串口中断优先级配置。优先级分组为第2组，USART1中断抢占优先级为1，副优先级为2。（以固件库定义的字符填写，不可以野火教材自定义名填写）NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); NVIC_InitStructure.NVIC_IRQChannel =； NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=； NVIC_InitStructure.NVIC_IRQChannelSubPriority = ； NVIC_InitStructure.NVIC_IRQChannelCmd =； NVIC_Init(&NVIC_InitStructure);