const byte pins[]={2,3,4,5,6};

struct LED{
  byte pin;
  unsigned int interval;
  unsigned long previousMillis;
};

LED led2={2,2000,0};
LED led3={3,3000,0};
LED led4={4,4000,0};
LED led5={5,5000,0};
LED led6={6,6000,0};
int lightless=0;
int lightfull=255;
LED leds[5]={led2,led3,led4,led5,led6};
byte ledsLength=sizeof(leds)/sizeof(leds[0]);

void setup(){
  Serial.begin(9600);
  for (LED led :leds){
    pinMode(led.pin,OUTPUT);
  }
}

void loop(){
  multitaskLED();
}


void onLED(){
  unsigned long interval=1000;
  for (byte pin:pins){
    if (millis()>=pin*interval)
    digitalWrite(pin,HIGH);

  }
}

void multitaskLED() {

unsigned long currentMillis = millis(); 

for (byte i=0; i<ledsLength;i++) {

if ((currentMillis - leds[i].previousMillis) >= leds[i].interval) {
  leds[i].previousMillis = currentMillis;

//digitalWrite(leds[i].pin, !digitalRead(leds [i].pin));

for (int light=lightless;light<=lightfull;light+=3){ 
  unsigned long a;
  a=currentMillis;
  analogWrite(leds[i].pin,light);      //控制pin号引脚所对应灯的亮度
  for (int i=0;i<50000;i++)
  {
    if (currentMillis==(a+6))
       break;
  }  
}
for (int light=lightfull;light>=lightless;light-=3){  //亮度从最大以每次减3的速度减到0
   unsigned long b;
  b=currentMillis;
  analogWrite(leds[i].pin,light);      //控制pin号引脚所对应灯的亮度
  for (int i=0;i<50000;i++)
  {
    if (currentMillis==(b+6))
       break;
}


}
}
}
}