rt_device_read 接收到16进制00 时 无返回数据

void serial_entry(void *parameter)
{
while(1)
{
    while(rt_device_read(u1_dev, -1, &buffer1, 1) !=1)
    {
        rt_sem_take(&sem, RT_WAITING_FOREVER);
    }
    Uart1_senddata(&buffer1);
}
}