Time Event class
- Description
- Time events are special QF events equipped with the notion of time passage. The basic usage model of the time events is as follows. An active object allocates one or more QTimeEvt objects (provides the storage for them). When the active object needs to arrange for a timeout, it arms one of its time events to fire either just once (one-shot) or periodically. Each time event times out independently from the others, so a QF application can make multiple parallel timeout requests (from the same or different active objects). When QF detects that the appropriate moment has arrived, it inserts the time event directly into the recipient's event queue. The recipient then processes the time event just like any other event.
Time events, as any other QF events derive from the QEvt base structure. Typically, you will use a time event as-is, but you can also further derive more specialized time events from it by adding some more data members and/or specialized functions that operate on the specialized time events.
Internally, the armed time events are organized into linked lists–one list for every supported ticking rate. These linked lists are scanned in every invocation of the QF_tickX_() function. Only armed (timing out) time events are in the list, so only armed time events consume CPU cycles.
- See also
- QTimeEvt for the description of the data members
Object Orientation
- Note
- QF manages the time events in the function QF_tickX_(), which must be called periodically, from the clock tick ISR or from the special QTicker active object.
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Even though QTimeEvt is a subclass of QEvt, QTimeEvt instances can NOT be allocated dynamically from event pools. In other words, it is illegal to allocate QTimeEvt instances with the Q_NEW() or Q_NEW_X() macros.
Definition at line 480 of file qf.h.
Data Fields inherited from QEvt