注意事项：软件平台：keil5  硬件：stm32f4xxxx

一、串口

串口通讯(Serial Communication)是一种设备间非常常用的串行通讯方式，因为它简单便捷，大部分电子设备都支持该通讯方式，电子工程师在调试设备时也经常使用该通讯方式输出调试信息。串行接口简称串口，也称串行通信接口或串行通讯接口（通常指COM接口），是采用串行通信方式的扩展接口。串行接口 (Serial Interface) 是指数据一位一位地顺序传送，其特点是通信线路简单，只要一对传输线就可以实现双向通信（可以直接利用电话线作为传输线），从而大大降低了成本，但是传送速度比较慢。

二、库函数

1.串口参数初始化

typedef struct
{
uint32_t USART_BaudRate;
uint16_t USART_WordLength;
uint16_t USART_StopBits;
uint16_t USART_Parity;
uint16_t USART_Mode;
uint16_t USART_HardwareFlowControl;
} USART_InitTypeDef;
/**
* @brief Initializes the USARTx peripheral according to the specified
* parameters in the USART_InitStruct .
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @param USART_InitStruct: pointer to a USART_InitTypeDef structure that contains
* the configuration information for the specified USART peripheral.
* @retval None
*/
void USART_Init(USART_TypeDef* USARTx, USART_InitTypeDef* USART_InitStruct)

2.串口工作使能
/**
* @brief Enables or disables the specified USART peripheral.
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @param NewState: new state of the USARTx peripheral.
* This parameter can be: ENABLE or DISABLE.
* @retval None
*/
void USART_Cmd(USART_TypeDef* USARTx, FunctionalState NewState)

3.串口中断使能
/**
* @brief Enables or disables the specified USART interrupts.
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @param USART_IT: specifies the USART interrupt sources to be enabled or disabled.
* This parameter can be one of the following values:
* @arg USART_IT_CTS: CTS change interrupt
* @arg USART_IT_LBD: LIN Break detection interrupt
* @arg USART_IT_TXE: Transmit Data Register empty interrupt
* @arg USART_IT_TC: Transmission complete interrupt
* @arg USART_IT_RXNE: Receive Data register not empty interrupt
* @arg USART_IT_IDLE: Idle line detection interrupt
* @arg USART_IT_PE: Parity Error interrupt
* @arg USART_IT_ERR: Error interrupt(Frame error, noise error, overrun error)
* @param NewState: new state of the specified USARTx interrupts.
* This parameter can be: ENABLE or DISABLE.
* @retval None
*/
void USART_ITConfig(USART_TypeDef* USARTx, uint16_t USART_IT, FunctionalState NewState)

4.串口发送数据
/**
* @brief Transmits single data through the USARTx peripheral.
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @param Data: the data to transmit.
* @retval None
*/
void USART_SendData(USART_TypeDef* USARTx, uint16_t Data)

5.串口接收数据
/**
* @brief Returns the most recent received data by the USARTx peripheral.
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @retval The received data.
*/
uint16_t USART_ReceiveData(USART_TypeDef* USARTx)

6.获取串口中断状态
/**
* @brief Checks whether the specified USART interrupt has occurred or not.
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @param USART_IT: specifies the USART interrupt source to check.
* This parameter can be one of the following values:
* @arg USART_IT_CTS: CTS change interrupt (not available for UART4 and UART5)
* @arg USART_IT_LBD: LIN Break detection interrupt
* @arg USART_IT_TXE: Transmit Data Register empty interrupt
* @arg USART_IT_TC: Transmission complete interrupt
* @arg USART_IT_RXNE: Receive Data register not empty interrupt
* @arg USART_IT_IDLE: Idle line detection interrupt
* @arg USART_IT_ORE_RX : OverRun Error interrupt if the RXNEIE bit is set
* @arg USART_IT_ORE_ER : OverRun Error interrupt if the EIE bit is set
* @arg USART_IT_NE: Noise Error interrupt
* @arg USART_IT_FE: Framing Error interrupt
* @arg USART_IT_PE: Parity Error interrupt
* @retval The new state of USART_IT (SET or RESET).
*/
ITStatus USART_GetITStatus(USART_TypeDef* USARTx, uint16_t USART_IT)

7.获取串口状态
/**
* @brief Checks whether the specified USART flag is set or not.
* @param USARTx: where x can be 1, 2, 3, 4, 5, 6, 7 or 8 to select the USART or
* UART peripheral.
* @param USART_FLAG: specifies the flag to check.
* This parameter can be one of the following values:
* @arg USART_FLAG_CTS: CTS Change flag (not available for UART4 and UART5)
* @arg USART_FLAG_LBD: LIN Break detection flag
* @arg USART_FLAG_TXE: Transmit data register empty flag
* @arg USART_FLAG_TC: Transmission Complete flag
* @arg USART_FLAG_RXNE: Receive data register not empty flag
* @arg USART_FLAG_IDLE: Idle Line detection flag
* @arg USART_FLAG_ORE: OverRun Error flag
* @arg USART_FLAG_NE: Noise Error flag
* @arg USART_FLAG_FE: Framing Error flag
* @arg USART_FLAG_PE: Parity Error flag
* @retval The new state of USART_FLAG (SET or RESET).
*/
FlagStatus USART_GetFlagStatus(USART_TypeDef* USARTx, uint16_t USART_FLAG)

三、自定义printf函数

printf()函数是标准c库的一个函数，调用起来很方便，但是很多嵌入式设备上没有标准输入输出设备，通常都是串口。那么，为了让嵌入式设备也可以用printf()，我们可以在编译的时候调用缺省的c库，然后重写一下这个函数。

#include "stdio.h"

#pragma import(__use_no_semihosting) //不使用半主机模式

//标准库需要的支持函数
struct __FILE
{
int handle;
};

FILE __stdout;
//定义_sys_exit()以避免使用半主机模式
_sys_exit(int x)
{
x = x;
}
//重定义fputc函数
int fputc(int ch, FILE *f)
{
USART_SendData(USART1,ch);
while(USART_GetFlagStatus(USART1,USART_FLAG_TXE)==RESET);

return ch;
}

注意：要勾选对应的选项。

stm32单片机串口开发

原文：https://www.cnblogs.com/qijiajun/p/14412770.html