SPI Protocols for Pixel LEDs

SPI Protocols for Pixel LEDs

Pixel LEDs communicate using serial data protocols. Understanding these helps you choose the right chip and troubleshoot issues.

Single-Wire NRZ (WS2812B, SK6812, WS2815)

Uses one data wire with strict timing:

WS2812B timing (800kHz):

Bit 1 (high):  0.85µs high, 0.40µs low
Bit 0 (low):   0.40µs high, 0.85µs low
Reset:         >280µs low (all zeros)

Pros: Single wire, simple wiring Cons: Strict timing, no error checking, limited refresh rate

2-Wire SPI (APA102, SK9822, P9813)

Uses clock (CI) and data (DI) wires:

• Clock provides synchronized timing
• Data carries pixel values
• No strict timing — clock handles synchronization

Pros: Higher refresh rates (2kHz+), global brightness control, no timing issues Cons: 2 wires instead of 1, slightly more expensive chips

Comparison

Other Protocols

• TM1814 — 4-channel (RGBW), 800kHz NRZ
• UCS1903 — 400kHz NRZ (older, slower)
• GS8208 — 12V, 800kHz NRZ with backup data line
• LPD6803 — 250kHz SPI-like (obsolete)