Raspberry Pi

1. Flash Raspberry Pi OS

Download Raspberry Pi Imager and flash Raspberry Pi OS Lite (32-bit) to a microSD card. Enable SSH and set hostname, user, and Wi-Fi credentials in the imager settings before writing.

In the imager, click the settings gear icon (or press Ctrl+Shift+X) before writing.

General Set hostname (e.g.) raspberrypi Username and Password.

Services Enable SSH and select "Use password authentication".

General Enter your Wi-Fi SSID and password, and set the locale and timezone. Click Save, then Write.

Boot the Pi, then connect via SSH:

ssh pi@raspberrypi.local

Update the system:

sudo apt update && sudo apt full-upgrade -y
sudo reboot

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2. Install Pure Data

sudo apt install puredata -y

Verify the installation:

pd --version

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3. Install Audio Injector drivers

The Audio Injector Zero / Stereo uses a custom ALSA driver. Add the overlay to the boot config:

sudo nano /boot/config.txt

Add at the bottom:

dtoverlay=audioinjector-wm8731-audio

Disable the onboard audio to avoid conflicts:

# Find and comment out or remove:
dtparam=audio=on

Save and reboot:

sudo reboot

Confirm the card is detected:

aplay -l

You should see audioinjector-pi-soundcard listed. Set it as the default ALSA device:

sudo nano /etc/asound.conf

Add:

pcm.!default {
    type hw
    card 0
}
ctl.!default {
    type hw
    card 0
}

Test playback:

speaker-test -t sine -f 440 -c 2

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4. Configure Pure Data for headless audio

Test that Pure Data opens with the Audio Injector:

pd -nogui -alsa -audiodev 0 -r 44100 -audiobuf 50 your-patch.pd

Adjust -audiodev index to match the card number from aplay -l if needed.

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5. Autorun a PD patch on boot

Place your patch in a fixed location:

mkdir -p /home/pi/pd-patches
cp your-patch.pd /home/pi/pd-patches/main.pd

Create a systemd service:

sudo nano /etc/systemd/system/pd-autorun.service

Paste:

[Unit]
Description=Pure Data autorun
After=sound.target

[Service]
User=pi
ExecStart=/usr/bin/pd -nogui -alsa -audiodev 0 -r 44100 -audiobuf 50 /home/pi/pd-patches/main.pd
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Enable and start the service:

sudo systemctl daemon-reload
sudo systemctl enable pd-autorun.service
sudo systemctl start pd-autorun.service

Check the status:

sudo systemctl status pd-autorun.service

View live logs:

journalctl -u pd-autorun.service -f

The patch will now launch automatically on every boot. To stop it temporarily:

sudo systemctl stop pd-autorun.service

To disable autorun:

sudo systemctl disable pd-autorun.service