OSSemSet
Description
Changes the current value of the semaphore count. This function is normally selected when a semaphore is used as a signaling mechanism. OSSemSet()
can then be used to reset the count to any value. If the semaphore count is already 0, the count is only changed if there are no tasks waiting on the semaphore.
Files
os.h/os_sem.c
Prototype
void OSSemSet (OS_SEM *p_sem, OS_SEM_CTR cnt, OS_ERR *p_err)
Arguments
p_sem
is a pointer to the semaphore that is used as a signaling mechanism.
cnt
is the desired count that the semaphore should be set to.
p_err
is a pointer to a variable used to hold an error code:
OS_ERR_NONE
If the count was changed.
OS_ERR_OBJ_PTR_NULL
If OS_CFG_ARG_CHK_EN
is set to DEF_ENABLED
in os_cfg.h
: if p_sem
is a NULL
pointer.
OS_ERR_OBJ_TYPE
If OS_CFG_OBJ_TYPE_CHK_EN
is set to DEF_ENABLED
in os_cfg.h
: if p_sem
is not pointing to a semaphore.
OS_ERR_SET_ISR
If OS_CFG_CALLED_FROM_ISR_CHK_EN
set to DEF_ENABLED
in os_cfg.h
: if this function was called from an ISR.
OS_ERR_TASK_WAITING
If tasks are waiting on the semaphore, the count is not changed.
Returned Value
None
Required Configuration
OS_CFG_SEM_EN
and OS_CFG_SEM_SET_EN
must be enabled in os_cfg.h
. Refer to µC-OS-III Configuration Manual.
Callers
Application.
Notes/Warnings
- Do not use this function if the semaphore is used to protect a shared resource.
Example Usage
OS_SEM SwSem; void Task (void *p_arg) { OS_ERR err; (void)&p_arg; while (DEF_ON) { OSSemSet(&SwSem, /* Reset the semaphore count */ 0, &err); /* Check "err" */ : : } }