void OSQCreate (OS_Q *p_q,
CPU_CHAR *p_name,
OS_MSG_QTY max_qty,
OS_ERR *p_err)
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OSQCreate()
creates a message queue. A message queue allows tasks or ISRs to send pointer-sized variables (messages) to one or more tasks. The meaning of the messages sent are application specific.
Arguments
p_q
is a pointer to the message queue control block. It is assumed that storage for the message queue will be allocated in the application. The user will need to declare a “global” variable as follows, and pass a pointer to this variable to OSQCreate()
:
OS_Q MyMsgQ;
p_name
is a pointer to an ASCII string used to name the message queue. The name can be displayed by debuggers or µC/Probe.
msg_qty
indicates the maximum size of the message queue (must be non-zero). If the user intends to not limit the size of the queue, simply pass a very large number. Of course, if there are not enough OS_MSGs
in the pool of OS_MSGs
, the post call (i.e., OSQPost()
) will simply fail and an error code will indicate that there are no more OS_MSGs
to use.
p_err
is a pointer to a variable that is used to hold an error code:
OS_ERR_NONE
If the call is successful and the mutex has been created.
OS_ERR_CREATE_ISR
If OS_CFG_CALLED_FROM_ISR_CHK_EN
set to 1
in os_cfg.h
: if attempting to create the message queue from an ISR.
OS_ERR_OBJ_PTR_NULL
If OS_CFG_ARG_CHK_EN
is set to 1
in os_cfg.h
: if p_q
is a NULL
pointer.
OS_ERR_Q_SIZE
If OS_CFG_ARG_CHK_EN
is set to 1
in os_cfg.h
: if the size specified is 0.
OS_ERR_ILLEGAL_CREATE_RUN_TIME
If OS_SAFETY_CRITICAL_IEC61508
is defined: you called this after calling OSSafetyCriticalStart()
and thus you are no longer allowed to create additional kernel objects.
Returned Value
None
Notes/Warnings
Queues must be created before they are used.