1:概述
1.1:本篇实现串口驱动,实现printf函数的重定向,实现串口的中断接受和发送,效仿modbus协议中的3.5T超时机制,判断是否接受完毕;
1.2:如果串口仅仅是实现一个控制台,打印一些debug数据,使用printf函数(串口发送数据忙等待),如果是需要用串口进行外设设备的控制,比如串口GPRS模块,需使用串口中断进行控制,因为受限于串口的传输速率,如果使用忙等待发送数据,会阻塞主程序中的其它任务;
1.3:使用sysclk作为超时定时器,sysclk的中断优先级需高于串口中断;
1.4:除过使用3.5T超时时间判断接受数据是否完成外,还可使用ASCLL码的形式,利用字符操作库函数,自定义串口通信协议;
1.5:开发板:stm32f103zert 软件环境:KEIL MKD5
1.6:115200 波特率,间隔1ms发送字符串 "PassWord",主程序将接收到"PassWord"后返回"123456rn",测试主程序响应迅速,不丢帧;
2:代码
main.c
#include "stm32f10x.h"
#include "usart_init.h"
#include "timer.h"
#include "Sys_Driver.h"
unsigned int baud[5] = {9600,14400,19200,56000,115200};
unsigned int T_35 = 0; //串口发送3.5个字节的时间,由波特率得出,单位为ms
int main(void)
{
T_35 = 3.5*(10000000/baud[4]);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //设置中断优先级分组
Usart_Init(baud[4]); //串口初始化
SysTick_Init(INT_1US,SysTick_CLKSource_HCLK_Div8); //sysclk初始化,设置1ms中断
timer_set(&usart_timer,T_35); //定义一个串口计时器
while(1)
{
if(Start_Receive_Flag == 1)
{
if(timer_expired(&usart_timer) == 1) //3.5T时间到达,一条串口数据接受成功
{
Start_Receive_Flag = 0;
Usart_Handle_Func();
}
}
}
}
usart_init.c
#include "usart_init.h"
u8 Usart_Receive_Ok = 0;
u8 Start_Receive_Flag = 0;
u8 Usart_TX_Buff[TX_RE_BUFF_LENGTH];
u8 Usart_RX_Buff[TX_RE_BUFF_LENGTH];
COMx_Define CYCLE;
/*******************printf()函数重定向***************/
//发送函数
int fputc(int ch, FILE *f)
{
USART_SendData(USART2, (unsigned char) ch);
while (!(USART2->SR & USART_FLAG_TXE));
return (ch);
}
//接受函数
int fgetc(FILE *f)
{
while (!(USART2->SR & USART_FLAG_RXNE));
return USART_ReceiveData(USART2);
}
void Usart_Init(u32 baud)
{
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); //使能USART2,GPIOA时钟
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE); //使能USART2,GPIOA时钟
//USART2_TX PA.2
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
//USART2_RX PA.3
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
//USART2 NVIC 配置
NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0; //抢占优先级2
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2; //子优先级2
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 = baud;
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(USART2, &USART_InitStructure); //初始化串口
USART_ITConfig(USART2, USART_IT_RXNE, ENABLE); //开启发送完成中断和接收完成中断
USART_ITConfig(USART2,USART_IT_TC,ENABLE); //开启发送完成中断和接收完成中断
USART_Cmd(USART2, ENABLE); //使能串口
}
void Usart_Send_Byte(u8 data)
{
Usart_TX_Buff[CYCLE.TX_write] = data; //装发送缓冲区
if(++CYCLE.TX_write == TX_RE_BUFF_LENGTH)
CYCLE.TX_write = 0;
if(CYCLE.TX_busy == 0) //发送空闲
{
CYCLE.TX_busy = 1;
USART_SendData(USART2,Usart_TX_Buff[CYCLE.TX_read]); //想串口发送数据,触发中断
if(++CYCLE.TX_read == TX_RE_BUFF_LENGTH)
CYCLE.TX_read = 0;
}
}
/*串口发送函数*/
void Usart_Send_Data(u8 *ptr,u8 num)
{
if(num == 0) //发送字符串
{
for(;*ptr!=';ptr++)
{
Usart_Send_Byte(*ptr);
}
}
else //发送num字节数据
{
for(;num>0;num--)
{
Usart_Send_Byte(*ptr++);
}
}
}
/*串口接收函数,当接收到可用的数据帧时,对接收到的数据进行处理,main函数中调用*/
void Usart_Handle_Func(void)
{
u8 i = 0;
u8 Buff[40];
while(CYCLE.RX_read != CYCLE.RX_write)
{
Buff[i++] = Usart_RX_Buff[CYCLE.RX_read];
if(++CYCLE.RX_read == TX_RE_BUFF_LENGTH)
CYCLE.RX_read = 0;
}
Buff[i] = ';
// Usart_Send_Data(Buff,0);
// Usart_Send_Data("rn",0);
if(memcmp(Buff,"PassWord",8) == 0)
{
Usart_Send_Data("123456rn",0);
}
}
///*中断处理函数*/
void USART2_IRQHandler(void)
{
u8 data;
if(USART_GetITStatus(USART2,USART_IT_TC) == SET) //发送完成中断
{
USART_ClearITPendingBit(USART2,USART_IT_TC);
if(CYCLE.TX_read != CYCLE.TX_write)
{
USART_SendData(USART2,Usart_TX_Buff[CYCLE.TX_read]);
if(++CYCLE.TX_read == TX_RE_BUFF_LENGTH)
CYCLE.TX_read = 0;
}
else
{
CYCLE.TX_busy = 0; //缓冲区数据发送完成,串口总线空闲,可以开始发送新的数据
}
}
else
if(USART_GetITStatus(USART2, USART_IT_RXNE) != RESET) //接收完成中断
{
USART_ClearITPendingBit(USART2,USART_IT_RXNE);
data = USART_ReceiveData(USART2);
Usart_RX_Buff[CYCLE.RX_write] = data;
if(++CYCLE.RX_write == TX_RE_BUFF_LENGTH)
CYCLE.RX_write = 0;
timer_reset(&usart_timer); //开始计时
Start_Receive_Flag = 1;
}
}
关键字:STM32 串口 环形缓冲区『本文转载自网络,版权归原作者所有,如有侵权请联系删除』