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[More about software timers…]
Configuring an application to use software timersTo make the FreeRTOS software timer API available in an application, simply:
Add the FreeRTOS/Source/timers.c source file to your project, and
Define the constants detailed in the table below in the applications FreeRTOSConfig.h header file.
|configUSE_TIMERS||Set to 1 to include timer functionality. The timer service task will be automatically created as the RTOS scheduler starts when configUSE_TIMERS is set to 1.|
Sets the priority of the timer service task. Like all tasks,
the timer service task can run at any priority between 0 and
( configMAX_PRIORITIES – 1 ).
This value needs to be chosen carefully to meet the requirements of the application. For example, if the timer service task is made the highest priority task in the system, then commands sent to the timer service task (when a timer API function is called) and expired timers will both get processed immediately. Conversely, if the timer service task is given a low priority, then commands sent to the timer service task and expired timers will not be processed until the timer service task is the highest priority task that is able to run. It is worth noting here however, that timer expiry times are calculated relative to when a command is sent, and not relative to when a command is processed.
This sets the maximum number of unprocessed commands that the
timer command queue can hold at any one time.
Reasons the timer command queue might fill up include:
Sets the size of the stack (in words, not bytes) allocated to the
timer service task.
Timer callback functions execute in the context of the timer service task. The stack requirement of the timer service task therefore depends on the stack requirements of the timer callback functions.