【一起来玩RTOS系列】之RT-Thread 信号量用于中断与线程的同步

bigfanofloT · 发表于 2017-12-2 13:04:26

信号量也能够方便的应用于中断与线程间的同步，例如一个中断触发，中断服务例程需要通知线程进行相应的数据处理。这个时候可以设置信号量的初始值是0，线程在试图持有这个信号量时，由于信号量的初始值是0，线程直接在这个信号量上挂起直到信号量被释放。当中断触发时，先进行与硬件相关的动作，例如从硬件的I/O口中读取相应的数据，并确认中断以清除中断源，而后释放一个信号量来唤醒相应的线程以做后续的数据处理。例如finsh shell线程的处理方式，如图 finsh shell的中断、线程间同步所示：

semaphore先初始为0，而后shell线程试图取得信号量，因为信号量值是0，所以它会被挂起。当console设备有数据输入时，将产生中断而进入中断服务例程。在中断服务例程中，它会读取console设备的数据，并把读得的数据放入uart buffer中进行缓冲，而后释放信号量，释放信号量的操作将唤醒shell线程。在中断服务例程运行完毕后，如果系统中没有比shell线程优先级更高的就绪线程存在时，shell线程将持有信号量并运行，从uart buffer缓冲区中获取输入的数据。

警告：中断与线程间的互斥不能采用信号量（锁）的方式，而应采用中断锁。

接下来在机智云 gokit开发板上演示如何创建并使用信号量进行中断与任务的同步，程序中初始化信号量的初始值是0，在systick中断回调中间隔1000ms释放信号量，线程等待信号量后翻转LED。

注意：要在systick中调用HAL库函数

/**
****************************************************
* File Name : main.c
* Description : Main program body
****************************************************
** This notice applies to any and all portions of this file
* that are not between comment pairs USER CODE BEGIN and
* USER CODE END. Other portions of this file, whether
* inserted by the user or by software development tools
* are owned by their respective copyright owners.
*
* COPYRIGHT(c) 2017 STMicroelectronics
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of STMicroelectronics nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
****************************************************
*/
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "STM32f1xx_hal.h"
#include "usart.h"
#include "gpio.h"
/* USER CODE BEGIN Includes */
#include "rtthread.h"
#include "string.h"
/* USER CODE END Includes */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/
/* USER CODE END PFP */
/* USER CODE BEGIN 0 */
//重映射串口1到rt_kprintf
void rt_hw_console_output(const char *str)
{
/* empty console output */
char aa='\r';
rt_enter_critical();
while(*str!='\0')
{
if(*str=='\n')
{
HAL_UART_Transmit(&huart1, (uint8_t *)&aa, 1, 10);
}
HAL_UART_Transmit(&huart1, (uint8_t *)(str++), 1, 10);
}
rt_exit_critical();
}
void rt_hw_us_delay(int us)
{
rt_uint32_t delta;
/* 获得延时经过的tick数 */
us = us * (SysTick->LOAD/(1000000/RT_TICK_PER_SECOND));
/* 获得当前时间 */
delta = SysTick->VAL;
/* 循环获得当前时间，直到达到指定的时间后退出循环 */
while (delta - SysTick->VAL< us);
}
void rt_hw_ms_delay(int ms)
{
int i=0,j=0;
for(j=0;j<ms;j++)
{
for (i=0;i<2;i++)
rt_hw_us_delay(500);
}
}
/*
* 程序清单：信号量用于中断和线程的同步，在systick中断中释放信号量，用户线程中等待信号量并翻转LED。
*
* 这个例子中将创建两个线程用于实现生产者消费者问题
*/
/* 指向线程控制块的指针 */
static rt_thread_t tid = RT_NULL;
struct rt_semaphore sem;
/* 线程入口 */
void thread_entry(void* parameter)
{
while(1)
{
rt_sem_take(&sem, RT_WAITING_FOREVER);
rt_kprintf("thread take a sem.\n");
LED1_Toggle();
LED2_Toggle();
LED3_Toggle();
LED4_Toggle();
}
}
uint32_t cnt=0;
void HAL_SYSTICK_Callback(void)
{
/* NOTE : This function Should not be modified, when the callback is needed,
the HAL_SYSTICK_Callback could be implemented in the user file
*/
cnt++;
if(cnt==1000)
{
rt_sem_release(&sem);
cnt=0;
}
}
/* USER CODE END 0 */
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration----------------------------------------------------------*/
// /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
// HAL_Init();
// /* USER CODE BEGIN Init */
// /* USER CODE END Init */
// /* Configure the system clock */
// SystemClock_Config();
// /* USER CODE BEGIN SysInit */
// /* USER CODE END SysInit */
// /* Initialize all configured peripherals */
// MX_GPIO_Init();
// MX_USART1_UART_Init();
/* USER CODE BEGIN 2 */
rt_sem_init(&sem, "sem", 0, RT_IPC_FLAG_FIFO);//初始化信号量
/* 创建线程1 */
tid = rt_thread_create("thread",
thread_entry, /* 线程入口是thread_entry */
RT_NULL, /* 入口参数是RT_NULL */
512, //堆栈大小
2, //优先级
20);//时间片
if (tid != RT_NULL)
rt_thread_startup(tid);
printf("\r\n机智云只为智能硬件而生\r\n");
printf("Gizwits Smart Cloud for Smart Products\r\n");
printf("链接|增值|开放|中立|安全|自有|自由|生态\r\n");
printf("www.gizwits.com\r\n");
printf("\r\nGokit RT-Thread Demo\r\n\r\n");
return 0;
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
// while (1)
// {
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
//
// }
/* USER CODE END 3 */
}
/** System Clock Configuration
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
/**Initializes the CPU, AHB and APB busses clocks
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
/**Initializes the CPU, AHB and APB busses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
/**Configure the Systick interrupt time
*/
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
/**Configure the Systick
*/
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
/* SysTick_IRQn interrupt configuration */
HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
/**
* @brief This function is executed in case of error occurrence.
* @param None
* @retval None
*/
void _Error_Handler(char * file, int line)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
while(1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t* file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif
/**
* @}
*/
/**
* @}
*/
/**************** (C) COPYRIGHT STMicroelectronics ****END OF FILE***/

复制代码

串口打印信息如下：

于此同时可以看到LED每隔1s翻转状态。

源码下载：

Gokit_RT-Thread.zip (8.7 MB, 下载次数: 10, 售价: 1 金钱)

qq1715497152 · 发表于 2018-8-31 12:12:23

学习一下，谢谢分享