Ambient Sound Machine

Create a meditative audio player

by John Park

published August 17, 2023, last edited January 22, 2025

posted in Tools/ Hand Tools CircuitPython Breakout Boards Tools/ Lasercutting Arduino Compatibles/ Adafruit METRO

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Intermediate

Project guide

Overview

Flip switches to fill your home with beautiful ambient sounds using this fun new project. Based on the beautiful work of Yuri Suzuki, this DIY version of The Ambient Machine can be built from a couple of inexpensive IKEA storage drawers.

Ambient Sound Machine uses CircuitPython to play up to ten audio samples simultaneously at the flip of a toggle switch. Mix and match to your liking. Each sound can be toggled between two volume levels as well.

Parts

Adafruit Metro M7 with AirLift - Featuring NXP iMX RT1011

Get ready for our fastest Metro ever - the NXP iMX RT1011 microcontroller powers this board with a 500 MHz ARM Cortex M7 processor. There's 8 MB of execute-in-place QSPI for...

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Out of Stock

2 x

Adafruit MCP23017 I2C GPIO Expander Breakout

We’ve gotten a lot of requests for a MCP23017 breakout and we’ve always sorta been like “ehh why not just use the DIP...

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$5.95

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20 x

Angled shot of blue, mini, SPDT toggle switch.

Mini Panel Mount SPDT Toggle Switch

This or that, one or the other, perhaps or perhaps not! So hard to make decisions these days without feeling like you're just going back and forth constantly. Deciding whether or...

$0.95

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Top shot of a feather, a humidity sensor, a potentiometer and an I2C quad board mounted on to the grid.

Adafruit Swirly Aluminum Mounting Grid for 0.1" Spaced PCBs

With most of our dev boards, sensors and feathers now sporting plug-and-play stemma QT ports it can be very fast to...

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Angled shot of blue, square-shaped, amplifier breakout with a pre-soldered terminal block.

Adafruit I2S 3W Class D Amplifier Breakout - MAX98357A

Listen to this good news - we now have an all in one digital audio amp breakout board that works incredibly well with the

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2 x STEMMA QT / Qwiic JST SH 4-pin Cable

100mm Long

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1 x Speaker 3" Diameter

4 Ohm 3 Watt

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1 x Arcade Button Quick-Connect Wire Pairs

0.11" (10 pack)

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1 x USB C Jack to USB C Jack Panel Mount Adapter

Round

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2 x DIY USB Cable Parts

Straight Type C Plug

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1 x DIY USB or HDMI Cable Parts

DIY 20 cm Ribbon Cable

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1 x USB-C Cable – Right Angle

Woven USB Cable with USB Type A to Right Angle USB Type C - Black 1 meter long

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1 x Silicone Cover Stranded-Core Wire

2m 26AWG Black

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1 x Black Nylon Machine Screw and Stand-off Set

M2.5 Thread

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Materials

IKEA Moppe Mini storage chest

Birch plywood storage chest with drawers. You can pick these up at most IKEA locations.

We'll use one medium drawer and one small drawer.

Any suitable box you find can also be used.

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The Ambient Machine Circuit

Below you'll find a circuit diagram and schematic for the Ambient Machine. The Metro M7 is the central controller. The two MCP23017 GPIO expanders are used for reading the twenty switches, sending their data to the Metro M7 over I2C. The MAX98357A amplifier receives digital audio from the M7 via I2S and converts that to an analog output for the speaker.

The switches each have their own unique pin on the expander boards, and share a common ground.

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Install CircuitPython

CircuitPython is a derivative of MicroPython designed to simplify experimentation and education on low-cost microcontrollers. It makes it easier than ever to get prototyping by requiring no upfront desktop software downloads. Simply copy and edit files on the CIRCUITPY drive to iterate.

CircuitPython Quickstart

Follow this step-by-step to quickly get CircuitPython running on your board.

Download the latest version of CircuitPython for this board via circuitpython.org

install_circuitpython_on_most_boards_CircuitPython_downloaded.jpg

Click the link above to download the latest CircuitPython UF2 file.

Save it wherever is convenient for you.

Plug your board into your computer, using a known-good data-sync cable, directly, or via an adapter if needed.

Click the reset button once (highlighted in red above), and then click it again when you see the RGB status LED(s) (highlighted in green above) turn purple (approximately half a second later). Sometimes it helps to think of it as a "slow double-click" of the reset button.

If you do not see the LED turning purple, you will need to reinstall the UF2 bootloader. See the Factory Reset page in this guide for details.

