stm32 USART串口通信总结
stm32 USART串口通信总结
库函数版
USART.h
#ifndef __USART_H
#define __USART_H
#include "stdio.h"
#include "sys.h"
#define USART_REC_LEN 200 //定义最大接收字节数 200
#define EN_USART1_RX 1 //使能（1）/禁止（0）串口1接收
extern u8 USART_RX_BUF[USART_REC_LEN]; //接收缓冲,最大USART_REC_LEN个字节.末字节为换行符
extern u16 USART_RX_STA; //接收状态标记
void uart_init(u32 bound); //USART初始化
#endif
USART.c
#include "sys.h"
#include "usart.h"
#if 1
#pragma import(__use_no_semihosting)
//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)
{
while((USART1->SR&0X40)==0);//循环发送,直到发送完毕
USART1->DR = (u8) ch;
return ch;
}
#endif
#if EN_USART1_RX //如果使能了接收
//串口1中断服务程序
//注意,读取USARTx->SR能避免莫名其妙的错误
u8 USART_RX_BUF[USART_REC_LEN]; //接收缓冲,最大USART_REC_LEN个字节.
//接收状态
//bit15， 接收完成标志
//bit14， 接收到0x0d
//bit13~0， 接收到的有效字节数目
u16 USART_RX_STA=0; //接收状态标记
void uart_init(u32 bound){
//GPIO端口设置
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE); //使能USART1，GPIOA时钟
//USART1_TX GPIOA.9
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //PA.9
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //复用推挽输出
GPIO_Init(GPIOA, &GPIO_InitStructure);//初始化GPIOA.9
//USART1_RX GPIOA.10初始化
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;//PA10
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//浮空输入
GPIO_Init(GPIOA, &GPIO_InitStructure);//初始化GPIOA.10
//Usart1 NVIC 配置
NVIC_InitStructure.NVIC_IRQChannel = USART1_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(USART1, &USART_InitStructure); //初始化串口1
USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);//开启串口接受中断
USART_Cmd(USART1, ENABLE); //使能串口1
}
void USART1_IRQHandler(void) //串口1中断服务程序
{
u8 Res;
if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET) //接收中断(接收到的数据必须是0x0d 0x0a结尾)
{
Res =USART_ReceiveData(USART1); //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
}
}
}
}
}
#endif
这里定义了一个GPIO_InitTypeDef结构体来设置GPIO口初始化数据代码如下：
typedef struct
{
uint16_t GPIO_Pin; /*!< Specifies the GPIO pins to be configured.
This parameter can be any value of @ref GPIO_pins_define */
指定要配置的GPIO PINS。
GPIOSpeed_TypeDef GPIO_Speed; /*!< Specifies the speed for the selected pins.
This parameter can be a value of @ref GPIOSpeed_TypeDef */
指定选定管脚的速度。
GPIOMode_TypeDef GPIO_Mode; /*!< Specifies the operating mode for the selected pins.
This parameter can be a value of @ref GPIOMode_TypeDef */
指定所选管脚的操作模式。
}GPIO_InitTypeDef;
用来设置指定要配置的GPIO。
这里还有定义了一个USART_InitTypeDef结构体来设置串口信息，代码如下：
typedef struct
{
uint32_t USART_BaudRate; /*!< This member configures the USART communication baud rate.
The baud rate is computed using the following formula:
- IntegerDivider = ((PCLKx) / (16 * (USART_InitStruct->USART_BaudRate)))
- FractionalDivider = ((IntegerDivider - ((u32) IntegerDivider)) * 16) + 0.5 */
- 设置波特率
uint16_t USART_WordLength; /*!< Specifies the number of data bits transmitted or received in a frame.
This parameter can be a value of @ref USART_Word_Length */
设置字长格式
uint16_t USART_StopBits; /*!< Specifies the number of stop bits transmitted.
This parameter can be a value of @ref USART_Stop_Bits */
设置停止位
uint16_t USART_Parity; /*!< Specifies the parity mode.
