目录
（6）创建群组指令\defgroup和群组分级指令\ingroup
一、常见的代码注释
单行注释和多行注释是最常见的代码注释，伴随程序工作人员的一生。
1、单行代码注释
单行注释用于对单行代码进行简短的解释。在不同编程语言中，单行注释的表示方法有所不同。例如，在C++、Java、JavaScript中使用//。单行注释适用于简单的代码说明、标记待办事项或临时禁用某段代码。
2、多行代码注释
多行注释用于解释多行代码或对复杂功能进行详细说明。在C++和Java中，多行注释以/*开始，以*/结束。多行注释适用于详细描述算法逻辑、复杂操作的步骤或编码规范说明。
以下会用到本文常用的定义，开启注释，就是使用// 或使用/*后即为开启注释。
二、具有特殊功能的代码注释
文档注释是最常用并有意义的特殊功能代码注释，用于生成指定目标样式的可阅读代码文档。我们都知道程序员编写的代码是很抽象的，非专业人士看不懂，专业人士也需要借助单行注释、多行注释、开发者记录的笔记等文件的辅助才能勉强阅读。但如果除了有了程序员编写的代码之外，还有按指定格式生成的代码注释文档，抽象的源程序就不再抽象了和玄奥了。
这个行业内通用的、指定格式的代码注释文档，就是用软件Doxygen对指定的源程序代码生成的代码注释文档。他就像一本书，把源程序，生成了电子书，书中记录了开发源程序的点点滴滴。想让书里展示什么，就注释什么文字（符号）。眼中所看，就是注释时的心中所想。
代码注释文档是很有意义的，显然，它十分有利于技术传承、技术培训。
doxygen注释文档的命令都开始于一个反斜杠\或者是一个符号@。二者是一样的，都是为了引出一个命令。例如'\brief'，'\details'，'@brief'， '@details'等等。使用空行当作段落分隔符号。
以下用到的案例来源于STM32CubeIDE自动生成的FreeRTOS中的代码，本文主要在于介绍该参考文件中出现的几种具有特殊功能的文档注释的方法和含义。
1、文档描述
文档注释用于自动生成代码文档。文档注释一般通过/** ... */实现。文档注释包含对函数、类、模块的描述、参数、返回值、抛出的异常等信息。高质量的文档注释需要详细和清晰，尽可能为使用者提供足够的信息来理解代码的功能和用途。
参考文件semphr.h：
/*
* FreeRTOS Kernel V10.3.1
* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://www.FreeRTOS.org
* http://aws.amazon.com/freertos
*
* 1 tab == 4 spaces!
*/
#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 QueueHandle_t SemaphoreHandle_t;
#define semBINARY_SEMAPHORE_QUEUE_LENGTH ( ( uint8_t ) 1U )
#define semSEMAPHORE_QUEUE_ITEM_LENGTH ( ( uint8_t ) 0U )
#define semGIVE_BLOCK_TIME ( ( TickType_t ) 0U )
/**
* semphr. h
* <pre>vSemaphoreCreateBinary( SemaphoreHandle_t xSemaphore )</pre>
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* This old vSemaphoreCreateBinary() macro is now deprecated in favour of the
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
* the vSemaphoreCreateBinary() macro are created in a state such that the
* first call to 'take' the semaphore would pass, whereas binary semaphores
* created using xSemaphoreCreateBinary() are created in a state such that the
* the semaphore must first be 'given' before it can be 'taken'.
*
* <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 SemaphoreHandle_t.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
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
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define vSemaphoreCreateBinary( xSemaphore ) \
{ \
( xSemaphore ) = xQueueGenericCreate( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE ); \
if( ( xSemaphore ) != NULL ) \
{ \
( void ) xSemaphoreGive( ( xSemaphore ) ); \
} \
}
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateBinary( void )</pre>
*
* Creates a new binary semaphore instance, and returns a handle by which the
* new semaphore can be referenced.
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, binary semaphores use a block
* of memory, in which the semaphore structure is stored. If a binary semaphore
* is created using xSemaphoreCreateBinary() then the required memory is
* automatically dynamically allocated inside the xSemaphoreCreateBinary()
* function. (see http://www.freertos.org/a00111.html). If a binary semaphore
* is created using xSemaphoreCreateBinaryStatic() then the application writer
* must provide the memory. xSemaphoreCreateBinaryStatic() therefore allows a
* binary semaphore to be created without using any dynamic memory allocation.
