790 lines
30 KiB
C
790 lines
30 KiB
C
/*
|
|
FreeRTOS V7.3.0 - Copyright (C) 2012 Real Time Engineers Ltd.
|
|
|
|
FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME. PLEASE VISIT
|
|
http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
|
|
|
|
***************************************************************************
|
|
* *
|
|
* FreeRTOS tutorial books are available in pdf and paperback. *
|
|
* Complete, revised, and edited pdf reference manuals are also *
|
|
* available. *
|
|
* *
|
|
* Purchasing FreeRTOS documentation will not only help you, by *
|
|
* ensuring you get running as quickly as possible and with an *
|
|
* in-depth knowledge of how to use FreeRTOS, it will also help *
|
|
* the FreeRTOS project to continue with its mission of providing *
|
|
* professional grade, cross platform, de facto standard solutions *
|
|
* for microcontrollers - completely free of charge! *
|
|
* *
|
|
* >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
|
|
* *
|
|
* Thank you for using FreeRTOS, and thank you for your support! *
|
|
* *
|
|
***************************************************************************
|
|
|
|
|
|
This file is part of the FreeRTOS distribution.
|
|
|
|
FreeRTOS is free software; you can redistribute it and/or modify it under
|
|
the terms of the GNU General Public License (version 2) as published by the
|
|
Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
|
|
>>>NOTE<<< The modification to the GPL is included to allow you to
|
|
distribute a combined work that includes FreeRTOS without being obliged to
|
|
provide the source code for proprietary components outside of the FreeRTOS
|
|
kernel. FreeRTOS is distributed in the hope that it will be useful, but
|
|
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
|
|
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
|
|
more details. You should have received a copy of the GNU General Public
|
|
License and the FreeRTOS license exception along with FreeRTOS; if not it
|
|
can be viewed here: http://www.freertos.org/a00114.html and also obtained
|
|
by writing to Richard Barry, contact details for whom are available on the
|
|
FreeRTOS WEB site.
|
|
|
|
1 tab == 4 spaces!
|
|
|
|
***************************************************************************
|
|
* *
|
|
* Having a problem? Start by reading the FAQ "My application does *
|
|
* not run, what could be wrong?" *
|
|
* *
|
|
* http://www.FreeRTOS.org/FAQHelp.html *
|
|
* *
|
|
***************************************************************************
|
|
|
|
|
|
http://www.FreeRTOS.org - Documentation, training, latest versions, license
|
|
and contact details.
|
|
|
|
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
|
|
including FreeRTOS+Trace - an indispensable productivity tool.
|
|
|
|
Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
|
|
the code with commercial support, indemnification, and middleware, under
|
|
the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
|
|
provide a safety engineered and independently SIL3 certified version under
|
|
the SafeRTOS brand: http://www.SafeRTOS.com.
|
|
*/
|
|
|
|
#ifndef SEMAPHORE_H
|
|
#define SEMAPHORE_H
|
|
|
|
#ifndef INC_FREERTOS_H
|
|
#error "include FreeRTOS.h" must appear in source files before "include semphr.h"
|
|
#endif
|
|
|
|
#include "queue.h"
|
|
|
|
typedef xQueueHandle xSemaphoreHandle;
|
|
|
|
#define semBINARY_SEMAPHORE_QUEUE_LENGTH ( ( unsigned char ) 1U )
|
|
#define semSEMAPHORE_QUEUE_ITEM_LENGTH ( ( unsigned char ) 0U )
|
|
#define semGIVE_BLOCK_TIME ( ( portTickType ) 0U )
|
|
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>vSemaphoreCreateBinary( xSemaphoreHandle xSemaphore )</pre>
|
|
*
|
|
* <i>Macro</i> that implements a semaphore by using the existing queue mechanism.
|
|
* The queue length is 1 as this is a binary semaphore. The data size is 0
|
|
* as we don't want to actually store any data - we just want to know if the
|
|
* queue is empty or full.
