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Last site update Jan 14 2014

Task Utilities
[API]

Modules


xTaskGetCurrentTaskHandle

task.h
TaskHandle_t xTaskGetCurrentTaskHandle( void );

INCLUDE_xTaskGetCurrentTaskHandle must be set to 1 for this function to be available.

Returns:
The handle of the currently running (calling) task.

xTaskGetIdleTaskHandle

task.h
TaskHandle_t xTaskGetIdleTaskHandle( void );

INCLUDE_xTaskGetIdleTaskHandle must be set to 1 for this function to be available.

Returns:
The task handle associated with the Idle task. The Idle task is created automatically when the RTOS scheduler is started.

eTaskGetState

task.h
eTaskState eTaskGetState( TaskHandle_t xTask );

Returns as an enumerated type the state in which a task existed at the time eTaskGetState() was executed.

INCLUDE_eTaskGetState must be set to 1 in FreeRTOSConfig.h for eTaskGetState() to be available.

Parameters:
xTask The handle of the subject task (the task being queried).
Returns:
The table below lists the value that eTaskGetState() will return for each possible state that the task referenced by the xTask parameter can exist in.

State
Returned Value
Ready eReady
Running eRunning (the calling task is querying its own priority)
Blocked eBlocked
Suspended eSuspended
Deleted eDeleted (the tasks TCB is waiting to be cleaned up)

pcTaskGetTaskName

task.h
char * pcTaskGetTaskName( TaskHandle_t xTaskToQuery );

INCLUDE_pcTaskGetTaskName must be set to 1 in FreeRTOSConfig.h for pcTaskGetTaskName() to be available.

Parameters:
xTaskToQuery The handle of the task being queried. xTaskToQuery can be set to NULL to query the name of the calling task.
Returns:
A pointer to the subject tasks name, which is a standard NULL terminated C string.

xTaskGetTickCount

task.h
volatile TickType_t xTaskGetTickCount( void );

This function cannot be called from an ISR. Use xTaskGetTickCountFromISR() instead.

Returns:
The count of ticks since vTaskStartScheduler was called.

xTaskGetTickCountFromISR

task.h
volatile TickType_t xTaskGetTickCountFromISR( void );

A version of xTaskGetTickCount() that can be called from an ISR.

Returns:
The count of ticks since vTaskStartScheduler was called.

xTaskGetSchedulerState

task.h
BaseType_t xTaskGetSchedulerState( void );

Returns:
One of the following constants (defined within task.h): taskSCHEDULER_NOT_STARTED, taskSCHEDULER_RUNNING, taskSCHEDULER_SUSPENDED.

uxTaskGetNumberOfTasks

task.h
unsigned BaseType_t uxTaskGetNumberOfTasks( void );

Returns:
The number of tasks that the RTOS kernel is currently managing. This includes all ready, blocked and suspended tasks. A task that has been deleted but not yet freed by the idle task will also be included in the count.

vTaskList

task.h
void vTaskList( char *pcWriteBuffer );
	

configUSE_TRACE_FACILITY and configUSE_STATS_FORMATTING_FUNCTIONS must be defined as 1 in FreeRTOSConfig.h for this function to be available. See the configuration section for more information.

NOTE: This function will disable interrupts for its duration. It is not intended for normal application runtime use but as a debug aid.

vTaskList() calls uxTaskGetSystemState(), then formats the raw data generated by uxTaskGetSystemState() into a human readable (ASCII) table that shows the state of each task, including the task's stack high water mark (the smaller the high water mark number the closer the task has come to overflowing its stack). Click here to see an example of the output generated.

In the ASCII table the following letters are used to denote the state of a task:

  • 'B' - Blocked
  • 'R' - Ready
  • 'D' - Deleted (waiting clean up)
  • 'S' - Suspended, or Blocked without a timeout

vTaskList() is a utility function provided for convenience only. It is not considered part of the kernel. See vTaskGetRunTimeStats() for a utility function that generates a similar table of run time task utilisation information.

Parameters:
pcWriteBuffer   A buffer into which the above mentioned details will be written, in ASCII form. This buffer is assumed to be large enough to contain the generated report. Approximately 40 bytes per task should be sufficient.

vTaskStartTrace

task.h
void vTaskStartTrace( char * pcBuffer, unsigned long ulBufferSize );

[The function relates to the legacy trace utility - which was removed in FreeRTOS V7.1.0 - users may find the newer Trace Hook Macros easier and more powerful to use.]

Starts a RTOS kernel activity trace. The trace logs the identity of which task is running when.

The trace file is stored in binary format. A separate DOS utility called convtrce.exe is used to convert this into a tab delimited text file which can be viewed and plotted in a spread sheet.

Parameters:
pcBuffer The buffer into which the trace will be written.
ulBufferSize The size of pcBuffer in bytes. The trace will continue until either the buffer in full, or ulTaskEndTrace() is called.

ulTaskEndTrace

task.h
unsigned long ulTaskEndTrace( void );

[The function relates to the legacy trace utility - which was removed in FreeRTOS V7.1.0 - users may find the newer Trace Hook Macros easier and more powerful to use.]

Stops an RTOS kernel activity trace. See vTaskStartTrace().

Returns:
The number of bytes that have been written into the trace buffer.

vTaskGetRunTimeStats

task.h
void vTaskGetRunTimeStats( char *pcWriteBuffer );
	

See the Run Time Stats page for a full description of this feature.

configGENERATE_RUN_TIME_STATS and configUSE_STATS_FORMATTING_FUNCTIONS must both be defined as 1 for this function to be available. The application must also then provide definitions for portCONFIGURE_TIMER_FOR_RUN_TIME_STATS() and portGET_RUN_TIME_COUNTER_VALUE to configure a peripheral timer/counter and return the timers current count value respectively. The counter should be at least 10 times the frequency of the tick count.

NOTE: This function will disable interrupts for its duration. It is not intended for normal application runtime use but as a debug aid.

vTaskGetRunTimeStats() calls uxTaskGetSystemState(), then formats the raw data generated by uxTaskGetSystemState() into a human readable (ASCII) table that shows the amount of time each task has spent in the Running state (how much CPU time each task has consumed). The data is provided as both an absolute and a percentage value. The resolution of the absolute value is dependent on the frequency of the run time stats clock provided by the application.

vTaskGetRunTimeStats() is a utility function provided for convenience only. It is not considered part of the kernel. See vTaskList() for a utility function that generates information on the state of each task.

Parameters:
pcWriteBuffer  A buffer into which the execution times will be written, in ASCII form. This buffer is assumed to be large enough to contain the generated report. Approximately 40 bytes per task should be sufficient.







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