今天拾起闲置很久的灰机，测试发现nrf2401坏掉，重新淘宝。还发现机上搭载的usart1坏掉，换成usart2，发现端口被电机占用，重映射到PD5，PD6

关键是后面两句不要忘记了

	RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);	//使能USART2，GPIOD时钟

	RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);

	GPIO_PinRemapConfig(GPIO_Remap_USART2, ENABLE);

修改后的原子printf代码usart.c

void uart_init(u32 bound){

  //GPIO端口设置

	GPIO_InitTypeDef GPIO_InitStructure;

	USART_InitTypeDef USART_InitStructure;

	NVIC_InitTypeDef NVIC_InitStructure;

	RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);	//使能USART2，GPIOD时钟

	RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);

	GPIO_PinRemapConfig(GPIO_Remap_USART2, ENABLE);

	//USART2_TX   GPIOD5

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; //PD5

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;	//复用推挽输出

  GPIO_Init(GPIOD, &GPIO_InitStructure);//初始化GPIOD5

  //USART2_RX	  GPIOD6初始化

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;//PD6

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//浮空输入

  GPIO_Init(GPIOD, &GPIO_InitStructure);//初始化GPIOD6

  //Usart2 NVIC 配置

  NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;

	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3 ;//抢占优先级3

	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;		//子优先级3

	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;			//IRQ通道使能

	NVIC_Init(&NVIC_InitStructure);	//根据指定的参数初始化VIC寄存器

   //USART 初始化设置

	USART_InitStructure.USART_BaudRate = bound;//串口波特率

	USART_InitStructure.USART_WordLength = USART_WordLength_8b;//字长为8位数据格式

	USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位

	USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位

	USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//无硬件数据流控制

	USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;	//收发模式

  USART_Init(USART2, &USART_InitStructure); //初始化串口2

  USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);//开启串口接受中断

  USART_Cmd(USART2, ENABLE);                    //使能串口2 

}

void USART2_IRQHandler(void)                	//串口2中断服务程序

	{

	u8 Res;

#if SYSTEM_SUPPORT_OS 		//如果SYSTEM_SUPPORT_OS为真，则需要支持OS.

	OSIntEnter();

#endif

	if(USART_GetITStatus(USART2, USART_IT_RXNE) != RESET)  //接收中断(接收到的数据必须是0x0d 0x0a结尾)

		{

		Res =USART_ReceiveData(USART2);	//读取接收到的数据

		if((USART_RX_STA&0x8000)==0)//接收未完成

			{

			if(USART_RX_STA&0x4000)//接收到了0x0d

				{

				if(Res!=0x0a)USART_RX_STA=0;//接收错误,重新开始

				else USART_RX_STA|=0x8000;	//接收完成了

				}

			else //还没收到0X0D

				{

				if(Res==0x0d)USART_RX_STA|=0x4000;

				else

					{

					USART_RX_BUF[USART_RX_STA&0X3FFF]=Res ;

					USART_RX_STA++;

					if(USART_RX_STA>(USART_REC_LEN-1))USART_RX_STA=0;//接收数据错误,重新开始接收

					}

				}

			}

     }