|
|
*
|
|
* This type of semaphore can be used for pure synchronisation between tasks or
|
|
* between an interrupt and a task. The semaphore need not be given back once
|
|
* obtained, so one task/interrupt can continuously 'give' the semaphore while
|
|
* another continuously 'takes' the semaphore. For this reason this type of
|
|
* semaphore does not use a priority inheritance mechanism. For an alternative
|
|
* that does use priority inheritance see xSemaphoreCreateMutex().
|
|
*
|
|
* @param xSemaphore Handle to the created semaphore. Should be of type xSemaphoreHandle.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xSemaphore;
|
|
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Semaphore cannot be used before a call to vSemaphoreCreateBinary ().
|
|
// This is a macro so pass the variable in directly.
|
|
vSemaphoreCreateBinary( xSemaphore );
|
|
|
|
if( xSemaphore != NULL )
|
|
{
|
|
// The semaphore was created successfully.
|
|
// The semaphore can now be used.
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup vSemaphoreCreateBinary vSemaphoreCreateBinary
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define vSemaphoreCreateBinary( xSemaphore ) \
|
|
{ \
|
|
( xSemaphore ) = xQueueGenericCreate( ( unsigned portBASE_TYPE ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE ); \
|
|
if( ( xSemaphore ) != NULL ) \
|
|
{ \
|
|
xSemaphoreGive( ( xSemaphore ) ); \
|
|
} \
|
|
}
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>xSemaphoreTake(
|
|
* xSemaphoreHandle xSemaphore,
|
|
* portTickType xBlockTime
|
|
* )</pre>
|
|
*
|
|
* <i>Macro</i> to obtain a semaphore. The semaphore must have previously been
|
|
* created with a call to vSemaphoreCreateBinary(), xSemaphoreCreateMutex() or
|
|
* xSemaphoreCreateCounting().
|
|
*
|
|
* @param xSemaphore A handle to the semaphore being taken - obtained when
|
|
* the semaphore was created.
|
|
*
|
|
* @param xBlockTime The time in ticks to wait for the semaphore to become
|
|
* available. The macro portTICK_RATE_MS can be used to convert this to a
|
|
* real time. A block time of zero can be used to poll the semaphore. A block
|
|
* time of portMAX_DELAY can be used to block indefinitely (provided
|
|
* INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h).
|
|
*
|
|
* @return pdTRUE if the semaphore was obtained. pdFALSE
|
|
* if xBlockTime expired without the semaphore becoming available.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xSemaphore = NULL;
|
|
|
|
// A task that creates a semaphore.
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Create the semaphore to guard a shared resource.
|
|
vSemaphoreCreateBinary( xSemaphore );
|
|
}
|
|
|
|
// A task that uses the semaphore.
|
|
void vAnotherTask( void * pvParameters )
|
|
{
|
|
// ... Do other things.
|
|
|
|
if( xSemaphore != NULL )
|
|
{
|
|
// See if we can obtain the semaphore. If the semaphore is not available
|
|
// wait 10 ticks to see if it becomes free.
|
|
if( xSemaphoreTake( xSemaphore, ( portTickType ) 10 ) == pdTRUE )
|
|
{
|
|
// We were able to obtain the semaphore and can now access the
|
|
// shared resource.
|
|
|
|
// ...
|
|
|
|
// We have finished accessing the shared resource. Release the
|
|
// semaphore.
|
|
xSemaphoreGive( xSemaphore );
|
|
}
|
|
else
|
|
{
|
|
// We could not obtain the semaphore and can therefore not access
|
|
// the shared resource safely.
|
|
}
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xSemaphoreTake xSemaphoreTake
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreTake( xSemaphore, xBlockTime ) xQueueGenericReceive( ( xQueueHandle ) ( xSemaphore ), NULL, ( xBlockTime ), pdFALSE )
|
|
|
|
/**
|
|
* semphr. h
|
|
* xSemaphoreTakeRecursive(
|
|
* xSemaphoreHandle xMutex,
|
|
* portTickType xBlockTime
|
|
* )
|
|
*
|
|
* <i>Macro</i> to recursively obtain, or 'take', a mutex type semaphore.