On some very old versions of the UF2 bootloader, the status LED turns red instead of purple.

Once successful, you will see the RGB status LED(s) turn green (highlighted in green above), and a disk drive ending in "...BOOT" should appear on your host computer. If you see red, try another port, or if you're using an adapter or hub, try without the hub, or different adapter or hub.

If double-clicking doesn't work the first time, try again. Sometimes it can take a few tries to get the rhythm right!

A lot of people end up using charge-only USB cables and it is very frustrating! Make sure you have a USB cable you know is good for data sync.

You will see a new disk drive appear called METROM7BOOT.

Drag the adafruit_circuitpython_etc.uf2 file to METROM7BOOT.

Copy or drag the UF2 file you downloaded to the BOOT drive.

The BOOT drive will disappear and a new disk drive called CIRCUITPY will appear.

That's it!

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Code the Ambient Machine

Text Editor

Adafruit recommends using the Mu editor for editing your CircuitPython code. You can get more info in this guide.

Alternatively, you can use any text editor that saves simple text files.

Download the Project Bundle

Your project will use a specific set of CircuitPython libraries, and the code.py file. To get everything you need, click on the Download Project Bundle link below, and uncompress the .zip file.

Connect your computer to the M7 board via a known good USB power+data cable. A new flash drive should show up as CIRCUITPY.

Drag the contents of the uncompressed bundle directory onto your board's CIRCUITPY drive, replacing any existing files or directories with the same names, and adding any new ones that are necessary.

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# SPDX-FileCopyrightText: 2023 John Park
#
# SPDX-License-Identifier: MIT
# Ambient Machine inspired by Yuri Suzuki https://www.yurisuzuki.com/projects/the-ambient-machine
import os
import gc
import board
import busio
import audiocore
import audiobusio
import audiomixer
from digitalio import Pull
from adafruit_debouncer import Debouncer
from adafruit_mcp230xx.mcp23017 import MCP23017

i2c = busio.I2C(board.SCL, board.SDA)
mcp_a = MCP23017(i2c, address=0x20)  # default address
mcp_b = MCP23017(i2c, address=0x21)  # MCP23017 w/ address 0 jumper set

switches = []  # set up all the switch pins on two MCP23017 boards as debouncer switches
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_a.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_b.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))

wav_files = []

for filename in os.listdir('/samples/'):  # on board flash
    if filename.lower().endswith('.wav') and not filename.startswith('.'):
        wav_files.append("/samples/"+filename)
        print(filename)

wav_files.sort()  # put in alphabetical/numberical order
gc.collect()
# Metro M7 pins for the I2S amp:
lck_pin, bck_pin, dat_pin = board.D9, board.D10, board.D12

audio = audiobusio.I2SOut(bit_clock=bck_pin, word_select=lck_pin, data=dat_pin)
mixer = audiomixer.Mixer(voice_count=len(wav_files), sample_rate=22050, channel_count=1,
                         bits_per_sample=16, samples_signed=True, buffer_size=2048)
audio.play(mixer)

for i in range(10):  # start playing all wavs on loop w levels down
    wave = audiocore.WaveFile(wav_files[i], bytearray(1024))
    mixer.voice[i].play(wave, loop=True)
    mixer.voice[i].level = 0.0

LOW_VOL = 0.2
HIGH_VOL = 0.5

while True:
    for i in range(len(switches)):
        switches[i].update()
        switch_row = i // 5
        if switch_row == 0:  # first row plays five samples
            if switches[i].fell:
                if switches[i+5].value is False:  # check vol switch (pull-down, so 'False' is 'on')
                    mixer.voice[i].level = HIGH_VOL  # if up
                else:
                    mixer.voice[i].level = LOW_VOL  # if down
            if switches[i].rose:
                mixer.voice[i].level = 0.0

        if switch_row == 1:  # second row adjusts volume of first row
            if switches[i].fell:
                if switches[i-5].value is False: # raise volume if it is on
                    mixer.voice[i-5].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:  # lower volume if it is on
                    mixer.voice[i-5].level = LOW_VOL

        if switch_row == 2:  # third row plays five different samples
            if switches[i].fell:
                if switches[i+5].value is False:
                    mixer.voice[i-5].level = HIGH_VOL
                else:
                    mixer.voice[i-5].level = LOW_VOL
            if switches[i].rose:
                mixer.voice[i-5].level = 0.0

        if switch_row == 3:  # fourth row adjust volumes of third row
            if switches[i].fell:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = LOW_VOL

