Description
Sets or rlears 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
Arguments
p_grp
is a pointer to the event flag group.
flags
specifies which bits to be set or cleared. If opt is OS_OPT_POST_FLAG_SET, each bit that is set in flags will set the corresponding bit in the event flag group. For example to set bits 0, 4, and 5, you would set flags to 0x31 (note that bit 0 is the least significant bit). If opt is OS_OPT_POST_FLAG_CLR, each bit that is set in flags will clear the corresponding bit in the event flag group. For example to clear bits 0, 4, and 5, you would specify flags as 0x31 (again, bit 0 is the least significant bit).
opt
indicates whether the flags are set (OS_OPT_POST_FLAG_SET) or cleared (OS_OPT_POST_FLAG_CLR).
The caller may also “add” OS_OPT_POST_NO_SCHED so that µC/OS-III will not call the scheduler after the post.
p_err
is a pointer to an error code and can be:
OS_ERR_NONE
the call is successful.
OS_ERR_FLAG_INVALID_OPT
If OS_CFG_ARG_CHK_EN is set to 1 in os_cfg.h: if you specified an invalid option.
OS_ERR_OBJ_PTR_NULL
If OS_CFG_ARG_CHK_EN is set to 1 in os_cfg.h: if the caller passed a NULL pointer.
OS_ERR_OBJ_TYPE
If OS_CFG_OBJ_TYPE_CHK_EN is set to 1 in os_cfg.h: p_grp is not pointing to an event flag group.
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
- Event flag groups must be created before they are used.
- 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.
- Although the example below shows that we are posting from a task,
OSFlagPost()can also be called from an ISR.
Example