*
* The old vSemaphoreCreateBinary() macro is now deprecated in favour of this
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
* the vSemaphoreCreateBinary() macro are created in a state such that the
* first call to 'take' the semaphore would pass, whereas binary semaphores
* created using xSemaphoreCreateBinary() are created in a state such that the
* the semaphore must first be 'given' before it can be 'taken'.
*
* 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().
*
* @return Handle to the created semaphore, or NULL if the memory required to
* hold the semaphore's data structures could not be allocated.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to xSemaphoreCreateBinary().
// This is a macro so pass the variable in directly.
xSemaphore = xSemaphoreCreateBinary();
if( xSemaphore != NULL )
{
// The semaphore was created successfully.
// The semaphore can now be used.
}
}
</pre>
* \defgroup xSemaphoreCreateBinary xSemaphoreCreateBinary
* \ingroup Semaphores
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define xSemaphoreCreateBinary() xQueueGenericCreate( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateBinaryStatic( StaticSemaphore_t *pxSemaphoreBuffer )</pre>
*
* Creates a new binary semaphore instance, and returns a handle by which the
* new semaphore can be referenced.
*
* NOTE: In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, binary semaphores use a block
* of memory, in which the semaphore structure is stored. If a binary semaphore
* is created using xSemaphoreCreateBinary() then the required memory is
* automatically dynamically allocated inside the xSemaphoreCreateBinary()
* function. (see http://www.freertos.org/a00111.html). If a binary semaphore
* is created using xSemaphoreCreateBinaryStatic() then the application writer
* must provide the memory. xSemaphoreCreateBinaryStatic() therefore allows a
* binary semaphore to be created without using any dynamic memory allocation.
*
* 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 pxSemaphoreBuffer Must point to a variable of type StaticSemaphore_t,
* which will then be used to hold the semaphore's data structure, removing the
* need for the memory to be allocated dynamically.
*
* @return If the semaphore is created then a handle to the created semaphore is
* returned. If pxSemaphoreBuffer is NULL then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
StaticSemaphore_t xSemaphoreBuffer;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to xSemaphoreCreateBinary().
// The semaphore's data structures will be placed in the xSemaphoreBuffer
// variable, the address of which is passed into the function. The
// function's parameter is not NULL, so the function will not attempt any
// dynamic memory allocation, and therefore the function will not return
// return NULL.
xSemaphore = xSemaphoreCreateBinary( &xSemaphoreBuffer );
// Rest of task code goes here.
}
</pre>
* \defgroup xSemaphoreCreateBinaryStatic xSemaphoreCreateBinaryStatic
* \ingroup Semaphores
*/
#if( configSUPPORT_STATIC_ALLOCATION == 1 )
#define xSemaphoreCreateBinaryStatic( pxStaticSemaphore ) xQueueGenericCreateStatic( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, NULL, pxStaticSemaphore, queueQUEUE_TYPE_BINARY_SEMAPHORE )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>xSemaphoreTake(
* SemaphoreHandle_t xSemaphore,
* TickType_t xBlockTime
* )</pre>
*
* <i>Macro</i> to obtain a semaphore. The semaphore must have previously been
* created with a call to xSemaphoreCreateBinary(), 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_PERIOD_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>
SemaphoreHandle_t xSemaphore = NULL;
// A task that creates a semaphore.
void vATask( void * pvParameters )
{
// Create the semaphore to guard a shared resource.
xSemaphore = xSemaphoreCreateBinary();
}
// 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, ( TickType_t ) 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 ) xQueueSemaphoreTake( ( xSemaphore ), ( xBlockTime ) )
/**
* semphr. h
* xSemaphoreTakeRecursive(
* SemaphoreHandle_t xMutex,
* TickType_t 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_PERIOD_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>
SemaphoreHandle_t 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, ( TickType_t ) 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, ( TickType_t ) 10 );
xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 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
*/
#if( configUSE_RECURSIVE_MUTEXES == 1 )
#define xSemaphoreTakeRecursive( xMutex, xBlockTime ) xQueueTakeMutexRecursive( ( xMutex ), ( xBlockTime ) )
#endif
/**
* semphr. h
* <pre>xSemaphoreGive( SemaphoreHandle_t xSemaphore )</pre>
*
* <i>Macro</i> to release a semaphore. The semaphore must have previously been
* created with a call to xSemaphoreCreateBinary(), 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>
SemaphoreHandle_t xSemaphore = NULL;
void vATask( void * pvParameters )
{
// Create the semaphore to guard a shared resource.