|
|
* The mutex must have previously been created using a call to
|
|
* xSemaphoreCreateRecursiveMutex();
|
|
*
|
|
* configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this
|
|
* macro to be available.
|
|
*
|
|
* This macro must not be used on mutexes created using xSemaphoreCreateMutex().
|
|
*
|
|
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
|
* doesn't become available again until the owner has called
|
|
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
|
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
|
* not be available to any other task until it has also 'given' the mutex back
|
|
* exactly five times.
|
|
*
|
|
* @param xMutex A handle to the mutex being obtained. This is the
|
|
* handle returned by xSemaphoreCreateRecursiveMutex();
|
|
*
|
|
* @param xBlockTime The time in ticks to wait for the semaphore to become
|
|
* available. The macro portTICK_RATE_MS can be used to convert this to a
|
|
* real time. A block time of zero can be used to poll the semaphore. If
|
|
* the task already owns the semaphore then xSemaphoreTakeRecursive() will
|
|
* return immediately no matter what the value of xBlockTime.
|
|
*
|
|
* @return pdTRUE if the semaphore was obtained. pdFALSE if xBlockTime
|
|
* expired without the semaphore becoming available.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xMutex = NULL;
|
|
|
|
// A task that creates a mutex.
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Create the mutex to guard a shared resource.
|
|
xMutex = xSemaphoreCreateRecursiveMutex();
|
|
}
|
|
|
|
// A task that uses the mutex.
|
|
void vAnotherTask( void * pvParameters )
|
|
{
|
|
// ... Do other things.
|
|
|
|
if( xMutex != NULL )
|
|
{
|
|
// See if we can obtain the mutex. If the mutex is not available
|
|
// wait 10 ticks to see if it becomes free.
|
|
if( xSemaphoreTakeRecursive( xSemaphore, ( portTickType ) 10 ) == pdTRUE )
|
|
{
|
|
// We were able to obtain the mutex and can now access the
|
|
// shared resource.
|
|
|
|
// ...
|
|
// For some reason due to the nature of the code further calls to
|
|
// xSemaphoreTakeRecursive() are made on the same mutex. In real
|
|
// code these would not be just sequential calls as this would make
|
|
// no sense. Instead the calls are likely to be buried inside
|
|
// a more complex call structure.
|
|
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
|
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
|
|
|
// The mutex has now been 'taken' three times, so will not be
|
|
// available to another task until it has also been given back
|
|
// three times. Again it is unlikely that real code would have
|
|
// these calls sequentially, but instead buried in a more complex
|
|
// call structure. This is just for illustrative purposes.
|
|
xSemaphoreGiveRecursive( xMutex );
|
|
xSemaphoreGiveRecursive( xMutex );
|
|
xSemaphoreGiveRecursive( xMutex );
|
|
|
|
// Now the mutex can be taken by other tasks.
|
|
}
|
|
else
|
|
{
|
|
// We could not obtain the mutex and can therefore not access
|
|
// the shared resource safely.
|
|
}
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xSemaphoreTakeRecursive xSemaphoreTakeRecursive
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreTakeRecursive( xMutex, xBlockTime ) xQueueTakeMutexRecursive( ( xMutex ), ( xBlockTime ) )
|
|
|
|
|
|
/*
|
|
* xSemaphoreAltTake() is an alternative version of xSemaphoreTake().
|
|
*
|
|
* The source code that implements the alternative (Alt) API is much
|
|
* simpler because it executes everything from within a critical section.
|
|
* This is the approach taken by many other RTOSes, but FreeRTOS.org has the
|
|
* preferred fully featured API too. The fully featured API has more
|
|
* complex code that takes longer to execute, but makes much less use of
|
|
* critical sections. Therefore the alternative API sacrifices interrupt
|
|
* responsiveness to gain execution speed, whereas the fully featured API
|
|
* sacrifices execution speed to ensure better interrupt responsiveness.
