Adafruit MAX98357 I2S Class-D Mono
Amp
Created by lady ada

https://learn.adafruit.com/adafruit-max98357-i2s-class-d-mono-amp

Last updated on 2024-06-03 01:56:09 PM EDT©Adafruit Industries

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Table of Contents
Overview

5

Pinouts

7• Speaker Output• Power Pins
• I2S Pins
• Other Pins
• Gain• SD / MODE

Assembly

12• Prepare the header strip:• Add the breakout board:• And Solder!

Raspberry Pi Wiring

16

Raspberry Pi Setup

17• Setup Virtual Environment• Installer script• Detailed Install• Update /etc/modprobe.d (if it exists)• Disable headphone audio (if it's set)
• Create asound.conf file
• Add Device Tree Overlay

Raspberry Pi Test

25

• Speaker Tests!
• Simple white noise speaker test
• Simple WAV speaker test
• Simple MP3 speaker test
• Volume adjustment

Pi I2S Tweaks

27• Reducing popping• Step 1• Add software volume control

Play Audio with PyGame

31• Install PyGame• Run Demo

Arduino Wiring & Test

33

• Wiring• Basic Test
• DMA Test

CircuitPython Wiring & Test

37

• Wiring• Code Examples• Tone Generation©Adafruit Industries

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• Wave File
• Where's my I2S?

I2S Audio FAQ

44

Downloads

45• Schematic• Fabrication Print• 3D Model©Adafruit Industries

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©Adafruit Industries

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Overview

If your microcontroller or microcomputer has digital audio capability, this amp is foryou! It takes standard I2S digital audio input and, not only decodes it into analog, butalso amplifies it directly into a speaker. Perfect for adding compact amplified sound, ittakes 2 breakouts (I2S DAC + Amp) and combines them into one.
I2S (not to be confused with I2C) is a digital sound protocol that is used on circuitboards to pass audio data around. Many high end chips and processors manage all of
the audio in digital I2S format. Then, to input or output data, three or four pins areused (data in, data out, bit clock and left-right channel select). Usually, for audio
devices, there's a DAC chip that will take I2S in and convert it to analog that can drivea headphone.
This small mono amplifier is surprisingly powerful - able to deliver 3.2 Watts of power
into a 4 ohm impedance speaker (5V power @ 10% THD). Inside the miniature chip is aclass D controller, able to run from 2.7V-5.5VDC. Since the amp is a class D, it's
incredibly efficient - making it perfect for portable and battery-powered projects. It
has built in thermal and over-current protection but we could barely tell it got hot.
The audio input is I2S standard, you can use 3.3V or 5V logic data. The outputs are"Bridge Tied" - that means they connect directly to the outputs, no connection to
ground. The output is a ~300KHz square wave PWM that is then 'averaged out' by the
speaker coil - the high frequencies are not heard. All the above means that you can'tconnect the output into another amplifier, it should drive the speakers directly.

©Adafruit Industries

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There's a Gain pin that can be manipulated to change the gain. By default, the amp
will give you 9dB of gain. By connecting a pullup or pull down resistor, or wiring
directly, the Gain pin can be set up to give 3dB, 6dB, 9dB, 12dB or 15dB.
the ShutDown/Mode pin can be used to put the chip in shutdown or set up which I2S
audio channel is piped to the speaker. By default, the amp will output (L+R)/2 stereo
mix into mono out. By adding a resistor, you can change it to be just left or just right
outputWorks great with Raspberry Pi, Arduino Zero, and any other microcontroller or
microcomputer with I2S audio outputs
Specs:• Output Power: 3.2W at 4Ω, 10% THD, 1.8W at 8Ω, 10% THD, with 5V supply• PSRR: 77 dB typ @ 1KHz
• I2S sample rates from 8kHz to 96kHz• No MCLK required• Click + Pop reduction• Five pin-selectable gains: 3dB, 6dB, 9dB, 12dB, 15dB
• Excellent click-and-pop suppression• Thermal shutdown protection©Adafruit Industries

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Comes as an assembled and tested breakout board, with a small piece of optionalheader and 3.5mm terminal block. Some soldering is required to attach the header
and terminal block if those are desired.

Pinouts

The MAX98357A is an I2S amplifier - it does not use analog inputs, it only has digitalaudio input support! Don't confuse I2S with I2C, I2S is a sound protocol whereas I2C
is for small amounts of data.

