Simple USB Audio Controller in CircuitPython

I have plans to build a multi-function macro keyboard using the new Raspberry Pi Pico RP2040 microcontroller and CircuitPython. While I was waiting for it to arrive, I wanted to figure out how I was going to handle controlling the audio on my computer with a rotary encoder, so I built this simple project using CircuitPython and the QT Py M0 microcontroller. Unfortunately, rotaryio has not been implemented for the RP2040 yet in CircuitPython, so there is a bonus code snippet at the end using a potentiometer to accomplish the same thing for the Pi Pico.


3D Printed SnapFit Enclosure

I modified the enclosure I made for my Zoom/Teams mute button and computer lock button projects.

CAD files for the QT Py rotary encoder enclosure.

Wiring Diagram

wiring diagram for the QT Py and rotary encoder


The file is also available on GitHub.

import board
import time
import usb_hid
from digitalio import DigitalInOut, Direction, Pull
from rotaryio import IncrementalEncoder
from adafruit_hid.consumer_control_code import ConsumerControlCode
from adafruit_hid.consumer_control import ConsumerControl

# Change the below code for different outcomes

# Button Press will mute
BUTTON_CODE = ConsumerControlCode.MUTE

# Rotating the encoder clockwise will increase the volume

# Rotating the encoder clockwise will decrease teh volume

# initialize as hid device
consumer_control = ConsumerControl(usb_hid.devices)

# initialize encoder on pins D0 and D1 (QT Py M0)
encoder = IncrementalEncoder(board.D0, board.D1)

# initialize encoder click on pin D2 (QT Py M0)
button = DigitalInOut(board.D2)
button.direction = Direction.INPUT
button.pull = Pull.UP

button_in = False
last_position = None

while True:

    if not button.value and not button_in:
        print("button press")
        button_in = True

    elif button.value and button_in:
        button_in = False

    elif button.value and not button_in:
        position = encoder.position

        if last_position is not None and position != last_position:

            if position > last_position:
                print("rotate clockwise")

            elif position < last_position:
                print("rotate counter-clockwise")

        last_position = position

Bonus: Pi Pico 2040 Potentiometer

Raspberry Pi Pico 2040 with potentiometer
import board
import time
import usb_hid
from analogio import AnalogIn
from adafruit_hid.consumer_control_code import ConsumerControlCode
from adafruit_hid.consumer_control import ConsumerControl

READ_TIME = .001

def map_function(x, in_min, in_max, out_min, out_max):

  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;

# initialize hid device as consumer control 
consumer_control = ConsumerControl(usb_hid.devices)

# initialize potentiometer (pot) wiper connected to GP26_A0
potentiometer = AnalogIn(board.GP26)  

# intialize the read time
last_read = time.monotonic()

# decrease volume all the way down 
# this allows the volume to be set by the current value of the pot
for i in range(32):

# initalize volume and last position
current_volume = 0
last_position = 0

while True:

    if time.monotonic() - last_read > READ_TIME:
        position = int(map_function(potentiometer.value , 200, 65520, 0, 32))

        if abs(position - last_position) > 1:

            last_position = position

            if current_volume < position:
                while current_volume < position:
                    # Raise volume.
                    print("Volume Up!")
                    current_volume+= 2
            elif current_volume > position:
                while current_volume > position:
                    # Lower volume.
                    print("Volume Down!")
                    current_volume -= 2

        # update last_read to current time
        last_read = time.monotonic()

    # handle time.monotonic() overflow
    if time.monotonic() < last_read:
        last_read = time.monotonic()

COVID-19 Vaccination Displays using CircuitPython

I built a scrolling COVID-19 Vaccination display for both the Adafruit MatrixPortal M4 and the Adafruit MagTag using CircuitPython, and data from Our World in Data and the CDC.


Our World in Data has aggregated massive data sets related to COVID-19. The vaccination data subset is available in a GitHub repository in csv format. The Matrix Portal is using data from this repository.

Our complete COVID-19 dataset is a collection of the COVID-19 data maintained by Our World in Data. It is updated daily and includes data on confirmed cases, deaths, hospitalizations, and testing, as well as other variables of potential interest.

The Center for Disease offers a much more limited data set that includes information for each state and the country as a whole in JSON format. The MagTag has been updated to use the data directly from the CDC




COVID-19 RGB Matrix with CircuitPython

I built a scrolling COVID-19 Tracking RGB using Adafruit’s new MatrixPortal M4, CircuitPython, and the API from The COVID Tracking Project at The Atlantic


The COVID Tracking Project at The Atlantic has a simple API with a robust data set that is published under a Creative Commons CC BY 4.0 license.

We collect, cross-check, and publish COVID-19 data from 56 US states and territories in three main areas: testing, patient outcomes, and, via The COVID Racial Data Tracker, racial and ethnic demographic information. We compile these numbers to provide the most complete picture we can assemble of the US COVID-19 testing effort and the outbreak’s effects on the people and communities it strikes.

The Covid Tracking Project at The Atlantic

CircuitPython Code

The below code is based on the: Example: Simple two-line text scroller

Custom 3 Button CircuitPython Keyboard


I have been doing audio editing for side project at work. These are long form audio recordings of an hour or more. I am using Adobe Audition to do my editing. After doing several of these, I noticed that I use two main functions frequently.

  1. ‘Silence’
  2. ‘Ripple Cut’ -> ‘ Time Selection in All Tracks’

The ripple cut function either used a significant number of mouse clicks or keyboard shortcuts that required both hands. There are probably a few different potential solutions to this problem. I could have changed the keyboard shortcuts to something else, but I wanted this to be easy to use and I wanted to be able to use it on any computer.

I recently completed a project that used the PyPortal to send keyboard commands to my computer to open applications. Also, I had purchased an Adafruit Trinket M0 recently and wanted to build a project with it, so I decided to build a mini keyboard that only had a few buttons.




I modified the the Trinket IO Demo code. I removed some stuff that I didn’t need and had to make sure that holding down a key was treated the exact same as a single key press.


The first button is used for play/pause, the second button is used to do the ripple cut and the third button is used to do the silencing. This tool has made it so much easier to edit audio content.

Update – 18 April 2020

If you liked this, check out this much more detailed project by Glen Akins (@bikerglen)