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Description
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.
Files
os.h/os_q.c
Prototype
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void OSQCreate (OS_Q *p_q,
CPU_CHAR *p_name,
OS_MSG_QTY max_qty,
OS_ERR *p_err) |
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():
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OS_Q
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MyMsgQ;
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p_nameis a pointer to an ASCII string used to name the message queue. The name can be displayed by debuggers or µC/Probe.
Anchor
msg_qtyindicates 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.
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p_erranchor
is a pointer to a variable that is used to hold an error code:
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OS_ERR_NONE
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If the call is successful and the mutex has been created.
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| class | WebWorks_Indent_1 |
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OS_ERR_CREATE_ISR
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If OS_CFG_CALLED_FROM_ISR_CHK_EN set to
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DEF_ENABLED in os_cfg.h: if attempting to create the message queue from an ISR.
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OS_ERR_ILLEGAL_CREATE_RUN_TIME
If OS_SAFETY_CRITICAL_IEC61508 is defined: you called this after calling OSStart() and thus you are no longer allowed to create additional kernel objects.
OS_ERR_OBJ_PTR_NULL
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If OS_CFG_ARG_CHK_EN is set to
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DEF_ENABLED in os_cfg.h: if p_q is a NULL pointer.
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OS_ERR_Q_SIZE
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| class | WebWorks_Indent_2 |
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If OS_CFG_ARG_CHK_EN is set to
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DEF_ENABLED in os_cfg.h: if the size specified is 0.
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Returned Value
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None
Required Configuration
OS_
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CFG_
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Anchor
Q_EN must be enabled in os_cfg.h. Refer to µC-OS-III Configuration Manual.Callers
Application.
Notes/Warnings
- Queues must be created before they are used.
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Example Usage
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| class | Code_Listing | |
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| Anchor | 1050597 | 1050597 | OS_Q CommQ;
| Anchor | 1050598 | 1050598 |
| Anchor | 1050599 | 1050599 |
| Anchor | 1050600 | 1050600 | void main (void)
| Anchor | 1050601 | 1050601 | {
| Anchor | 1050602 | 1050602 | OS_ERR err;
| Anchor | 1050603 | 1050603 |
| Anchor | 1050604 | 1050604 |
| Anchor | 1050605 | 1050605 | OSInit(&err); /* Initialize µC/OS-III */
| Anchor | 1050606 | 1050606 | :
| Anchor | 1050607 | 1050607 | :
| Anchor | 1050608 | 1050608 | OSQCreate(&CommQ,
| Anchor | 1050609 | 1050609 | “Comm Queue”,
| Anchor | 1050610 | 1050610 | 10,
| Anchor | 1050611 | 1050611 | &err); /* Create COMM Q */
| Anchor | 1050612 | 1050612 | /* Check “err” */
| Anchor | 1050613 | 1050613 | :
| Anchor | 1050614 | 1050614 | :
| Anchor | 1050615 | 1050615 | OSStart(); /* Start Multitasking */
| Anchor | 1050616 | 1050616 | }
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OS_Q CommQ;
void main (void)
{
OS_ERR err;
OSInit(&err); /* Initialize µC/OS-III */
:
:
OSQCreate(&CommQ,
"Comm Queue",
10,
&err); /* Create COMM Q */
/* Check "err" */
:
:
OSStart(); /* Start Multitasking */
} |