5 如果利用硬件定时器超时时间判断串口接收一帧结束？

void read_uart(void *parameter)
{
    rt_uint32_t recv_cnt = 0, old_recv_cnt = 0;
    rt_uint8_t     recv_buff[4096] = {0};
    rt_uint8_t    *tmp_ptr= recv_buff;
    rt_uint16_t cnt = 0;//统计一次接收读取几次，可以知道一帧数据被dma分成几次
    rt_hwtimerval_t timeout_s;      /* 定时器超时值 */
    timeout_s.sec = 0;      /* 秒 */
    timeout_s.usec = 100000;     /* 微秒  250ms */
       hwtimer_sample();
    while(1)
    {
        if (rt_sem_take(&env_rx,500) != RT_EOK)
        {
            continue;
        }
        //循环从串口读数据，放到tmpptr里，然后tmpptr每次增加接收的字符数，避免覆盖
        while (recv_cnt = rt_device_read(dev, -1, tmp_ptr, 4096)  )
        {
            rt_device_write(hw_dev, 0, &timeout_s, sizeof(timeout_s)) ;
            cnt += recv_cnt;
            tmp_ptr += recv_cnt;
            old_recv_cnt = recv_cnt;
            // rt_kprintf("第 %d 次",cnt);
        }
//得到一帧数据，stop定时器，处理数据
        if (timeout == 1 && old_recv_cnt != 0 && recv_cnt == 0)
        {
            timeout = 0;
            old_recv_cnt = 0;
            tmp_ptr = recv_buff;
            rt_device_control(hw_dev, HWTIMER_CTRL_STOP, RT_NULL);
            dump_hex(recv_buff, cnt);
            cnt = 0;
        }
        rt_thread_delay(50);
    }
}

/* 定时器超时回调函数 */
static rt_err_t timeout_cb(rt_device_t dev, rt_size_t size)
{
    // rt_kprintf("this is hwtimer timeout callback fucntion!\n");
     rt_kprintf("tick is :%d !\n", rt_tick_get());
    timeout = 1;
    return 0;
}

static void timer_stop(rt_hwtimer_t *timer)
{
    TIM_HandleTypeDef *tim = RT_NULL;
    RT_ASSERT(timer != RT_NULL);
    tim = (TIM_HandleTypeDef *)timer->parent.user_data;
    /* stop timer */
    HAL_TIM_Base_Stop_IT(tim);
    /* set tim cnt */
    __HAL_TIM_SET_COUNTER(tim, 0);
}
static const struct rt_hwtimer_ops _ops =
{
    .init = timer_init,
    .start = timer_start,
    .stop = timer_stop,
    .count_get = timer_counter_get,
    .control = timer_ctrl,
};

static rt_err_t timer_ctrl(rt_hwtimer_t *timer, rt_uint32_t cmd, void *arg)
{
    TIM_HandleTypeDef *tim = RT_NULL;
    rt_err_t result = RT_EOK;
    RT_ASSERT(timer != RT_NULL);
    RT_ASSERT(arg != RT_NULL);
    tim = (TIM_HandleTypeDef *)timer->parent.user_data;
    switch (cmd)
    {
    case HWTIMER_CTRL_FREQ_SET:
    {
        rt_uint32_t freq;
        rt_uint16_t val;
        /* set timer frequence */
        freq = *((rt_uint32_t *)arg);
#if defined(SOC_SERIES_STM32F2) || defined(SOC_SERIES_STM32F4) || defined(SOC_SERIES_STM32F7)
        if (tim->Instance == TIM9 || tim->Instance == TIM10 || tim->Instance == TIM11)
#elif defined(SOC_SERIES_STM32L4)
        if (tim->Instance == TIM15 || tim->Instance == TIM16 || tim->Instance == TIM17)
#elif defined(SOC_SERIES_STM32F1) || defined(SOC_SERIES_STM32F0) || defined(SOC_SERIES_STM32G0)
        if (0)
#endif
        {
#if defined(SOC_SERIES_STM32L4)
            val = HAL_RCC_GetPCLK2Freq() / freq;
#elif defined(SOC_SERIES_STM32F1) || defined(SOC_SERIES_STM32F2) || defined(SOC_SERIES_STM32F4) || defined(SOC_SERIES_STM32F7)
            val = HAL_RCC_GetPCLK2Freq() * 2 / freq;
#endif
        }
        else
        {
#if defined(SOC_SERIES_STM32F1) || defined(SOC_SERIES_STM32F2) || defined(SOC_SERIES_STM32F4) || defined(SOC_SERIES_STM32F7)
            val = HAL_RCC_GetPCLK1Freq() * 2 / freq;
#elif defined(SOC_SERIES_STM32F0) || defined(SOC_SERIES_STM32G0)
            val = HAL_RCC_GetPCLK1Freq() / freq;
#endif
        }
        __HAL_TIM_SET_PRESCALER(tim, val - 1);
        /* Update frequency value */
        tim->Instance->EGR |= TIM_EVENTSOURCE_UPDATE;
    }
    break;
    default:
    {
        result = -RT_ENOSYS;
    }
    break;
    }
    return result;
}