基于freertos的xTaskUntilDelay函数问题解析

来源：互联网发布：地面站软件下载编辑：程序博客网时间：2024/06/06 01:13

具体定义三个任务：
1.任务一，任务优先级默认定义为6，每taskDelayUntil（500）输出一次字符串并输出一次本函数运行次数。
2.任务二，任务优先级默认定义为7，每taskDelayUntil（10000）修改一次任务一的任务优先级，设置为6或者4（相当于任务一是否能得到运行的开关）
3.任务三，任务优先级默认定义为5，里面就一个while（1）空循环，为了使得任务一被设置为优先级为4的时候，不给任务一运行权限。
代码如下：
#include "sys.h"
#include "delay.h"
#include "usart.h"
#include "FreeRTOS.h"
#include "task.h"
#include "led.h"

#define StackDepth 120
TaskHandle_t LED_TASK_HANDLE;
TaskHandle_t UART_TASK_HANDLE;
TaskHandle_t TASK_HANDLE;
void LED_TASK(void *para)
{
TickType_t m;
u8 f=0;
int i=0;
m=xTaskGetTickCount();
while(1)
{
   i++;
   if(f==0)
   {
   printf("LED is on!\r\n");
   LED0=!LED0;
   f=1;
   }
   else
   {
   printf("LED is off!\r\n");
   LED1=!LED1;
   f=0;
   }
   printf("LED has cycled %d times!\r\n",i);
   printf("LED'priority is%d!!\r\n",(u8)uxTaskPriorityGet(NULL));
   vTaskDelayUntil(&m, pdMS_TO_TICKS(1000));
}
vTaskDelete(NULL);
}

void UART_TASK(void *para)
{
TickType_tm=xTaskGetTickCount();

u8 f=0;
while(1)
{

   if(f==0)
   {
   f=1;
   vTaskPrioritySet(LED_TASK_HANDLE,4);
   printf("LED has beenstopped!\r\n");
   }
   else if(f==1)
   {
   f=0;
   vTaskPrioritySet(LED_TASK_HANDLE,6);
   printf("LED has beenstarted!\r\n");
   }

   vTaskDelayUntil(&m, pdMS_TO_TICKS(10000));

}
vTaskDelete(NULL);
}
void  TASK(void *para)
{
u8 i=0;

while(1)
{
   i=0;
}
vTaskDelete(NULL);
}

int main(void)
{
uart_init(115200);
LED_Init();
xTaskCreate(   (TaskFunction_t) LED_TASK,
      "LED_TASK",
      StackDepth,
      NULL,
      6,
      &LED_TASK_HANDLE );
xTaskCreate(   (TaskFunction_t) UART_TASK,
      "UART_TASK",
      StackDepth,
      NULL,
      7,
      &UART_TASK_HANDLE );
xTaskCreate(   (TaskFunction_t) TASK,
      "TASK",
      StackDepth,
      NULL,
      5,
      &TASK_HANDLE );
vTaskStartScheduler();


}

然而，运行结果如下:

LED has been stopped![2017-12-1611:40:25.518]

LED has been started![2017-12-1611:40:35.542]

LED is on![2017-12-16 11:40:35.542]

LED has cycled 1 times![2017-12-1611:40:35.542]

LED'priority is 6!![2017-12-1611:40:35.542]

LED is off![2017-12-16 11:40:36.520]

LED has cycled 2 times![2017-12-1611:40:36.520]

LED'priority is 6!![2017-12-1611:40:36.524]

LED is on![2017-12-16 11:40:37.554]

LED has cycled 3 times![2017-12-1611:40:37.554]

LED'priority is 6!![2017-12-16 11:40:37.554]

LED is off![2017-12-16 11:40:38.543]

LED has cycled 4 times![2017-12-1611:40:38.543]

LED'priority is 6!![2017-12-1611:40:38.543]

LED is on![2017-12-16 11:40:39.521]

LED has cycled 5 times![2017-12-1611:40:39.521]

LED'priority is 6!![2017-12-16 11:40:39.521]

LED is off![2017-12-16 11:40:40.524]

LED has cycled 6 times![2017-12-1611:40:40.524]

LED'priority is 6!![2017-12-1611:40:40.524]

LED is on![2017-12-16 11:40:41.522]

LED has cycled 7 times![2017-12-1611:40:41.522]

LED'priority is 6!![2017-12-1611:40:41.522]

