//Define constants
#define LED_INTERNAL 13
#define LED_External 10
#define LEDPORT PORTB //port registers for controlling LED states
#define LEDDDR DDRB //data direction port for setting pins as outputs
#define L_I_BIT 1<<7
#define L_E_BIT 1<<4
#define NTASKS

//define Global variables
void(*tasks [NTASKS]) ();
int delay[NTASKS] = {0};
int task_active = 0;

void sleep (int sleeptime){
  delay[task_active] = sleeptime;
}


void setup() {
  // put your setup code here, to run once:
  LEDDDR |= (L_I_BIT | L_E_BIT);

  tasks[0] = taskA;
  tasks[1] = taskB;
  tasks[2] = NULL;

}

void loop() {
  // put your main code here, to run repeatedly:

  for(task_active = 0; task_active < NTASKS; task_active++){
    if((task_active != NULL) && (delays[task_active] <=0 )){
      (*tasks[task_active])();//exciute the task
    } 
    else if (tasks[tasl_active] != NULL){
      delays[task_active]--;//
    }
  }
  delay(1); //sync
}

void taskA() {
  
  static int flag = 0; //because its a static variable it retains its value

  flag ^=1;
  sleep(1000);

  if(flag){
    LEDPORT |= L_I_BIT;
  }
  else{
    LEDPORT &= ~L_I_BIT; 
  }

}

void taskB(){
  static int time = 0;

  time++;

  if(time == 500){
    LED_Port |= L_E_BIT;
  }

  if(time == 100) {
    LEDPORT &= ~L_E_BIT;
    time = 0;
  }
}