Contiki Rtimer 模块

一、rtimer概述

The Contiki rtimer library provides scheduling and execution of real-time tasks (with predictable execution times)

数据结构:

struct rtimer {
  rtimer_clock_t time;
  rtimer_callback_t func;
  void *ptr;
};

typedef void (* rtimer_callback_t)(struct rtimer *t, void *ptr);

 1、rtimer_init

void
rtimer_init(void)
{
  rtimer_arch_init();
}

rtimer_arch_init是跟平台相关的，rtimer_arch_init() is called by the rtimer library to initialize the rtimer architecture code.

2、rtimer_set

int
rtimer_set(struct rtimer *rtimer, rtimer_clock_t time,
       rtimer_clock_t duration,
       rtimer_callback_t func, void *ptr)
{
  int first = 0;

  PRINTF("rtimer_set time %d
", time);

  if(next_rtimer == NULL) {//空，first置1
    first = 1;
  }

  rtimer->func = func;//设置回调函数
  rtimer->ptr = ptr;//回调函数第一个参数

  rtimer->time = time;//设置
  next_rtimer = rtimer;//设置next_rtimer

  if(first == 1) {//如果是1
    rtimer_arch_schedule(time);
  }
}

rtimer用来设置rtimer，即在特定的时间（time）执行特定的回调函数（func）。 

其中rtimer_arch_schedule函数是跟平台相关的，被底层用来确定调用rtimer_run_next的时间，rtimer_run_next会在特定的时间执行回调函数。

3、rtimer_run_next

void
rtimer_run_next(void)
{
  struct rtimer *t;
  if(next_rtimer == NULL) {
    return;
  }
  t = next_rtimer;
  next_rtimer = NULL;//重新设置为NULL
  t->func(t, t->ptr);//执行回调函数
  if(next_rtimer != NULL) {//在执行回调函数期间有rtimer set，在调用一次rtimer_arch_schedule
    rtimer_arch_schedule(next_rtimer->time);
  }
  return;
}

rtimer_run_next会调用特定的next_rtimer的回调函数。

rtimer_run_next是在底层被调用的。

直观的流程：

rtimer_set（设置rtimer） --->  rtimer_arch_schedule(通知底层在特定时间)    ------>   rtimer_run_next（在特定时间执行回调函数）   ------->   rtimer_set

注：RTIMER_NOW() RTIMER_SECOND rtimer_arch_init() rtimer_arch_now() rtimer_arch_schedule()等都是跟平台有关的。