shawn
c65e4816c4
_gather_channel_state() was accessing pl.sample_rate but AudioPipeline only had private _sample_rate. Added public properties so the /api/state endpoint doesn't crash with AttributeError.
Pi Multi-FX Pedal 🎸
A real-time guitar multi-FX pedal running on Raspberry Pi 4B with 32 DSP effects, NAM A2 neural amp modeling, IR cab simulation, 4-Cable Method routing, and a web UI on pedal.local:8080.
Quick Install (Focusrite 2i2 Test)
Get the pedal running on a fresh RPi with a Focusrite 2i2 in under 10 minutes.
1. OS Setup
Start with Raspberry Pi OS Lite (64-bit) or DietPi.
Configure hostname, enable SSH, and connect to WiFi:
sudo hostnamectl set-hostname pedal
# Or on DietPi: use dietpi-config
2. System Packages
sudo apt update && sudo apt upgrade -y
sudo apt install -y \
git python3 python3-pip python3-venv python3-dev \
jackd2 libjack-jackd2-dev \
libsndfile1-dev \
cmake build-essential \
avahi-daemon # for pedal.local mDNS
3. Clone the Repo
git clone https://gitea.ourpad.casa/shawn/pi-multifx-pedal.git ~/projects/pi-multifx-pedal
cd ~/projects/pi-multifx-pedal
4. Python Environment
python3 -m venv .venv
source .venv/bin/activate
pip install --upgrade pip
pip install -r requirements.txt
Note:
neural-amp-modelerneeds PyTorch. On RPi 4B aarch64:pip install torch --index-url https://download.pytorch.org/whl/nightly/cpu
5. Focusrite-Specific Config
Kill PulseAudio (it grabs USB audio):
pulseaudio --kill
Verify Focusrite is detected:
aplay -l
# Look for: card 1: USB Audio [Scarlett 2i2 USB], device 0
arecord -l
# Look for same
Copy the mono test config:
mkdir -p ~/.pedal
cp etc/config-focusrite-mono.yaml ~/.pedal/config.yaml
6. Run the Pedal
cd ~/projects/pi-multifx-pedal
source .venv/bin/activate
python3 main.py
7. Open the Web UI
From any device on the same network:
- Browser: http://pedal.local:8080
- Or use the IP: http://192.168.x.x:8080
WiFi Hotspot (No Network? No Problem)
If there's no WiFi network to join — stage, rehearsal space, park bench — the Pi can create its own:
# Run once to set up
sudo bash scripts/setup-wifi-ap.sh
# Or with custom SSID/password:
sudo bash scripts/setup-wifi-ap.sh --ssid "Pi-Pedal" --psk "yourpassword"
# Phone connects to "Pi-Pedal" → open http://pedal.local:8080
# To turn it off and go back to client mode:
sudo bash scripts/setup-wifi-ap.sh --disable
Pro tip: Add a USB WiFi dongle for dual-network — Pi creates hotspot on built-in WiFi, dongle handles internet access for git pulls and updates.
8. Wire It Up
Mono mode (standard pedal):
Guitar jack → Focusrite Input 1 (front)
Focusrite Output 1 (rear) → Amp
4CM mode (four cable method):
Guitar → Focusrite Input 1
Amp FX Send → Focusrite Input 2
Focusrite Output 1 → Amp Input (Send)
Focusrite Output 2 → Amp FX Return (Output)
Then switch config:
cp etc/config-focusrite-4cm.yaml ~/.pedal/config.yaml
Toggle 4CM on/off from the Settings page in the web UI.
Hardware
| Component | Spec |
|---|---|
| SBC | Raspberry Pi 4B (2GB+ RAM) |
| Audio I/O | I2S DAC + ADC (PCM1808 + PCM5102 custom HAT, or USB via Focusrite 2i2) |
| Footswitches | 3-6 momentary soft-touch (e.g. MXR-style) |
| LEDs | RGB WS2812B or APA102 per footswitch + status LEDs |
| Display | 128x64 OLED SSD1306 (I2C) or 5" DSI touch |
| MIDI | 5-pin DIN in/out via UART + optoisolator |
| Power | 5V/3A USB-C (with buck for 3.3V rail) |
| Enclosure | 1590BB or 3D-printed custom |
32 Effects
| Category | Effects |
|---|---|
| Dynamics | Noise Gate, Compressor, Expander, De-esser, Transient Shaper, Sidechain Compressor |
| Drive | Boost, Overdrive, Distortion, Fuzz, Bitcrusher, Wavefolder, Rectifier |
| Amp + Cab | NAM Amp Model (any .nam file), IR Cab Sim (any .wav) |
| Modulation | Chorus, Flanger, Phaser, Tremolo, Vibrato, Ring Mod, Auto-Wah, Envelope Filter, Rotary Speaker, Uni-Vibe, Auto-Pan, Stereo Widener |
| Time | Delay, Ping-pong Delay, Multi-tap Delay, Reverse Delay, Tape Echo, Reverb, Shimmer Reverb, Early Reflections, Looper |
| Pitch | Octaver, Detune, Harmonizer, Whammy, Pitch Shifter |
| Filter | EQ, Parametric EQ, High-Pass, Low-Pass, Band-Pass, Notch, Formant, Wah |
| Utility | Volume, Tuner |
Project Structure
├── src/
│ ├── dsp/ Audio processing pipeline
│ │ ├── pipeline.py FX chain orchestration (mono + 4CM split)
│ │ ├── ir_loader.py IR convolution engine
│ │ ├── nam_host.py NAM model loading & inference
│ ├── midi/ MIDI subsystem
│ │ ├── handler.py MIDI event parse & dispatch
│ ├── presets/ Preset system
│ │ ├── manager.py Save/load/bank/preset CRUD + 4CM routing
│ │ └── types.py Preset & chain data model + FXType enum
│ ├── ui/ Hardware UI layer
│ │ ├── footswitch.py Debounced GPIO input
│ │ ├── leds.py RGB LED controller
│ │ └── display.py OLED display manager
│ ├── web/ Web UI (FastAPI + WebSocket)
│ │ ├── server.py REST + WebSocket endpoints
│ │ ├── templates/ Jinja2 HTML pages
│ │ └── static/ CSS + JS
│ └── system/ System integration
│ ├── audio.py ALSA/JACK/I2S configuration
│ └── config.py YAML config loader
├── etc/ Config file templates
├── scripts/ Build & utility scripts
├── tests/ Tests
├── docs/ Documentation + test plans
└── hardware/ KiCad/PCB schematics
Development
# Tests
source .venv/bin/activate
python -m pytest tests/ -v
# All 574 tests should pass
Early development — initial scaffold.