amounts of data.

There are 3 required data pins used on the Pi for I2S Audio, and 2 pins that are optional but good to know about.

Required pins

  • Pin #18 - I2S Clock
  • Pin #19 - I2S LR Clock (also sometimes called WS Clock)
  • Pin #21 - I2S Data Into the amplifier (out from Pi)

Optional pins

  • Pin #16 - Mute pin, you can use this to mute the output complete, sometimes helpful if you want to keep audio running and then turn it on/off with a switch or button.
  • Pin #20 - I2S Data Out from a microphone (into the Pi)

You don't have to do anything with that info other than know that pins 18, 19, 21 are not available for to use and pin #16 is by default used for muting. Pin #20 isnt used by the bonnet, but its handy if you plan to connect some other I2S microphone in.

Audio Output

The output from the DAC is into a standard 3.5mm stereo headphone jack. Output is 'live level' (approx 1Vpp). You can plug in a set of headphones but the output isn't designed for driving low impedance so you will get some distortions at loud volume. The output is fully AC coupled with 47uF capacitors, sleeve ground is connected to the Pi ground.

There's also a breakout slot for soldering in dual/stereo RCA jacks, not included with the bonnet.

Or you can just use one of these cables:

3.5mm Stereo to RCA (Composite Audio) Cable 6 feet

One of the most common converter cables you'll want in your cable collection - this 6 foot long cable converts a standard 3.5mm stereo jack to two color-coded mono RCA coaxial...

Raspberry Pi Setup

At this time, Raspbery Pi linux kernel does not support mono audio out of the I2S interface, you can only play stereo, so any mono audio files may need conversion to stereo!
2017-11-2 Raspbian PIXEL ('full') has broken something in volume control. I2S works, but there's no software volume setup, if you need this, try Raspbian Lite - will try to fix as soon as we figure out why :)

Fast Install

Luckily its quite easy to install support for I2S DACs on Raspbian.

These instructions are totally cribbed from the PhatDAC instructions at the lovely folks at Pimoroni!

Run the following from your Raspberry Pi with Internet connectivity:

curl -sS https://raw.githubusercontent.com/adafruit/Raspberry-Pi-Installer-Scripts/master/i2samp.sh | bash

We've added an extra helper systemd script that will play quiet audio when the I2S peripheral isn't in use. This removes popping when playback starts or stops. It uses a tiny amount of CPU time (on a Pi Zero, 5%, on a Pi 2 or 3 its negligible). You don't need this on RetroPie because it never releases the I2S device, but it's great for Raspbian.

You will need to reboot once installed.

You must reboot to enable the speaker hardware!

After rebooting, log back in and re-run the script again...It will ask you if you want to test the speaker. Say yes and listen for audio to come out of your speakers...

If it sounds really distorted, it could be the volume is too high. However, in order to have volume control appear in Raspbian desktop or Retropie you must reboot a second time after doing the speaker test, with sudo reboot

You must reboot *twice* to enable alsamixer volume (really!)

Once rebooted, try running alsamixer and use arrow keys to lower the volume, 50% is a good place to start.

If you're still having audio problems, try re-running the script and saying N (disable) the /dev/zero playback service.

You can then go to the next page on testing and optimizing your setup. Skip the rest of this page on Detailed Installation if the script worked for you!

Detailed Install

If, for some reason, you can't just run the script and you want to go through the install by hand - here's all the steps!

Update /etc/modprobe.d (if it exists)

Log into your Pi and get into a serial console (either via a console cable, the TV console, RXVT, or what have you)

Edit the raspi blacklist with

sudo nano /etc/modprobe.d/raspi-blacklist.conf

If the file is empty, just skip this step

However, if you see the following lines:

blacklist i2c-bcm2708
blacklist snd-soc-pcm512x
blacklist snd-soc-wm8804

Update the lines by putting a # before each line

Save by typing Control-X Y <return>

Disable headphone audio (if it's set)

Edit the raspi modules list with

sudo nano /etc/modules

If the file is empty, just skip this step

However, if you see the following line:


Put a # in front of it

and save with Control-X Y <return>

Create asound.conf file

Edit the raspi modules list with

sudo nano /etc/asound.conf

This file ought to be blank!

Copy and paste the following text into the file

Download: file
pcm.speakerbonnet {
   type hw card 0

pcm.dmixer {
   type dmix
   ipc_key 1024
   ipc_perm 0666
   slave {
     pcm "speakerbonnet"
     period_time 0
     period_size 1024
     buffer_size 8192
     rate 44100
     channels 2

ctl.dmixer {
    type hw card 0

pcm.softvol {
    type softvol
    slave.pcm "dmixer"
    control.name "PCM"
    control.card 0

ctl.softvol {
    type hw card 0

pcm.!default {
    type             plug
    slave.pcm       "softvol"

Save the file as usual

Add Device Tree Overlay

 Edit your Pi configuration file with

sudo nano /boot/config.txt

And scroll down to the bottom. If you see a line that says: dtparam=audio=on 

Disable it by putting a # in front.

Then add:

on the next line. Save the file.

Reboot your Pi with sudo reboot

Raspberry Pi Test

Speaker Tests!

OK you can use whatever software you like to play audio but if you'd like to test the speaker output, here's some quick commands that will let you verify your amp and speaker are working as they should!

Simple white noise speaker test

Run speaker-test -c2 to generate white noise out of the speaker, alternating left and right.