This parameter can be a value of @ref USART_Parity
@note When parity is enabled, the computed parity is inserted
at the MSB position of the transmitted data (9th bit when
the word length is set to 9 data bits; 8th bit when the
word length is set to 8 data bits). */
设置校验方式
uint16_t USART_Mode; /*!< Specifies wether the Receive or Transmit mode is enabled or disabled.
This parameter can be a value of @ref USART_Mode */
设置收发模式
uint16_t USART_HardwareFlowControl; /*!< Specifies wether the hardware flow control mode is enabled
or disabled.
This parameter can be a value of @ref USART_Hardware_Flow_Control */
设置硬件数据流控制
} USART_InitTypeDef;
这里还定义了一个NVIC_InitTypeDef结构体来设置中断优先级，代码如下：
typedef struct
{
uint8_t NVIC_IRQChannel; /*!< Specifies the IRQ channel to be enabled or disabled.
This parameter can be a value of @ref IRQn_Type
(For the complete STM32 Devices IRQ Channels list, please
refer to stm32f10x.h file) */
指定要启用或禁用的IRQ通道
uint8_t NVIC_IRQChannelPreemptionPriority; /*!< Specifies the pre-emption priority for the IRQ channel
specified in NVIC_IRQChannel. This parameter can be a value
between 0 and 15 as described in the table @ref NVIC_Priority_Table */
指定IRQ通道的优先级
uint8_t NVIC_IRQChannelSubPriority; /*!< Specifies the subpriority level for the IRQ channel specified
in NVIC_IRQChannel. This parameter can be a value
between 0 and 15 as described in the table @ref NVIC_Priority_Table */
为指定的IRQ通道指定子优先级级别
FunctionalState NVIC_IRQChannelCmd; /*!< Specifies whether the IRQ channel defined in NVIC_IRQChannel
will be enabled or disabled.
This parameter can be set either to ENABLE or DISABLE */
指定是否在NVIC IrqChannel中定义IRQ通道
} NVIC_InitTypeDef;
/**
* @}
*/
/** @defgroup NVIC_Priority_Table
* @{
*/
/**
@code
The table below gives the allowed values of the pre-emption priority and subpriority according
to the Priority Grouping configuration performed by NVIC_PriorityGroupConfig function
============================================================================================================================
NVIC_PriorityGroup | NVIC_IRQChannelPreemptionPriority | NVIC_IRQChannelSubPriority | Description
============================================================================================================================
NVIC_PriorityGroup_0 | 0 | 0-15 | 0 bits for pre-emption priority
| | | 4 bits for subpriority
----------------------------------------------------------------------------------------------------------------------------
NVIC_PriorityGroup_1 | 0-1 | 0-7 | 1 bits for pre-emption priority
| | | 3 bits for subpriority
----------------------------------------------------------------------------------------------------------------------------
NVIC_PriorityGroup_2 | 0-3 | 0-3 | 2 bits for pre-emption priority
| | | 2 bits for subpriority
----------------------------------------------------------------------------------------------------------------------------
NVIC_PriorityGroup_3 | 0-7 | 0-1 | 3 bits for pre-emption priority
| | | 1 bits for subpriority
----------------------------------------------------------------------------------------------------------------------------
