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Message Mailboxes API Changes

Message Mailboxes API Changes

Mar 23, 2021

The table below shows the API for message mailbox management. Note that µC/OS-III does not directly provide services for managing message mailboxes. Given that a message mailbox is a message queue of size one, µC/OS-III can easily emulate message mailboxes.

Message Mailbox API

µC/OS-II (os_mbox.c)

µC/OS-III (os_q.c)

Note

void * OSMboxAccept( OS_EVENT *pevent);

(1)

OS_EVENT * OSMboxCreate( void *pmsg);

void OSQCreate( OS_Q *p_q, CPU_CHAR *p_name, OS_MSG_QTY max_qty, OS_ERR *p_err);

(2)

void * OSMboxDel( OS_EVENT *pevent, INT8U opt, INT8U *perr);

OS_OBJ_QTY, OSQDel( OS_Q *p_q, OS_OPT opt, OS_ERR *p_err);

void * OSMboxPend( OS_EVENT *pevent, INT32U timeout, INT8U *perr);

void * OSQPend( OS_Q *p_q, OS_TICK timeout, OS_OPT opt, OS_MSG_SIZE *p_msg_size, CPU_TS *p_ts, OS_ERR *p_err);

(3)

INT8U OSMBoxPendAbort( OS_EVENT *pevent, INT8U opt, INT8U *perr);

OS_OBJ_QTY OSQPendAbort( OS_Q *p_q, OS_OPT opt OS_ERR *p_err);

INT8U OSMboxPost( OS_EVENT *pevent, void *pmsg);

void OSQPost( OS_Q *p_q, Void *p_void, OS_MSG_SIZE msg_size, OS_OPT opt, OS_ERR *p_err);

(4)

INT8U OSMboxPostOpt( OS_EVENT *pevent, void *pmsg, INT8U opt);

(4)

INT8U OSMboxQuery( OS_EVENT *pevent, OS_MBOX_DATA *p_mbox_data);

(5)

(1) In µC/OS-III, there is no “accept” API since this feature is built into the OSQPend() by specifying the OS_OPT_PEND_NON_BLOCKING option.

(2) In µC/OS-II, OSMboxCreate() returns the address of an OS_EVENT, which is used as the “handle” to the message mailbox. In µC/OS-III, the application must allocate storage for an OS_Q, 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 message queues at compile time. Also, to create the equivalent of a message mailbox, you would specify 1 for the max_qty argument.

(3) µC/OS-III returns additional information about the message received. Specifically, the sender specifies the size of the message as a snapshot of the current timestamp is taken and stored as part of the message. The receiver of the message therefore knows when the message was sent.

(4) In µC/OS-III, OSQPost() offers a number of options that replaces the two post functions provided in µC/OS-II.

(5) µC/OS-III does not provide query services, as they were rarely used in µC/OS-II.