Introduction

CircuitPython driver library for Cirrus CS42L42 audio codec

Dependencies

This driver depends on:

• Adafruit CircuitPython

• Bus Device

• Register

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle or individual libraries can be installed using circup.

Installing from PyPI

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:

pip3 install adafruit-circuitpython-cs42l42

To install system-wide (this may be required in some cases):

sudo pip3 install adafruit-circuitpython-cs42l42

To install in a virtual environment in your current project:

mkdir project-name && cd project-name
python3 -m venv .venv
source .env/bin/activate
pip3 install adafruit-circuitpython-cs42l42

Installing to a Connected CircuitPython Device with Circup

Make sure that you have circup installed in your Python environment. Install it with the following command if necessary:

pip3 install circup

With circup installed and your CircuitPython device connected use the following command to install:

circup install adafruit_cs42l42

Or the following command to update an existing version:

circup update

Usage Example

import time

import audiobusio
import board
import digitalio
import synthio

import adafruit_cs42l42

RATE = 48000
# CircuitPython sends 32 bit clocks per stereo frame, so the bit clock the
# codec sees -- and the number configure_clocks wants -- is 32 x the rate.
SCLK = RATE * 32

# Mixer attenuation, dB. 0 is full scale; the quickstart starts at -20.
DAC_VOLUME = -20

# MIDI note numbers for a C-major scale, C4 up to C5.
SCALE = (60, 62, 64, 65, 67, 69, 71, 72)

# CAUTION: this drives a headphone amplifier. Take the headphones off before
# the first run and confirm the level is comfortable before wearing them.

oscillator = digitalio.DigitalInOut(board.OSC_EN)
oscillator.direction = digitalio.Direction.OUTPUT
oscillator.value = True

reset = digitalio.DigitalInOut(board.CS42_RESET)
reset.direction = digitalio.Direction.OUTPUT
reset.value = False  # active low: hold the codec in reset while clocks start

i2s = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DOUT)

synth = synthio.Synthesizer(sample_rate=RATE)

# Playing the synth starts the bit clock, which the codec needs before it can
# switch off its own oscillator. The synth streams silence until a note is
# pressed, so nothing is audible yet.
i2s.play(synth)

# Constructing the driver releases the reset
codec = adafruit_cs42l42.CS42L42(board.I2C(), reset_pin=reset)
codec.configure_clocks(sclk_hz=SCLK)
codec.configure_asp(sample_rate=RATE, bit_depth=16)

codec.headphone_output = True
codec.dac_volume = DAC_VOLUME

print("playing scale")
try:
    while True:
        for note in SCALE:
            synth.press(note)
            time.sleep(0.25)
            synth.release(note)
            time.sleep(0.125)
finally:
    codec.muted = True
    i2s.stop()
    i2s.deinit()
    reset.value = False
    reset.deinit()
    oscillator.value = False
    oscillator.deinit()

Documentation

API documentation for this library can be found on Read the Docs.

For information on building library documentation, please check out this guide.

Contributing

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.