Code the Player
Once you've finished setting up your Feather Prop Maker with CircuitPython, you can access the code, MP3 files and necessary libraries by downloading the Project Bundle.
To do this, click on the Download Project Bundle button in the window below. It will download to your computer as a zipped folder.
# SPDX-FileCopyrightText: 2026 Liz Clark for Adafruit Industries
# SPDX-License-Identifier: MIT
"""Duplo Color Boombox"""
import board
import sdcardio
import storage
import audiobusio
import audiomixer
import audiomp3
from digitalio import DigitalInOut, Direction
from adafruit_as7341 import AS7341
from adafruit_seesaw import digitalio, neopixel, rotaryio, seesaw
#Power Setup
external_power = DigitalInOut(board.EXTERNAL_POWER)
external_power.direction = Direction.OUTPUT
external_power.value = True
#SD Card setup
spi = board.SPI()
cs = board.D10
sdcard = sdcardio.SDCard(spi, cs)
vfs = storage.VfsFat(sdcard)
storage.mount(vfs, "/sd")
#Audio
try:
mp3 = audiomp3.MP3Decoder(open("/sd/blue.mp3", "rb"))
except OSError as error:
print(f"{error} - did you put the mp3 files on the micro SD card?")
i2s = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(voice_count=1, sample_rate=mp3.sample_rate, channel_count=1,
bits_per_sample=mp3.bits_per_sample)
i2s.play(mixer)
mixer.voice[0].level = 0.5
#Color Sensor
i2c = board.STEMMA_I2C()
sensor = AS7341(i2c)
sensor.led_current = 4 # increments in units of 4
sensor.led = False
brick_dictionary = [
{'song': "/sd/blue.mp3", 'value': (1619, 13852, 19215, 18562, 12912, 8818, 9512, 5440),
'color': ((0, 255, 255))},
{'song': "/sd/orange.mp3", 'value': (2517, 3983, 5661, 6864, 16857, 39049, 55151, 35696),
'color': ((255, 60, 0))},
{'song': "/sd/coral.mp3", 'value': (3004, 6712, 7499, 7160, 13858, 46007, 65535, 39278),
'color': ((250, 50, 50))},
{'song': "/sd/purple.mp3", 'value': (2562, 20704, 19222, 15806, 16624, 18399, 27316, 22525),
'color': ((125, 0, 255))},
{'song': "/sd/red.mp3", 'value': (1453, 2629, 4050, 4656, 5527, 13403, 31096, 21368),
'color': ((255, 0, 0))},
{'song': "/sd/yellow.mp3", 'value': (3051, 4446, 8633, 17412, 37450, 48224, 56249, 34726),
'color': ((255, 150, 0))},
{'song': "/sd/butter.mp3", 'value': (4102, 8631, 13692, 29000, 58147, 63230, 65535, 43143),
'color': ((255, 255, 0))},
{'song': "/sd/green.mp3", 'value': (1383, 2767, 5850, 12964, 22118, 16304, 12669, 7008),
'color': ((120, 255, 0))},
{'song': "/sd/lime.mp3", 'value': (3017, 8109, 17948, 36761, 48754, 38009, 31671, 19457),
'color': ((150, 255, 0))},
{'song': "/sd/lightblue.mp3", 'value': (4188, 29507, 42326, 53214, 54067, 37512, 34129, 23544),
'color':((100, 250, 255))},
{'song': "/sd/white.mp3", 'value': (5246, 27506, 33883, 44702, 62766, 64254, 65535, 48334),
'color':((255, 255, 255))},
]
def find_closest_brick(reading, dictionary, max_distance=50000):
"""
Find the brick with the closest matching sensor values.