|
|
*/
|
|
#define xSemaphoreAltTake( xSemaphore, xBlockTime ) xQueueAltGenericReceive( ( xQueueHandle ) ( xSemaphore ), NULL, ( xBlockTime ), pdFALSE )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>xSemaphoreGive( xSemaphoreHandle xSemaphore )</pre>
|
|
*
|
|
* <i>Macro</i> to release a semaphore. The semaphore must have previously been
|
|
* created with a call to vSemaphoreCreateBinary(), xSemaphoreCreateMutex() or
|
|
* xSemaphoreCreateCounting(). and obtained using sSemaphoreTake().
|
|
*
|
|
* This macro must not be used from an ISR. See xSemaphoreGiveFromISR () for
|
|
* an alternative which can be used from an ISR.
|
|
*
|
|
* This macro must also not be used on semaphores created using
|
|
* xSemaphoreCreateRecursiveMutex().
|
|
*
|
|
* @param xSemaphore A handle to the semaphore being released. This is the
|
|
* handle returned when the semaphore was created.
|
|
*
|
|
* @return pdTRUE if the semaphore was released. pdFALSE if an error occurred.
|
|
* Semaphores are implemented using queues. An error can occur if there is
|
|
* no space on the queue to post a message - indicating that the
|
|
* semaphore was not first obtained correctly.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xSemaphore = NULL;
|
|
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Create the semaphore to guard a shared resource.
|
|
vSemaphoreCreateBinary( xSemaphore );
|
|
|
|
if( xSemaphore != NULL )
|
|
{
|
|
if( xSemaphoreGive( xSemaphore ) != pdTRUE )
|
|
{
|
|
// We would expect this call to fail because we cannot give
|
|
// a semaphore without first "taking" it!
|
|
}
|
|
|
|
// Obtain the semaphore - don't block if the semaphore is not
|
|
// immediately available.
|
|
if( xSemaphoreTake( xSemaphore, ( portTickType ) 0 ) )
|
|
{
|
|
// We now have the semaphore and can access the shared resource.
|
|
|
|
// ...
|
|
|
|
// We have finished accessing the shared resource so can free the
|
|
// semaphore.
|
|
if( xSemaphoreGive( xSemaphore ) != pdTRUE )
|
|
{
|
|
// We would not expect this call to fail because we must have
|
|
// obtained the semaphore to get here.
|
|
}
|
|
}
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xSemaphoreGive xSemaphoreGive
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreGive( xSemaphore ) xQueueGenericSend( ( xQueueHandle ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>xSemaphoreGiveRecursive( xSemaphoreHandle xMutex )</pre>
|
|
*
|
|
* <i>Macro</i> to recursively release, or 'give', a mutex type semaphore.
|
|
* The mutex must have previously been created using a call to
|
|
* xSemaphoreCreateRecursiveMutex();
|
|
*
|
|
* configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this
|
|
* macro to be available.
|
|
*
|
|
* This macro must not be used on mutexes created using xSemaphoreCreateMutex().
|
|
*
|
|
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
|
* doesn't become available again until the owner has called
|
|
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
|
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
|
* not be available to any other task until it has also 'given' the mutex back
|
|
* exactly five times.
|
|
*
|
|
* @param xMutex A handle to the mutex being released, or 'given'. This is the
|
|
* handle returned by xSemaphoreCreateMutex();
|
|
*
|
|
* @return pdTRUE if the semaphore was given.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xMutex = NULL;
|
|
|
|
// A task that creates a mutex.
