STM32F429 422串口通信

1. 422串口的硬件原理图如下：
   

2. 422串口和232串口不同的是引脚的电平控制，还有DE是发送使能，置高即可：RE是接收使能，置低即可。422接出来的是4根线，有RS485_A、RS485_B、RS485_Z、RS485_Y，对应422串口线的DB1、DB2、DB3、DB4,，DB5连接地线，其他的配置用232串口的代码即可。

3. GPIO的配置：
   void RS422_Config()
   {
   GPIO_InitTypeDef GPIO_InitStructure;
   USART_InitTypeDef USART_InitStructure;
   /* PC6/USART6_TX , PC7/USART6_RX, PG12/USART6_RTS, PG13/USART6_CTS */

   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC |RCC_AHB1Periph_GPIOG, ENABLE);

   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13;
   GPIO_Init(GPIOG, &GPIO_InitStructure);

   GPIO_ResetBits(GPIOG,GPIO_Pin_12); //USART6_RTS
   GPIO_SetBits(GPIOG,GPIO_Pin_13); //USART6_CTS

   RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART6, ENABLE);

   GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_USART6);

   GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_USART6);

   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
   GPIO_Init(GPIOC, &GPIO_InitStructure);

   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
   GPIO_Init(GPIOC, &GPIO_InitStructure);

   USART422_NVIC_Config();

   USART_InitStructure.USART_BaudRate = 115200;
   USART_InitStructure.USART_WordLength = USART_WordLength_8b;
   USART_InitStructure.USART_StopBits = USART_StopBits_1;
   USART_InitStructure.USART_Parity = USART_Parity_No ;
   //USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_RTS_CTS;
   USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
   USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
   USART_Init(USART6, &USART_InitStructure);

   USART_ITConfig(USART6, USART_IT_RXNE, ENABLE);

   USART_Cmd(USART6, ENABLE);

   USART_ClearFlag(USART6, USART_FLAG_TC);
   }

4. 422串口中断的配置：
   void USART422_NVIC_Config(void)
   {
   NVIC_InitTypeDef NVIC_InitStructure;
   NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //设置中断分组2

   NVIC_InitStructure.NVIC_IRQChannel = USART6_IRQn; // 选择 USART6 通道
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; //抢占优先级设置为3
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; //响应优先级设置为1
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //开启中断
   NVIC_Init(&NVIC_InitStructure); //初始化配置
   }

void USART6_IRQHandler (void)
{
char Date422 = 0;

if(USART_GetITStatus(USART6,USART_IT_RXNE)!=RESET)	
{		
	Date422 = USART_ReceiveData(USART6)& 0xff;	//将接收到的串口数据存入数组
	
	USART_SendData(USART6, Date422);  
}	 

USART_ClearITPendingBit(USART6, USART_IT_RXNE);

}

5. 主函数的发送：
   int main(void)
   {

   Delay_Init(); //延时函数初始化
   RS422_Config(); //422串口初始化
   while(1)
   {
   Delay_ms(1000);
   USART_SendData(USART6,3); //将接收到的数据发回
   }
   }