xTaskDelayUntil() function

task. h @code{c} BaseType_t xTaskDelayUntil( TickType_t *pxPreviousWakeTime, const TickType_t xTimeIncrement ); @endcode INCLUDE_xTaskDelayUntil must be defined as 1 for this function to be available. See the configuration section for more information. Delay a task until a specified time. This function can be used by periodic tasks to ensure a constant execution frequency. This function differs from vTaskDelay () in one important aspect: vTaskDelay () will cause a task to block for the specified number of ticks from the time vTaskDelay () is called. It is therefore difficult to use vTaskDelay () by itself to generate a fixed execution frequency as the time between a task starting to execute and that task calling vTaskDelay () may not be fixed [the task may take a different path though the code between calls, or may get interrupted or preempted a different number of times each time it executes]. Whereas vTaskDelay () specifies a wake time relative to the time at which the function is called, xTaskDelayUntil () specifies the absolute (exact) time at which it wishes to unblock. The macro pdMS_TO_TICKS() can be used to calculate the number of ticks from a time specified in milliseconds with a resolution of one tick period. Example usage: @code{c} // Perform an action every 10 ticks. void vTaskFunction( void * pvParameters ) { TickType_t xLastWakeTime; const TickType_t xFrequency = 10; BaseType_t xWasDelayed; // Initialise the xLastWakeTime variable with the current time. xLastWakeTime = xTaskGetTickCount (); for( ;; ) { // Wait for the next cycle. xWasDelayed = xTaskDelayUntil( &xLastWakeTime, xFrequency ); // Perform action here. xWasDelayed value can be used to determine // whether a deadline was missed if the code here took too long. } } @endcode