xSemaphore = vSemaphoreCreateBinary();
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, ( TickType_t ) 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( ( QueueHandle_t ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK )
/**
* semphr. h
* <pre>xSemaphoreGiveRecursive( SemaphoreHandle_t 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>
SemaphoreHandle_t 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, ( TickType_t ) 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, ( TickType_t ) 10 );
xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 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
*/
#if( configUSE_RECURSIVE_MUTEXES == 1 )
#define xSemaphoreGiveRecursive( xMutex ) xQueueGiveMutexRecursive( ( xMutex ) )
#endif
/**
* semphr. h
* <pre>
xSemaphoreGiveFromISR(
SemaphoreHandle_t xSemaphore,
BaseType_t *pxHigherPriorityTaskWoken
)</pre>
*
* <i>Macro</i> to release a semaphore. The semaphore must have previously been
* created with a call to xSemaphoreCreateBinary() 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
SemaphoreHandle_t 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 uint8_t ucLocalTickCount = 0;
static BaseType_t 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 ) xQueueGiveFromISR( ( QueueHandle_t ) ( xSemaphore ), ( pxHigherPriorityTaskWoken ) )
/**
* semphr. h
* <pre>
xSemaphoreTakeFromISR(
SemaphoreHandle_t xSemaphore,
BaseType_t *pxHigherPriorityTaskWoken
)</pre>
*
* <i>Macro</i> to take a semaphore from an ISR. The semaphore must have
* previously been created with a call to xSemaphoreCreateBinary() 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( ( QueueHandle_t ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ) )
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateMutex( void )</pre>
*
* Creates a new mutex type semaphore instance, and returns a handle by which
* the new mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, mutex semaphores use a block
* of memory, in which the mutex structure is stored. If a mutex is created
* using xSemaphoreCreateMutex() then the required memory is automatically
* dynamically allocated inside the xSemaphoreCreateMutex() function. (see
* http://www.freertos.org/a00111.html). If a mutex is created using
* xSemaphoreCreateMutexStatic() then the application writer must provided the
* memory. xSemaphoreCreateMutexStatic() therefore allows a mutex to be created
* without using any dynamic memory allocation.
*
* Mutexes created using this function can be accessed using the xSemaphoreTake()
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
* xSemaphoreGiveRecursive() macros must 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 xSemaphoreCreateBinary() 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 If the mutex was successfully created then a handle to the created
* semaphore is returned. If there was not enough heap to allocate the mutex
* data structures then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t 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 xSemaphoreCreateMutex xSemaphoreCreateMutex
* \ingroup Semaphores
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define xSemaphoreCreateMutex() xQueueCreateMutex( queueQUEUE_TYPE_MUTEX )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateMutexStatic( StaticSemaphore_t *pxMutexBuffer )</pre>
*
* Creates a new mutex type semaphore instance, and returns a handle by which
* the new mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, mutex semaphores use a block
* of memory, in which the mutex structure is stored. If a mutex is created
* using xSemaphoreCreateMutex() then the required memory is automatically
* dynamically allocated inside the xSemaphoreCreateMutex() function. (see
* http://www.freertos.org/a00111.html). If a mutex is created using
* xSemaphoreCreateMutexStatic() then the application writer must provided the
* memory. xSemaphoreCreateMutexStatic() therefore allows a mutex to be created
* without using any dynamic memory allocation.
*
* Mutexes created using this function can be accessed using the xSemaphoreTake()
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
* xSemaphoreGiveRecursive() macros must 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 xSemaphoreCreateBinary() 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.
*
* @param pxMutexBuffer Must point to a variable of type StaticSemaphore_t,
* which will be used to hold the mutex's data structure, removing the need for
* the memory to be allocated dynamically.
*
* @return If the mutex was successfully created then a handle to the created
* mutex is returned. If pxMutexBuffer was NULL then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
StaticSemaphore_t xMutexBuffer;
void vATask( void * pvParameters )
{
// A mutex cannot be used before it has been created. xMutexBuffer is
// into xSemaphoreCreateMutexStatic() so no dynamic memory allocation is
// attempted.
xSemaphore = xSemaphoreCreateMutexStatic( &xMutexBuffer );
// As no dynamic memory allocation was performed, xSemaphore cannot be NULL,
// so there is no need to check it.
