Once your CPB is set up with CircuitPython, you'll also need to add some libraries. Follow this page for info on how to download and add libraries to your CPB.
From the library bundle you downloaded in that guide page, transfer the following libraries onto the CPB board's /lib directory:
- adafruit_ble
- adafruit_hid
- neopixel
Text Editor
Adafruit recommends using the Mu editor for using your CircuitPython code with the Circuit Playground Bluefruit boards. You can get more info in this guide.
Alternatively, you can use any text editor that saves files.
# SPDX-FileCopyrightText: 2020 John Park for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""
A CircuitPython 'multimedia' dial demo
Uses a Circuit Playground Bluefruit + Rotary Encoder -> BLE out
Knob controls volume, push encoder for mute, CPB button A for Play/Pause
Once paired, bonding will auto re-connect devices
"""
import time
import digitalio
import board
import rotaryio
import neopixel
from adafruit_hid.consumer_control import ConsumerControl
from adafruit_hid.consumer_control_code import ConsumerControlCode
import adafruit_ble
from adafruit_ble.advertising.standard import ProvideServicesAdvertisement
from adafruit_ble.services.standard.hid import HIDService
from adafruit_ble.services.standard.device_info import DeviceInfoService
ble = adafruit_ble.BLERadio()
ble.name = "Bluefruit-Volume-Control"
# Using default HID Descriptor.
hid = HIDService()
device_info = DeviceInfoService(software_revision=adafruit_ble.__version__,
manufacturer="Adafruit Industries")
advertisement = ProvideServicesAdvertisement(hid)
cc = ConsumerControl(hid.devices)
FILL_COLOR = (0, 32, 32)
UNMUTED_COLOR = (0, 128, 128)
MUTED_COLOR = (128, 0, 0)
DISCONNECTED_COLOR = (40, 40, 0)
# NeoPixel LED ring
# Ring code will auto-adjust if not 16 so change to any value!
ring = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=0.05, auto_write = False)
ring.fill(DISCONNECTED_COLOR)
ring.show()
dot_location = 0 # what dot is currently lit
# CPB button for Play/Pause
button_A = digitalio.DigitalInOut(board.BUTTON_A)
button_A.switch_to_input(pull=digitalio.Pull.DOWN)
button_a_pressed = False # for debounce state
# Encoder button is a digital input with pullup on A1
# so button.value == False means pressed.
button = digitalio.DigitalInOut(board.A1)
button.pull = digitalio.Pull.UP
encoder = rotaryio.IncrementalEncoder(board.A2, board.A3)
last_pos = encoder.position
muted = False
command = None
# Disconnect if already connected, so that we pair properly.
if ble.connected:
for connection in ble.connections:
connection.disconnect()
def draw():
if not muted:
ring.fill(FILL_COLOR)
ring[dot_location] = UNMUTED_COLOR
else:
ring.fill(MUTED_COLOR)
ring.show()
advertising = False
connection_made = False
print("let's go!")
while True:
if not ble.connected:
ring.fill(DISCONNECTED_COLOR)
ring.show()
connection_made = False
if not advertising:
ble.start_advertising(advertisement)
advertising = True
continue
else:
if connection_made:
pass
else:
ring.fill(FILL_COLOR)
ring.show()
connection_made = True
advertising = False
pos = encoder.position
delta = pos - last_pos
last_pos = pos
direction = 0
if delta > 0:
command = ConsumerControlCode.VOLUME_INCREMENT
direction = -1
elif delta < 0:
command = ConsumerControlCode.VOLUME_DECREMENT
direction = 1
if direction:
muted = False
for _ in range(abs(delta)):
cc.send(command)
# spin neopixel LED around in the correct direction!
dot_location = (dot_location + direction) % len(ring)
draw()
if not button.value:
if not muted:
print("Muting")
cc.send(ConsumerControlCode.MUTE)
muted = True
else:
print("Unmuting")
cc.send(ConsumerControlCode.MUTE)
muted = False
draw()
while not button.value: # debounce
time.sleep(0.1)
if button_A.value and not button_a_pressed: # button is pushed
cc.send(ConsumerControlCode.PLAY_PAUSE)
print("Play/Pause")
button_a_pressed = True # state for debouncing
time.sleep(0.05)
if not button_A.value and button_a_pressed:
button_a_pressed = False
time.sleep(0.05)
Code Explainer
Here are the main things our code does:
- Loading libraries for time, digitalio, rotaryio, neopixel, hid consumer control (media buttons), and adafruit BLE
- Advertising that it is a BLE device that can be connected to
- setting up the button A on the CPB and rotary encoder for reading
- lighting up the NeoPixels yellow until there's a connection made
- lighting the NeoPixels cyan, with one brighter NeoPixel to represent relative volume position
- lighting the NeoPixels red when the push encoder is pressed to mute the volume
Pairing and Bonding
One of the more advanced features used in this project is BLE bonding.
When the Central (your mobile device or computer) connects with the Peripheral (the CPB), you will be asked on the mobile device or computer if you want to Pair with the CPB. Once you agree to pair, a bonding process takes place.
During bonding, encrypted keys are exchanged between the two devices and saved away for use the next time the devices attempt to connect. Since they are bonded, the two will connect automatically without asking for a pairing confirmation. This is really convenient, because it means you can walk one of the devices out of range, thus dropping the connection, and when you return, the two devices will re-connect as if nothing ever happened!
Now, let's build the volume knob!
Beyond the Code
Want to try some variations on the code? A user pointed out:
Maybe this should use the Circuit Playground to simplify accessing the button: https://learn.adafruit.com/circuitpython-made-easy-on-circuit-playground-express/circuit-playground-express-library
Maybe this could use the Debouncing library: https://learn.adafruit.com/debouncer-library-python-circuitpython-buttons-sensors/overview
Page last edited January 22, 2025
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