文章目录
定时器工作原理资源定时器模块初始化定时器创建启动定时器定时器超时函数定时器工作原理
定时器主要是使用waitdog进行实现，周期处理是通过timer_timeout进行处理
资源
nuttx_posix_timer.md
闫刚 nuttx的posix的定时器原理
定时器模块初始化
主要是创建定时器的资源， 静态分配资源到链表中。
void weak_function timer_initialize(void)
{
#if CONFIG_PREALLOC_TIMERS > 0
int i;
/* Place all of the pre-allocated timers into the free timer list */
sq_init((FAR sq_queue_t *)&g_freetimers);
for (i = 0; i < CONFIG_PREALLOC_TIMERS; i++)
{
g_prealloctimers[i].pt_flags = PT_FLAGS_PREALLOCATED;
sq_addlast((FAR sq_entry_t *)&g_prealloctimers[i],
(FAR sq_queue_t *)&g_freetimers);
}
#endif
/* Initialize the list of allocated timers */
sq_init((FAR sq_queue_t *)&g_alloctimers);
}
定时器创建
创建定时器主要是设置1个signal信号，后期通过发信号通知用户程序
int timer_create(clockid_t clockid, FAR struct sigevent *evp,
FAR timer_t *timerid)
wdog = wd_create();
ret = timer_allocate();
ret->pt_wdog = wdog;
信号实现
ret->pt_event.sigev_notify = SIGEV_SIGNAL; //设置信号ALARM
ret->pt_event.sigev_signo = SIGALRM;
ret->pt_event.sigev_value.sival_ptr = ret;
启动定时器
启动定时器是通过timer_settime进行启动的
int timer_settime(timer_t timerid, int flags,
FAR const struct itimerspec *value,
FAR struct itimerspec *ovalue)
->
timer->pt_last = delay;
ret = wd_start(timer->pt_wdog, delay, (wdentry_t)timer_timeout,
1, (uint32_t)((wdparm_t)timer));
定时器超时函数
static void timer_timeout(int argc, wdparm_t itimer)
timer_restart(u.timer, itimer);
