Reviving an iPad 2 as a Spotify Controller with a Milkdrop Visualizer

The Problem

I had an iPad 2 sitting in a drawer — too old for modern iOS, but the hardware still works perfectly. Rather than e-waste it, I wanted to give it a dedicated purpose: an always-on Spotify controller with a beautiful music visualizer.

The Architecture

Two repositories work together:

RepoPurposeTech
iPad2SpotifyBackend + Spotify API bridgeNode.js, Redis, Vercel
OldMilkWebGL 1 Milkdrop visualizerJavaScript, WebGL, WebAMP

iPad2Spotify (Backend)

  • Redis for session/token storage — survives iPad Safari restarts
  • Spotify Web API for playback control and "now playing" metadata
  • Vercel serverless functions — zero-cost hosting, global CDN
  • WebAMP integration for Winamp 2 skin compatibility

OldMilk (Visualizer)

  • WebGL 1 — runs on iPad 2's PowerVR SGX543MP2 (iOS 9.3.5 Safari supports it)
  • Milkdrop preset parsing — loads .milk files natively
  • AudioContext analyser node for real-time frequency data
  • Zero dependencies — single HTML file, ~50 KB gzipped

Data Flow

iPad 2 Safari → Vercel (iPad2Spotify) → Redis ↔ Spotify API
                    ↓
              WebSocket → OldMilk (WebGL visualizer)

The iPad polls /now-playing every 2 seconds. When track changes, it pushes new metadata to the visualizer via WebSocket.

Key Challenges

1. iOS 9.3.5 Safari Limitations

  • No ES6 modules → all code transpiled to ES5
  • No fetch polyfill needed — used XMLHttpRequest
  • WebGL 1 only — shaders written in GLSL 1.0 (#version 100)
  • AudioContext requires user gesture → "Tap to Start" overlay

2. Spotify Token Refresh

Access tokens expire hourly. Solution: store refresh_token in Redis (encrypted), background cron refreshes every 50 min.

// Simplified token refresh
async function getValidToken(sessionId) {
  const session = await redis.get(`spotify:${sessionId}`);
  if (Date.now() > session.expiresAt - 60000) {
    const newToken = await refreshToken(session.refreshToken);
    await redis.set(`spotify:${sessionId}`, { ...session, ...newToken });
    return newToken.accessToken;
  }
  return session.accessToken;
}

3. Visualizer Performance on 2011 GPU

  • Reduced fragment shader complexity
  • Limited to 30 fps via requestAnimationFrame throttle
  • Disabled expensive Milkdrop features (per-pixel motion, waveforms)

Deployment

# iPad2Spotify
cd iPad2Spotify
vercel --prod

# OldMilk (static)
cd OldMilk
vercel --prod

Both deploy to *.vercel.app subdomains. iPad 2 Safari bookmarks the visualizer URL to home screen for "app-like" experience.

Result

The iPad 2 has been running 24/7 on a wall mount for 6 months — zero crashes, ~2% battery drain per day (always plugged in).

Built with ☕ and nostalgia. The iPad 2 deserves a second life.