# SPDX-FileCopyrightText: 2023 John Park
#
# SPDX-License-Identifier: MIT
# Ambient Machine inspired by Yuri Suzuki https://www.yurisuzuki.com/projects/the-ambient-machine
import os
import gc
import board
import busio
import audiocore
import audiobusio
import audiomixer
from digitalio import Pull
from adafruit_debouncer import Debouncer
from adafruit_mcp230xx.mcp23017 import MCP23017

i2c = busio.I2C(board.SCL, board.SDA)
mcp_a = MCP23017(i2c, address=0x20)  # default address
mcp_b = MCP23017(i2c, address=0x21)  # MCP23017 w/ address 0 jumper set

switches = []  # set up all the switch pins on two MCP23017 boards as debouncer switches
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_a.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_b.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))

wav_files = []

for filename in os.listdir('/samples/'):  # on board flash
    if filename.lower().endswith('.wav') and not filename.startswith('.'):
        wav_files.append("/samples/"+filename)
        print(filename)

wav_files.sort()  # put in alphabetical/numberical order
gc.collect()
# Metro M7 pins for the I2S amp:
lck_pin, bck_pin, dat_pin = board.D9, board.D10, board.D12

audio = audiobusio.I2SOut(bit_clock=bck_pin, word_select=lck_pin, data=dat_pin)
mixer = audiomixer.Mixer(voice_count=len(wav_files), sample_rate=22050, channel_count=1,
                         bits_per_sample=16, samples_signed=True, buffer_size=2048)
audio.play(mixer)

for i in range(10):  # start playing all wavs on loop w levels down
    wave = audiocore.WaveFile(wav_files[i], bytearray(1024))
    mixer.voice[i].play(wave, loop=True)
    mixer.voice[i].level = 0.0

LOW_VOL = 0.2
HIGH_VOL = 0.5

while True:
    for i in range(len(switches)):
        switches[i].update()
        switch_row = i // 5
        if switch_row == 0:  # first row plays five samples
            if switches[i].fell:
                if switches[i+5].value is False:  # check vol switch (pull-down, so 'False' is 'on')
                    mixer.voice[i].level = HIGH_VOL  # if up
                else:
                    mixer.voice[i].level = LOW_VOL  # if down
            if switches[i].rose:
                mixer.voice[i].level = 0.0

        if switch_row == 1:  # second row adjusts volume of first row
            if switches[i].fell:
                if switches[i-5].value is False: # raise volume if it is on
                    mixer.voice[i-5].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:  # lower volume if it is on
                    mixer.voice[i-5].level = LOW_VOL

        if switch_row == 2:  # third row plays five different samples
            if switches[i].fell:
                if switches[i+5].value is False:
                    mixer.voice[i-5].level = HIGH_VOL
                else:
                    mixer.voice[i-5].level = LOW_VOL
            if switches[i].rose:
                mixer.voice[i-5].level = 0.0

        if switch_row == 3:  # fourth row adjust volumes of third row
            if switches[i].fell:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = LOW_VOL

How It Works

The code has two key functions:

Play ten wav file audio samples and use the audio mixer to mute/unmute them and adjust their volume levels.
Watch for the toggle switches to be flipped in order to adjust the audio mixer levels.

Import Libraries

First, you'll import libraries:

os: Operating system functions for file and directory operations
gc: garbage collection module for managing memory
board: Provide pin mappings for the board
busio: Handle communication on I2C bus
audiocore, audiobusio: handle audio playback
audiomixer: for mixing audio channels
digitalio: handle digital GPIO pins
adafruit_debouncer: handle switch debouncing/switch events
adafruit_mcp230xx.mcp23017: interact with the MCP23017 GPIO expander

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import os
import gc
import board
import busio
import audiocore
import audiobusio
import audiomixer
from digitalio import Pull
from adafruit_debouncer import Debouncer
from adafruit_mcp230xx.mcp23017 import MCP23017

import os
import gc
import board
import busio
import audiocore
import audiobusio
import audiomixer
from digitalio import Pull
from adafruit_debouncer import Debouncer
from adafruit_mcp230xx.mcp23017 import MCP23017

GPIO and I2C Setup

Next, you'll set up the I2C object and two instances of the MCP23017 GPIO expanders. You'll set up the two lists of pins used per board.