If you have a mono output amplifier, the I2S amp merges left and right channels, so you'll hear continuous white noise

Simple WAV speaker test

Once you've got something coming out, try to play an audio file with speaker-test (for WAV files, not MP3)

speaker-test -c2 --test=wav -w /usr/share/sounds/alsa/Front_Center.wav

You'll hear audio coming from left and right alternating speakers

Simple MP3 speaker test

If you want to play a stream of music, you can try

sudo apt-get install -y mpg123
mpg123 http://ice1.somafm.com/u80s-128-mp3

If you want to play MP3's on command, check out this tutorial which covers how to set that up

At this time, Jessie Raspbery Pi kernel does not support mono audio out of the I2S interface, you can only play stereo, so any mono audio files may need conversion to stereo!

omxplayer does not seem use the I2S interface for audio - only HDMI - so you won't be able to use it

Volume adjustment

Many programs like PyGame and Sonic Pi have volume control within the application. For other programs you can set the volume using the command line tool called alsamixer. Just type alsamixer in and then use the up/down arrows to set the volume. Press Escape once its set

In Raspbian PIXEL you can set the volume using the menu item control. If it has an X through it, try restarting the Pi (you have to restart twice after install to get PIXEL to recognize the volume control

Play Audio with PyGame

You can use mpg123 for basic testing but it's a little clumsy for use where you want to dynamically change the volume or have an interactive program. For more powerful audio playback we suggest using PyGame to playback a variety of audio formats (MP3 included!)

Install PyGame

Start by installing pygame support, you'll need to open up a console on your Pi with network access and run:

Download: file
sudo apt-get install python-pygame

Next, download this pygame example zip to your Pi

Run Demo

Inside the zip is an example called pygameMP3.py

This example will playback all MP3's within the script's folder. To demonstrate that you can also adjust the volume within pygame, the second argument is the volume for playback. Specify a volume to playback with a command line argument between 0.0 and 1.0

For example here is how to play at 75% volume:

Download: file
python pygameMP3.py 0.75

Here's the code if you have your own mp3s!

Download: file
''' pg_midi_sound101.py
play midi music files (also mp3 files) using pygame
tested with Python273/331 and pygame192 by vegaseat
#code modified by James DeVito from here: https://www.daniweb.com/programming/software-development/code/454835/let-pygame-play-your-midi-or-mp3-files


import sys
import pygame as pg
import os
import time

def play_music(music_file):
    stream music with mixer.music module in blocking manner
    this will stream the sound from disk while playing
    clock = pg.time.Clock()
        print("Music file {} loaded!".format(music_file))
    except pygame.error:
        print("File {} not found! {}".format(music_file, pg.get_error()))

    # If you want to fade in the audio...
    # for x in range(0,100):
    #     pg.mixer.music.set_volume(float(x)/100.0)
    #     time.sleep(.0075)
    # # check if playback has finished
    while pg.mixer.music.get_busy():

freq = 44100    # audio CD quality
bitsize = -16   # unsigned 16 bit
channels = 2    # 1 is mono, 2 is stereo
buffer = 2048   # number of samples (experiment to get right sound)
pg.mixer.init(freq, bitsize, channels, buffer)

if len(sys.argv) > 1:

        user_volume = float(sys.argv[1])
    except ValueError:
        print "Volume argument invalid. Please use a float (0.0 - 1.0)"
        raise SystemExit

    print("Playing at volume: " + str(user_volume)+ "\n")
    mp3s = []
    for file in os.listdir("."):
        if file.endswith(".mp3"):

    print mp3s

    for x in mp3s: 
        except KeyboardInterrupt:
            # if user hits Ctrl/C then exit
            # (works only in console mode)
            raise SystemExit
    print("Please specify volume as a float! (0.0 - 1.0)")

I2S Audio FAQ

Hey in Raspbian Pixel desktop, the speaker icon is X'd out!

Try rebooting once after playing some audio. Also make sure you have our latest alsa configuration (check the detailed install page on the Raspberry Pi Setup page for the /etc/asound.conf!

If its still not working, you can still change the volume, just use alsamixer from a Terminal command prompt.

Even with dmixer enabled, I get a staticy-pop when the Pi first boots or when it first starts playing audio

Yep, this is a known Raspbian Linux thing. Yay Linux! We don't have a fix for it. If it makes you feel better, my fancy Windows development computer does the same thing with my desktop speakers.

You can reduce popping a lot with the '/dev/zero play' option in the i2s setup script. (We added it in October 2018) but you still might get that one initial pop

The audio on my DAC sounds really bad/distorted

Make sure you've lowered the volume. The default is 100% which is waaaay too high! Use alsamixer to reduce the volume to 50% or so

Does this work with my favorite software?

It will work with anything that has alsa audio support. There's thousands of linux programs so we can't guarantee all of them will work but here's what we found does for sure!

  • PyGame - see our page on playing audio with PyGame for example code. Volume can be controlled within pygame
  • mpg123 - command line mp3 audio playback. use alsamixer to control the volume
  • aplay - for playing wav files on the command line
  • Sonic Pi - tested in the Pixel Desktop. Use the Sonic Pi settings panel to change the volume - it does not seem to care about what global audio volume you set!
  • Scratch 2 - tested in the Pixel Desktop. Works fine but may have a delay and make a popping sound the first time you play audio. You can set volume with alsamixer and also via the app by using the set volume to nn% block
  • Scratch 1 - doesn't work, something not set up with Scratch 1 to use alsa?
  • RetroPie/Emulation Station - audio works within games (we tested NES and MAME libretro) but does not work in the 'main screen' (selecting which game to play interface)


Schematic & Fabrication Print

Click to embiggen

This guide was first published on Nov 28, 2018. It was last updated on Nov 28, 2018.