#include <Arduino_FreeRTOS.h>
#include <semphr.h>

SemaphoreHandle_t mutex;


void setup() {
  Serial.begin(9600);
  xTaskCreate(task1, "print task", 128,  NULL, 2,  NULL );
  xTaskCreate(task2, "print task", 128,  NULL, 2,  NULL );
  mutex = xSemaphoreCreateMutex();
}

void loop()
{
  // Empty. Things are done in Tasks.
}

void task1(void *pvParameters)  
{
  while(1){
    if (xSemaphoreTake(mutex, 10) == pdTRUE){
      Serial.println("hello from task 1");
      xSemaphoreGive(mutex);
      taskYIELD();
    }
  }
}

void task2(void *pvParameters)  
{
  while(1){
    if (xSemaphoreTake(mutex, 10) == pdTRUE){
      Serial.println("hello from task 2");
      xSemaphoreGive(mutex);
      taskYIELD();
    }
  }
}