FreeRTOS计数型信号量

API函数

//创建

#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )

    #define xSemaphoreCreateCounting( uxMaxCount, uxInitialCount )

                                xQueueCreateCountingSemaphore( ( uxMaxCount ), ( uxInitialCount ) )

    QueueHandle_t xQueueCreateCountingSemaphore( const UBaseType_t uxMaxCount,

                                                const UBaseType_t uxInitialCount )

#endif

//释放

#define xSemaphoreGive( xSemaphore )

xQueueGenericSend( ( QueueHandle_t ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK )

BaseType_t xQueueGenericSend( QueueHandle_t xQueue, const void * const pvItemToQueue,

                            TickType_t xTicksToWait, const BaseType_t xCopyPosition )

//获取信号量值

#define uxSemaphoreGetCount( xSemaphore ) uxQueueMessagesWaiting( ( QueueHandle_t ) ( xSemaphore ) )

UBaseType_t uxQueueMessagesWaiting( const QueueHandle_t xQueue )

//等待

#define xSemaphoreTake( xSemaphore, xBlockTime )

xQueueGenericReceive( ( QueueHandle_t ) ( xSemaphore ), NULL, ( xBlockTime ), pdFALSE )

BaseType_t xQueueGenericReceive( QueueHandle_t xQueue, void * const pvBuffer,

                                TickType_t xTicksToWait, const BaseType_t xJustPeeking )

使用举例

SemaphoreHandle_t semaphore;

void start_task(void *pvParameters)

{

    semaphore = xSemaphoreCreateCounting(10, 0);

}

void give_task(void *pvParameters)

{

    UBaseType_t count;

    while(1)

    {

        key = KEY_Scan(0);

        if(key == WKUP_PRES)

        {

            err = xSemaphoreGive(semaphore);

            count = uxSemaphoreGetCount(semaphore);

            printf("give_task uxSemaphoreGetCount %d\r\n", count);

        }

        vTaskDelay(10);

    }

}

void take_task(void *pvParameters)

{

    while(1)

    {

        xSemaphoreTake(semaphore, portMAX_DELAY);

        count = uxSemaphoreGetCount(semaphore);

        printf("take_task uxSemaphoreGetCount %d\r\n", count);

        vTaskDelay(1000);

    }

}

实验现象