串口接收不到数据，串口RX配置（f407），f103和f407的区别

问题

芯片：STM32F407，软件：标准库

使用串口时，直接把之前STM32F103的串口配置移植过来，同样以串口4为例，代码如下：

STM32F103 UART4：

void UART4_Configuration(uint32_t BaudRate)
{USART_InitTypeDef USART_InitStructure;GPIO_InitTypeDef  GPIO_InitStructure;  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4, ENABLE); 	RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE); //配置端口的TXGPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOC, &GPIO_InitStructure);//配置端口的RXGPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOC, &GPIO_InitStructure); USART_InitStructure.USART_BaudRate = BaudRate;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_None;USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;USART_Init(UART4, &USART_InitStructure); //Enables UART4 Receive Data register not empty interruptUSART_ITConfig(UART4,USART_IT_RXNE,ENABLE);//Enables UART4USART_Cmd(UART4,ENABLE);      
}

STM32F407 UART4（错误）：


void UART4_Init(uint32_t BaudRate)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC);RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4, ENABLE);GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_UART4);GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_UART4);//UART4_TX	  PC10GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;GPIO_Init(GPIOC, &GPIO_InitStructure);
//UART4_RX    PC11GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;GPIO_Init(GPIOC, &GPIO_InitStructure);  USART_InitStructure.USART_BaudRate = BaudRate;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_None;USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;USART_ITConfig(UART4, USART_IT_RXNE, ENABLE); //Enable rx enable, /* Configure the USARTx */ USART_Init(UART4, &USART_InitStructure);/* Enable the USARTx */USART_Cmd(UART4, ENABLE);
}

问题来了，同样的配置，在F103中串口的收发都是正常的。但在F407中，串口就死活接收不到数据。为啥嘞？

解决

仔细检查代码发现：时钟使能，串口参数配置都没有问题，
那问题应该出现在引脚配置上。
果然！是UART4_RX的配置出了问题，没有开启AF功能。

STM32F407 UART4（正确）：


void UART4_Init(uint32_t BaudRate)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC);RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4, ENABLE);GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_UART4);GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_UART4);//UART4_TX	  PC10GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;GPIO_Init(GPIOC, &GPIO_InitStructure);
//UART4_RX    PC11GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;GPIO_Init(GPIOC, &GPIO_InitStructure);  USART_InitStructure.USART_BaudRate = BaudRate;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_None;USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;USART_ITConfig(UART4, USART_IT_RXNE, ENABLE); //Enable rx enable, /* Configure the USARTx */ USART_Init(UART4, &USART_InitStructure);/* Enable the USARTx */USART_Cmd(UART4, ENABLE);
}