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Your First Blink Example

cookbook/getting-started/first-example.md

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Your First Blink Example

Write and run your first LED program with FastLED.

Difficulty Level: ⭐ Beginner Time to Complete: 30 minutes (including hardware setup) Prerequisites:

  • FastLED Concepts - Understanding of basic LED control concepts
  • Arduino IDE or PlatformIO installed
  • LED strip connected to your microcontroller

You'll Learn:

  • How to write a complete FastLED program from scratch
  • The essential setup() and loop() pattern in action
  • How to use fill_solid() to set all LEDs to one color
  • Why FastLED.show() is required to update your LED strip
  • How to customize pin numbers, LED counts, and timing for your hardware

Complete Example

This program blinks all LEDs between red and off:

cpp
#include <FastLED.h>

// Configuration
#define LED_PIN     5
#define NUM_LEDS    60
#define LED_TYPE    WS2812B
#define COLOR_ORDER GRB

// LED array
CRGB leds[NUM_LEDS];

void setup() {
    // Initialize FastLED
    FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
    FastLED.setBrightness(50);  // Start with low brightness
}

void loop() {
    // Turn all LEDs red
    fill_solid(leds, NUM_LEDS, CRGB::Red);
    FastLED.show();
    delay(1000);

    // Turn all LEDs off
    fill_solid(leds, NUM_LEDS, CRGB::Black);
    FastLED.show();
    delay(1000);
}

How It Works

Setup Phase

cpp
void setup() {
    FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
    FastLED.setBrightness(50);
}
  • FastLED.addLeds<>() - Tells FastLED about your hardware
  • FastLED.setBrightness(50) - Sets brightness to ~20% (safe for testing)

Loop Phase

cpp
void loop() {
    fill_solid(leds, NUM_LEDS, CRGB::Red);  // Set all LEDs to red
    FastLED.show();                          // Send to strip
    delay(1000);                             // Wait 1 second

    fill_solid(leds, NUM_LEDS, CRGB::Black); // Set all LEDs to off
    FastLED.show();                          // Send to strip
    delay(1000);                             // Wait 1 second
}

Customization

Change the Pin

cpp
#define LED_PIN     6  // Use pin 6 instead of 5

Change Number of LEDs

cpp
#define NUM_LEDS    30  // For a 30-LED strip

Change Color

cpp
fill_solid(leds, NUM_LEDS, CRGB::Blue);   // Blue instead of red
fill_solid(leds, NUM_LEDS, CRGB::Green);  // Green
fill_solid(leds, NUM_LEDS, CRGB::Purple); // Purple
cpp
delay(500);   // Faster (0.5 seconds)
delay(2000);  // Slower (2 seconds)

Troubleshooting

LEDs Don't Light Up

  1. Check power connections - Verify 5V and GND are connected
  2. Check data pin - Ensure LED_PIN matches your wiring
  3. Try different brightness - Increase to FastLED.setBrightness(100)
  4. Verify LED type - Confirm LED_TYPE matches your strip

Wrong Colors

Try different COLOR_ORDER values:

cpp
#define COLOR_ORDER GRB  // Try GRB first (most common)
// If that doesn't work, try:
#define COLOR_ORDER RGB
#define COLOR_ORDER BGR

Only First LED Works

  • Add a 220-470Ω resistor on the data line
  • Check for damaged LEDs in your strip

What's Next?

More Color Options

cpp
// Named colors
CRGB::Red
CRGB::Green
CRGB::Blue
CRGB::White
CRGB::Purple
CRGB::Orange
CRGB::Yellow

// Custom RGB colors
CRGB(255, 0, 0)     // Red
CRGB(0, 255, 0)     // Green
CRGB(128, 0, 128)   // Purple

// HSV colors
CHSV(0, 255, 255)    // Red
CHSV(96, 255, 255)   // Green
CHSV(160, 255, 255)  // Blue

Individual LED Control

cpp
void loop() {
    // Turn on first 3 LEDs to different colors
    leds[0] = CRGB::Red;
    leds[1] = CRGB::Green;
    leds[2] = CRGB::Blue;

    // Rest of LEDs stay off
    FastLED.show();
    delay(1000);
}

Fill a Range

cpp
// Fill LEDs 10-19 with green
fill_solid(&leds[10], 10, CRGB::Green);

Next Steps

Now that you have a working program: