5 硬件定时器超时影响串口接收回调的原因？

发布于 2022-08-10 10:01:03 浏览：556 订阅该版

串口DMA方式接收，在接收回调里打开硬件定时器
```c
int hwtimer_sample(void)
{
    rt_err_t ret = RT_EOK;
    rt_hwtimerval_t timeout_s;      /* 定时器超时值 */
    
    rt_hwtimer_mode_t mode;         /* 定时器模式 */
    rt_uint32_t freq = 10000;               /* 计数频率 */

/* 查找定时器设备 */
    hw_dev = rt_device_find(HWTIMER_DEV_NAME);
    if (hw_dev == RT_NULL)
    {
        rt_kprintf("hwtimer sample run failed! can't find %s device!\n", HWTIMER_DEV_NAME);
        return RT_ERROR;
    }

/* 以读写方式打开设备 */
    ret = rt_device_open(hw_dev, RT_DEVICE_OFLAG_RDWR);
    if (ret != RT_EOK)
    {
        rt_kprintf("open %s device failed!\n", HWTIMER_DEV_NAME);
        return ret;
    }

/* 设置超时回调函数 */
    rt_device_set_rx_indicate(hw_dev, timeout_cb);

/* 设置计数频率(若未设置该项，默认为1Mhz 或 支持的最小计数频率) */
    rt_device_control(hw_dev, HWTIMER_CTRL_FREQ_SET, &freq);
    /* 设置模式为周期性定时器（若未设置，默认是HWTIMER_MODE_ONESHOT）*/
    mode = HWTIMER_MODE_ONESHOT;
    ret = rt_device_control(hw_dev, HWTIMER_CTRL_MODE_SET, &mode);
    if (ret != RT_EOK)
    {
        rt_kprintf("set mode failed! ret is :%d\n", ret);
        return ret;
    }

return ret;｝
```
定时器超时回调
```c
/* 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());
	rt_uint32_t len = 0;
	timeout = 1;
	len = rt_device_read(dev, 0, USART3_RX_BUF, USART3_RX_LEN);
	dump_hex(USART3_RX_BUF, len);
	rt_sem_release(&recv_comp);
    // if (rx9_length > 0)
    // {
    //     rt_kprintf("rx9_length = %d \n", rx9_length);
    // }

return 0;
}
```
串口接收回调
```c
rt_err_t env_recv_ind(rt_device_t dev, rt_size_t size)
{
	rt_hwtimerval_t timeout_s;      /* 定时器超时值 */
	timeout_s.sec = 0;      /* 秒 */
    timeout_s.usec = 999000;     /* 微秒  100ms的时候是正常的，但是DTU数据间隔大，改成这个试试 DTU用延时做了*/
	USART3_RX_LEN += size;
	rt_kprintf("receive time is %d   size == %d\n", rt_tick_get(), size);
//	rt_device_write(hw_dev, 0, &timeout_s, sizeof(timeout_s)) ;

/* release semaphore to let finsh thread rx data */
//	if (size > 0)
//		rt_sem_release(&env_rx);
    return RT_EOK;
}
```

现象：加上开启定时器的时候，如下，相当于卡了1s，没接收新的数据

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220810/e6ca142917bf5155927de77d57ff897d.png)

去掉开启定时器的时候，如下，一直能接收到

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220810/01aada7a67f879a96819cc672255484f.png)

这个开启定时器还影响串口接收吗？
我之前也用到了这两个，可以正常，现在是想优化一下，谢谢