Server Features

Feature	Description
250 Hz streaming	WebSocket (`ws://<host>:1616`), plain JSON, language-agnostic
8 & 16 channel	PiEEG-8 / PiEEG-16 shields (SPI) and IronBCI / EAREEG headsets (8 ch, Bluetooth LE)
Bandpass filter	Butterworth IIR (SOS), per-channel state, adjustable live via WebSocket
CSV recording	Start/stop from dashboard or CLI; auto-timestamped; optional duration limit
Session annotations	Text notes on any frame; sidecar `.annotations.json`
Terminal monitor	Rich TUI with per-channel sparklines and µV readout; works over SSH
Mock mode	Realistic synthetic EEG (alpha rhythm, drift, noise, blink artifacts)
Authentication	Optional 6-digit code, rate limiting, HMAC timing-safe verify, HttpOnly cookies
VRChat OSC	Band powers via UDP OSC; chatbox + avatar parameters; rolling normalization
LSL	Push raw samples to LSL network; discoverable by OpenViBE, MNE, LabRecorder
Webhooks	HTTP callbacks on EEG events; IFTTT & Zapier presets; per-rule cooldown
Self-diagnostics	`pieeg-server doctor` checks Pi model, SPI/GPIO, ports, deps, systemd
Self-update	Detects pip/git install; checks PyPI or remote; one-click upgrade from dashboard
Systemd service	Auto-starts on boot; standard `systemctl` management
Zero-dep GPIO	Direct Linux chardev v1 ioctl; stable ABI since Linux 4.8
Spike rejection	Two-layer: hardware delta-threshold (SPI glitches) + Hampel filter (per-channel, median-based, all devices)
Cloud-ready	Dockerfile + Fly.io config for mock-mode demo hosting

Architecture

hardware.py     → SPI/GPIO init, ADS1299 config (PiEEG)
ironbci.py      → BLE scan, GATT notifications, ADS1299 parsing (IronBCI)
     ↓
acquisition.py  → 250 Hz read loop (background thread)
     ↓ spike_filter.py → Hampel filter (per-channel, all devices)
     ↓ pub/sub
     ├── server.py     → WebSocket broadcast
     ├── recorder.py   → CSV writer
     ├── monitor.py    → Terminal sparklines
     ├── osc_vrchat.py → VRChat OSC bridge
     └── lsl.py        → Lab Streaming Layer outlet

webhooks.py  → event rules + HTTP relay
dashboard.py → HTTP server (React UI)
auth.py      → session + WS token management
filters.py   → Butterworth bandpass (SOS)
spike_filter.py → Hampel spike filter (per-channel, median/MAD)
updater.py   → version check + upgrade
doctor.py    → system diagnostics

Data Flow

Hardware/Mock/BLE → AcquisitionLoop (threaded, 250 Hz)
Each sample: 8 or 16 channels of float values in µV
Subscription-based queue system — each subscriber gets its own asyncio.Queue
Subscribers: WebSocket server, recorder, monitor, OSC, LSL
WebSocket broadcasts plain JSON to all connected clients

Tech Stack

Layer	Tech
Language	Python 3.10+ (asyncio)
WebSocket	`websockets` library
Filter	`scipy` Butterworth IIR
Terminal UI	`rich`
GPIO	Direct `/dev/gpiochip` ioctl (no dependencies)
Dashboard	React 19 + Vite 6

Configuration Dashboard