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