KernelinsideTask control

Updated Jun 2025

vTaskDelay()

[Task Control]

task. h

1void vTaskDelay( const TickType_t xTicksToDelay );



INCLUDE_vTaskDelay
must be defined as 1 for this function to be available. See the RTOS Configuration documentation for more information.

Delay a task for a given number of ticks. The actual time that the task remains blocked depends on the tick rate. The constant 

portTICK_PERIOD_MS
can be used to calculate real time from the tick rate - with the resolution of one tick period.

vTaskDelay()
specifies a time at which the task wishes to unblock relative to the time at which 
vTaskDelay()
is called. For example, specifying a block period of 100 ticks will cause the task to remain blocked for 100 ticks after vTaskDelay() is called. The task will be unblocked on the 100th tick after 
vTaskDelay()
is called. 
vTaskDelay()
does not therefore provide a good method of controlling the frequency of a periodic task as the path taken through the code, as well as other task and interrupt activity, will effect the frequency at which 
vTaskDelay()
gets called and therefore the time at which the task next executes. See 
vTaskDelayUntil()
for an alternative API function designed to facilitate fixed frequency execution. It does this by specifying an absolute time (rather than a relative time) at which the calling task should unblock.
Passing 0 to 
vTaskDelay()
shall yield to next ready task of equal priority.

Parameters:

  • xTicksToDelay

    The amount of time, in tick periods, that the calling task should block.

Example usage:

1void vTaskFunction( void * pvParameters )
2{
3    /* Block for 500ms. */
4    const TickType_t xDelay = 500 / portTICK_PERIOD_MS;
5

6    for( ;; )
7    {
8        /* Simply toggle the LED every 500ms, blocking between each toggle. */
9        vToggleLED();
10        vTaskDelay( xDelay );
11    }
12}