FreeRTOS With Arduino 09 : Read Task Info : VTaskList()

In earlier tutorials, we have seen how to create, delete, suspend and resume the tasks. In this tutorial, we will see how to read the Task info(state, Stack size, priority).

Step 1: API Details :

Here we will discuss some of the most frequently used API's related to tasks.

xTaskCreate(): This interface is used to create a new Task, if the task is successfully created then it returns pdPass(1) or else errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY(-1). Check this link for more details.

vTaskDelay(): This function is used to delay/block the task for specified delay time(ticks). INCLUDE_vTaskDelay needs to be set to 1 in FreeRtosConfig.h file for using this function. Check this link for more details.

vTaskSuspend(): This function is used to Suspend a task, the suspended remains in the same state util it is resumed.For this, we need to pass the handle of the tasks that needs to be suspended. Passing NULL will suspend own task. Check this link for more details.

vTaskResume(): This function is used to resume a suspended task. If the Resumed task has higher priority than the running task then it will preempt the running task or else stays in ready stateFor this, we need to pass the handle of the task to be resumed. Check this link for more details.

vTaskList(): This function is used to read the task details(name, state, priority, num). We need to pass a string pointer(buffer) to which it copies the above task details. The buffer size should be minimum 40 bytes per task. Check this link for more details.

Step 2: Example1 :

In this example, we will be creating 3-tasks which run for some time and enter the blocked state allowing other tasks to run. We will include INT0 falling edge interrupt to read and display the current task list with all the task info. Every time interrupt is generated it will take the snapshot of tasks(name, state, priority, num) and sends on Serial port.

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 * File:   10-ReadTaskInfo
 * Version: 15.0
 * Author: ExploreEmbedded
 * Website: http://www.exploreembedded.com/wiki
 * Description: File contains the free rtos example to demonstarte task Suspend and Resume.
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#include 
TaskHandle_t TaskHandle_1;
TaskHandle_t TaskHandle_2;
TaskHandle_t TaskHandle_3;
char ptrTaskList[250];
void setup()
{  
    Serial.begin(9600);
    Serial.println(F("In Setup function"));
    /* Use INT0(pin2) falling edge interrupt for resuming tasks */
    attachInterrupt(digitalPinToInterrupt(2), ExternalInterrupt, FALLING); 
    /* Create a task with priority 3. Capture the Task details to its handler*/
    xTaskCreate(MyTask1, "Task1", 120, NULL, 1, &TaskHandle_1);
    xTaskCreate(MyTask2, "Task2", 120, NULL, 2, &TaskHandle_2);  
    xTaskCreate(MyTask3, "Task3", 120, NULL, 3, &TaskHandle_3);
}
void loop()
{
    // Hooked to IDle task, it will run whenever CPU is idle
    Serial.println(F("Loop function"));
    delay(1000);
}
/* 
 *  Task info(state, Priority, Stack available) is read immediately the switch is pressed and sent on Serial Port
 *  Serial data is printed in ISR for demonstarting the control flow. This should not be done as it takes long time to send data on Serial port.
 *  Taking to much ISR time will starve the other tasks or User application.  *  
 */
static void ExternalInterrupt()
{
    vTaskList(ptrTaskList);
    Serial.println(F("**********************************"));
    Serial.println(F("Task  State   Prio    Stack    Num")); 
    Serial.println(F("**********************************"));
    Serial.print(ptrTaskList);
    Serial.println(F("**********************************"));
}
/* Task1 with priority 1 */
static void MyTask1(void* pvParameters)
{
    while(1)
    {
        Serial.println(F("Task1 Running"));
        delay(200);
        vTaskDelay(250/portTICK_PERIOD_MS);
    }
}
/* Task2 with priority 2 */
static void MyTask2(void* pvParameters)
{
    while(1)
    {    
        Serial.println(F("Task2 Running"));
        delay(200);
        vTaskDelay(300/portTICK_PERIOD_MS);
    }
}
/* Task3 with priority 3 */
static void MyTask3(void* pvParameters)
{
    char suspendFlag=0;
    while(1)
    {    
        Serial.println(F("Task3 Running"));
        if(suspendFlag==1)                 //Task1 is suspended and resumed alternatively whenever Task3 runs.
        {
            vTaskSuspend(TaskHandle_1);
            suspendFlag = 0;
        }
        else
        {
            vTaskResume(TaskHandle_1);
            suspendFlag = 1;
        }
        delay(200);
        vTaskDelay(400/portTICK_PERIOD_MS);
    }
}

Step 3: Output1 :

All the tasks will be running for some time and enter the blocked state allowing other tasks to run. Task3 suspends and resumes the Task1 alternatively. Whenever INT0 interrupt is generated, ISR will take the snapshot of all the task and sends it on the serial port.