}
</pre>
* \defgroup xSemaphoreCreateMutexStatic xSemaphoreCreateMutexStatic
* \ingroup Semaphores
*/
#if( configSUPPORT_STATIC_ALLOCATION == 1 )
#define xSemaphoreCreateMutexStatic( pxMutexBuffer ) xQueueCreateMutexStatic( queueQUEUE_TYPE_MUTEX, ( pxMutexBuffer ) )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateRecursiveMutex( void )</pre>
*
* Creates a new recursive mutex type semaphore instance, and returns a handle
* by which the new recursive mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, recursive mutexs use a block
* of memory, in which the mutex structure is stored. If a recursive mutex is
* created using xSemaphoreCreateRecursiveMutex() then the required memory is
* automatically dynamically allocated inside the
* xSemaphoreCreateRecursiveMutex() function. (see
* http://www.freertos.org/a00111.html). If a recursive mutex is created using
* xSemaphoreCreateRecursiveMutexStatic() then the application writer must
* provide the memory that will get used by the mutex.
* xSemaphoreCreateRecursiveMutexStatic() therefore allows a recursive mutex to
* be created without using any dynamic memory allocation.
*
* Mutexes created using this macro can be accessed using the
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
* xSemaphoreTake() and xSemaphoreGive() macros must 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 xSemaphoreCreateBinary() 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
* SemaphoreHandle_t.
*
* Example usage:
<pre>
SemaphoreHandle_t 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 xSemaphoreCreateRecursiveMutex xSemaphoreCreateRecursiveMutex
* \ingroup Semaphores
*/
#if( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configUSE_RECURSIVE_MUTEXES == 1 ) )
#define xSemaphoreCreateRecursiveMutex() xQueueCreateMutex( queueQUEUE_TYPE_RECURSIVE_MUTEX )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateRecursiveMutexStatic( StaticSemaphore_t *pxMutexBuffer )</pre>
*
* Creates a new recursive mutex type semaphore instance, and returns a handle
* by which the new recursive mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, recursive mutexs use a block
* of memory, in which the mutex structure is stored. If a recursive mutex is
* created using xSemaphoreCreateRecursiveMutex() then the required memory is
* automatically dynamically allocated inside the
* xSemaphoreCreateRecursiveMutex() function. (see
* http://www.freertos.org/a00111.html). If a recursive mutex is created using
* xSemaphoreCreateRecursiveMutexStatic() then the application writer must
* provide the memory that will get used by the mutex.
* xSemaphoreCreateRecursiveMutexStatic() therefore allows a recursive mutex to
* be created without using any dynamic memory allocation.
*
* Mutexes created using this macro can be accessed using the
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
* xSemaphoreTake() and xSemaphoreGive() macros must 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 xSemaphoreCreateBinary() 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.
*
* @param pxMutexBuffer Must point to a variable of type StaticSemaphore_t,
* which will then be used to hold the recursive mutex's data structure,
* removing the need for the memory to be allocated dynamically.
*
* @return If the recursive mutex was successfully created then a handle to the
* created recursive mutex is returned. If pxMutexBuffer was NULL then NULL is
* returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
StaticSemaphore_t xMutexBuffer;
void vATask( void * pvParameters )
{
// A recursive semaphore cannot be used before it is created. Here a
// recursive mutex is created using xSemaphoreCreateRecursiveMutexStatic().
// The address of xMutexBuffer is passed into the function, and will hold
// the mutexes data structures - so no dynamic memory allocation will be
// attempted.
xSemaphore = xSemaphoreCreateRecursiveMutexStatic( &xMutexBuffer );
// As no dynamic memory allocation was performed, xSemaphore cannot be NULL,
// so there is no need to check it.
}
</pre>
* \defgroup xSemaphoreCreateRecursiveMutexStatic xSemaphoreCreateRecursiveMutexStatic
* \ingroup Semaphores
*/
#if( ( configSUPPORT_STATIC_ALLOCATION == 1 ) && ( configUSE_RECURSIVE_MUTEXES == 1 ) )
#define xSemaphoreCreateRecursiveMutexStatic( pxStaticSemaphore ) xQueueCreateMutexStatic( queueQUEUE_TYPE_RECURSIVE_MUTEX, pxStaticSemaphore )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateCounting( UBaseType_t uxMaxCount, UBaseType_t uxInitialCount )</pre>
*
* Creates a new counting semaphore instance, and returns a handle by which the
* new counting semaphore can be referenced.
