怎么把dac_vol_sample这个函数写到main里？

#include <rtthread.h>
#include <rtdevice.h>
#include <stdlib.h>
#define DAC_DEV_NAME        "dac1"  /* DAC 设备名称 */
#define DAC_DEV_CHANNEL     1       /* DAC 通道 */
#define REFER_VOLTAGE       330         /* 参考电压 3.3V,数据精度乘以100保留2位小数*/
#define CONVERT_BITS        (1 << 12)   /* 转换位数为12位 */
static int dac_vol_sample(int argc, char *argv[])
{
    rt_dac_device_t dac_dev;
    rt_uint32_t value, vol;
    rt_err_t ret = RT_EOK;
    /* 查找设备 */
    dac_dev = (rt_dac_device_t)rt_device_find(DAC_DEV_NAME);
    if (dac_dev == RT_NULL)
    {
        rt_kprintf("dac sample run failed! can't find %s device!\n", DAC_DEV_NAME);
        return RT_ERROR;
    }
    /* 打开通道 */
    ret = rt_dac_enable(dac_dev, DAC_DEV_CHANNEL);
    /* 设置输出值 */
    value = atoi(argv[1]);
    rt_dac_write(dac_dev, DAC_DEV_CHANNEL, &value);
    rt_kprintf("the value is :%d \n", value);
    /* 转换为对应电压值 */
    vol = value * REFER_VOLTAGE / CONVERT_BITS;
    rt_kprintf("the voltage is :%d.%02d \n", vol / 100, vol % 100);
    /* 延时查看效果，关闭通道后无输出 */
    rt_thread_mdelay(500);
    /* 关闭通道 */
    ret = rt_dac_disabled(dac_dev, DAC_DEV_CHANNEL);
    return ret;
}