// Include header files of FreeRTOS and event groups 
#include <Arduino_FreeRTOS.h>
#include "event_groups.h"

// define three event flag bit variable 
#define TASK1_BIT   (1UL << 0UL) // zero shift for bit0
#define TASK2_BIT   (1UL << 1UL) // 1 shift for flag  bit 1
#define TASK3_BIT   (1UL << 2UL) // 2 shift for flag bit 2

//  declare a event grounp handler variable 
EventGroupHandle_t  xEventGroup;

// A constant to define 500ms delay
//because we use to periodically execute each task
//after every 500ms 
const TickType_t xDelay500ms =  pdMS_TO_TICKS(500);

void setup()
{
   // intialize uart module with baud rate of 9600
   Serial.begin(9600);
   //create event group and assign it a earlier created referene handler
   xEventGroup  =  xEventGroupCreate();
   // Create three tasks which are used to release event with
   // the help of above defined event flags 
   xTaskCreate(InputTask1, "Input Task 1", 100,NULL,1,NULL);
   xTaskCreate(InputTask2, "Input Task 2", 100, NULL, 1, NULL );
   xTaskCreate(InputTask3, "Input Task 3", 100, NULL, 1,NULL);
   //Create output task that will execute only when all three events occured
   xTaskCreate(OutputTask, "Output Task", 100, NULL, 1, NULL);
   
}

// defintion of input task1 
void InputTask1(void *pvParameters)
{
  while(1)
  {
     // set flag bit TASK1_BIT
     xEventGroupSetBits(xEventGroup, TASK1_BIT);
     //delay this task for 500ms
     vTaskDelay(xDelay500ms);
  }
}

// defintion of input task2

void InputTask2(void *pvParameters)
{
  while(1)
  {
     // set flag bit TASK2_BIT
    xEventGroupSetBits(xEventGroup, TASK2_BIT);
     //delay this task for 500ms
    vTaskDelay(xDelay500ms);
  }
}

// defintion of input task3

void InputTask3(void *pvParameters)
{
  while(1)
  {
     // set flag bit TASK2_BIT
    xEventGroupSetBits(xEventGroup,TASK3_BIT);
    //delay this task for 500ms
    vTaskDelay(xDelay500ms);
  }
}

//  Definition of output task
void OutputTask(void *pvParameters)
{ 
  // define a variable which holds the state of events 
  const EventBits_t xBitsToWaitFor  = (TASK1_BIT | TASK2_BIT | TASK3_BIT);
  EventBits_t xEventGroupValue;
  while(1)
  {
    xEventGroupValue  = xEventGroupWaitBits(xEventGroup,
                                            xBitsToWaitFor,
                                            pdTRUE,
                                            pdTRUE,
                                            portMAX_DELAY
                                            );
   if((xEventGroupValue & TASK1_BIT) !=0)
   {
   Serial.println("Task1 event occured");
   }
   if((xEventGroupValue & TASK2_BIT !=0))
   {
   Serial.println("Task2 event occured");
   }
   if((xEventGroupValue & TASK3_BIT !=0))
   {
   Serial.println("Task3 event occured");
   }
  }
}
void loop(){}