OS_SEM Struct Reference

Semaphores are used to control access to shared resources or or to communicate between tasks in a multithreaded system or with interrupt service routines. Semaphores can be 0 or 1, or they can be counting semaphores that increment and decreement based on calls to Pend() and Post() functions. More...

#include <nbrtos.h>

Inherits OS_TASK_DLY_OBJ.

Public Member Functions
	OS_SEM (int32_t cnt=0)
	Create and initialize a semaphore.
uint8_t	Init (int32_t cnt=0)
	Initialize the semaphore object count value.
uint8_t	Post ()
	Posts to the semaphore, increasing it's value by 1.
uint8_t	Pend (uint32_t timeoutTicks=WAIT_FOREVER)
	Wait timeout ticks for the value of the semaphore to be non zero.
uint8_t	PendUntil (uint32_t timeout_time)
	Wait until the specified timeout time for a task to post to the semaphore.
uint8_t	Pend (TickTimeout &t)
	Wait for the specified number of system time ticks for a task to post to the semaphore.
uint8_t	PendNoWait ()
	Pend on a semaphore with no waiting period.
uint32_t	Avail ()
	Returns the number of semaphore counts availble.

Detailed Description

Semaphores are used to control access to shared resources or or to communicate between tasks in a multithreaded system or with interrupt service routines. Semaphores can be 0 or 1, or they can be counting semaphores that increment and decreement based on calls to Pend() and Post() functions.

Constructor & Destructor Documentation

OS_SEM()

OS_SEM::OS_SEM ( int32_t cnt = 0 )

inline

Create and initialize a semaphore.

Parameters

cnt	Starting semaphore count value. If not specified, default is 0.

See also

Init(int32_t cnt = 0)

Member Function Documentation

Avail()

uint32_t OS_SEM::Avail ( )

inline

Returns the number of semaphore counts availble.

Difference between the number of counts used and the total count value.

Returns

The number of available semaphore counts

See also

Pend(), Post()

Init()

uint8_t OS_SEM::Init

(

int32_t

cnt = 0

)

Initialize the semaphore object count value.

Warning

This must be done before using the semaphore.

Parameters

cnt	Starting semaphore count value. If not specified, default is 0.

Returns

OS_NO_ERR on success, otherwise NBRTOS Error Codes

Pend() [1/2]

uint8_t OS_SEM::Pend

(

TickTimeout &

t

)

Wait for the specified number of system time ticks for a task to post to the semaphore.

Parameters

t	The number of TickTiemout ticks to wait. A value of 0 will wait forever.

Returns

OS_NO_ERR on success, otherwise NBRTOS Error Codes

See also

PendNoWait(), PendUntil()

Pend() [2/2]

uint8_t OS_SEM::Pend ( uint32_t timeoutTicks = WAIT_FOREVER )

inline

Wait timeout ticks for the value of the semaphore to be non zero.

Parameters

timeoutTicks

Number of system time ticks to wait. If not specified, will wait forever.

Returns

OS_NO_ERR on success, otherwise NBRTOS Error Codes

See also

PendNoWait(), PendUntil()

PendNoWait()

uint8_t OS_SEM::PendNoWait

(

)

Pend on a semaphore with no waiting period.

Identical to the Pend() function, but it does not wait.

Returns

OS_NO_ERR on success, otherwise NBRTOS Error Codes

See also

Pend(), PendUntil()

PendUntil()

uint8_t OS_SEM::PendUntil ( uint32_t timeout_time )

inline

Wait until the specified timeout time for a task to post to the semaphore.

Parameters

timeout_time

The system TimeTick value to wait until

Returns

OS_NO_ERR on success, otherwise NBRTOS Error Codes

See also

PendNoWait(), Pend()

Post()

uint8_t OS_SEM::Post

(

)

Posts to the semaphore, increasing it's value by 1.

If a higher priority task was pending on the semaphore it will be released.

Returns

OS_NO_ERR on success, otherwise NBRTOS Error Codes

See also

Pend(), PendUntil(), PendNoWait()

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The documentation for this struct was generated from the following file:

• nbrtos.h