STM32的通信接口
STM32主要用的通信接口有USART、IIC、SPI、USB、CAN。这些通信接口的主要目的是将设备的数据传送到另一个设备,扩展硬件系统。
在串口通信中有着TTL、RS232、RS485等电平标准。其中TTL和RS485都为正逻辑,只有RS232为负电压表示1,正电压表示0.
TTL:+3.3V或+5V表示1,0V表示0.
RS232:-3V—— -15V表示1,+3V——+15V表示0.
RS485:+2——+6V表示1,-2V——— -6V表示0。
串口参数时序
波特率:串口通信的速率。
起始位:数据帧的开始,固定为低电平。
数据位:数据的有效载荷,1为高电平,0为低电平。(数据位低位先行)
校验位:用于数据验证。
停止位:数据帧的间隔,固定为高电平。
无校验数据帧:
有校验数据帧:
STM32中USART的基本结构图
STM32串口收发代码
初始化串口
void Serial_Init(void)
{
//配置GPIO管脚
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
GPIO_InitTypeDef GPIOInitStructure;
GPIOInitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIOInitStructure.GPIO_Pin = GPIO_Pin_9;
GPIOInitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA,&GPIOInitStructure);
GPIOInitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIOInitStructure.GPIO_Pin = GPIO_Pin_10;
GPIOInitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA,&GPIOInitStructure);
//开启USART中断
USART_InitTypeDef USART_InitStruture;
USART_InitStruture.USART_BaudRate = 9600;
USART_InitStruture.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStruture.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
USART_InitStruture.USART_Parity = USART_Parity_No;
USART_InitStruture.USART_StopBits = USART_StopBits_1;
USART_InitStruture.USART_WordLength = USART_WordLength_8b;
USART_Init(USART1,&USART_InitStruture);
USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2 );
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_Init(&NVIC_InitStructure);
USART_Cmd(USART1, ENABLE);
}
`
发送单字节函数
void Serial_SendByte(uint8_t Byte)
{
USART_SendData(USART1,Byte);
while((USART_GetFlagStatus(USART1,USART_FLAG_TXE))==RESET);
}
发送数组函数
//发送数组函数
void Serial_SendArray(uint8_t *Array, uint16_t Length)
{
uint16_t i;
for(i=0; i<Length; i++)
{
Serial_SendByte(Array[i]);
}
}
发送字符串函数
//发送字符串函数
void Serial_SendString(char *String)
{
uint8_t i;
for(i=0; String[i]!='\0'; i++)
{
Serial_SendByte(String[i]);
}
}
中断函数
自己定义了RxFlag标志位,目的是保证本次读取完成后在进行下一次读取
uint8_t Serial_GetRxFlag(void)
{
if(Serial_RxFlag ==1)
{
Serial_RxFlag = 0;
return 1;
}
return 0;
}
uint8_t Serial_GetRxData(void)
{
return Serial_RxData;
}
void USART1_IRQHandler(void)
{
if((USART_GetITStatus(USART1,USART_IT_RXNE)==1))
{
Serial_RxData = USART_ReceiveData(USART1);
Serial_RxFlag = 1;
USART_ClearITPendingBit(USART1,USART_IT_RXNE);
}
}
串口发送Hex数据包
在日常使用中通常会通过数据包来进行通信,在确定起始位和停止位后,就可以确定一个数据包的长度。为了防止数据与起始位或者停止位相同,一般会根据实际情况来设置起始位和停止位,在这里我把起始位设置位FF,停止位设置为FE数据位为8位,无校验位。
先通过单个函数将起始位发送,再通过数组发送函数发送固定长度的数据位,最后再发送停止位。
void Serial_SendPacket(void)
{
Serial_SendByte(0xFF);
Serial_SendArray(Serial_TxPacket, 4);
Serial_SendByte(0xFE);
}
void USART1_IRQHandler(void)
{
static uint8_t RxState = 0;
static uint8_t pRxState = 0;
if((USART_GetITStatus(USART1,USART_IT_RXNE)==1))
{
uint8_t RxData = USART_ReceiveData(USART1);
if(RxState == 0)
{
if(RxData == 0xFF)
{
RxState = 1;
pRxState = 0;
}
}
else if(RxState == 1)
{
Serial_RxPacket[pRxState] = RxData;
pRxState++;
if(pRxState>=4)
{
RxState = 2;
