RTThread的定时器中断时间不准确，存在抖动现象

int us_temp[1000];
int us_idx = 0;
/* Timer timeout callback */
static rt_err_t timeout_cb(rt_device_t dev, rt_size_t size)
{
    rt_device_read(hw_dev, 0, &timeout_s, sizeof(timeout_s));
    int us = timeout_s.sec * 1000000 + timeout_s.usec;
    if(us_idx < 1000)
    {
        us_temp[us_idx] = us;
        us_idx++;
    }
    return 0;
}