Using FastLED for photon--meteor/chase animation

General
1

I’m using FastLED library to eventually create a comet animation, where another comet get incrementally added as an event happens.

I’m starting out trying to do a simpler chase animation first with a single comet.

Why is it that I can’t make the comet tail longer? If I try to set the color of “leds[-7]”, the program crashes. So I’m stuck with making the comet only 5 LEDS long.

#Here is my code:

//================================================

// This #include statement was automatically added by the Particle IDE.
#include <FastLED.h>

FASTLED_USING_NAMESPACE

#define LED_COUNT 144
#define LED_PIN D1

// Block of memory that will be used for storing and manipulating the led data. 
// This sets up an array that we can manipulate to set/clear led data
struct CRGB leds[LED_COUNT];

uint8_t hue = 32;
//================================================




// Now, let's actually set up our leds.
void setup() {
    // sanity check delay - allows reprogramming if accidently blowing power w/leds
   	delay(2000);
   	// This tells the library that there's a strand of ws2812b NEOPIXELs on pin D1,
   	// and those leds will use the led array leds, and there are LED_COUNT (aka 144) of them.
    LEDS.addLeds<WS2812B, LED_PIN>(leds, LED_COUNT);
    LEDS.setBrightness(200);
    FastLED.clear();
    FastLED.show();
}

void loop(){
    meteorShower(); 
}


void meteorShower(){
    
    for(uint16_t i=0; i<LED_COUNT+6; i++) {
        leds[i-1] = CHSV(0, 0, 100); // Draw new pixel
        leds[i-2] = CHSV((hue - 20), 255, 210);
        leds[i-3] = CHSV((hue - 22), 255, 180);
        leds[i-4] = CHSV((hue - 25), 255, 90);
        leds[i-5] = CHSV((hue - 28), 140, 40);
        leds[i-6] = CRGB::Black; // Erase pixel a few steps back
        FastLED.show();
        delay(50);
    };
}
2

@kkwak, this may not be the whole problem but the array indexes wont work as expected for values of i below 6. Since you are using a uint16_t, instead of a negative number (when i = 0 for example), you will get a large positive number and write to some other memory location instead of the array. You need to rethink how you address your LEDs so the index values are always positive and in range.

        leds[i-1] = CHSV(0, 0, 100); // Draw new pixel
        leds[i-2] = CHSV((hue - 20), 255, 210);
        leds[i-3] = CHSV((hue - 22), 255, 180);
        leds[i-4] = CHSV((hue - 25), 255, 90);
        leds[i-5] = CHSV((hue - 28), 140, 40);
        leds[i-6] = CRGB::Black; // Erase pixel a few steps back
2 Likes