©Adafruit Industries

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Speaker Output

This amplifier is designed to drive moving coil loudpeakers only. Speaker
impedence must be 4Ω or more. The output signal is a 330KHz PWM square wave
with a duty cycle proportional to the audio signal. The inductance of the speaker coilserves as a low-pass filter to average out the high-frequency components. Do not try
to use this as a pre-amplifier.
The outputs of each channel are "Bridge-Tied" with no connection to ground. Thismeans that for each channels, the + and - alternate polarity to create a single channel
amplifier with twice the available power.
Connect your speakers using the 3.5mm screw-terminal blocks.
• 5V into 4Ω @ 10% THD - 3W max• 5V into 4Ω @ 1% THD - 2.5W max• 3.3V into 4Ω @ 10% THD - 1.3W max• 3.3V into 4Ω @ 1% THD - 1.0W max• 5V into 8Ω @ 10% THD - 1.8W max• 5V into 8Ω @ 1% THD - 1.4W max• 3.3V into 8Ω @ 10% THD - 0.8W max• 3.3V into 8Ω @ 1% THD - 0.6W max©Adafruit Industries

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Power Pins

This is the power for the amplifier and logic of the amplifier. You can provide 2.5V up
to 5.5V. Note that at 5V you can end up putting up to 2.8W into your speaker, so
make sure your power supply can easily handle up to 650mA and we recommend a
power supply spec'd for at least 800mA to give yourself some 'room'
If you have a 3.3V logic device, you can still power the amp from 5V, and that's
recommended to get the most power output!

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I2S Pins

Three pins are used to receive audio data. These can be 3.3-5V logic• LRC (Left/Right Clock) - this is the pin that tells the amplifier when the data is forthe left channel and when its for the right channel• BCLK (Bit Clock) - This is the pin that tells the amplifier when to read data on thedata pin.
• DIN (Data In) - This is the pin that has the actual data coming in, both left andright data are sent on this pin, the LRC pin indicates when left or right is beingtransmitted
Note that this amplifier does not require an MCLK pin, if you have an MCLK output,
you can leave it disconnected!

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Other Pins

The other settings are handled by GAIN and SD

Gain
GAIN is, well, the gain setting. You can have a gain of 3dB, 6dB, 9dB, 12dB or 15dB.
• 15dB if a 100K resistor is connected between GAIN and GND• 12dB if GAIN is connected directly to GND• 9dB if GAIN is not connected to anything (this is the default)• 6dB if GAIN is connected directly to Vin• 3dB if a 100K resistor is connected between GAIN and Vin
This way, the default gain is 9dB but you can easily change it by tweaking theconnection to the GAIN pin. Note you may need to perform a power reset to adjust
the gain.

©Adafruit Industries

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SD / MODE
This pin is used for shutdown mode but is also used for setting which channel is
output. It's a little confusing but essentially:• If SD is connected to ground directly (voltage is under 0.16V) then the amp is
shut down• If the voltage on SD is between 0.16V and 0.77V then the output is (Left + Right)/
2, that is the stereo average.
• If the voltage on SD is between 0.77V and 1.4V then the output is just the Right
channel• If the voltage on SD is higher than 1.4V then the output is the Left channel.
This is compounded by an internal 100K pulldown resistor on SD so you need to use
a pullup resistor on SD to balance out the 100K internal pulldown.
For the breakout board, there's a 1Mohm resistor from SD to Vin which, whenpowering from 5V will give you the 'stereo average' output. If you want left or rightchannel only, or if you are powering from non-5V power, you may need to experimentwith different resistors to get the desired voltage on SD

Assembly©Adafruit Industries

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Prepare the header strip:

Cut the strip to length if necessary. It will
be easier to solder if you insert it into a
breadboard - long pins down

Add the breakout board:

Place the breakout board over the pins sothat the short pins poke through the
breakout pads

©Adafruit Industries

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And Solder!

Be sure to solder all pins for reliable
electrical contact.
(For tips on soldering, be sure to check out
our Guide to Excellent Soldering (https://
adafru.it/aTk)).

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You're done! Check your solder joints
visually and continue onto the next steps

If you want to use a terminal block forconnecting a speaker, place the 3.5mm
terminal so the mouthes point out.

©Adafruit Industries

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Solder in both pins with plenty of solder!

