Semaphores API Changes
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- WES Admin
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The table below shows the difference in API for semaphore management.
µC/OS-II (os_sem.c) | µC/OS-III (os_sem.c) | Note |
|---|---|---|
INT16U
OSSemAccept(
OS_EVENT *pevent); | (1) | |
OS_EVENT *
OSSemCreate(
INT16U cnt); | void
OSSemCreate(
OS_SEM *p_sem,
CPU_CHAR *p_name,
OS_SEM_CTR cnt,
OS_ERR *p_err); | (2) |
OS_EVENT *
OSSemDel(
OS_EVENT *pevent,
INT8U opt,
INT8U *perr); | OS_OBJ_QTY,
OSSemDel(
OS_SEM *p_sem,
OS_OPT opt,
OS_ERR *p_err); | |
void
OSSemPend(
OS_EVENT *pevent,
INT32U timeout,
INT8U *perr); | OS_SEM_CTR
OSSemPend(
OS_SEM *p_sem,
OS_TICK timeout,
OS_OPT opt,
CPU_TS *p_ts,
OS_ERR *p_err); | (3) |
INT8U
OSSemPendAbort(
OS_EVENT *pevent,
INT8U opt,
INT8U *perr); | OS_OBJ_QTY
OSSemPendAbort(
OS_SEM *p_sem,
OS_OPT opt,
OS_ERR *p_err); | |
void
OSSemPost(
OS_EVENT *pevent); | void
OSSemPost(
OS_SEM *p_sem,
OS_OPT opt,
OS_ERR *p_err); | |
INT8U
OSSemQuery(
OS_EVENT *pevent,
OS_SEM_DATA *p_sem_data); | (4) | |
void
OSSemSet(
OS_EVENT *pevent,
INT16U cnt,
INT8U *perr); | void
OSSemSet(
OS_SEM *p_sem,
OS_SEM_CTR cnt,
OS_ERR *p_err); |
(1) In µC/OS-III, there is no “accept” API since this feature is built into the OSSemPend() by specifying the OS_OPT_PEND_NON_BLOCKING option.
(2) In µC/OS-II, OSSemCreate() returns the address of an OS_EVENT, which is used as the “handle” to the semaphore. In µC/OS-III, the application must allocate storage for an OS_SEM object, which serves the same purpose as the OS_EVENT. The benefit in µC/OS-III is that it is not necessary to predetermine the number of semaphores at compile time.
(3) µC/OS-III returns additional information when a semaphore is signaled. The ISR or task that signals the semaphore takes a snapshot of the current timestamp and stores this in the OS_SEM object signaled. The receiver of the signal therefore knows when the signal was sent.
(4) µC/OS-III does not provide query services, as they were rarely used.