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a counting semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, counting semaphores use a
* block of memory, in which the counting semaphore structure is stored. If a
* counting semaphore is created using xSemaphoreCreateCounting() then the
* required memory is automatically dynamically allocated inside the
* xSemaphoreCreateCounting() function. (see
* http://www.freertos.org/a00111.html). If a counting semaphore is created
* using xSemaphoreCreateCountingStatic() then the application writer can
* instead optionally provide the memory that will get used by the counting
* semaphore. xSemaphoreCreateCountingStatic() therefore allows a counting
* semaphore to be created without using any dynamic memory allocation.
*
* 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>
SemaphoreHandle_t xSemaphore;
void vATask( void * pvParameters )
{
SemaphoreHandle_t 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
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define xSemaphoreCreateCounting( uxMaxCount, uxInitialCount ) xQueueCreateCountingSemaphore( ( uxMaxCount ), ( uxInitialCount ) )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateCountingStatic( UBaseType_t uxMaxCount, UBaseType_t uxInitialCount, StaticSemaphore_t *pxSemaphoreBuffer )</pre>
*
* Creates a new counting semaphore instance, and returns a handle by which the
* new counting semaphore can be referenced.
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a counting semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, counting semaphores use a
* block of memory, in which the counting semaphore structure is stored. If a
* counting semaphore is created using xSemaphoreCreateCounting() then the
* required memory is automatically dynamically allocated inside the
* xSemaphoreCreateCounting() function. (see
* http://www.freertos.org/a00111.html). If a counting semaphore is created
* using xSemaphoreCreateCountingStatic() then the application writer must
* provide the memory. xSemaphoreCreateCountingStatic() therefore allows a
* counting semaphore to be created without using any dynamic memory allocation.
*
* 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.
*
* @param pxSemaphoreBuffer Must point to a variable of type StaticSemaphore_t,
* which will then be used to hold the semaphore's data structure, removing the
* need for the memory to be allocated dynamically.
*
* @return If the counting semaphore was successfully created then a handle to
* the created counting semaphore is returned. If pxSemaphoreBuffer was NULL
* then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
StaticSemaphore_t xSemaphoreBuffer;
void vATask( void * pvParameters )
{
SemaphoreHandle_t xSemaphore = NULL;
// Counting semaphore cannot be used before they have been created. Create
// a counting semaphore using xSemaphoreCreateCountingStatic(). The max
// value to which the semaphore can count is 10, and the initial value
// assigned to the count will be 0. The address of xSemaphoreBuffer is
// passed in and will be used to hold the semaphore structure, so no dynamic
// memory allocation will be used.
xSemaphore = xSemaphoreCreateCounting( 10, 0, &xSemaphoreBuffer );
// No memory allocation was attempted so xSemaphore cannot be NULL, so there
// is no need to check its value.
}
</pre>
* \defgroup xSemaphoreCreateCountingStatic xSemaphoreCreateCountingStatic
* \ingroup Semaphores
*/
#if( configSUPPORT_STATIC_ALLOCATION == 1 )
#define xSemaphoreCreateCountingStatic( uxMaxCount, uxInitialCount, pxSemaphoreBuffer ) xQueueCreateCountingSemaphoreStatic( ( uxMaxCount ), ( uxInitialCount ), ( pxSemaphoreBuffer ) )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>void vSemaphoreDelete( SemaphoreHandle_t 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.
*
* \defgroup vSemaphoreDelete vSemaphoreDelete
* \ingroup Semaphores
*/
#define vSemaphoreDelete( xSemaphore ) vQueueDelete( ( QueueHandle_t ) ( xSemaphore ) )
/**
* semphr.h
* <pre>TaskHandle_t xSemaphoreGetMutexHolder( SemaphoreHandle_t 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 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 ) )
/**
* semphr.h
* <pre>TaskHandle_t xSemaphoreGetMutexHolderFromISR( SemaphoreHandle_t 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.
