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[Event Group API]
StaticEventGroup_t *pxEventGroupBuffer );
Creates a new RTOS event group, and returns a handle by which the newly created event group can be referenced. configSUPPORT_STATIC_ALLOCATION must be set to 1 in FreeRTOSConfig.h and the RTOS source file FreeRTOS/source/event_groups.c must be included in the build for the xEventGroupCreateStatic() function to be available.
Each event group requires a [very] small amount of RAM that is used to hold the event group’s state. If an event group is created using xEventGroupCreate() then the required RAM is automatically allocated from the FreeRTOS heap. If an event group is created using xEventGroupCreateStatic() then the RAM is provided by the application writer, which requires an additional parameter, but allows the RAM to be statically allocated at compile time. See the Static Vs Dynamic allocation page for more information.
Event groups are stored in variables of type EventBits_t. The number of bits (or flags) implemented within an event group is 8 if configUSE_16_BIT_TICKS is set to 1, or 24 if configUSE_16_BIT_TICKS is set to 0. The dependency on configUSE_16_BIT_TICKS results from the data type used for thread local storage in the internal implementation of RTOS tasks.
pxEventGroupBuffer Must point to a variable of type StaticEventGroup_t, in which the event group data structure will be stored.
- If the event group was created successfully then a handle to the event group is returned. If pxEventGroupBuffer was NULL then NULL is returned.
/* Declare a variable to hold the handle of the created event group. */ EventGroupHandle_t xEventGroupHandle; /* Declare a variable to hold the data associated with the created event group. */ StaticEventGroup_t xCreatedEventGroup; /* Attempt to create the event group. */ xEventGroupHandle = xEventGroupCreateStatic( &xCreatedEventGroup ); /* pxEventGroupBuffer was not null so expect the event group to have been created? */ configASSERT( xEventGroupHandle );