Basic Concepts

Difficulty Level: ⭐ Beginner Time to Complete: 20 minutes Prerequisites: None (this is your starting point!)

You'll Learn:

How to address and control individual LEDs in a strip
The difference between RGB and HSV color models and when to use each
The essential setup() and loop() pattern for FastLED programs
How to configure FastLED for your specific LED hardware
Key concepts like brightness control and static variables

Core ideas behind LED programming with FastLED.

LED Addressing

Each LED in your strip has an index (position) starting from 0.

LED Strip:  [0] [1] [2] [3] [4] [5] ... [59]
             ^                           ^
           First                       Last

You control LEDs by setting color values in an array:

cpp

CRGB leds[60];  // Array for 60 LEDs

leds[0] = CRGB::Red;    // First LED is red
leds[5] = CRGB::Blue;   // Sixth LED is blue

Color Models

FastLED supports two main color models:

RGB (Red, Green, Blue)

Each color channel ranges from 0-255:

cpp

CRGB color = CRGB(255, 0, 0);      // Red
CRGB color = CRGB(0, 255, 0);      // Green
CRGB color = CRGB(0, 0, 255);      // Blue
CRGB color = CRGB(255, 255, 255);  // White

HSV (Hue, Saturation, Value)

Hue (0-255): Color (red → orange → yellow → green → blue → purple → red)
Saturation (0-255): Color intensity (0 = white, 255 = full color)
Value (0-255): Brightness (0 = off, 255 = full brightness)

cpp

CHSV hsv1 = CHSV(0, 255, 255);      // Red
CHSV hsv2 = CHSV(96, 255, 255);     // Green
CHSV hsv3 = CHSV(160, 255, 255);    // Blue

// Automatic conversion to RGB
leds[0] = hsv1;

Why use HSV?

Easier to create smooth color transitions (just change hue)
Natural for rainbow effects
Simple brightness control without changing color

The Main Loop Pattern

Every FastLED program follows this pattern:

cpp

void setup() {
    // 1. Initialize FastLED (runs once)
    FastLED.addLeds<LED_TYPE, DATA_PIN>(leds, NUM_LEDS);
    FastLED.setBrightness(50);
}

void loop() {
    // 2. Calculate/update LED colors
    leds[0] = CRGB::Red;

    // 3. Send colors to LEDs
    FastLED.show();

    // 4. Optional: delay or manage frame rate
    delay(20);
}

Key points:

setup() runs once at startup - configure your LEDs here
loop() runs repeatedly - update your LED colors here
You must call FastLED.show() to actually update the physical LEDs
Changes to the leds[] array are not visible until you call FastLED.show()

LED Type Configuration

Tell FastLED about your hardware:

cpp

#define LED_PIN     5           // Data pin number
#define NUM_LEDS    60          // Number of LEDs
#define LED_TYPE    WS2812B     // Your LED strip type
#define COLOR_ORDER GRB         // Color channel order

CRGB leds[NUM_LEDS];

void setup() {
    FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
}

Common LED types:

WS2812B - Most common (NeoPixel)
APA102 - DotStar (requires clock pin)
SK6812 - Similar to WS2812B

Common color orders:

GRB - WS2812B (most common)
RGB - Some WS2811
BGR - APA102

If your colors are wrong, try different COLOR_ORDER values.

Brightness Control

Control overall brightness (0-255):

cpp

void setup() {
    FastLED.addLeds<LED_TYPE, LED_PIN>(leds, NUM_LEDS);
    FastLED.setBrightness(50);  // 0-255 (50 = ~20% brightness)
}

Tip: Start with low brightness (50) when testing to avoid eye strain and reduce power draw.

Static vs Dynamic Variables

Use static variables to remember values between loop iterations:

cpp

void loop() {
    static uint8_t hue = 0;  // Remembers value across loops

    leds[0] = CHSV(hue, 255, 255);
    FastLED.show();

    hue++;  // Increment for next loop
}

Without static, the variable resets to 0 every loop.

Next Steps

Now that you understand the basics:

Your First Blink Example - Write your first program
Core Concepts - Deeper dive into LED programming