Raspberry Pi Wiring
if you have a Raspberry Pi and you want higher quality audio than the headphone jackcan provide, I2S is a good option! You only use 3 pins, and since its a pure-digital
output, there can be less noise and interference. Of course, you'll need to make surethat you have a nice strong 5V power supply so make sure to add 500mA or more toyour power supply requirements!
This board also works very well with boards that don't have audio like the Pi Zero
This technique will work with any Raspberry Pi with the 2x20 connector. Older Pi
1's with a 2x13 connector do not bring out the I2S pins as easily©Adafruit Industries

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Connect:• Amp Vin to Raspbery Pi 5V Power• Amp GND to Raspbery Pi Ground• Amp DIN to Raspbery Pi GPIO 21• Amp BCLK to Raspbery Pi GPIO 18• Amp LRCLK to Raspbery Pi GPIO 19
Check Raspberry Pi documentation for which pins are GPIO 18, 19, 21, 5V and
GND (https://adafru.it/112A)

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 :)©Adafruit Industries

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Setup Virtual Environment
If you are installing on the Bookworm version of Raspberry Pi OS or later, you willneed to install your python modules in a virtual environment. You can find more
information in the Python Virtual Environment Usage on Raspberry Pi (https://adafru.it/
19a5) guide. To Install and activate the virtual environment, use the following
commands:
sudo apt install python3-venv
python -m venv env --system-site-packages

To activate the virtual environment:
source env/bin/activate

Installer script
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! (https://adafru.it/nFy)
Run the following from your Raspberry Pi with Internet connectivity:
sudo apt install -y wget
wget https://github.com/adafruit/Raspberry-Pi-Installer-Scripts/raw/main/i2samp.py
sudo -E env PATH=$PATH python3 i2samp.py©Adafruit Industries

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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 atiny 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 totest the speaker. Say yes and listen for audio to come out of your speakers...

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If it sounds really distorted, it could be the volume is too high. However, in order tohave volume control appear in Raspbian desktop or Retropie you must reboot asecond 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% isa 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 restof this page on Detailed Installation if the script worked for you!

Detailed InstallIf, for some reason, you can't just run the script and you want to go through the installby 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

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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>©Adafruit Industries

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Disable headphone audio (if it's set)
Edit the raspi modules list withsudo nano /etc/modules

If the file is empty, just skip this step
However, if you see the following line:
snd_bcm2835

Put a # in front of itand save with Control-X Y <return>Create asound.conf file
Edit the raspi modules list withsudo nano /etc/asound.conf

This file ought to be blank!

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Copy and paste the following text into the filepcm.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 {typeslave.pcm}©Adafruit Industries

plug"softvol"Page 23 of 46

Save the file as usual

Add Device Tree Overlay
Edit your Pi configuration file withFor older versions of Raspberry Pi, edit /boot/config.txt instead.

sudo nano /boot/firmware/config.txt

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

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Disable it by putting a # in front.
Then add:
dtoverlay=max98357aon the next line. Save the file and reboot your Pi withsudo 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 andspeaker are working as they should!

Simple white noise speaker testRun
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©Adafruit Industries

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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 setthat up (https://adafru.it/aTD)
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 tostereo!
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 calledalsamixer. 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 torecognize the volume control©Adafruit Industries

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Pi I2S Tweaks
This page is deprecated, our installer already performs these steps for you, but
we'll keep them here for archival use!

Reducing popping
For people who followed our original installation instructions with the simple alsa
config, they may find that the I2S audio pops when playing new audio.
The workaround is to use a software mixer to output a fixed sample rate to the I2S
device so the bit clock does not change. I use ALSA so I configured dmixer and I no
longer have any pops or clicks. Note that the RaspPi I2S driver does not support
dmixer by default and you must follow these instructions provided (https://adafru.it/sHF) to add it. Continue on for step-by-step on how to enable it!