}
}
else if (RxState == 2)
{
if(RxData == 0xFE)
{
RxState = 0;
Serial_RxFlag = 1;
}
}
USART_ClearITPendingBit(USART1,USART_IT_RXNE);
}
}
最后附上整个代码
在使用时记得在头文件中加上
extern uint8_t Serial_TxPacket[];
extern uint8_t Serial_RxPacket[];
#include "stm32f10x.h" // Device header
#include "stdio.h"
uint8_t Serial_TxPacket[4];
uint8_t Serial_RxPacket[4];
uint8_t Serial_RxFlag;
void Serial_Init(void)
{
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
GPIO_InitTypeDef GPIOInitStructure;
GPIOInitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIOInitStructure.GPIO_Pin = GPIO_Pin_9;
GPIOInitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA,&GPIOInitStructure);
GPIOInitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIOInitStructure.GPIO_Pin = GPIO_Pin_10;
GPIOInitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA,&GPIOInitStructure);
USART_InitTypeDef USART_InitStruture;
USART_InitStruture.USART_BaudRate = 9600;
USART_InitStruture.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStruture.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
USART_InitStruture.USART_Parity = USART_Parity_No;
USART_InitStruture.USART_StopBits = USART_StopBits_1;
USART_InitStruture.USART_WordLength = USART_WordLength_8b;
USART_Init(USART1,&USART_InitStruture);
USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2 );
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_Init(&NVIC_InitStructure);
USART_Cmd(USART1, ENABLE);
}
//发送单个字节函数
void Serial_SendByte(uint8_t Byte)
{
USART_SendData(USART1,Byte);
while((USART_GetFlagStatus(USART1,USART_FLAG_TXE))==RESET);
}
//重定向printf函数至串口
int fputc(int ch, FILE *f)
{
Serial_SendByte(ch);
return ch;
}
//发送数组函数
void Serial_SendArray(uint8_t *Array, uint16_t Length)
{
uint16_t i;
for(i=0; i<Length; i++)
{
Serial_SendByte(Array[i]);
}
}
//发送字符串函数
void Serial_SendString(char *String)
{
uint8_t i;
for(i=0; String[i]!='\0'; i++)
{
Serial_SendByte(String[i]);
}
}
//发送数字函数
//需要将发送的数字进行拆分
uint32_t Serial_Pow(uint32_t x, uint32_t y)
{
uint32_t Result = 1;
while(y--)
{
Result *= x;
}
return Result;
}
void Serial_SendNum(uint32_t Number, uint8_t Length)
{
uint8_t i ;
for(i=0; i<Length; i++)
{
Serial_SendByte(Number/Serial_Pow(10,Length-i-1)%10+ '0');
}
}
//标志位
uint8_t Serial_GetRxFlag(void)
{
if(Serial_RxFlag ==1)
{
Serial_RxFlag = 0;
return 1;
}
return 0;
}
//发送数据包函数
void Serial_SendPacket(void)
{
Serial_SendByte(0xFF);
Serial_SendArray(Serial_TxPacket, 4);
Serial_SendByte(0xFE);
}
//中断函数
void USART1_IRQHandler(void)
{
static uint8_t RxState = 0;
static uint8_t pRxState = 0;
if((USART_GetITStatus(USART1,USART_IT_RXNE)==1))
{
uint8_t RxData = USART_ReceiveData(USART1);
if(RxState == 0)
{
if(RxData == 0xFF)
{
RxState = 1;
pRxState = 0;
}
}
else if(RxState == 1)
{
Serial_RxPacket[pRxState] = RxData;
pRxState++;
if(pRxState>=4)
{
RxState = 2;
}
}
else if (RxState == 2)
{
if(RxData == 0xFE)
{
RxState = 0;
Serial_RxFlag = 1;
}
}
USART_ClearITPendingBit(USART1,USART_IT_RXNE);
}
}