*
*/
#define xSemaphoreGetMutexHolderFromISR( xSemaphore ) xQueueGetMutexHolderFromISR( ( xSemaphore ) )
/**
* semphr.h
* <pre>UBaseType_t uxSemaphoreGetCount( SemaphoreHandle_t xSemaphore );</pre>
*
* If the semaphore is a counting semaphore then uxSemaphoreGetCount() returns
* its current count value. If the semaphore is a binary semaphore then
* uxSemaphoreGetCount() returns 1 if the semaphore is available, and 0 if the
* semaphore is not available.
*
*/
#define uxSemaphoreGetCount( xSemaphore ) uxQueueMessagesWaiting( ( QueueHandle_t ) ( xSemaphore ) )
#endif /* SEMAPHORE_H */
注释生成的文档描述一般有两种，一个是简短描述用于描述大致信息，比如，用//开始的单行标注，用/*开始的单行、多行标注；另一个是详细描述，描述更为具体的文档信息。将注释块标记为描述的方法：
（1）文档块注释/** text */
打开注释后再加上一个'*'，并以‘*/’结束。它的注释是C风格的，它的规则，空行或只有‘*’开始的行，意味着换行：
/**
*
* ... text ...
*
*/例如，参考代码中关于#define vSemaphoreCreateBinary()的文档块注释：
/**
* semphr. h
* <pre>vSemaphoreCreateBinary( SemaphoreHandle_t xSemaphore )</pre>
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* This old vSemaphoreCreateBinary() macro is now deprecated in favour of the
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
* the vSemaphoreCreateBinary() macro are created in a state such that the
* first call to 'take' the semaphore would pass, whereas binary semaphores
* created using xSemaphoreCreateBinary() are created in a state such that the
* the semaphore must first be 'given' before it can be 'taken'.
*
* <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 SemaphoreHandle_t.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
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
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define vSemaphoreCreateBinary( xSemaphore ) \
{ \
( xSemaphore ) = xQueueGenericCreate( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE ); \
if( ( xSemaphore ) != NULL ) \
{ \
( void ) xSemaphoreGive( ( xSemaphore ) ); \
} \
}
#endif这段文档块注释的显示效果：
（2）文档块注释/*! text */
打开注释后加上一个'!'，并以‘*/’结束。它的注释也是C风格的，它的规则，空行或只有‘*’开始的行，意味着换行，它的注释规则：
/*!
* ... text ...
*/（3）文档块注释/// text 或 //! text
使用'//'打开注释的每行后，额外添加一个'/'或者'!'。它的注释是C++风格的，它的注释规则：
///
/// ... text ...
///或者
//!
//!... text ...
//!（4）显示预格式化的文本<pre></pre>
<pre>标签是HTML中的一个标签，当然，现在也常用于C/C++中，用于显示预格式化的文本。当文本包含在<pre>标签中时，浏览器（或输出的文档）会保留文本的空格和换行符，并将其显示为等宽字体。这使得<pre>标签特别适用于显示源代码、诗歌、歌词等需要保持原有格式的文本内容。 <pre>标签的基本语法规则如下：
<pre>
这里是预格式化文本
</pre>比如上面参考过的文件里的一段 <pre>标签里：
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
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>生成文档后，这部分 <pre>标签对里的文字输出后的显示效果为：
（5）显示预格式化的源代码<code></code>
在HTML中，可以通过结合`<pre>`和`<code>`标签来保留代码的格式和语义，强调了在展示源代码时使用`<code>`元素的重要性，以提高可读性和明确表示代码内容。
<code>，是单行代码，不能保留内容中的空格、换行符。
<pre>，是多行代码，它虽能保留内容中的空格、换行符，但<pre>缺少了“语义化”。 可以把这两个标签结合起来嵌套使用，这样就能让<code>保留内容的空格以及换行符。
特别地，<pre>元素并不局限于只能代码放入，里面的内容可以是歌词，可以是代码，可以是其它文本。当<pre>元素用来展示源代码的时候最好的方式是用<code>元素来包裹代码，这样既可以保持格式又可以代表语义，一举数得。
<pre>元素和<code>元素嵌套组合时，谁包裹谁，我在应用时，没有发现区别，尤其，在用于C/C++时。
* Example usage:
<pre>
<code>
SemaphoreHandle_t xSemaphore = NULL;
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.