Step 1
Start by modify /boot/firmware/config.txt to add dtoverlay=i2s-mmap
Run sudo nano /boot/firmware/config.txt and add the text to the bottom like so:©Adafruit Industries

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If you are using an older version of Raspberry Pi OS and there is no firmware
folder, you may need to edit the /boot/config.txt file.
Save and exit.
Then change /etc/asound.conf to:
pcm.speakerbonnet {type hw card 0}
pcm.!default {type plugslave.pcm "dmixer"}
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}

By running sudo nano /etc/asound.conf
This creates a PCM device called speakerbonnet which is connected to the hardware
I2S device. Then we make a new 'dmix' device ( type dmix ) called pcm.dmixer . We
give it a unique Inter Process Communication key ( ipc_key 1024 ) and permissions
that are world-read-writeable (ipc_perm 0666 ) The mixer will control the hardware
pcm device speakerbonnet (pcm "speakerbonnet") and has a buffer set up so its nice

©Adafruit Industries

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and fast. The communication buffer is set up so there's no delays ( period_time 0 ,period_size 1024 and buffer_size 8192 work well). The default mixed rate is
44.1khz stereo ( rate 44100 channels 2 )Finally we set up a control interface but it ended up working best to just put in the
hardware device here - ctl.dmixer { type hw card 0 }Save and exit. Then reboot the Pi to enable the mixer. Also, while it will greatly reduce
popping, you still may get one once in a while - especially when first playing audio!

Add software volume control
The basic I2S chipset used here does not have software control built in. So we haveto 'trick' the Pi into creating a software volume control. Luckily, its not hard once you
know how to do it (https://adafru.it/ydQ).
Create a new audio config file in ~/.asoundrc with nano ~/.asoundrc and inside put
the following text:
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

©Adafruit Industries

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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 {typeslave.pcm}

plug"softvol"This assumes you set up the dmixer for no-popping above!

Save and exit
Now, here's the trick, you have to reboot, then play some audio through alsa, thenreboot to get the alsamixer to sync up right:
speaker-test -c2 --test=wav -w /usr/share/sounds/alsa/
Front_Center.wav©Adafruit Industries

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Then you can type alsamixer to control the volume with the 'classic' alsa mixing
interface

Just press the up and down arrows to set the volume, and ESC to quit

Play Audio with PyGame
You can use mpg123 for basic testing but it's a little clumsy for use where you want todynamically change the volume or have an interactive program. For more powerfulaudio playback we suggest using PyGame to playback a variety of audio formats (MP3included!)Install PyGame
Start by installing pygame support, you'll need to open up a console on your Pi with
network access and run:sudo apt-get install python3-pygame

Next, download this pygame example zip to your Pi

Click to download PyGame example
code & sample mp3s
https://adafru.it/wbp
On the command line, run©Adafruit Industries

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wget https://cdn-learn.adafruit.com/assets/assets/000/041/506/
original/pygame_example.zip (https://adafru.it/wbq)
unzip pygame_example.zip (https://adafru.it/wbq)

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 forplayback. 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:
python pygameMP3.py 0.75

Here's the code if you have your own mp3s!
''' 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#!/usr/bin/python
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()try:
pg.mixer.music.load(music_file)
print("Music file {} loaded!".format(music_file))
except pygame.error:
print("File {} not found! {}".format(music_file, pg.get_error()))
returnpg.mixer.music.play()# If you want to fade in the audio...
# for x in range(0,100):#
pg.mixer.music.set_volume(float(x)/100.0)©Adafruit Industries

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#time.sleep(.0075)# # check if playback has finishedwhile pg.mixer.music.get_busy():clock.tick(30)freq = 44100# audio CD quality
bitsize = -16# unsigned 16 bitchannels = 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) &gt; 1:
try:
user_volume = float(sys.argv[1])except ValueError:
print "Volume argument invalid. Please use a float (0.0 - 1.0)"
pg.mixer.music.fadeout(1000)
pg.mixer.music.stop()raise SystemExit
print("Playing at volume: " + str(user_volume)+ "\n")pg.mixer.music.set_volume(user_volume)
mp3s = []for file in os.listdir("."):
if file.endswith(".mp3"):
mp3s.append(file)
print mp3s
for x in mp3s:
try:play_music(x)time.sleep(.25)
except KeyboardInterrupt:# if user hits Ctrl/C then exit
# (works only in console mode)
pg.mixer.music.fadeout(1000)
pg.mixer.music.stop()raise SystemExit
else:
print("Please specify volume as a float! (0.0 - 1.0)")

Arduino Wiring & Test
The classic ATmega328P-based Arduino's like the UNO and Metro 328 don't have I2S
interfaces, so you can't use this breakout with themBut the newer ATSAMD21-based boards like the Zero, Metro M0, Feather M0 can!
(Note, Gemma M0 & Trinket M0 do not have I2S pins available). And so can the evennewer ATSAMD51-based boards like the Metro M4 and Feather M4.
To use I2S with M0 or M4 boards, you'll need to install the Adafruit Zero I2S
library (https://adafru.it/DHD). It is available through the Library Manager. You cansearch for (see below) and then just click the install button.

