关于在L4潘多拉上定时器TIM3跑hwtimer_sample例程出错的问题

发布于 2020-09-29 18:43:31 浏览：1316 订阅该版

使用的是RT-Thread master 4.0.3，在hwtimer_sample.c中使用了TIM3，但是出现以下问题：
1.在hwtimer_sample.c设置定时器超时值为5s启动定时器，但是tick返回的值间66/67ms
![2.PNG](/uploads/20200929/7a92c3bda242fcfab31a95cf4a8e5866.png)

2.在cubemx中系统时钟设置的为80M，在hwtimer_sample.c设置定时器超时值为1s启动定时器，经过验证TIM3中断了16次（若使用TIM15亦中断16次且问题1中的tick返回值正好相差1s），如果timer_init函数中的以下代码是有效的，那经过计算，系统时钟应该是256M，请问以下代码有否有效，如果没有，那定时器的分频系数等是在哪里设置的？
```c
        tim->Init.Period            = 10000 - 1;
        tim->Init.Prescaler         = prescaler_value;
        tim->Init.ClockDivision     = TIM_CLOCKDIVISION_DIV1;
        if (timer->info->cntmode == HWTIMER_CNTMODE_UP)
        {
            tim->Init.CounterMode   = TIM_COUNTERMODE_UP;
        }
        else
        {
            tim->Init.CounterMode   = TIM_COUNTERMODE_DOWN;
        }
        tim->Init.RepetitionCounter = 0;
```
以下为问题相关代码：
hwtimer_sample.c例程：
```

#define HWTIMER_DEV_NAME   "timer3"     /* 定时器名称 */

/* 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());

return 0;
}

static int hwtimer_sample(int argc, char *argv[])
{
    rt_err_t ret = RT_EOK;
    rt_hwtimerval_t timeout_s;      /* 定时器超时值 */
    rt_device_t hw_dev = RT_NULL;   /* 定时器设备句柄 */
    rt_hwtimer_mode_t mode;         /* 定时器模式 */

/* 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);

/* 设置模式为周期性定时器 */
    mode = HWTIMER_MODE_PERIOD;
    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;
    }

/* 设置定时器超时值为5s并启动定时器 */
    timeout_s.sec = 5;      /* 秒 */
    timeout_s.usec = 0;     /* 微秒 */

if (rt_device_write(hw_dev, 0, &timeout_s, sizeof(timeout_s)) != sizeof(timeout_s))
    {
        rt_kprintf("set timeout value failed\n");
        return RT_ERROR;
    }

/* 延时3500ms */
    rt_thread_mdelay(3500);

/* 读取定时器当前值 */
    rt_device_read(hw_dev, 0, &timeout_s, sizeof(timeout_s));
    rt_kprintf("Read: Sec = %d, Usec = %d\n", timeout_s.sec, timeout_s.usec);

return ret;
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(hwtimer_sample, hwtimer sample);
```