Args:
new_reading: Tuple of 8 sensor values
brick_dictionary: List of brick dictionaries
max_distance: Maximum distance to consider a valid match
Returns:
Tuple of (matched_brick, distance) or (None, distance) if no good match
"""
best_match = None
best_distance = float('inf')
for brick in dictionary:
# Calculate total distance (sum of absolute differences)
distance = sum(abs(v1 - v2) for v1, v2 in zip(reading, brick['value']))
if distance < best_distance:
best_distance = distance
best_match = brick
# Only return a match if it's close enough
if best_distance > max_distance:
return None
return best_match
#Rotary STEMMA I2C
seesaw = seesaw.Seesaw(i2c, 0x36)
encoder = rotaryio.IncrementalEncoder(seesaw)
seesaw.pin_mode(24, seesaw.INPUT_PULLUP)
switch = digitalio.DigitalIO(seesaw, 24)
switch_state = False
pixel = neopixel.NeoPixel(seesaw, 6, 1)
pixel.brightness = 1
pixel.fill((0, 0, 0))
last_position = -1
volume = 0.5 # volume
play = False
play_state = False
mp3 = audiomp3.MP3Decoder(open("/sd/boot.mp3", "rb"))
mixer.voice[0].play(mp3, loop=False)
while True:
# make clockwise rotation positive
position = -encoder.position
if position != last_position:
if position > last_position:
#decrease volume
volume = volume - 0.05
volume = max(volume, 0)
else:
#increase volume
volume = volume + 0.05
volume = min(volume, 1)
# set the audio volume
mixer.voice[0].level = volume
print(volume)
last_position = position
if not switch.value and not switch_state:
print("Button pressed")
switch_state = True
if not play:
sensor.led = True
sensor_color = sensor.all_channels
matched_brick = find_closest_brick(sensor_color, brick_dictionary)
print(sensor_color)
if matched_brick is not None:
print(matched_brick['song'])
mp3 = audiomp3.MP3Decoder(open(matched_brick['song'], "rb"))
pixel.fill(matched_brick['color'])
play = True
mixer.voice[0].play(mp3, loop=False)
play_state = True
else:
print("insert brick")
mp3 = audiomp3.MP3Decoder(open("/sd/uhoh.mp3", "rb"))
mixer.voice[0].play(mp3, loop=False)
else:
if play_state:
i2s.pause()
play_state = False
else:
i2s.resume()
play_state = True
if switch.value and switch_state:
sensor.led = False
switch_state = False
print("Button released")
if not mixer.playing:
play_state = False
play = False
pixel.fill((0,0,0))
Upload the Code and Libraries to the Feather Prop Maker
After downloading the Project Bundle, plug your Feather Prop Maker into the computer's USB port with a known good USB data+power cable. You should see a new flash drive appear in the computer's File Explorer or Finder (depending on your operating system) called CIRCUITPY. Unzip the folder and copy the following items to the Feather Prop Maker's CIRCUITPY drive.
- lib folder
- code.py
Your Feather Prop Maker CIRCUITPY drive should look like this after copying the lib folder and code.py file:
Add MP3s to microSD Card
Mount the microSD card (FAT formatted) to your computer and add the MP3 audio files from the /mp3_files_for_sd_card folder from the Project Bundle to the root directly of the storage device. After adding the MP3s to the microSD card, remove it from the computer and pop it into the microSD card slot on the Adalogger FeatherWing.
How the CircuitPython Code Works
At the top of the code, the EXTERNAL_POWER pin is enabled to power up the peripherals on the Feather.
#Power Setup external_power = DigitalInOut(board.EXTERNAL_POWER) external_power.direction = Direction.OUTPUT external_power.value = True
SD Card
The SD card is set up using sdcardio and is mounted to the /sd mount point. The mount point is set to readonly within CircuitPython so that it can be read/write on your OS when the CircuitPython drive is mounted. This means that you can drag and drop audio files to the SD card over USB.
#SD Card setup spi = board.SPI() cs = board.D10 sdcard = sdcardio.SDCard(spi, cs) vfs = storage.VfsFat(sdcard) storage.mount(vfs, "/sd")
Audio
Next is the audio setup. For this project, MP3 audio files are used. The MP3 decoder and built-in I2S output are passed to a Mixer object. This lets you control the volume via software.
#Audio
mp3 = audiomp3.MP3Decoder(open("/sd/blue.mp3", "rb"))
i2s = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(voice_count=1, sample_rate=mp3.sample_rate, channel_count=1,
bits_per_sample=mp3.bits_per_sample)
i2s.play(mixer)
mixer.voice[0].level = 0.5
#Color Sensor i2c = board.STEMMA_I2C() sensor = AS7341(i2c) sensor.led_current = 4 # increments in units of 4 sensor.led = False
A dictionary is used to hold each Duplo brick's MP3 audio file name, color reading and NeoPixel color. You can add or edit entries to the dictionary for additional bricks or to change up the associated MP3.
