RGB LED matrix — Sam Witte

3D render of the 16 by 16 LED matrix board — The 16×16 v0 in KiCad's 3D viewer.

v0 was a prototype: the boards arrived, and it runs. v1, a bigger and more capable panel, is in the works.

v0 hardware

256 LEDs in a 16×16 grid at 3 mm pitch: XL-1615RGBC-2812B-S, 1.6 × 1.5 mm and WS2812B-compatible.
Seeed XIAO ESP32-C6 on the back, hand-soldered.
Two data chains of 128 LEDs on two GPIOs, driven by the ESP32's RMT peripheral. That's about 250 fps: 128 × 24 bits at 800 kbps, plus a 200 µs reset.
5 V over USB-C, with 3.3 V logic from the onboard regulator.
4 layers, with full 5 V and ground planes. The board's layers are what the exploded view on my PCB design page is built from.

v0 power budget

Each LED is set to 5 mA per channel, so full white across the panel would draw about 3.84 A. That's more than USB-C's 5 V/3 A budget, so brightness is capped in firmware rather than in hardware. The firmware estimates each frame's draw and scales it down only when that frame would go over:

I_leds = (sum of all 768 channel bytes / 255) × 5 mA + 90 mA static

The static term is real: each LED IC draws about 0.35 mA even with every channel off.

The full schematic: the XIAO and bulk capacitors on the left, two zones of 128 LEDs on the right — The schematic: two zones of 128 LEDs, one per data chain, with a 100 nF capacitor per pair and a 100 µF bulk capacitor per 16 LEDs.

What v0 was for

v0 was never meant to be a product. It was a prototype, built to answer questions like:

How bright is 5 mA per channel in practice, with and without a diffuser?
Does 3 mm pitch read well at desk distance?
Does the per-frame current estimator hold up without visible brightness pumping?
Is hand-soldering the XIAO annoying enough to design around?
Is two chains the right split, or would one (or four) make more sense?

It was also descoped from an earlier modular design, with seamless magnetic tiles and one controller per tile, to make it finishable. That idea is shelved, not abandoned.

v1, in progress

With v0 running, v1 takes the panel from test board to something you'd want on a desk or a wall:

32×32 LEDs (1,024 of them) at a 4.0 mm pitch.
USB Power Delivery at 20 V, with its own power circuitry on the board, instead of being capped by USB-C's 5 V budget.
An accelerometer and gyroscope, for animations that react to tilting and shaking the panel.
Still a single, integrated panel: the controller stays on the board.