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Create the mutex to guard a shared resource.
|
|
xMutex = xSemaphoreCreateRecursiveMutex();
|
|
}
|
|
|
|
// A task that uses the mutex.
|
|
void vAnotherTask( void * pvParameters )
|
|
{
|
|
// ... Do other things.
|
|
|
|
if( xMutex != NULL )
|
|
{
|
|
// See if we can obtain the mutex. If the mutex is not available
|
|
// wait 10 ticks to see if it becomes free.
|
|
if( xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ) == pdTRUE )
|
|
{
|
|
// We were able to obtain the mutex and can now access the
|
|
// shared resource.
|
|
|
|
// ...
|
|
// For some reason due to the nature of the code further calls to
|
|
// xSemaphoreTakeRecursive() are made on the same mutex. In real
|
|
// code these would not be just sequential calls as this would make
|
|
// no sense. Instead the calls are likely to be buried inside
|
|
// a more complex call structure.
|
|
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
|
xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 );
|
|
|
|
// The mutex has now been 'taken' three times, so will not be
|
|
// available to another task until it has also been given back
|
|
// three times. Again it is unlikely that real code would have
|
|
// these calls sequentially, it would be more likely that the calls
|
|
// to xSemaphoreGiveRecursive() would be called as a call stack
|
|
// unwound. This is just for demonstrative purposes.
|
|
xSemaphoreGiveRecursive( xMutex );
|
|
xSemaphoreGiveRecursive( xMutex );
|
|
xSemaphoreGiveRecursive( xMutex );
|
|
|
|
// Now the mutex can be taken by other tasks.
|
|
}
|
|
else
|
|
{
|
|
// We could not obtain the mutex and can therefore not access
|
|
// the shared resource safely.
|
|
}
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xSemaphoreGiveRecursive xSemaphoreGiveRecursive
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreGiveRecursive( xMutex ) xQueueGiveMutexRecursive( ( xMutex ) )
|
|
|
|
/*
|
|
* xSemaphoreAltGive() is an alternative version of xSemaphoreGive().
|
|
*
|
|
* The source code that implements the alternative (Alt) API is much
|
|
* simpler because it executes everything from within a critical section.
|
|
* This is the approach taken by many other RTOSes, but FreeRTOS.org has the
|
|
* preferred fully featured API too. The fully featured API has more
|
|
* complex code that takes longer to execute, but makes much less use of
|
|
* critical sections. Therefore the alternative API sacrifices interrupt
|
|
* responsiveness to gain execution speed, whereas the fully featured API
|
|
* sacrifices execution speed to ensure better interrupt responsiveness.
|
|
*/
|
|
#define xSemaphoreAltGive( xSemaphore ) xQueueAltGenericSend( ( xQueueHandle ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>
|
|
xSemaphoreGiveFromISR(
|
|
xSemaphoreHandle xSemaphore,
|
|
signed portBASE_TYPE *pxHigherPriorityTaskWoken
|
|
)</pre>
|
|
*
|
|
* <i>Macro</i> to release a semaphore. The semaphore must have previously been
|
|
* created with a call to vSemaphoreCreateBinary() or xSemaphoreCreateCounting().
|
|
*
|
|
* Mutex type semaphores (those created using a call to xSemaphoreCreateMutex())
|
|
* must not be used with this macro.
|
|
*
|
|
* This macro can be used from an ISR.
|
|
*
|
|
* @param xSemaphore A handle to the semaphore being released. This is the
|
|
* handle returned when the semaphore was created.
|
|
*
|
|
* @param pxHigherPriorityTaskWoken xSemaphoreGiveFromISR() will set
|
|
* *pxHigherPriorityTaskWoken to pdTRUE if giving the semaphore caused a task
|
|
* to unblock, and the unblocked task has a priority higher than the currently
|
|
* running task. If xSemaphoreGiveFromISR() sets this value to pdTRUE then
|
|
* a context switch should be requested before the interrupt is exited.
|
|
*
|
|
* @return pdTRUE if the semaphore was successfully given, otherwise errQUEUE_FULL.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
\#define LONG_TIME 0xffff
|
|
\#define TICKS_TO_WAIT 10
|
|
xSemaphoreHandle xSemaphore = NULL;
|
|
|
|
// Repetitive task.
