Esp8266Uart Directory Reference

Directory dependency graph for Esp8266Uart:

Files
	Esp8266Uart.ino

Detailed Description

This example demonstrates the opt-in UART-based WS2812 driver for ESP8266, which provides improved stability under Wi-Fi load compared to the default bit-bang driver.

Overview

The ESP8266's single-core architecture and frequent NMI/RTOS interrupts can disrupt bit-bang timing loops, especially when Wi-Fi is active. This UART driver solves this problem by using the hardware UART1 peripheral to generate precise LED timing automatically.

How It Works

The driver encodes WS2812 LED data into a UART byte stream at 3.2 Mbps:

• Each LED bit is represented by 4 UART bits (1.25 µs total)
• "0" bit → 1000 (0.35 µs high, 0.8 µs low)
• "1" bit → 1100 (0.7 µs high, 0.6 µs low)
• Two LED bits are packed into each UART byte using a lookup table

Usage

Enable the UART driver

Option 1: Define before including FastLED

#define FASTLED_ESP8266_UART
#include <FastLED.h>
 
CRGB leds[NUM_LEDS];
 
void setup() {
    FastLED.addLeds<UARTController_ESP8266<GRB>>(leds, NUM_LEDS);
}

Option 2: Explicit controller type

#include <FastLED.h>
 
CRGB leds[NUM_LEDS];
 
void setup() {
    FastLED.addLeds<UARTController_ESP8266<GRB>>(leds, NUM_LEDS);
}

Advantages

✅ Hardware timing - UART peripheral shifts bits automatically ✅ Minimal CPU overhead - Main loop remains responsive ✅ Wi-Fi stable - No NMI interrupt timing issues ✅ Precise timing - Maintains ±150ns WS2812 tolerance

Trade-offs

⚠️ Higher RAM usage - ~12 bytes per LED (300 LEDs = 3.6 KB buffer) ⚠️ Single pin only - GPIO2 (UART1 TX-only on ESP8266) ⚠️ No parallel output - Not compatible with multi-strip modes

Pin Assignment

• GPIO2 - UART1 TX (the only usable pin for this driver)
• This is the same as D4 on NodeMCU boards

Configuration

You can optionally configure the baud rate and reset time:

UARTController_ESP8266<GRB> controller;
controller.setBaud(3200000);      // Default: 3.2 Mbps
controller.setResetTimeUs(300);   // Default: 300 µs (WS2812 requires >= 50 µs)
FastLED.addLeds(&controller, leds, NUM_LEDS);

Performance

• Frame rate: Up to 30-60 FPS for typical strip sizes (<1000 LEDs)
• Latency: ~11.25 ms for 300 LEDs (3600 bytes @ 3.2 Mbps + 300 µs latch)
• Memory overhead: 12 bytes per LED (temporary encode buffer)

When to Use This Driver

Use the UART driver when:

• You're experiencing LED flickering with Wi-Fi enabled
• Your application needs reliable Wi-Fi + LED operation
• You have RAM available for the encode buffer
• You only need a single LED strip

Stick with the default bit-bang driver when:

• You need multiple parallel LED strips
• RAM is constrained
• Wi-Fi is not in use
• You need pins other than GPIO2

Credits

This implementation is based on the proven technique from the NeoPixelBus library, adapted to work seamlessly with FastLED's API and features.