mcgutschy
### The Problem
Smart speakers and streaming devices have a fundamental flaw: they assume you can see. Voice assistants help, but they need a cloud connection, they listen all the time, and they get frustrating when they mishear you. For blind and visually impaired users, the alternatives are either expensive specialized hardware or being locked into Amazon, Google, or Apple ecosystems.
### The Solution
Feel the Knobs is a self-contained media center that needs no screen and no internet account. Two large 11-position rotary switches — one for program selection (radio, YouTube, audiobooks), one for station or channel — give you tactile, muscle-memory-friendly control. A potentiometer handles volume. Text-to-speech confirms every selection. That's it. No app, no touchscreen, no cloud.
It lives in a laser-cut 6mm MDF enclosure and drives two 75W full-range speakers through a HiFiBerry AMP2. The whole thing runs off a single 20V power brick.
### How It Works
Two Arduino Nanos act as I2C slaves, each reading one rotary switch via analog voltage dividers. The Raspberry Pi 4 polls their positions over I2C every 200ms and launches the right player — mpd for radio, yt-dlp for YouTube, VLC for audiobooks. A GPIO pin switches audio output between the speakers and Bluetooth headphones.
A companion VPS backend (also open source) provides a web interface for managing radio stations, YouTube channels, and uploading audiobooks. The Pi syncs every 10 minutes via cron. No static IP, no port forwarding needed.
### Why This Matters
This is not an accessibility feature bolted onto a general-purpose device. It was designed from the ground up around haptic interaction and acoustic feedback. The entire interface is physical — you operate it by feel alone, without touching a screen or talking to a voice assistant.
### Hardware Architecture
┌───────────────────────────────────────────────┐
│ MDF Enclosure (3mm) │
│ │
│ ┌──────────┐ ┌──────────┐ ┌─────────┐ │
│ │ Rotary │ │ Rotary │ │ Volume │ │
│ │ Switch 1 │ │ Switch 2 │ │ Pot │ │
│ │ (Program)│ │ (Station)│ │ │ │
│ └────┬─────┘ └────┬─────┘ └────┬────┘ │
│ │ │ │ │
│ ┌────┴───────────┐ ┌───┴────────────┴─────┐ │
│ │ Arduino Nano 1 │ │ Arduino Nano 2 │ │
│ │ (0x08) │ │ (0x09) │ │
│ │ Reads Switch 1 │ │ Reads Switch 2 + Pot │ │
│ └────────┬───────┘ └───────────┬──────────┘ │
│ │ │ │
│ ┌────────┴────────┐ ┌─────────┴───────────┐ │
│ │ Level Shifter 1 │ │ Level Shifter 2 │ │
│ │ (3.3V <-> 5V) │ │ (3.3V <-> 5V) │ │
│ └────────┬────────┘ └────────┬────────────┘ │
│ │ │ │
│ └──────────┬─────────┘ │
│ │ I2C bus │
│ ┌───────────────────┴───────────────────────┐ │
│ │ Raspberry Pi 4 (4GB) │ │
│ │ Boots from SSD (USB-SATA adapter) │ │
│ │ GPIO4 -> audio output switch │ │
│ └───────────────────┬───────────────────────┘ │
│ │ I2S │
│ ┌───────────────────┴───────────────────────┐ │
│ │ HiFiBerry AMP2 (2x60W Class-D) │ │
│ └───────────────────┬───────────────────────┘ │
│ │ │
│ ┌────────────┴────────────┐ │
│ │ 2x Lonpoo 75W Speakers │ │
│ └─────────────────────────┘ │
└───────────────────────────────────────────────┘
```
### Software Stack
| Layer | Technology |
|---|---|
| Audio backend | PipeWire + PulseAudio |
| Radio playback | mpd + mpc |
| YouTube playback | yt-dlp then VLC |
| Audiobook playback | VLC + TTS (position tracking) |
| Bluetooth audio | PipeWire bluez5, custom bt-agent systemd service |
| I2C communication | Python smbus, polling at 200ms |
| GPIO switching | RPi.GPIO (GPIO4 toggles AMP2/headphones) |
| Remote management | FileBrowser web UI + PHP admin panel on VPS |
| Sync | Cron every 10 min, pulls from VPS via REST API |
| Remote access | Tailscale VPN (primary) + reverse SSH tunnel (fallback) |
### Three Audio Paths
The system supports three audio outputs, switched via GPIO4:
1. **AMP2** — HiFiBerry amplifier driving the...
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