|
|
void vATask( void * pvParameters )
|
|
{
|
|
for( ;; )
|
|
{
|
|
// We want this task to run every 10 ticks of a timer. The semaphore
|
|
// was created before this task was started.
|
|
|
|
// Block waiting for the semaphore to become available.
|
|
if( xSemaphoreTake( xSemaphore, LONG_TIME ) == pdTRUE )
|
|
{
|
|
// It is time to execute.
|
|
|
|
// ...
|
|
|
|
// We have finished our task. Return to the top of the loop where
|
|
// we will block on the semaphore until it is time to execute
|
|
// again. Note when using the semaphore for synchronisation with an
|
|
// ISR in this manner there is no need to 'give' the semaphore back.
|
|
}
|
|
}
|
|
}
|
|
|
|
// Timer ISR
|
|
void vTimerISR( void * pvParameters )
|
|
{
|
|
static unsigned char ucLocalTickCount = 0;
|
|
static signed portBASE_TYPE xHigherPriorityTaskWoken;
|
|
|
|
// A timer tick has occurred.
|
|
|
|
// ... Do other time functions.
|
|
|
|
// Is it time for vATask () to run?
|
|
xHigherPriorityTaskWoken = pdFALSE;
|
|
ucLocalTickCount++;
|
|
if( ucLocalTickCount >= TICKS_TO_WAIT )
|
|
{
|
|
// Unblock the task by releasing the semaphore.
|
|
xSemaphoreGiveFromISR( xSemaphore, &xHigherPriorityTaskWoken );
|
|
|
|
// Reset the count so we release the semaphore again in 10 ticks time.
|
|
ucLocalTickCount = 0;
|
|
}
|
|
|
|
if( xHigherPriorityTaskWoken != pdFALSE )
|
|
{
|
|
// We can force a context switch here. Context switching from an
|
|
// ISR uses port specific syntax. Check the demo task for your port
|
|
// to find the syntax required.
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xSemaphoreGiveFromISR xSemaphoreGiveFromISR
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreGiveFromISR( xSemaphore, pxHigherPriorityTaskWoken ) xQueueGenericSendFromISR( ( xQueueHandle ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>
|
|
xSemaphoreTakeFromISR(
|
|
xSemaphoreHandle xSemaphore,
|
|
signed portBASE_TYPE *pxHigherPriorityTaskWoken
|
|
)</pre>
|
|
*
|
|
* <i>Macro</i> to take a semaphore from an ISR. The semaphore must have
|
|
* previously been created with a call to vSemaphoreCreateBinary() or
|
|
* xSemaphoreCreateCounting().
|
|
*
|
|
* Mutex type semaphores (those created using a call to xSemaphoreCreateMutex())
|
|
* must not be used with this macro.
|
|
*
|
|
* This macro can be used from an ISR, however taking a semaphore from an ISR
|
|
* is not a common operation. It is likely to only be useful when taking a
|
|
* counting semaphore when an interrupt is obtaining an object from a resource
|
|
* pool (when the semaphore count indicates the number of resources available).
|
|
*
|
|
* @param xSemaphore A handle to the semaphore being taken. This is the
|
|
* handle returned when the semaphore was created.
|
|
*
|
|
* @param pxHigherPriorityTaskWoken xSemaphoreTakeFromISR() will set
|
|
* *pxHigherPriorityTaskWoken to pdTRUE if taking the semaphore caused a task
|
|
* to unblock, and the unblocked task has a priority higher than the currently
|
|
* running task. If xSemaphoreTakeFromISR() sets this value to pdTRUE then
|
|
* a context switch should be requested before the interrupt is exited.
