Dim on and off

adalight.cpp

/*
 * Arduino interface for the use of WS2812 strip LEDs
 * Uses Adalight protocol and is compatible with Boblight, Prismatik etc...
 * "Magic Word" for synchronisation is 'Ada' followed by LED High, Low and Checksum
 * @author: Wifsimster <wifsimster@gmail.com> 
 * @library: FastLED v3.001
 * @date: 11/22/2015
 */
#include "FastLED.h"
#define MAX_LEDS 156
#define DATA_PIN 8

//Baudrate, higher rate allows faster refresh rate and more LEDs (defined in /etc/boblight.conf)
const uint32_t _serialRate = 500000;

//Adalight sends a "Magic Word" (defined in /etc/boblight.conf) before sending the pixel data
uint8_t _prefix[] = {'A', 'd', 'a'};

//Initialise LED-array
CRGB _leds[MAX_LEDS];

void setup() {  
  //Use NEOPIXEL to keep true colors
  FastLED.addLeds<NEOPIXEL, DATA_PIN>(_leds, MAX_LEDS);
  FastLED.setDither(DISABLE_DITHER);
  
  //Initial RGB flash
  LEDS.showColor(CRGB(10, 0, 0));
  delay(500);
  LEDS.showColor(CRGB(0, 10, 0));
  delay(500);
  LEDS.showColor(CRGB(0, 0, 10));
  delay(500);
  LEDS.showColor(CRGB(0, 0, 0));

  //Initialize serial connection
  Serial.begin(_serialRate);
  
  //Send "Magic Word" string to host
  Serial.print("Ada\n");
}

struct led_count_t
{
  uint8_t high, low;
  uint8_t checksum;
};

uint16_t _lastLedCount = 0;
uint32_t _lastOnTime = 0, _lastOffTime = 0;
bool _isActive = false;
const uint32_t _timeout = 1000;
const uint32_t _dimTime = 2000;

void loop() {  
waitLoop:
  
  //Search for frame
  for(auto i = 0; i < sizeof _prefix; ++i) {
    //Wait for data and dim OFF
    while (!Serial.available()) {
        
        if(_isActive)
        {
          auto now = millis();
          auto timeDiff = now - _lastOnTime;
          if(timeDiff > _timeout)
          {
            auto overTime = timeDiff - _timeout;
            if(overTime < _dimTime)
            {
              FastLED.setBrightness(255 * (1.0f - (float)overTime / (float)_dimTime));
              FastLED.show();
              
              _lastOffTime = now;
            }
            else
            {
              memset((char*)_leds, 0, MAX_LEDS * sizeof(CRGB));
              FastLED.show();
              _isActive = false;
            }            
          }
        }
      };
      
    //Check next byte in Magic Word
    if(_prefix[i] == Serial.read()) continue;
    // otherwise, start over
    i = 0;
    goto waitLoop;
  }
  
  //Read LED count
  led_count_t rawLedCount;
  Serial.readBytes((char*)&rawLedCount, sizeof(led_count_t));
  
  // If checksum does not match go back to wait
  if (rawLedCount.checksum != (rawLedCount.high ^ rawLedCount.low ^ 0x55)) {
    goto waitLoop;
  }

  //Dim ON
  auto now = millis();
  if(!_isActive)
  {
    _isActive = true;
    _lastOffTime = now;
  }
  
  {
    auto timeDiff = now - _lastOffTime;
    if(timeDiff < _dimTime)
    {
      FastLED.setBrightness(255 * (float)timeDiff / (float)_dimTime);
    }
    else
    {
      FastLED.setBrightness(255);
    }
  }
  _lastOnTime = now;
  
  //Read LED colors
  auto requestedLedCount = (rawLedCount.high << 8) + rawLedCount.low + 1;
  auto actualLedCount = max(requestedLedCount, MAX_LEDS);
  Serial.readBytes((char*)_leds, actualLedCount * sizeof(CRGB));

  //Zero out further bytes
  if(_lastLedCount != actualLedCount)
  {
    _lastLedCount = actualLedCount;
    if(actualLedCount < MAX_LEDS) memset((char*)(_leds + actualLedCount), 0, (MAX_LEDS - actualLedCount) * sizeof(CRGB));
  }
  
  //Show new values
  FastLED.show();
}