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WiringWiring connections are the same as those used for CircuitPython. So go to the
CircuitPython Wiring & Test page to see how to wire the breakout for your specificboard.

Basic Test
To test things out, try running the demo below. It comes with the library installation, so
you can find it by going to:File -> Examples -> Adafruit Zero I2S Library -> basic
Be sure to change this line:
Adafruit_ZeroI2S i2s(0, 1, 9, 2);

to match the pins used for your setup. If you've wired as shown in this guide, then you
can try using the default pins by changing that line to this:Adafruit_ZeroI2S i2s;#include <Arduino.h>#include <Adafruit_ZeroI2S.h>#include <math.h>/* max volume for 32 bit data */#define VOLUME ( (1UL << 31) - 1)/* create a buffer for both the left and right channel data */#define BUFSIZE 128
int left[BUFSIZE];
int right[BUFSIZE];©Adafruit Industries

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// Use default pins in board variant
Adafruit_ZeroI2S i2s = Adafruit_ZeroI2S();
void setup(){
while (!Serial) delay(10);Serial.println("I2S demo");for(int i=0; i<BUFSIZE; i++){/* create a sine wave on the left channel */left[i] = sin( (2*PI / (BUFSIZE) ) * i) * VOLUME;/* create a cosine wave on the right channel */right[i] = cos( (2*PI / (BUFSIZE) ) * i) * VOLUME;}/* begin I2S on the default pins. 24 bit depth at* 44100 samples per second*/
i2s.begin(I2S_32_BIT, 44100);i2s.enableTx();}
void loop(){/* write the output buffers* note that i2s.write() will block until both channels are written.
*/
for(int i=0; i<BUFSIZE; i++){i2s.write(left[i], right[i]);}}DMA Test
The basic test above created the output directly by using the i2s.write() function
in a loop. Another approach is to use DMA to generate the output. With this approach,
you do some initial setup to configure the DMA engine for playback. It can then takecare of generating the output in the background allowing you to do other things inyour code.
To take this approach, you will need to install the Zero DMA library (https://adafru.it/lnb). You can do that through the Library Manager:©Adafruit Industries

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And then you can use the DMA example found in the Zero I2S library:File -> Examples -> Adafruit Zero I2S Library -> dma#include <Adafruit_ZeroI2S.h>#include <Adafruit_ZeroDMA.h>#include "utility/dma.h"#include <math.h>/* max volume for 32 bit data */#define VOLUME ( (1UL << 31) - 1)/* create a buffer for both the left and right channel data */#define BUFSIZE 256
int data[BUFSIZE];
Adafruit_ZeroDMA myDMA;
ZeroDMAstatusstat; // DMA status codes returned by some functions
Adafruit_ZeroI2S i2s;
void dma_callback(Adafruit_ZeroDMA *dma) {/* we don't need to do anything here */}void setup(){
Serial.begin(115200);//while(!Serial);// Wait for Serial monitor before continuing

Serial.println("I2S output via DMA");int *ptr = data;/*the I2S module will be expecting data interleaved LRLR*/
for(int i=0; i<BUFSIZE/2; i++){/* create a sine wave on the left channel */*ptr++ = sin( (2*PI / (BUFSIZE/2) ) * i) * VOLUME;/* create a cosine wave on the right channel */*ptr++ = cos( (2*PI / (BUFSIZE/2) ) * i) * VOLUME;}
Serial.println("Configuring DMA trigger");
myDMA.setTrigger(I2S_DMAC_ID_TX_0);
myDMA.setAction(DMA_TRIGGER_ACTON_BEAT);©Adafruit Industries

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Serial.print("Allocating DMA channel...");
stat = myDMA.allocate();myDMA.printStatus(stat);
Serial.println("Setting up transfer");
myDMA.addDescriptor(
data,// move data from here
#if defined(__SAMD51__)(void *)(&I2S->TXDATA.reg), // to here (M4)#else(void *)(&I2S->DATA[0].reg), // to here (M0+)#endifBUFSIZE,// this many...
DMA_BEAT_SIZE_WORD,// bytes/hword/wordstrue,// increment source addr?
false);
myDMA.loop(true);
Serial.println("Adding callback");
myDMA.setCallback(dma_callback);/* begin I2S on the default pins. 24 bit depth at* 44100 samples per second*/
i2s.begin(I2S_32_BIT, 44100);i2s.enableTx();
stat = myDMA.startJob();}
void loop(){
Serial.println("do other things here while your DMA runs in the background.");delay(2000);}

