Arduino · ESP32 + LED

Status: ✅ works (community-proven)

An Arduino or ESP32 microcontroller driving a single LED is the most reliable VLL emitter: timing is microsecond-accurate with no browser jitter. The microcontroller toggles the LED in the VLL pattern, which the LEGO sensor reads as light pulses.

Wiring (minimal — no transistor)

GPIO → 220 Ω → LED anode, LED cathode → GND. A 5 mm LED at ~10–15 mA is within a pin's limit; the Micro Scout sensor is close, so no power LED needed.

• On 3.3 V boards (ESP32), a white LED is dim — use red/IR LED + ~150 Ω, or drive a white LED from 5V via a small transistor.

Boards

• Arduino Nano — cheapest wired option; send commands over USB serial or buttons.
• ESP32 ⭐ — Wi-Fi + Bluetooth; host a web UI (phone → its Wi-Fi → tap a command). Dual-core = Wi-Fi on one core, exact LED timing on the other. Compact all-in-one: M5Atom (built-in RGB LED) or M5StickC Plus2 (built-in IR LED + screen + battery).
• Power: USB / power bank / LiPo base.

Firmware

Port the VLL — Visible Light Link engine (vllInit/vll0/vll1/vllEnd) with delayMicroseconds(), plus the VLL opcode table and VLL checksum.

Best for

Perfect timing, optional wireless control, and invisible programming via IR LED (invisible VLL).

Links

• JorgePe/mindstorms-vll — VLL emitter code
• ESP Web Tools — flash ESP firmware from the browser