xTimerCreateStatic() function

Creates a new software timer instance, and returns a handle by which the created software timer can be referenced. Internally, within the FreeRTOS implementation, software timers use a block of memory, in which the timer data structure is stored. If a software timer is created using xTimerCreate() then the required memory is automatically dynamically allocated inside the xTimerCreate() function. (see https://www.FreeRTOS.org/a00111.html). If a software timer is created using xTimerCreateStatic() then the application writer must provide the memory that will get used by the software timer. xTimerCreateStatic() therefore allows a software timer to be created without using any dynamic memory allocation. Timers are created in the dormant state. The xTimerStart(), xTimerReset(), xTimerStartFromISR(), xTimerResetFromISR(), xTimerChangePeriod() and xTimerChangePeriodFromISR() API functions can all be used to transition a timer into the active state. Example usage: @verbatim // The buffer used to hold the software timer's data structure. static StaticTimer_t xTimerBuffer; // A variable that will be incremented by the software timer's callback // function. UBaseType_t uxVariableToIncrement = 0; // A software timer callback function that increments a variable passed to // it when the software timer was created. After the 5th increment the // callback function stops the software timer. static void prvTimerCallback( TimerHandle_t xExpiredTimer ) { UBaseType_t *puxVariableToIncrement; BaseType_t xReturned; // Obtain the address of the variable to increment from the timer ID. puxVariableToIncrement = ( UBaseType_t * ) pvTimerGetTimerID( xExpiredTimer ); // Increment the variable to show the timer callback has executed. ( *puxVariableToIncrement )++; // If this callback has executed the required number of times, stop the // timer. if( *puxVariableToIncrement == 5 ) { // This is called from a timer callback so must not block. xTimerStop( xExpiredTimer, staticDONT_BLOCK ); } } void main( void ) { // Create the software time. xTimerCreateStatic() has an extra parameter // than the normal xTimerCreate() API function. The parameter is a pointer // to the StaticTimer_t structure that will hold the software timer // structure. If the parameter is passed as NULL then the structure will be // allocated dynamically, just as if xTimerCreate() had been called. xTimer = xTimerCreateStatic( "T1", // Text name for the task. Helps debugging only. Not used by FreeRTOS. xTimerPeriod, // The period of the timer in ticks. pdTRUE, // This is an auto-reload timer. ( void * ) &uxVariableToIncrement, // A variable incremented by the software timer's callback function prvTimerCallback, // The function to execute when the timer expires. &xTimerBuffer ); // The buffer that will hold the software timer structure. // The scheduler has not started yet so a block time is not used. xReturned = xTimerStart( xTimer, 0 ); // ... // Create tasks here. // ... // Starting the scheduler will start the timers running as they have already // been set into the active state. vTaskStartScheduler(); // Should not reach here. for( ;; ); } @endverbatim