FastLED 1 Array multiple strips + Map

gistfile1.txt

#include "FastLED.h"

#define NUM_LEDS_PER_STRIP 10
#define NUM_LEDS 20

int mappedLEDs [] { 
  9,8,7,6,5,4,3,2,1,0,10,11,12,13,14,15,16,17,18,19
};

CRGBArray<NUM_LEDS> leds;

void setup() {
  // tell FastLED there's 10 NEOPIXEL leds on pin 10, starting at index 0 in the led array
  FastLED.addLeds<NEOPIXEL, 10>(leds, 0, NUM_LEDS_PER_STRIP);

  // tell FastLED there's 10 NEOPIXEL leds on pin 11, starting at index 10 in the led array
  FastLED.addLeds<NEOPIXEL, 11>(leds, NUM_LEDS_PER_STRIP, NUM_LEDS_PER_STRIP);

}

void loop() {
  for(int i = 0; i < NUM_LEDS; i++) {
    leds[mappedLEDs[i]] = CRGB::Red;
    FastLED.show();
    leds[mappedLEDs[i]] = CRGB::Black;
    delay(100);
  }
}

If you have an strip with 159 pixels you might not want to type all those numbers out though! Here's a way to fill that array with a for loop:

uint8_t mappedLEDs[NUM_LEDS];
for (int x=0; x<NUM_LEDS; x=x+1) { mappedLEDs[x]=x; } //this fills the array with range 0 to NUM_LEDS-1

Adjust your for loop as needed to fill numbers in reverse order. Can use two loops, one to fill reverse numbers and a second to continue filling, putting in the forward counting numbers.