CircuitPython Wiring & Test
CircuitPython 3.0 and higher has I2S built in which means you can use this breakout
super easily with the supported M0 and M4 Express CircuitPython boards! Supported
boards are Feather M0 Express, Feather M4 Express, Metro M0 Express, Metro M4
Express, and ItsyBitsy M0 Express.
Note that Trinket M0, Gemma M0 and ItsyBitsy M4 do not support I2S (the last one is
not a typo!)
The M0 boards have multiple I2S pin combinations available. We're going todemonstrate a single pin combination for each board.

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Wiring
The following wiring diagrams show how to connect the MAX98357 breakout to yourCircuitPython board. You'll be using voltage in, ground, bit clock, left/right clock anddata pins.
• VIN is the red wire.
• GND is the black wire.
• BCLK is the blue wire.
• LRC is the yellow wire.
• DIN is the green wire.

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For Feather M0 Express, ItsyBitsy M0
Express and Metro M0 Express:

Connect VIN on the breakout to 3V/3.3 on
the board.
Connect GND on the breakout to G/GND
on the board.
Connect BCLK on the breakout to D1/TX
on the board.
Connect LRC on the breakout to D0/RX on
the board.
Connect DIN on the breakout to D9 on theboard.

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For Feather M4 Express:

Connect VIN on the breakout to 3V on theboard.
Connect GND on the breakout to Gnd on
the board.
Connect BCLK on the breakout to TX on
the board.
Connect LRC on the breakout to D10 on
the board.
Connect DIN on the breakout to D11 on
the board.
For Metro M4 Express:

Connect VIN on the breakout to 3.3 on
the board.
Connect GND on the breakout to GND on
the board.
Connect BCLK on the breakout to D3 on
the board.
Connect LRC on the breakout to D9 on
the board.
Connect DIN on the breakout to D8 on theboard.

Code Examples
We have two CircuitPython code examples. The first plays a generated tone throughthe speaker on the breakout. The second plays a wave file. Let's take a look!

Tone Generation
The first example generates one period of a sine wave and then loops it to generate atone. You can change the volume and the Hz of the tone by changing the associatedvariables. Inside the loop, we play the tone for one second and stop it for one second.
# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries#©Adafruit Industries

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# SPDX-License-Identifier: MIT
import time
import array
import mathimport audiocore
import board
import audiobusio
sample_rate = 8000
tone_volume = .1 # Increase or decrease this to adjust the volume of the tone.
frequency = 440 # Set this to the Hz of the tone you want to generate.
length = sample_rate // frequency # One freqency period
sine_wave = array.array("H", [0] * length)
for i in range(length):sine_wave[i] = int((math.sin(math.pi * 2 * frequency * i / sample_rate) *tone_volume + 1) * (2 ** 15 - 1))# For Feather M0 Express, ItsyBitsy M0 Express, Metro M0 Express
audio = audiobusio.I2SOut(board.D1, board.D0, board.D9)# For Feather M4 Express# audio = audiobusio.I2SOut(board.D1, board.D10, board.D11)# For Metro M4 Express# audio = audiobusio.I2SOut(board.D3, board.D9, board.D8)
sine_wave_sample = audiocore.RawSample(sine_wave, sample_rate=sample_rate)
while True:
audio.play(sine_wave_sample, loop=True)time.sleep(1)audio.stop()
time.sleep(1)For Feather M0 Express, ItsyBitsy M0 Express and Metro M0 Express, no changes
are needed for the code to work.
For Feather M4 Express, comment out audio = audiobusio.I2SOut(board.D1,
board.D0, board.D9) and uncomment # audio =audiobusio.I2SOut(board.D1, board.D10, board.D11) .
For Metro M4 Express, comment out audio = audiobusio.I2SOut(board.D1,
board.D0, board.D9) and uncomment # audio =audiobusio.I2SOut(board.D3, board.D3, board.D8) .
Now you'll hear one second of a 440Hz tone, and one second of silence.
You can try changing the Hz of the tone to produce different tones. Try changing thenumber of seconds in time.sleep() to produce longer or shorter tones.