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i2c = busio.I2C(board.SCL, board.SDA)
mcp_a = MCP23017(i2c, address=0x20)  # default address
mcp_b = MCP23017(i2c, address=0x21)  # MCP23017 w/ address 0 jumper set

switches = []  # set up all the switch pins on two MCP23017 boards as debouncer switches
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_a.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_b.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))

i2c = busio.I2C(board.SCL, board.SDA)
mcp_a = MCP23017(i2c, address=0x20)  # default address
mcp_b = MCP23017(i2c, address=0x21)  # MCP23017 w/ address 0 jumper set

switches = []  # set up all the switch pins on two MCP23017 boards as debouncer switches
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_a.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))
for p in (8,9,10,11,12,4,3,2,1,0):
    pin = mcp_b.get_pin(p)
    pin.switch_to_input(pull=Pull.UP)
    switches.append(Debouncer(pin))

Audio File Handling

Here you'll create a list of wav files by getting a filtered list of files from on-board flash in the /samples directory. These are filtered to remove any possible operating system hidden . dot files and to only include files ending in .wav

The wav_files[] list is then re-sorted alphabetically.

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wav_files = []

for filename in os.listdir('/samples/'):  # on board flash
    if filename.lower().endswith('.wav') and not filename.startswith('.'):
        wav_files.append("/samples/"+filename)
        print(filename)

wav_files.sort()  # put in alphabetical/numerical order

wav_files = []

for filename in os.listdir('/samples/'):  # on board flash
    if filename.lower().endswith('.wav') and not filename.startswith('.'):
        wav_files.append("/samples/"+filename)
        print(filename)

wav_files.sort()  # put in alphabetical/numerical order

I2S Audio Playback Setup

The D9, D10, and D12 pins on the Metro M7 are assigned to lck_pin, bck_pin, and dat_pin, respectively, for the I2S digital audio amplifier board.

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lck_pin, bck_pin, dat_pin = board.D9, board.D10, board.D12

audio = audiobusio.I2SOut(bit_clock=bck_pin, word_select=lck_pin, data=dat_pin)

lck_pin, bck_pin, dat_pin = board.D9, board.D10, board.D12

audio = audiobusio.I2SOut(bit_clock=bck_pin, word_select=lck_pin, data=dat_pin)

Audio Mixer

You'll create an instance of audiomixer.Mixer with the correct number of voices (10), sample rate, channel count, bits per sample, and buffer size of 2048.

Then, all ten samples are started playing and looping, with their mixer levels initially set to 0 so no sound will play until you toggle sample switches.

Two volume constants are created to set the mixer levels low and high when the volume toggles are flipped, per sample.

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mixer = audiomixer.Mixer(voice_count=len(wav_files), sample_rate=22050, channel_count=1,
                         bits_per_sample=16, samples_signed=True, buffer_size=2048)
audio.play(mixer)

for i in range(10):  # start playing all wavs on loop w levels down
    wave = audiocore.WaveFile(wav_files[i], bytearray(1024))
    mixer.voice[i].play(wave, loop=True)
    mixer.voice[i].level = 0.0

LOW_VOL = 0.2
HIGH_VOL = 0.5

mixer = audiomixer.Mixer(voice_count=len(wav_files), sample_rate=22050, channel_count=1,
                         bits_per_sample=16, samples_signed=True, buffer_size=2048)
audio.play(mixer)

for i in range(10):  # start playing all wavs on loop w levels down
    wave = audiocore.WaveFile(wav_files[i], bytearray(1024))
    mixer.voice[i].play(wave, loop=True)
    mixer.voice[i].level = 0.0

LOW_VOL = 0.2
HIGH_VOL = 0.5

Main Loop

In the main loop, the switches are checked for events. If a switch is flipped the code checks to see which row it is in.

The first row plays samples 0-4. The second row sets the volume low or high for the sample switch directly above it. The third row plays samples 5-9, and the fourth row sets the volume of the samples above them.

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while True:
    for i in range(len(switches)):
        switches[i].update()
        switch_row = i // 5
        if switch_row == 0:  # first row plays five samples
            if switches[i].fell:
                if switches[i+5].value is False:  # check vol switch (pull-down, so 'False' is 'on')
                    mixer.voice[i].level = HIGH_VOL  # if up
                else:
                    mixer.voice[i].level = LOW_VOL  # if down
            if switches[i].rose:
                mixer.voice[i].level = 0.0

        if switch_row == 1:  # second row adjusts volume of first row
            if switches[i].fell:
                if switches[i-5].value is False: # raise volume if it is on
                    mixer.voice[i-5].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:  # lower volume if it is on
                    mixer.voice[i-5].level = LOW_VOL

