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对于这款板子，官方并没有提供串口例程，只能自行添加。
一、PA9/PA10复用成串口1功能不可用
驱动测试代码如下：
main.c:
#include "main.h"
#include <stdio.h>void usart1_init(void)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;//(1)串口时钟和 GPIO 时钟使能RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);//GPIO口时钟使能, 引脚PA9,PA10可以复用为串口功能RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);//串口UART1时钟使能, 串口1是挂载在 APB2总线下的外设//(2)配置GPIO引脚为复用功能[PA9+PA10]GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//复用功能GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;//电平翻转速度100MHzGPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推挽复用输出GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;//上拉GPIO_Init(GPIOA,&GPIO_InitStructure); //初始化 PA9，PA10//(3)配置串口1参数USART_InitStructure.USART_BaudRate = 115200;//波特率USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//不使用硬件流控制USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;//收发模式USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位USART_InitStructure.USART_WordLength = USART_WordLength_8b;//8个数据位USART_Init(USART1, &USART_InitStructure); //初始化串口1//(4) 开启中断并且初始化 NVIC，使能相应中断[接收一个byte触发中断一次]USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;//抢占优先级 3NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;//响应优先级 3NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化NVIC寄存器//(5) 使能串口1USART_Cmd(USART1, ENABLE);
}//串口1中断服务函数
void USART1_IRQHandler(void)
{char res;//检查标志位if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET){res = USART_ReceiveData(USART1);//收到数据后读出来USART_SendData(USART1,res);//读到数据后立刻发送出去//清空标志位USART_ClearITPendingBit(USART1, USART_IT_RXNE);}
}int main(void)
{usart1_init();while(1){;}return 0;
}固件烧录后，连接PC端串口工具，串口收发功能不可用。原因：PA9/PA10设计给板载USB使用，打开原理如下：
所以，只能换一组GPIO，换成PB6/PB7(原理图上可确认没有其他外设使用)，测试代码如下：
#if 0
void usart1_init(void)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;//(1)串口时钟和 GPIO 时钟使能RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);//GPIO口时钟使能, 引脚PA9,PA10可以复用为串口功能RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);//串口UART1时钟使能, 串口1是挂载在 APB2总线下的外设//(2)配置GPIO引脚为复用功能[PA9+PA10]GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//复用功能GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;//电平翻转速度100MHzGPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推挽复用输出GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;//上拉GPIO_Init(GPIOA,&GPIO_InitStructure); //初始化 PA9，PA10//(3)配置串口1参数USART_InitStructure.USART_BaudRate = 115200;//波特率USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//不使用硬件流控制USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;//收发模式USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位USART_InitStructure.USART_WordLength = USART_WordLength_8b;//8个数据位USART_Init(USART1, &USART_InitStructure); //初始化串口1//(4) 开启中断并且初始化 NVIC，使能相应中断[接收一个byte触发中断一次]USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;//抢占优先级 3NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;//响应优先级 3NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化NVIC寄存器//(5) 使能串口1USART_Cmd(USART1, ENABLE);
}//串口1中断服务函数
void USART1_IRQHandler(void)
{char res;//检查标志位if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET){res = USART_ReceiveData(USART1);//收到数据后读出来USART_SendData(USART1,res);//读到数据后立刻发送出去//清空标志位USART_ClearITPendingBit(USART1, USART_IT_RXNE);}
}#else
