#include <FastLED.h>
const unsigned long speed = 100;
const byte brightness = 80;

const byte DATAPIN1 = 5;
const byte CLOCKPIN1 = 11;
const byte DATAPIN2 = 12;
const byte CLOCKPIN2 = 2;
const byte NUM_STRIPS = 2;
const size_t NUM_LEDS_PER_STRIP = 6*12; // needs to be a multiple of 6

CRGB leds[NUM_STRIPS][NUM_LEDS_PER_STRIP];
int ledsarray[NUM_STRIPS][NUM_LEDS_PER_STRIP / 6] ;

void setup() {
  for (size_t strip = 0; strip < NUM_STRIPS; strip++)
    for (int groupStart = 0, n = 0; groupStart < NUM_LEDS_PER_STRIP; groupStart += 6, n++)
      ledsarray[strip][n] = groupStart;

  FastLED.addLeds<DOTSTAR, DATAPIN1, CLOCKPIN1 >(leds[0], NUM_LEDS_PER_STRIP);
  FastLED.addLeds<DOTSTAR, DATAPIN2, CLOCKPIN2 >(leds[1], NUM_LEDS_PER_STRIP);
  FastLED.setBrightness(brightness);
  FastLED.clear();
  FastLED.show();
  delay(1000);
}

void loop() {

  for (size_t strip = 0; strip < NUM_STRIPS; strip++)
    for (size_t group = 0; group < NUM_LEDS_PER_STRIP / 6; group++) {
      fill_solid(&(leds[strip][ledsarray[strip][group]]), 6, CRGB::White);
      FastLED.show();
      delay(speed);
    }
  delay(1000);

  for (size_t strip = 0; strip < NUM_STRIPS; strip++)
    for (size_t group = 0; group < NUM_LEDS_PER_STRIP / 6; group++) {
      fill_solid(&(leds[strip][ledsarray[strip][group]]), 6, CRGB::Black);
      FastLED.show();
      delay(speed);
    }
  delay(1000);
}