xTaskCreate

task. h

BaseType_t xTaskCreate(
                          TaskFunction_t pvTaskCode,
                          const char * const pcName,
                          uint16_t usStackDepth,
                          void *pvParameters,
                          UBaseType_t uxPriority,
                          TaskHandle_t *pvCreatedTask
                      );

Create a new task and add it to the list of tasks that are ready to run.

Internally, within the FreeRTOS implementation, tasks use two blocks of memory. The first block is used to hold the task's data structures. The second block is used by the task as its stack. If a task is created using xTaskCreate() then both blocks of memory are automatically dynamically allocated inside the xTaskCreate() function. (see http://www.freertos.org/a00111.html). If a task is created using xTaskCreateStatic() then the application writer must provide the required memory. xTaskCreateStatic() therefore allows a task to be created without using any dynamic memory allocation.

See xTaskCreateStatic() for a version that does not use any dynamic memory allocation.

xTaskCreate() can only be used to create a task that has unrestricted access to the entire microcontroller memory map. Systems that include MPU support can alternatively create an MPU constrained task using xTaskCreateRestricted().

Parameters

pvTaskCode	Pointer to the task entry function. Tasks must be implemented to never return (i.e. continuous loop).
pcName	A descriptive name for the task. This is mainly used to facilitate debugging. Max length defined by configMAX_TASK_NAME_LEN - default is 16.
usStackDepth	The size of the task stack specified as the number of variables the stack can hold - not the number of bytes. For example, if the stack is 16 bits wide and usStackDepth is defined as 100, 200 bytes will be allocated for stack storage.
pvParameters	Pointer that will be used as the parameter for the task being created.
uxPriority	The priority at which the task should run. Systems that include MPU support can optionally create tasks in a privileged (system) mode by setting bit portPRIVILEGE_BIT of the priority parameter. For example, to create a privileged task at priority 2 the uxPriority parameter should be set to ( 2 | portPRIVILEGE_BIT ).
pvCreatedTask	Used to pass back a handle by which the created task can be referenced.

Returns

pdPASS if the task was successfully created and added to a ready list, otherwise an error code defined in the file projdefs.h

Example usage:

// Task to be created.
void vTaskCode( void * pvParameters )
{
    for( ;; )
    {
     // Task code goes here.
    }
}

// Function that creates a task.
void vOtherFunction( void )
{
static uint8_t ucParameterToPass;
TaskHandle_t xHandle = NULL;

    // Create the task, storing the handle.  Note that the passed parameter ucParameterToPass
    // must exist for the lifetime of the task, so in this case is declared static.  If it was just an
    // an automatic stack variable it might no longer exist, or at least have been corrupted, by the time
    // the new task attempts to access it.
    xTaskCreate( vTaskCode, "NAME", STACK_SIZE, &ucParameterToPass, tskIDLE_PRIORITY, &xHandle );
    configASSERT( xHandle );

    // Use the handle to delete the task.
    if( xHandle != NULL )
    {
        vTaskDelete( xHandle );
    }
}