|
|
*
|
|
* @return pdTRUE if the semaphore was successfully taken, otherwise
|
|
* pdFALSE
|
|
*/
|
|
#define xSemaphoreTakeFromISR( xSemaphore, pxHigherPriorityTaskWoken ) xQueueReceiveFromISR( ( xQueueHandle ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ) )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>xSemaphoreHandle xSemaphoreCreateMutex( void )</pre>
|
|
*
|
|
* <i>Macro</i> that implements a mutex semaphore by using the existing queue
|
|
* mechanism.
|
|
*
|
|
* Mutexes created using this macro can be accessed using the xSemaphoreTake()
|
|
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
|
|
* xSemaphoreGiveRecursive() macros should not be used.
|
|
*
|
|
* This type of semaphore uses a priority inheritance mechanism so a task
|
|
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
|
|
* semaphore it is no longer required.
|
|
*
|
|
* Mutex type semaphores cannot be used from within interrupt service routines.
|
|
*
|
|
* See vSemaphoreCreateBinary() for an alternative implementation that can be
|
|
* used for pure synchronisation (where one task or interrupt always 'gives' the
|
|
* semaphore and another always 'takes' the semaphore) and from within interrupt
|
|
* service routines.
|
|
*
|
|
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
|
|
* xSemaphoreHandle.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xSemaphore;
|
|
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Semaphore cannot be used before a call to xSemaphoreCreateMutex().
|
|
// This is a macro so pass the variable in directly.
|
|
xSemaphore = xSemaphoreCreateMutex();
|
|
|
|
if( xSemaphore != NULL )
|
|
{
|
|
// The semaphore was created successfully.
|
|
// The semaphore can now be used.
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup vSemaphoreCreateMutex vSemaphoreCreateMutex
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreCreateMutex() xQueueCreateMutex( queueQUEUE_TYPE_MUTEX )
|
|
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>xSemaphoreHandle xSemaphoreCreateRecursiveMutex( void )</pre>
|
|
*
|
|
* <i>Macro</i> that implements a recursive mutex by using the existing queue
|
|
* mechanism.
|
|
*
|
|
* Mutexes created using this macro can be accessed using the
|
|
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
|
|
* xSemaphoreTake() and xSemaphoreGive() macros should not be used.
|
|
*
|
|
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
|
|
* doesn't become available again until the owner has called
|
|
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
|
|
* if a task successfully 'takes' the same mutex 5 times then the mutex will
|
|
* not be available to any other task until it has also 'given' the mutex back
|
|
* exactly five times.
|
|
*
|
|
* This type of semaphore uses a priority inheritance mechanism so a task
|
|
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
|
|
* semaphore it is no longer required.
|
|
*
|
|
* Mutex type semaphores cannot be used from within interrupt service routines.
|
|
*
|
|
* See vSemaphoreCreateBinary() for an alternative implementation that can be
|
|
* used for pure synchronisation (where one task or interrupt always 'gives' the
|
|
* semaphore and another always 'takes' the semaphore) and from within interrupt
|
|
* service routines.
|
|
*
|
|
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
|
|
* xSemaphoreHandle.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xSemaphore;
|
|
|
|
void vATask( void * pvParameters )
|
|
{
|
|
// Semaphore cannot be used before a call to xSemaphoreCreateMutex().
|
|
// This is a macro so pass the variable in directly.
|
|
xSemaphore = xSemaphoreCreateRecursiveMutex();
|
|
|
|
if( xSemaphore != NULL )
|
|
{
|
|
// The semaphore was created successfully.
|
|
// The semaphore can now be used.
