PI9696 - Raspberry Pi Audio Recorder

A professional audio recording interface for Raspberry Pi 5 designed to fit in a 1U rack unit.

Hardware Requirements

• Raspberry Pi 5
• 2.7" 256×64 OLED Display (SSD1322) via SPI
• Rotary Encoder (EC11) with push button
• 3x Momentary buttons (Record, Stop, Play)
• Audio interface (USB or HAT)

Wiring

OLED Display (SPI)

• VCC → 3.3V
• GND → GND
• D0/SCLK → GPIO11 (SPI0 SCLK)
• D1/MOSI → GPIO10 (SPI0 MOSI)
• CS → GPIO8 (SPI0 CE0)
• DC → GPIO25
• RES → GPIO24

Rotary Encoder

• A → GPIO17
• B → GPIO27
• SW (Push) → GPIO22
• VCC → 3.3V
• GND → GND

Buttons

• Record → GPIO5
• Stop → GPIO6
• Play → GPIO13
• All buttons use internal pull-ups

Software Setup

Prerequisites

1. Enable SPI interface:

sudo raspi-config
# Navigate to Interface Options > SPI > Enable

2. Install Go (if not already installed):

wget https://go.dev/dl/go1.21.0.linux-arm64.tar.gz
sudo tar -C /usr/local -xzf go1.21.0.linux-arm64.tar.gz
echo 'export PATH=$PATH:/usr/local/go/bin' >> ~/.bashrc
source ~/.bashrc

3. Install Inferno Audio over IP server and dependencies:

sudo apt update
sudo apt install alsa-utils ffmpeg
# Run the setup script to configure Inferno server integration
./setup.sh

4. Create recording directories:

sudo mkdir -p /rec/raw
sudo chown -R pi:pi /rec

Building

1. Clone or copy the project files to your Pi
2. Build the application:

cd PI9696
go mod tidy
go build -o pi9696 .

Running

sudo ./pi9696

Note: Requires sudo for GPIO access.

Auto-start on boot

Create a systemd service:

sudo tee /etc/systemd/system/pi9696.service > /dev/null <<EOF
[Unit]
Description=PI9696 Audio Recorder
After=network.target

[Service]
Type=simple
User=root
WorkingDirectory=/home/pi/PI9696
ExecStart=/home/pi/PI9696/pi9696
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl enable pi9696.service
sudo systemctl start pi9696.service

Usage

Controls

• Record Button: Start recording (only when idle, requires Inferno server running)
• Stop Button: Stop current recording (leaves Inferno server running)
• Play Button: Reserved for future playback functionality
• Rotary Encoder: Navigate menus, toggle between elapsed/remaining time
• Encoder Push: Enter menus, confirm selections
• Encoder Hold (3s): Cancel copy operations

Display Layout

• Left Panel: Status information (time, storage, settings)
• Right Panel: Menu system (when active)
• Full Width: Status display when not in menu

Menu System

1. Sample Rate: 44.1kHz, 48kHz, 96kHz, 192kHz (auto-restarts Inferno server)
2. Channel Count: Adjust from 1 to 128 channels (auto-restarts Inferno server)
3. Copy Files: Transfer recordings to USB drive
4. System Options: System management submenu
5. Network Info: Display network connection details
6. Restart Inferno: Manually restart Inferno Audio over IP server
7. Exit: Return to main display

System Options Submenu

1. Delete All: Remove all recordings with confirmation
2. Format USB: Format connected USB drive (FAT32)
3. Shutdown: Power off system with confirmation
4. Restart: Reboot system with confirmation
5. Exit: Return to settings menu

File Copy Options

• [All]: Select all recordings
• [NONE]: Deselect all recordings
• Individual file selection with checkboxes
• Start Copy: Begin transfer operation

Recording Format

• Output Format: WAV (PCM 24-bit)
• Internal Pipeline: 32-bit signed little-endian via FIFO
• Sample Rates: 44.1kHz, 48kHz, 96kHz, 192kHz
• Channel Support: 1-128 channels
• File Naming: recording_YYYYMMDD_HHMMSS_chN_NNkHz.wav
• Raw FIFO: /rec/raw/inferno_YYYYMMDD_HHMMSS_chN_NNkHz.raw (temporary)

Inferno Server Operation

• Startup: Automatic when eth0 networking becomes available
• Persistence: Runs continuously between recordings
• Auto-Restart: When sample rate or channel count changes
• Status Display: Flame icon (🔥) in status bar when running
• Manual Control: "Restart Inferno" option in settings menu

Troubleshooting

Display Issues

• Check SPI is enabled: lsmod | grep spi
• Verify wiring connections
• Check permissions: ls -l /dev/spidev*

Audio Issues

• List audio devices: arecord -l
• Test recording: arecord -D hw:0 -f S32_LE -r 48000 -c 2 test.wav
• Check ALSA configuration: cat /proc/asound/cards
• Check Inferno server: Look for flame icon in status bar
• Test Inferno manually: cd inferno && INFERNO_SAMPLE_RATE=48000 cargo run -- -c 2 -o /tmp/test.fifo

Network Issues

• Check eth0 interface: ip addr show eth0
• Monitor network status: Watch network icon in status bar
• Check connectivity: ping 8.8.8.8
• Inferno server requires network: Ensure eth0 is up and configured

GPIO Issues

• Ensure running as root/sudo
• Check GPIO permissions: ls -l /dev/gpiomem
• Verify pin assignments don't conflict

USB Mount Issues

• Check USB device: lsblk
• Manual mount: sudo mount /dev/sda1 /media/usb
• Check filesystem: sudo fsck /dev/sda1

Development

The project is structured as follows:

• main.go: Main application logic, state management, and Inferno server control
• hardware/: Hardware abstraction layer with display, encoder, buttons, and network detection
• inferno/: Inferno Audio over IP server project directory (Rust/Cargo)
• svg/: Icon assets including inferno.svg for status bar
• rec/: Final recording output directory
• rec/raw/: Temporary FIFO files for audio pipeline

Inferno Server Integration

• Directory: ./inferno/ contains the Rust/Cargo project
• Command: INFERNO_SAMPLE_RATE=<rate> cargo run -- -c <channels> -o <fifo>
• Pipeline: Inferno → FIFO → FFmpeg → WAV file
• Management: Automatic startup, restart, and monitoring

License

This project is licensed under the MIT License - see the LICENSE file for details.