Catalog

Initialization of Lists and List Items

Insertion of List Items

Lists are a data structure in FreeRTOS. They are similar in concept to linked lists. Lists are used to track tasks in FreeRTOS. Everything related to lists is in the files list.c and list. H. In list.h, a structure called List_t is defined as follows:

typedef struct xLIST
{
    listFIRST_LIST_INTEGRITY_CHECK_VALUE;
    configLIST_VOLATILE UBaseType_t   uxNumberOfltems; 
    ListItem_t * configLIST_VOLATILE  pxIndex;
    MiniListItem_t                    xListEnd;
    listSECOND_LIST_INTEGRITY_CHECK_VALUE
} List_t;

                                               

 

List items are items stored in the list. FreeRTOS provides two kinds of list items: list items and mini-list items. Both are defined in the file list.h. Let's first look at the list items and define them as follows:

struct xLIST_ITEM
{
    listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE
    configLIST_VOLATILE TickType_t	xItemValue; 
    struct xLIST_ITEM * configLIST_VOLATILE	  pxNext; 
    struct xLIST_ITEM * configLIST_VOLATILE	pxPrevious;
    void *                      pvOwner;
    void * configLIST           pvContainer;
    listSECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE_VOLATILE
};
typedef struct  xLIST_ITEM	ListItem_t

struct xMINI_LIST_ITEM
{
    listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE
    configLIST_VOLATILE TickType_t	xItemValue;
    struct xLIST_ITEM * configLIST_VOLATILE	pxNext; 
    struct xLIST_ITEM * configLIST_VOLATILE	pxPrevious;
};
typedef struct xMINI_LIST_ITEM MiniListItem_t;

 

• List and list item initialization

The initialization of a list is actually to initialize the member variables in the List_t structure. The initialization of a list is accomplished by making the function vListInitialise(), which is defined in list.c. The functions are as follows:

void vListInitialise( List_t * const pxList )
{
    pxList->pxIndex = ( ListItem_t * ) &( pxList->xListEnd );	
    pxList->xListEnd.xItemValue = portMAX_DELAY;	
    pxList->xListEnd.pxNext = ( ListItem_t * ) &( pxList->xListEnd );	
    pxList->xListEnd.pxPrevious = ( ListItem_t * ) &( pxList->xListEnd );
    pxList->uxNumberOfItems = ( UBaseType_t ) 0U;	
    listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList );
    listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList );
}

Initialization of list items is accomplished by the function vListInitialiseItem(), which is as follows:

void vListInitialiseItem( ListItem_t * const pxItem )
{
    pxItem->pvContainer = NULL;    //Initialize pvContainer to NULL
    
    //Initialize variables for integrity checking if this function is turned on.
    listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem );             
    listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem );
}

​​​​

• List item insertion

The insertion of list items is accomplished by the function vListInsert(). The function prototype is as follows:

void vListInsert( List_t * const   pxList,ListItem_t * const   pxNewListItem )

To illustrate the insertion process, insert three list items into an empty list with values of 40, 60 and 50, respectively.

 

• Insertion and deletion experiments

This experiment designed three tasks: start_task, task 1_task and list_task. The task functions of these three tasks are as follows:

 

Settings of task priority, stack size, task handle, etc.

#define START_TASK_PRIO 1//Task Priority
#Define START_STK_SIZE 128 // Task Stack Size
TaskHandle_t StartTask_Handler;      //task handle
void start_task(void *pvParameters); //Task function	

#define TASK1_TASK_PRIO 2//Task Priority
#Define TASK1_STK_SIZE 128 // Task Stack Size
TaskHandle_t Task1Task_Handler;      //task handle
void task1_task(void *pvParameters); //Task function	


#define LIST_TASK_PRIO 3//Task Priority
#define LIST_STK_SIZE 128 // / Task Stack Size
TaskHandle_t ListTask_Handler;		 //task handle
void list_task(void *pvParameters);  //Task function

 

Definitions of lists and list items:

 

main function:

int main(void)
{
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_4);//Setting System Interrupt Priority Group 4         
    delay_init(168);	//Initialization Delay Function
    uart_init(115200);	//Initialize Serial Port
    LED_Init();	//Initialization of LED Port
    KEY_Init();	//Initialization key
    LCD_Init();	//Initialize LCD

    POINT_COLOR = RED; LCD_ShowString(30,10,200,16,16,"ATK STM32F103/407");
    LCD_ShowString(30,30,200,16,16,"FreeRTOS Examp 7-1");                 
    LCD_ShowString(30,50,200,16,16,"list and listItem");     
    LCD_ShowString(30,70,200,16,16,"ATOM@ALIENTEK");     
    LCD_ShowString(30,90,200,16,16,"2016/11/25");
    
    //Create Start Tasks		
    xTaskCreate((TaskFunction_t	)start_task,	//Task function
    (const char*	)"start_task",	//Task Name
    (uint16_t	)START_STK_SIZE,	//Task Stack Size
    (void*	)NULL,	//Parameters passed to task functions
    (UBaseType_t	)START_TASK_PRIO,	//Task Priority
    (TaskHandle_t*	)&StartTask_Handler);	//task handle
    vTaskStartScheduler();		//Open Task Scheduling
}

 

Verification: