Palette rainbow march with FastLED

/* Simple rainbow march using palettes
 *
 * By: Andrew Tuline
 *
 * Date: January, 2018
 *
 * This rainbow march uses palettes instead of the fill_rainbow() function.
 *
 * This routine also uses millis() instead of the dreaded delay statement for timing. As a result, the frame rate will be high
 * so that button or other polling routines can be added in the future. It was also animated at the same rate no matter
 * which Arduino you're using.
 *
 */

#include "FastLED.h"                                          // FastLED library.

// Fixed definitions cannot change on the fly.
#define LED_DT D4                                             // Data pin to connect to the strip.
#define COLOR_ORDER GRB                                       // It's GRB for WS2812 and BGR for APA102.
#define LED_TYPE WS2812                                       // Using APA102, WS2812, WS2801. Don't forget to modify LEDS.addLeds to suit.
#define NUM_LEDS 30                                           // Number of LED's.

struct CRGB leds[NUM_LEDS];

CRGBPalette16 currentPalette = PartyColors_p;



void setup() {

  delay(1000);

  LEDS.addLeds<LED_TYPE, LED_DT, COLOR_ORDER>(leds, NUM_LEDS);

} // setup()



void loop () {

    rainbow_pal();
    FastLED.show();

} // loop()



void rainbow_pal() {

  uint16_t locn = millis()/20;
  uint8_t hueChg = 5;

  for (int i=0; i<NUM_LEDS; i++) {
    leds[i] = ColorFromPalette(currentPalette, locn + i*hueChg, 255, LINEARBLEND);
  }

} // rainbow_pal