A FastLED US flag

// A flag

#include "FastLED.h"

#define LED_PIN     12
#define CLK_PIN     11
#define NUM_LEDS    20
#define BRIGHTNESS  64
#define LED_TYPE    APA102
#define COLOR_ORDER BGR
CRGB leds[NUM_LEDS];

int indexspeed = 2;
int indexinc = 25;
uint8_t updates_per_second = 100;

CRGBPalette16 currentPalette;
TBlendType    currentBlending;


void setup() {
  delay( 1000 ); // power-up safety delay
  FastLED.addLeds<LED_TYPE, LED_PIN, CLK_PIN, COLOR_ORDER>(leds, NUM_LEDS);
  FastLED.setBrightness(BRIGHTNESS);
  SetupFlagPalette();
}


void loop() {
  static uint8_t startIndex = 0;
  startIndex = startIndex + indexspeed; /* motion speed */
  FillLEDsFromPaletteColors(startIndex);
  FastLED.show();
  FastLED.delay(1000 / updates_per_second);
}

void FillLEDsFromPaletteColors(uint8_t colorIndex) {
  for( int i = 0; i < NUM_LEDS; i++) {
    leds[i] = ColorFromPalette(currentPalette, colorIndex, 255, currentBlending);
    colorIndex += indexinc;     // How quickly we change colours
  }
}


// This function sets up a palette of red white and blue.
void SetupFlagPalette() {

  CRGB red    = CRGB::Red;
  CRGB white  = CRGB::White;
  CRGB blue   = CRGB::Blue;

  currentPalette = CRGBPalette16(
    red, red, red, red, red,
    white, white, white, white, white, white,
    blue, blue, blue, blue, blue );
}