brick_dictionary = [
{'song': "/sd/blue.mp3", 'value': (1619, 13852, 19215, 18562, 12912, 8818, 9512, 5440),
'color': ((0, 255, 255))},
{'song': "/sd/orange.mp3", 'value': (2517, 3983, 5661, 6864, 16857, 39049, 55151, 35696),
'color': ((255, 60, 0))},
{'song': "/sd/coral.mp3", 'value': (3004, 6712, 7499, 7160, 13858, 46007, 65535, 39278),
'color': ((250, 50, 50))},
{'song': "/sd/purple.mp3", 'value': (2562, 20704, 19222, 15806, 16624, 18399, 27316, 22525),
'color': ((125, 0, 255))},
{'song': "/sd/red.mp3", 'value': (1453, 2629, 4050, 4656, 5527, 13403, 31096, 21368),
'color': ((255, 0, 0))},
{'song': "/sd/yellow.mp3", 'value': (3051, 4446, 8633, 17412, 37450, 48224, 56249, 34726),
'color': ((255, 150, 0))},
{'song': "/sd/butter.mp3", 'value': (4102, 8631, 13692, 29000, 58147, 63230, 65535, 43143),
'color': ((255, 255, 0))},
{'song': "/sd/green.mp3", 'value': (1383, 2767, 5850, 12964, 22118, 16304, 12669, 7008),
'color': ((120, 255, 0))},
{'song': "/sd/lime.mp3", 'value': (3017, 8109, 17948, 36761, 48754, 38009, 31671, 19457),
'color': ((150, 255, 0))},
{'song': "/sd/lightblue.mp3", 'value': (4188, 29507, 42326, 53214, 54067, 37512, 34129, 23544),
'color':((100, 250, 255))},
{'song': "/sd/white.mp3", 'value': (5246, 27506, 33883, 44702, 62766, 64254, 65535, 48334),
'color':((255, 255, 255))},
]
A function called find_closest_brick() is used to determine if the Duplo brick that is held up to the color sensor matches one of the defined colors in the dictionary. Since the color readings are analog and can vary depending on external light, the function returns the closest match to the current reading. If there isn't a close enough match, it returns None. You can change the sensitivity by adjusting the max_distance value.
def find_closest_brick(reading, dictionary, max_distance=50000):
"""
Find the brick with the closest matching sensor values.
Args:
new_reading: Tuple of 8 sensor values
brick_dictionary: List of brick dictionaries
max_distance: Maximum distance to consider a valid match
Returns:
Tuple of (matched_brick, distance) or (None, distance) if no good match
"""
best_match = None
best_distance = float('inf')
for brick in dictionary:
# Calculate total distance (sum of absolute differences)
distance = sum(abs(v1 - v2) for v1, v2 in zip(reading, brick['value']))
if distance < best_distance:
best_distance = distance
best_match = brick
# Only return a match if it's close enough
if best_distance > max_distance:
return None
return best_match
Rotary Encoder
The seesaw rotary encoder is next. The built-in switch is used in the code, along with the NeoPixel.
#Rotary STEMMA I2C seesaw = seesaw.Seesaw(i2c, 0x36) encoder = rotaryio.IncrementalEncoder(seesaw) seesaw.pin_mode(24, seesaw.INPUT_PULLUP) switch = digitalio.DigitalIO(seesaw, 24) switch_state = False pixel = neopixel.NeoPixel(seesaw, 6, 1) pixel.brightness = 1 pixel.fill((0, 0, 0))
States and Variables
There are a few variables and states that are used in the loop:
-
last_position- tracks the last position of the rotary encoder -
volume- volume for the audio output through the Mixer object -
play- state to track if a song has started playing -
play_state- state to track if a song is actually playing or is paused\
Right before the loop, the boot.mp3 file is played through the speaker.
last_position = -1
volume = 0.5 # volume
play = False
play_state = False
mp3 = audiomp3.MP3Decoder(open("/sd/boot.mp3", "rb"))
mixer.voice[0].play(mp3, loop=False)
The Loop
In the loop, the rotary encoder position is monitored. If the position increases, the volume increases. If it decreases, the volume decreases.
while True:
# make clockwise rotation positive
position = -encoder.position
if position != last_position:
if position > last_position:
#decrease volume
volume = volume - 0.05
volume = max(volume, 0)
else:
#increase volume
volume = volume + 0.05
volume = min(volume, 1)
# set the audio volume
mixer.voice[0].level = volume
print(volume)
last_position = position
Pressing the rotary encoder button initiates the color sensor to get a reading. The sensor LED turns on, gets a reading on all channels and passes the reading to the find_closest_brick() function. If the code finds a match, then it starts playing the associated MP3 file and lights up the NeoPixel with the associated color.
If a song is currently playing and the button is pressed, then the button toggles play/pause.
When the mixer is no longer playing the song, it resets play and play_state to False and turns off the NeoPixel.
if not switch.value and not switch_state:
print("Button pressed")
switch_state = True
if not play:
sensor.led = True
sensor_color = sensor.all_channels
matched_brick = find_closest_brick(sensor_color, brick_dictionary)
print(sensor_color)
if matched_brick is not None:
print(matched_brick['song'])
mp3 = audiomp3.MP3Decoder(open(matched_brick['song'], "rb"))
pixel.fill(matched_brick['color'])
play = True
mixer.voice[0].play(mp3, loop=False)
play_state = True
else:
print("insert brick")
mp3 = audiomp3.MP3Decoder(open("/sd/uhoh.mp3", "rb"))
mixer.voice[0].play(mp3, loop=False)
else:
if play_state:
i2s.pause()
play_state = False
else:
i2s.resume()
play_state = True
if switch.value and switch_state:
sensor.led = False
switch_state = False
print("Button released")
if not mixer.playing:
play_state = False
play = False
pixel.fill((0,0,0))
Page last edited January 28, 2026
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