NeoCandle for FastLED (without delay)

// candle for Adafruit NeoPixel
// 1 pixel version
// by Tim Bartlett, December 2013

// current settings for 5v Trinket

#include <FastLED.h>
#define LED_PIN 2
#define NUM_LEDS 1
#define BRIGHTNESS  100 // set at 25 for power saving

struct CRGB leds[NUM_LEDS];

byte onLedNumber = 0;
unsigned long previousMillis = 0;

// color variables: mix RGB (0-255) for desired yellow
int redPx = 255;
int grnHigh = 110; //110-120 for 5v, 135 for 3.3v
int bluePx = 10; //10 for 5v, 15 for 3.3v

// animation time variables, with recommendations
int burnDepth = 20; //10 for 5v, 14 for 3.3v -- how much green dips below grnHigh for normal burn
int flutterDepth = 30; //25 for 5v, 30 for 3.3v -- maximum dip for flutter
int cycleTime = 120; //120 -- duration of one dip in milliseconds

// pay no attention to that man behind the curtain
unsigned int fDelay;
unsigned int fRep;
int flickerDepth;
int burnDelay;
int burnLow;
int flickDelay;
int flickLow;
int flutDelay;
int flutLow;


void flutter(unsigned int f);
void flicker(unsigned int f);
void burn(unsigned int f);
void on(unsigned int f);
void fire(int grnLow);


void setup() {
  FastLED.addLeds<WS2811, LED_PIN, RGB>(leds, NUM_LEDS);
  FastLED.setBrightness( BRIGHTNESS );
  flickerDepth = (burnDepth + flutterDepth) / 2.4;
  burnLow = grnHigh - burnDepth;
  burnDelay = (cycleTime / 2) / burnDepth;
  flickLow = grnHigh - flickerDepth;
  flickDelay = (cycleTime / 2) / flickerDepth;
  flutLow = grnHigh - flutterDepth;
  flutDelay = ((cycleTime / 2) / flutterDepth);
}

// In loop, call CANDLE STATES, with duration in seconds
// 1. on() = solid yellow
// 2. burn() = candle is burning normally, flickering slightly
// 3. flicker() = candle flickers noticeably
// 4. flutter() = the candle needs air!

void loop() {
  burn(10);
  flicker(5);
  burn(8);
  flutter(6);
  burn(3);
  on(10);
  burn(10);
  flicker(10);
}


// basic fire function - not called in main loop
void fire(int grnLow) {
  for (int grnPx = grnHigh; grnPx > grnLow; grnPx--) {
    previousMillis = 0;
    unsigned long currentMillis = millis();
    if (currentMillis - previousMillis > fRep) {
      previousMillis = currentMillis;
      leds[onLedNumber] = CRGB(redPx, grnPx, bluePx);
      FastLED.show();
    }
  }
  for (int grnPx = grnLow; grnPx < grnHigh; grnPx++) {
    previousMillis = 0;
    unsigned long currentMillis = millis();
    if (currentMillis - previousMillis > fRep) {
      previousMillis = currentMillis;
      leds[onLedNumber] = CRGB(redPx, grnPx, bluePx);
      FastLED.show();
    }
  }
}

// fire animation
void on(unsigned int f) {
  previousMillis = 0;
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis > fRep) {
    previousMillis = currentMillis;
    fRep = f * 1000;
    int grnPx = grnHigh - 5;
    leds[onLedNumber] = CRGB(redPx, grnPx, bluePx);
    FastLED.show();
  }
}

void burn(unsigned int f) {
  fRep = f * 8;
  fDelay = burnDelay;
  for (unsigned int var = 0; var < fRep; var++) {
    fire(burnLow);
  }
}

void flicker(unsigned int f) {
  fRep = f * 8;
  fDelay = burnDelay;
  fire(burnLow);
  fDelay = flickDelay;
  for (unsigned int var = 0; var < fRep; var++) {
    fire(flickLow);
  }
  fDelay = burnDelay;
  fire(burnLow);
  fire(burnLow);
  fire(burnLow);
}

void flutter(unsigned int f) {
  fRep = f * 8;
  fDelay = burnDelay;
  fire(burnLow);
  fDelay = flickDelay;
  fire(flickLow);
  fDelay = flutDelay;
  for (unsigned int var = 0; var < fRep; var++) {
    fire(flutLow);
  }
  fDelay = flickDelay;
  fire(flickLow);
  fire(flickLow);
  fDelay = burnDelay;
  fire(burnLow);
  fire(burnLow);
}