Select your cookie preferences

We use essential cookies and similar tools that are necessary to provide our site and services. We use performance cookies to collect anonymous statistics, so we can understand how customers use our site and make improvements. Essential cookies cannot be deactivated, but you can choose “Customize” or “Decline” to decline performance cookies.

If you agree, AWS and approved third parties will also use cookies to provide useful site features, remember your preferences, and display relevant content, including relevant advertising. To accept or decline all non-essential cookies, choose “Accept” or “Decline.” To make more detailed choices, choose “Customize.”

KernelinsideTasks and co-routines

Updated Mar 2025

Tasks

[More about tasks...]

The FreeRTOS Tutorial Books provide additional detailed information on tasks and their behaviour.

Task Priorities

Each task is assigned a priority from 0 to ( configMAX_PRIORITIES - 1 ), where configMAX_PRIORITIES is defined within FreeRTOSConfig.h.

If the port in use implements a port optimised task selection mechanism that uses a 'count leading zeros' type instruction (for task selection in a single instruction) and configUSE_PORT_OPTIMISED_TASK_SELECTION is set to 1 in FreeRTOSConfig.h, then configMAX_PRIORITIES cannot be higher than 32. In all other cases configMAX_PRIORITIES can take any value within reason - but for reasons of RAM usage efficiency should be kept to the minimum value actually necessary.

Low priority numbers denote low priority tasks. The idle task has priority zero (tskIDLE_PRIORITY).

The FreeRTOS scheduler ensures that tasks in the Ready or Running state will always be given processor (CPU) time in preference to tasks of a lower priority that are also in the ready state. In other words, the task placed into the Running state is always the highest priority task that is able to run.

Any number of tasks can share the same priority. If configUSE_TIME_SLICING is not defined, or if configUSE_TIME_SLICING is set to 1, then Ready state tasks of equal priority will share the available processing time using a time sliced round robin scheduling scheme.