LED is off![2017-12-16 11:40:42.521]

LED has cycled 8 times![2017-12-1611:40:42.521]

LED'priority is 6!![2017-12-1611:40:42.521]

LED is on![2017-12-16 11:40:43.522]

LED has cycled 9 times![2017-12-1611:40:43.522]

LED'priority is 6!![2017-12-1611:40:43.522]

LED is off![2017-12-16 11:40:44.526]

LED has cycled 10 times![2017-12-1611:40:44.526]

LED'priority is 6!![2017-12-1611:40:44.526]

LED has been stopped![2017-12-1611:40:45.520]

LED has been started![2017-12-1611:40:55.520]

LED is on![2017-12-16 11:40:55.520]

LED has cycled 11 times![2017-12-1611:40:55.520]

LED'priority is 6!![2017-12-1611:40:55.520]

LED is off![2017-12-16 11:40:55.532]

LED has cycled 12 times![2017-12-1611:40:55.532]

LED'priority is 6!![2017-12-16 11:40:55.532]

LED is on![2017-12-16 11:40:55.532]

LED has cycled 13 times![2017-12-1611:40:55.532]

LED'priority is 6!![2017-12-1611:40:55.532]

LED is off![2017-12-16 11:40:55.542]

LED has cycled 14 times![2017-12-1611:40:55.542]

LED'priority is 6!![2017-12-16 11:40:55.542]

LED is on![2017-12-16 11:40:55.542]

LED has cycled 15 times![2017-12-1611:40:55.542]

LED'priority is 6!![2017-12-1611:40:55.551]

LED is off![2017-12-16 11:40:55.551]

LED has cycled 16 times![2017-12-1611:40:55.551]

LED'priority is 6!![2017-12-1611:40:55.551]

LED is on![2017-12-16 11:40:55.551]

LED has cycled 17 times![2017-12-1611:40:55.551]

LED'priority is 6!![2017-12-1611:40:55.557]

LED is off![2017-12-16 11:40:55.557]

LED has cycled 18 times![2017-12-1611:40:55.564]

LED'priority is 6!![2017-12-1611:40:55.564]

LED is on![2017-12-16 11:40:55.564]

LED has cycled 19 times![2017-12-1611:40:55.564]

LED'priority is 6!![2017-12-1611:40:55.572]

LED is off![2017-12-16 11:40:55.572]

LED has cycled 20 times![2017-12-1611:40:55.572]

LED'priority is 6!![2017-12-1611:40:55.572]

LED is on![2017-12-16 11:40:55.578]

LED has cycled 21 times![2017-12-1611:40:55.578]

LED'priority is 6!![2017-12-1611:40:55.578]

LED is off![2017-12-16 11:40:56.553]

LED has cycled 22 times![2017-12-16 11:40:56.553]

LED'priority is 6!![2017-12-1611:40:56.553]

LED is on![2017-12-16 11:40:57.525]

LED has cycled 23 times![2017-12-1611:40:57.525]

LED'priority is 6!![2017-12-1611:40:57.525]

请看红色标注部分，相当于瞬间，任务一瞬间运行了10次，与我设置的逻辑出错，

出错部分，1.应该是间隔500ms

2.应该优先级为4，低于任务三的优先级5，不该被执行

3.而且瞬间十次的优先级检测为都为6

在观察xTaskUntilDelay函数的过程中，，发现xTimeToWake = *pxPreviousWakeTime +xTimeIncrement;唤醒时间只根据上一次唤醒时间，以及时间间隔有关，假设在1s时间点我把函数xTaskUntilDelay100ms，同时把该任务优先级调低使其无法运行，等10s之后再调高他的优先级，那么下一次执行本函数的xTaskUntilDelay的时候，它默认的下次唤醒时间为1s+100ms+100ms；前面的1s+100ms是它认为的现在的时间点，后面100ms就是它认为要延时的，我们的系统时钟已经运行到了11s+100ms了，（所以出现了1s+100ms+100ms的时间点任务就自动运行了？这个是我猜测的，这样解释是可以解释的通的）

为了证明我那个解释：于是我把xTaskUntilDelay函数总的xTimeToWake = *pxPreviousWakeTime + xTimeIncrement;修改成了xTimeToWake = xTaskGetTickCount() + xTimeIncrement;整个系统完全按照理论走，所以，初步认为我的解释是对的，如果有大神有更高见解，勿喷，请分享，谢谢！

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