void usart1_init(void)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;//(1)串口时钟和 GPIO 时钟使能RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB,ENABLE); //使能GPIOB时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);//串口UART1时钟使能, 串口1是挂载在 APB2总线下的外设//(2)配置GPIO引脚为复用功能[PB6+PB7]GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1);GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1);GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//复用功能GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;//电平翻转速度100MHzGPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推挽复用输出GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;//上拉GPIO_Init(GPIOB, &GPIO_InitStructure); //初始化 PA9，PA10//(3)配置串口1参数USART_InitStructure.USART_BaudRate = 115200;//波特率USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//不使用硬件流控制USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;//收发模式USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位USART_InitStructure.USART_WordLength = USART_WordLength_8b;//8个数据位USART_Init(USART1, &USART_InitStructure); //初始化串口1//(4) 开启中断并且初始化 NVIC，使能相应中断[接收一个byte触发中断一次]USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;//抢占优先级 3NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;//响应优先级 3NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化NVIC寄存器//(5) 使能串口1USART_Cmd(USART1, ENABLE);
}//串口1中断服务函数
void USART1_IRQHandler(void)
{char res;STM_EVAL_LEDOn(LED4);//检查标志位if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET){res = USART_ReceiveData(USART1);//收到数据后读出来STM_EVAL_LEDOn(LED5);USART_SendData(USART1,res);//读到数据后立刻发送出去//清空标志位USART_ClearITPendingBit(USART1, USART_IT_RXNE);}
}
#endifint main(void)
{usart1_init();while(1){;}return 0;
}板子实物图连接如下：
串口工具测试如下：
二、串口标准输入输出重定向打印实现
直接重写标准输入输出函数的底层接口即可，如下：
| //重写printf底层函数接口 int fputc(int c, FILE *stream) { USART1->DR=c; //发送一个字符 while(!(USART1->SR&1<<7)){} return c; } //重写scanf底层函数接口 int fgetc(FILE *stream) { while(!(USART1->SR&1<<5)){} return USART1->DR; } |
烧录固件，并按reset键，观察串口调试助手上的打印：使用ST-LINK的方式进行烧录
串口助手：
三、完整代码
usart.c
/* Includes ------------------------------------------------------------------*/
#include "stm32f4xx.h"
#include <stdio.h>void usart1_init(uint32_t BaudRate)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;//(1)串口时钟和 GPIO 时钟使能RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB,ENABLE); //使能GPIOB时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);//串口UART1时钟使能, 串口1是挂载在 APB2总线下的外设//(2)配置GPIO引脚为复用功能[PB6+PB7]GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1);GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1);GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//复用功能GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;//电平翻转速度100MHzGPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推挽复用输出GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;//上拉GPIO_Init(GPIOB, &GPIO_InitStructure); //初始化 PA9，PA10//(3)配置串口1参数USART_InitStructure.USART_BaudRate = BaudRate;//波特率USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//不使用硬件流控制USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;//收发模式USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位USART_InitStructure.USART_WordLength = USART_WordLength_8b;//8个数据位USART_Init(USART1, &USART_InitStructure); //初始化串口1//(4) 开启中断并且初始化 NVIC，使能相应中断[接收一个byte触发中断一次]USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;//抢占优先级 3NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;//响应优先级 3NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化NVIC寄存器//(5) 使能串口1USART_Cmd(USART1, ENABLE);
}//串口1中断服务函数
void USART1_IRQHandler(void)
{char res;//检查标志位if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET){res = USART_ReceiveData(USART1);//收到数据后读出来USART_SendData(USART1,res);//读到数据后立刻发送出去//清空标志位USART_ClearITPendingBit(USART1, USART_IT_RXNE);}
}//重写printf底层函数接口
int fputc(int c, FILE *stream)
{USART1->DR=c; //发送一个字符while(!(USART1->SR&1<<7)){}return c;
}//重写scanf底层函数接口
int fgetc(FILE *stream)
{while(!(USART1->SR&1<<5)){}return USART1->DR;
}/******************* (C) COPYRIGHT 2011 STMicroelectronics *****END OF FILE****/
usart.h
#ifndef __USART__H__
#define __USART__H__void usart1_init(uint32_t BaudRate);#endif /* __USART__H__ */main.c
#include "usart.h"
#include <stdio.h>int main(void)
{usart1_init(115200);printf("hello world!\n");while(1){;}return 0;
}注：这款Discovery开发板是基于标准外设库函数来开发的，因此工程中要把串口相关的库函数文件添加进来，如下：
