TLDR
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Purdue CS student built a reed-switch-triggered WS2812B LED array on a rental graduation cap, firmware written in Rust on an ATtiny85.
Key Takeaways
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Stack: Digispark ATtiny85, 48 WS2812B LEDs, reed switch and magnet for tassel detection, USB-C PD trigger board, power bank.
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avr-hal and ws2812-avr lack ATtiny85 support by default; required forking both crates and patching the default clock to 16 MHz.
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Hardware assembly took 3+ hours vs 2 hours for firmware; wiring sourced from a stripped Apple USB-C cable.
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Chose ATtiny85 over ESP32 for size and weight; decided against wearing it due to aesthetics.
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Code is open source at github.com/ericswpark/gradcap-rs.
Hacker News Comment Review
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Thin discussion; one commenter sees skipping the live wear as a missed opportunity for a memorable public moment and career-story origin.
Original | Discuss on HN
