Merge pull request #1579 from skliper/fix1390-event_filter_doc

Fix #1390, Improve event filter documentation

modules/core_api/fsw/inc/cfe_evs.h

@@ -286,8 +286,9 @@ CFE_Status_t CFE_EVS_SendTimedEvent(CFE_TIME_SysTime_t Time, uint16 EventID, uin
 ** \brief Resets the calling application's event filter for a single event ID.
 **
 ** \par Description
-**          The effect of resetting an event filter depends on the filter scheme.
-**          The #CFE_EVS_EventFilter_BINARY scheme resets the filter counter for the specified Event ID.
+**          Resets the filter such that the next event is treated like the first.
+**          For example, if the filter was set to only send the first event, the
+**          next event following the reset would be sent.
 **
 ** \par Assumptions, External Events, and Notes:
 **          None

modules/core_api/fsw/inc/cfe_evs_api_typedefs.h

@@ -39,7 +39,9 @@
 #include "common_types.h" /* Basic data types */
 #include "cfe_evs_extern_typedefs.h"
 
-/** \name Common Event Filter Mask Values  */
+/** \name Common Event Filter Mask Values
+ * Message is sent if (previous event count) & MASK == 0
+ */
 /** \{ */
 #define CFE_EVS_NO_FILTER        0x0000 /**< \brief Stops any filtering.  All messages are sent. */
 #define CFE_EVS_FIRST_ONE_STOP   0xFFFF /**< \brief Sends the first event.  All remaining messages are filtered. */