}
}
</code>
</pre>或者，输出文档后的显示效果是一样的：
* Example usage:
<code>
<pre>
SemaphoreHandle_t xSemaphore = NULL;
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>
</code>（6）标记宏<i>macro</i>
<i>macro</i>这样的注释在编程中用于标记和解释宏相关的代码，提高代码的可读性和可维护性。 <i>macro</i>这样的注释可能用于以下几种情况：
- 标记宏定义：在宏定义的代码段前使用
<i>macro</i>注释，以便开发者快速识别该部分代码是宏定义。 - 标记宏调用：在宏调用的代码段前使用
<i>macro</i>注释，帮助开发者理解该部分代码是通过宏生成的。 - 解释宏功能：在宏定义或调用的代码段后使用
<i>macro</i>注释，详细说明该宏的功能和使用方法
比如上面参考过的文件里有这样的标记宏注释：
* <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.生成文档后的显示效果为：
2、用于生成特殊文档格式的指令（关键字）
（1） 参数描述指令@param或\param
在Doxygen中，@param注解用于描述函数的参数。它的基本语法是：@param 参数名 参数描述。其中，参数名是函数参数的名称，参数描述是对该参数的详细说明。
比如上面参考过的文件里有这样的参数描述注释：
* @param xSemaphore Handle to the created semaphore. Should be of type SemaphoreHandle_t.生成文档后的显示效果为：
（2）简短表述指令@brief或\brief
使用 @brief 指令，用于类、函数等的概述。通常放在整个文件开头。
单行注释：以// 或者 //！开始； 多行注释：以/* 或 /*! 开始，以*/结束；
/** @brief Brief description.
Brief description continued.
*
* @details
* Detailed description starts here.
*/* @brief 本函数负责打印错误信息串（3）详细描述指令@details或\details
在Doxygen中，@details用于在函数或类的注释中添加更详细的描述。它通常出现在@brief简要描述之后，用于提供更多的背景信息、操作步骤、注意事项等。使用时，只需在@brief简要描述之后添加@details标签，并跟随详细描述内容即可。Doxygen会将这些内容组织在一起，生成易于阅读的文档
/**
* @ brief
* Brief description.
* Brief description.
* Brief description.
*
* @details
* Detailed description.
* Detailed description.
*/在简要描述和详细描述之间，要增加一个空行。
（4）返回值情况描述指令@return或\return
在Doxygen中，@return关键字用于描述函数的返回值情况。在函数的注释中使用@return时，你应当紧接着写出该函数返回的是什么，或者是返回值的类型和意义。例如，如果你的函数返回一个表示操作成功或失败的布尔值，你可以这样写：
* @return 本函数返回执行结果，若成功则返回TRUE，否则返回FALSE。再比如，参考文件中，有这样一段关于返回值情况描述的注释：
* @return Handle to the created semaphore, or NULL if the memory required to
* hold the semaphore's data structures could not be allocated.生成文档后，输出文档的显示效果为：
（5） 描述返回值类型指令@retval
在Doxygen中，@retval 用于描述返回值类型。
/**
* @retval NULL 空字符串。
* @retval !NULL 非空字符串。
*/（6）创建群组指令\defgroup和群组分级指令\ingroup
Doxygen的\defgroup命令用于在文档中首次定义和组织内容，创建一个全新的群组。
\defgroup命令的基本语法如下：
\defgroup [group_name] [description]- [group_name]：指定群组的名称。
- [description]：提供群组的描述信息。
使用\defgroup命令时，可以在注释中定义一个新群组，并为其提供名称和描述。例如：
/** \defgroup CoreModule 核心模块
* 这个群组包含应用程序的核心功能类。
* @{
* @}
*/在这个例子中，CoreModule是群组的名称，而“这个群组包含应用程序的核心功能类”是对该群组的描述。使用@{和@}标记来标识群组的开始和结束，确保Doxygen能够正确解析和归类相关内容。
所有的命令都开始于一个反斜杠\或者是一个符号@。如果喜欢，可以把所有的以反斜杠\开头的命令都换成以@符号开头的命令。
一般情况下，通过@defgroup或\defgroup创建了新的分组后，就要和@ingroup或\ingroup配套使用，以确定新创建的分组是哪个组的成员。
比如，参考文件中有这样创建分组和确定分组位置的注释：
* \defgroup vSemaphoreCreateBinary vSemaphoreCreateBinary
* \ingroup Semaphores
*/其含义是：
第1句，创建分组，分组名vSemaphoreCreateBinary，分组描述vSemaphoreCreateBinary。
第2句，描述新创建的分组的位置，该分组属于Semaphores的组成员。
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