NVIC_PriorityGroup_4 | 0-15 | 0 | 4 bits for pre-emption priority
| | | 0 bits for subpriority
============================================================================================================================
@endcode
*/
然后调用了一个 RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);时钟函数来初始化usart1和gpio时钟
具体代码如下：
//功能为打开或关闭对应的外设输出时钟端口
void RCC_APB2PeriphClockCmd(uint32_t RCC_APB2Periph, FunctionalState NewState)
{
assert_param(IS_RCC_APB2_PERIPH(RCC_APB2Periph)); //参数纠正
assert_param(IS_FUNCTIONAL_STATE(NewState)); //参数验证
/*参考结构体RCC_TypeDef,APB2NR为外设时钟使能寄存器，偏移地址0x18 */
if (NewState != DISABLE)
{
RCC->APB2ENR |= RCC_APB2Periph; //打开对应的外设时钟输出口
}
else
{
RCC->APB2ENR &= ~RCC_APB2Periph;//关闭对应的外设时钟输出口
}
}
main.c文件
main.c
#include "delay.h"
#include "sys.h"
#include "usart.h"
int main(void)
{
u16 t;
u16 len;
delay_init(); //延时函数初始化
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //设置NVIC中断分组2:2位抢占优先级，2位响应优先级
uart_init(115200); //串口初始化为115200
while(1)
{
if(USART_RX_STA&0x8000)
{
len=USART_RX_STA&0x3fff;//得到此次接收到的数据长度
printf("\r\n您发送的消息为:\r\n\r\n");
for(t=0;t寄存器版
usart.h
usart.h与库函数版本一致
usart.c
//加入以下代码,支持printf函数
#if 1
#pragma import(__use_no_semihosting)
//标准库需要的支持函数
struct __FILE
{
int handle;
/* Whatever you require here. If the only file you are using is */
/* standard output using printf() for debugging, no file handling */
/* is required. */
};
/* FILE is typedef’ d in stdio.h. */
FILE __stdout;
//定义_sys_exit()以避免使用半主机模式
_sys_exit(int x)
{
x = x;
}
//重定向fputc函数
//printf的输出，指向fputc，由fputc输出到串口
//这里使用串口1(USART1)输出printf信息
int fputc(int ch, FILE *f)
{
while((USART1->SR&0X40)==0);//等待上一次串口数据发送完成
USART1->DR = (u8) ch; //写DR,串口1将发送数据
return ch;
}
#endif
//end
#if EN_USART1_RX //如果使能了接收
//串口1中断服务程序
//注意,读取USARTx->SR能避免莫名其妙的错误
u8 USART_RX_BUF[USART_REC_LEN]; //接收缓冲,最大USART_REC_LEN个字节.
//接收状态
//bit15， 接收完成标志
//bit14， 接收到0x0d
//bit13~0， 接收到的有效字节数目
u16 USART_RX_STA=0; //接收状态标记
void USART1_IRQHandler(void) //串口接收中断函数
{
u8 res;
if(USART1->SR&(1<<5)) //接收到数据
{
res=USART1->DR;
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
}
}
}
}
}
#endif
//初始化IO 串口1
//pclk2:PCLK2时钟频率(Mhz)
//bound:波特率
void uart_init(u32 pclk2,u32 bound)
{
float temp;
u16 mantissa;
u16 fraction;
temp=(float)(pclk2*1000000)/(bound*16);//得到USARTDIV
mantissa=temp; //得到整数部分
fraction=(temp-mantissa)*16; //得到小数部分
mantissa<<=4;
mantissa+=fraction;
RCC->APB2ENR|=1<<2; //使能PORTA口时钟
RCC->APB2ENR|=1<<14; //使能串口时钟
GPIOA->CRH&=0XFFFFF00F;//IO状态设置
GPIOA->CRH|=0X000008B0;//IO状态设置
RCC->APB2RSTR|=1<<14; //复位串口1
RCC->APB2RSTR&=~(1<<14);//停止复位
//波特率设置
USART1->BRR=mantissa; // 波特率设置
USART1->CR1|=0X200C; //1位停止,无校验位.
#if EN_USART1_RX //如果使能了接收
//使能接收中断
USART1->CR1|=1<<5; //接收缓冲区非空中断使能
MY_NVIC_Init(3,3,USART1_IRQn,2);//组2，最低优先级
#endif
}
main.c文件
#include "sys.h"
#include "usart.h"
#include "delay.h"
int main(void)
{
u16 t;
u16 len;
Stm32_Clock_Init(9); //系统时钟设置
uart_init(72,115200); //串口初始化为115200
delay_init(72); //延时初始化
LED_Init(); //初始化与LED连接的硬件接口
while(1)
{
if(USART_RX_STA&0x8000)
{
len=USART_RX_STA&0x3FFF;//得到此次接收到的数据长度
for(t=0;tDR=USART_RX_BUF[t];
while((USART1->SR&0X40)==0);//等待发送结束
}
USART_RX_STA=0;
}
}
}
注USART寄存器TX中断标志位清零的方法是往DR寄存器写入数据或者手动清零，而置位的方法是等DR里面的数据从TX引脚上全部发出来。