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Description

Sets or clears event flag bits. The bits set or cleared are specified in a bit mask (i.e., the flags argument). OSFlagPost() readies each task that has its desired bits satisfied by this call. The caller can set or clear bits that are already set or cleared.

Files

os.h/os_flag.c

Prototype

OS_FLAGS  OSFlagPost (OS_FLAG_GRP  *p_grp,

...

                      OS_FLAGS      flags,

...

                      OS_OPT        opt,

...

                      OS_ERR       *p_err)

...

...

Called from

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Code enabled by

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os_flag.c

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Task or ISR

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OS_CFG_FLAG_EN

You can set or clear event flag bits by calling OSFlagPost(). The bits set or cleared are specified in a bit mask (i.e., the flags argument). OSFlagPost() readies each task that has its desired bits satisfied by this call. The caller can set or clear bits that are already set or cleared.

Arguments

p_grp

is a pointer to the event flag group.

...

is a pointer to an error code and can be:

OS_ERR_NONE

the call is successful.

OS_ERR_FLAGOBJ_INVALIDPTR_OPTNULL

If OS_CFG_ARG_CHK_EN is set to 1 in DEF_ENABLED in os_cfg.h: if you specified an invalid optionthe caller passed a NULL pointer.

OS_ERR_OBJ_PTR_NULLTYPE

If OS_CFG_ARGOBJ_TYPE_CHK_EN is set to 1 in DEF_ENABLED in os_cfg.h: p_grp is not pointing to an event flag group.

OS_ERR_OPT_INVALID

If OS_CFG_ARG_CHK_EN is set to DEF_ENABLED in os_cfg.h: if the caller passed a NULL pointeryou specified an invalid option.

OS_ERR_OS_OBJNOT_TYPERUNNING

If If OS_CFG_OBJINVALID_OS_TYPECALLS_CHK_EN is set to 1 in  is set to DEF_ENABLED in os_cfg.h: p_grp is not pointing to an event flag groupif µC/OS-III is not running yet.

Returned Value

The new value of the event flags.

Required Configuration

OS_CFG_FLAG_EN must be enabled in os_cfg.h. Refer to µC-OS-III Configuration Manual.

Callers

Application and ISRs.

Notes/Warnings

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1. Event flag groups must be created before they are used.

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1. The execution time of this function depends on the number of tasks waiting on the event flag group. However, the execution time is still deterministic.

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1. Although the example below shows that we are posting from a task, OSFlagPost() can also be called from an ISR.

Example Usage

          #define  ENGINE_OIL_PRES_OK   0x01
          #define  ENGINE_OIL_TEMP_OK   0x02
          #define  ENGINE_START         0x04
           
          OS_FLAG_GRP  EngineStatusFlags;
           
           
          void  TaskX (void *p_arg)
          {
              OS_ERR    err;
              OS_FLAGS  flags;
           
           
              (void)&p_arg;
              while (DEF_ON) {
                  :
                  :
                  flags = OSFlagPost(&EngineStatusFlags,
                                     ENGINE_START,
                                     OS_OPT_POST_FLAG_SET,
                                     &err);
                  /* Check 'err" */
                  :
                  :
              }
          }