        if switch_row == 2:  # third row plays five different samples
            if switches[i].fell:
                if switches[i+5].value is False:
                    mixer.voice[i-5].level = HIGH_VOL
                else:
                    mixer.voice[i-5].level = LOW_VOL
            if switches[i].rose:
                mixer.voice[i-5].level = 0.0

        if switch_row == 3:  # fourth row adjust volumes of third row
            if switches[i].fell:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = LOW_VOL

while True:
    for i in range(len(switches)):
        switches[i].update()
        switch_row = i // 5
        if switch_row == 0:  # first row plays five samples
            if switches[i].fell:
                if switches[i+5].value is False:  # check vol switch (pull-down, so 'False' is 'on')
                    mixer.voice[i].level = HIGH_VOL  # if up
                else:
                    mixer.voice[i].level = LOW_VOL  # if down
            if switches[i].rose:
                mixer.voice[i].level = 0.0

        if switch_row == 1:  # second row adjusts volume of first row
            if switches[i].fell:
                if switches[i-5].value is False: # raise volume if it is on
                    mixer.voice[i-5].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:  # lower volume if it is on
                    mixer.voice[i-5].level = LOW_VOL

        if switch_row == 2:  # third row plays five different samples
            if switches[i].fell:
                if switches[i+5].value is False:
                    mixer.voice[i-5].level = HIGH_VOL
                else:
                    mixer.voice[i-5].level = LOW_VOL
            if switches[i].rose:
                mixer.voice[i-5].level = 0.0

        if switch_row == 3:  # fourth row adjust volumes of third row
            if switches[i].fell:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = HIGH_VOL
            if switches[i].rose:
                if switches[i-5].value is False:
                    mixer.voice[i-10].level = LOW_VOL

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Fabrication and Assembly

Switch Holes

The bottom of the medium sized drawer will become the front panel of the Ambient Sound Machine.

Use the drilling template linked below to print out a guide for drilling the switches. Then, use a center punch and a 6mm drill bit (15/64" if using Imperial) to create all 20 holes for the toggle switches.

If you have access to a laser cutter this can be a very quick way to create the holes, as shown here.

ambient_box_v1.svg

You can mask and paint the front panel if you like, or cut a piece of colored card stock on a Cricut or laser cutter to fit.

Switch Ground

You can use the medium box as a jig for the switches while soldering the center position tabs to a common ground line.

Just put the switches into the panel backwards (from the outside-in), then use short lengths of black wire to solder the center lugs.

You can do a couple of rows at a time, then flip them and screw them in from the inside. This keeps things a bit more manageable than trying to do all 20 at once.

Switch Pins

You'll use the arcade quick connect cables to connect the GPIO expanders to the switches.

Clip the JST connector off and then strip and solder the wires as shown.

Then, plug the spade connector of each wire into its associated switch lower lug as shown.

Then, add the second two sets of switches with their common grounds soldered.

Do this for the first ten switches using the first expander board.

Second Set

In order to use both expander boards on the I2C bus, you'll give the second one a unique address. Heat a blob of solder across the pads for the Addr +1 jumper as shown.

Then, solder the wires and connect the lower lugs as before.

Grid Layout

Use M2.5 nylon screws and standoffs to fasten the boards to the mounting grid.

This is a suggested layout you can use, as well as a photo with the wiring connected as per the circuit diagram.

You can use zip ties to neaten the wiring before assembling into the case.

Speaker Enclosure

Drill or laser cut holes into the back of the small MOPPE drawer to act as a speaker grill and mounting surface for the speaker. You can use the .svg file provided below to get the hole spacing correct for the speaker's four mounting points.

You'll also use a Forstner bit or hole saw to make a hole for the panel-mount USB-C connector.

Push the USB-C panel connector into the hole from the outside and screw the retaining nut in from the inside.

Connect the inside of the USB-C panel mount to the USB-C of the Metro M7 via a suitable USB cable.

Optional Switch Locks

Rather than drill/cut 20 tiny holes to register the anti-twist tab of the switches, I decided to cut small plywood switch body locks, as shown here. They are glued in place to the inside of the front panel.

Feet

Cut four feet from 1/2" x 1-1/2" poplar or similar hardwood.

Glue and clamp them to the larger MOPPE drawer/front enclosure as shown.

Be careful with the retaining clips in the next step - they can be easily broken with too much force.

USB Cable

Assemble the DIY USB-C cable for the inside of the box by pulling the gray retention clip out a tiny amount, then inserting the ribbon cable end with the metal conductors visible from the top side of the board as shown. When fully inserted, press the retaining clip back in to secure the cable.

Repeat for both ends.