Wave File
The second example plays a wave file. We open the file in a readable format. Theninside the loop, we play the file and tell the code to continue playing the file until it's

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completed. You can use any supported wave file (https://adafru.it/BRj). We've included
the wave file used in the code.

StreetChicken.wav
https://adafru.it/BUC# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries## SPDX-License-Identifier: MIT
import audiocore
import board
import audiobusio
wave_file = open("StreetChicken.wav", "rb")wave = audiocore.WaveFile(wave_file)# For Feather M0 Express, ItsyBitsy M0 Express, Metro M0 Express
audio = audiobusio.I2SOut(board.D1, board.D0, board.D9)# For Feather M4 Express# audio = audiobusio.I2SOut(board.D1, board.D10, board.D11)# For Metro M4 Express# audio = audiobusio.I2SOut(board.D3, board.D9, board.D8)
while True:
audio.play(wave)
while audio.playing:pass

The object setup in the code is the same as above.
For Feather M0 Express, ItsyBitsy M0 Express and Metro M0 Express, no changes
are needed for the code to work.
For Feather M4 Express, comment out audio = audiobusio.I2SOut(board.D1,
board.D0, board.D9) and uncomment # audio =audiobusio.I2SOut(board.D1, board.D10, board.D11) .
For Metro M4 Express, comment out audio = audiobusio.I2SOut(board.D1,
board.D0, board.D9) and uncomment # audio =audiobusio.I2SOut(board.D3, board.D3, board.D8) .
Now you'll hear the wave file play through and loop.
There's plenty you can do with this example. Try playing a different wave file, or,instead of including while audio.playing: pass , include a time.sleep() tohave it play for a specified number of seconds. Check out the Audio Out page in the
CircuitPython Essentials guide (https://adafru.it/BRj) for pause and resume features.

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Where's my I2S?
We mentioned earlier that the supported M0 boards have multiple I2S pin
combinations available to you. The M4 boards have one option. Either way, if you'd
like to know what options are available to you, copy the following code into yourcode.py, connect to the serial console, and check out the output.
These are the results from the ItsyBitsy M0 Express.

# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries## SPDX-License-Identifier: MIT
import board
import audiobusio
from microcontroller import Pin
def is_hardware_i2s(bit_clock, word_select, data):try:
p = audiobusio.I2SOut(bit_clock, word_select, data)p.deinit()
return True
except ValueError:
return False
def get_unique_pins():
exclude = ['NEOPIXEL', 'APA102_MOSI', 'APA102_SCK']
pins = [pin for pin in [getattr(board, p) for p in dir(board) if p not in exclude]
if isinstance(pin, Pin)]unique = []for p in pins:
if p not in unique:unique.append(p)return uniquefor bit_clock_pin in get_unique_pins():
for word_select_pin in get_unique_pins():
for data_pin in get_unique_pins():
if bit_clock_pin is word_select_pin or bit_clock_pin is data_pin or
word_select_pin\©Adafruit Industries

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is data_pin:
continue
if is_hardware_i2s(bit_clock_pin, word_select_pin, data_pin):
print("Bit clock pin:", bit_clock_pin, "\t Word select pin:",
word_select_pin,"\t Data pin:", data_pin)
else:
pass

I2S Audio FAQ
Hey in Raspbian Pixel desktop, the speaker icon is X'dout!
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 pagefor 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 samething 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 founddoes for sure!
• PyGame - see our page on playing audio with PyGame (https://adafru.it/ydS)
for example code. Volume can be controlled within pygame©Adafruit Industries

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• mpg123 - command line mp3 audio playback. use alsamixer to control thevolume• aplay - for playing wav files on the command line
• Sonic Pi - tested in the Pixel Desktop. Use the Sonic Pi settings panel tochange 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 andmake a popping sound the first time you play audio. You can set volume withalsamixer 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 gameto play interface)

Downloads• MAX98357 Datasheet (http://adafru.it/30069835798357)• GitHub with EagleCAD PCB Files (https://adafru.it/nFB)• 3D Models on GitHub (https://adafru.it/10fp)• Fritzing object in the Adafruit Fritzing library (https://adafru.it/aP3)

Schematic
Click to embiggen©Adafruit Industries

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Fabrication Print
Dimensions in Inches

3D Model©Adafruit Industries

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