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup vSemaphoreCreateMutex vSemaphoreCreateMutex
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreCreateRecursiveMutex() xQueueCreateMutex( queueQUEUE_TYPE_RECURSIVE_MUTEX )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>xSemaphoreHandle xSemaphoreCreateCounting( unsigned portBASE_TYPE uxMaxCount, unsigned portBASE_TYPE uxInitialCount )</pre>
|
|
*
|
|
* <i>Macro</i> that creates a counting semaphore by using the existing
|
|
* queue mechanism.
|
|
*
|
|
* Counting semaphores are typically used for two things:
|
|
*
|
|
* 1) Counting events.
|
|
*
|
|
* In this usage scenario an event handler will 'give' a semaphore each time
|
|
* an event occurs (incrementing the semaphore count value), and a handler
|
|
* task will 'take' a semaphore each time it processes an event
|
|
* (decrementing the semaphore count value). The count value is therefore
|
|
* the difference between the number of events that have occurred and the
|
|
* number that have been processed. In this case it is desirable for the
|
|
* initial count value to be zero.
|
|
*
|
|
* 2) Resource management.
|
|
*
|
|
* In this usage scenario the count value indicates the number of resources
|
|
* available. To obtain control of a resource a task must first obtain a
|
|
* semaphore - decrementing the semaphore count value. When the count value
|
|
* reaches zero there are no free resources. When a task finishes with the
|
|
* resource it 'gives' the semaphore back - incrementing the semaphore count
|
|
* value. In this case it is desirable for the initial count value to be
|
|
* equal to the maximum count value, indicating that all resources are free.
|
|
*
|
|
* @param uxMaxCount The maximum count value that can be reached. When the
|
|
* semaphore reaches this value it can no longer be 'given'.
|
|
*
|
|
* @param uxInitialCount The count value assigned to the semaphore when it is
|
|
* created.
|
|
*
|
|
* @return Handle to the created semaphore. Null if the semaphore could not be
|
|
* created.
|
|
*
|
|
* Example usage:
|
|
<pre>
|
|
xSemaphoreHandle xSemaphore;
|
|
|
|
void vATask( void * pvParameters )
|
|
{
|
|
xSemaphoreHandle xSemaphore = NULL;
|
|
|
|
// Semaphore cannot be used before a call to xSemaphoreCreateCounting().
|
|
// The max value to which the semaphore can count should be 10, and the
|
|
// initial value assigned to the count should be 0.
|
|
xSemaphore = xSemaphoreCreateCounting( 10, 0 );
|
|
|
|
if( xSemaphore != NULL )
|
|
{
|
|
// The semaphore was created successfully.
|
|
// The semaphore can now be used.
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xSemaphoreCreateCounting xSemaphoreCreateCounting
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define xSemaphoreCreateCounting( uxMaxCount, uxInitialCount ) xQueueCreateCountingSemaphore( ( uxMaxCount ), ( uxInitialCount ) )
|
|
|
|
/**
|
|
* semphr. h
|
|
* <pre>void vSemaphoreDelete( xSemaphoreHandle xSemaphore );</pre>
|
|
*
|
|
* Delete a semaphore. This function must be used with care. For example,
|
|
* do not delete a mutex type semaphore if the mutex is held by a task.
|
|
*
|
|
* @param xSemaphore A handle to the semaphore to be deleted.
|
|
*
|
|
* \page vSemaphoreDelete vSemaphoreDelete
|
|
* \ingroup Semaphores
|
|
*/
|
|
#define vSemaphoreDelete( xSemaphore ) vQueueDelete( ( xQueueHandle ) ( xSemaphore ) )
|
|
|
|
/**
|
|
* semphr.h
|
|
* <pre>xTaskHandle xSemaphoreGetMutexHolder( xSemaphoreHandle xMutex );</pre>
|
|
*
|
|
* If xMutex is indeed a mutex type semaphore, return the current mutex holder.
|
|
* If xMutex is not a mutex type semaphore, or the mutex is available (not held
|
|
* by a task), return NULL.
|
|
*
|
|
* Note: This Is is a good way of determining if the calling task is the mutex
|
|
* holder, but not a good way of determining the identity of the mutex holder as
|
|
* the holder may change between the function exiting and the returned value
|
|
* being tested.
|
|
*/
|
|
#define xSemaphoreGetMutexHolder( xSemaphore ) xQueueGetMutexHolder( ( xSemaphore ) )
|
|
|
|
#endif /* SEMAPHORE_H */
|
|
|
|
|