LINUX下串口通信开发

摘要：

1.打开串口函数open_port()中要实现的函数：
(1)open("/dev/ttys0",O_RDWR | O_NOCTTY | O_NDELAY);/*打开串口0*/
(2)fcntl(fd,F_SETFL,0)/*恢复串口为阻塞状态*/
(3)isatty(STDIN_FILENO) /*测试是否为中断设备 非0即是中断设备*/

2.配置串口参数函数set_opt()中要实现的函数:
(1)保存原先有串口配置
tcgetattr(fd,&oldtio);

(2)先将新串口配置清0
bzore(&newtio,sizeof(newito));

(3)激活选项CLOCAL和CREAD 并设置数据位大小
newtio.c_cflag |=CLOCAL | CREAD;
newtio.c_cflag &= ~CSIZE;
newtio.c_cflag |=CS8;

(4)设置奇偶校验
奇校验:
newtio.c_cflag |= PARENB;
newtio.c_cflag |= PARODD;
newtio.c_iflag |= (INPCK | ISTRIP);
偶校验:
newtio.c_iflag |= (INPCK | ISTRIP);
newtio.c_cflag |= PAREND;
newtio.c_cflag &= ~PARODD;
无奇偶校验：
newtio.c_cflag &= ~PARENB;

(5) 设置停止位
newtio.c_cflag &= ~CSTOPB; /*停止位为1*/
newtio.c_cflag |= CSTOPB;/*停止位为0*/

(6)设置波特率:
cfsetispeed(&newtio,B115200);
cfsetospeed(&newtio,B115200);

(7)设置等待时间和最小接受字符:
newtio.c_cc[VTIME] = 0;
newtio.c_cc[VMIN] = 0;

(8)处理为接收字符:
tcflush(fd,TCIFLUSH);

(9)激活新配置:
tcsetattr(fd,TCSANOW,&newtio);
3.读写串口
write(fd,buff,8);
read(fd,buff,8);

例程：

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <stdlib.h>
int set_opt(int fd,int nSpeed, int nBits, char nEvent, int nStop)
{
/* 五个参量 fd打开文件 speed设置波特率 bit数据位设置 neent奇偶校验位 stop停止位 */
struct termios newtio,oldtio;
if ( tcgetattr( fd,&oldtio) != 0) {
perror("SetupSerial 1");
return -1;
}
bzero( &newtio, sizeof( newtio ) );
newtio.c_cflag |= CLOCAL | CREAD;
newtio.c_cflag &= ~CSIZE;
switch( nBits )
{
case 7:
newtio.c_cflag |= CS7;
break;
case 8:
newtio.c_cflag |= CS8;
break;
}
switch( nEvent )
{
case 'O':
newtio.c_cflag |= PARENB;
newtio.c_cflag |= PARODD;
newtio.c_iflag |= (INPCK | ISTRIP);
break;
case 'E':
newtio.c_iflag |= (INPCK | ISTRIP);
newtio.c_cflag |= PARENB;
newtio.c_cflag &= ~PARODD;
break;
case 'N':
newtio.c_cflag &= ~PARENB;
break;
}
switch( nSpeed )
{
case 2400:
cfsetispeed(&newtio, B2400);
cfsetospeed(&newtio, B2400);
break;
case 4800:
cfsetispeed(&newtio, B4800);
cfsetospeed(&newtio, B4800);
break;
case 9600:
cfsetispeed(&newtio, B9600);
cfsetospeed(&newtio, B9600);
break;
case 115200:
cfsetispeed(&newtio, B115200);
cfsetospeed(&newtio, B115200);
break;
default:
cfsetispeed(&newtio, B9600);
cfsetospeed(&newtio, B9600);
break;
}
if( nStop == 1 )
newtio.c_cflag &= ~CSTOPB;
else if ( nStop == 2 )
newtio.c_cflag |= CSTOPB;
newtio.c_cc[VTIME] = 0;
newtio.c_cc[VMIN] = 0;
tcflush(fd,TCIFLUSH);
if((tcsetattr(fd,TCSANOW,&newtio))!=0)
{
perror("com set error");
return -1;
}
printf("set done!\n");
return 0;
}
int open_port(int fd,int comport)
{
/* fd 打开串口 comport表示第几个串口 */
char *dev[]={"/dev/ttyS0","/dev/ttyS1","/dev/ttyS2"};
long vdisable;
if (comport==1)
{ fd = open( "/dev/ttyS0", O_RDWR|O_NOCTTY|O_NDELAY);
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttyS0 .....\n");
}
else if(comport==2)
{ fd = open( "/dev/ttyS1", O_RDWR|O_NOCTTY|O_NDELAY);

if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttyS1 .....\n");
}
else if (comport==3)
{
fd = open( "/dev/ttyS2", O_RDWR|O_NOCTTY|O_NDELAY);
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttyS2 .....\n");
}
if(fcntl(fd, F_SETFL, 0)<0)
printf("fcntl failed!\n");
else
printf("fcntl=%d\n",fcntl(fd, F_SETFL,0));
if(isatty(STDIN_FILENO)==0)
printf("standard input is not a terminal device\n");
else
printf("isatty success!\n");
printf("fd-open=%d\n",fd);
return fd;
}
int main(void)
{
int fd;
int nread,i;
char buff[]="Hello\n";
if((fd=open_port(fd,1))<0){
perror("open_port error");
return;
}
if((i=set_opt(fd,115200,8,'N',1))<0){
perror("set_opt error");
return;
}
printf("fd=%d\n",fd);
// fd=3;
nread=read(fd,buff,8);
printf("nread=%d,%s\n",nread,buff);
close(fd);
return;

}

我自己的程序：

/////////////////////////////////////////////////////////////////////////////////////////

#ifndef _COM_H
#define _COM_H

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <stdlib.h>

int set_opt(int fd,int nSpeed, int nBits, char nEvent, int nStop);
int open_port(int fd,int comport);
unsigned char uart_cmd(unsigned char *buffer,int tx, int rx);

#endif

/////////////////////////////////////////////////////////////////////////////////////////////////////////

#include "com.h"

//使用开发板的con2(con0,con1,con2)

int set_opt(int fd,int nSpeed, int nBits, char nEvent, int nStop)
{
/* 五个参量 fd打开文件 speed设置波特率 bit数据位设置 neent奇偶校验位 stop停止位 */
struct termios newtio,oldtio;
if ( tcgetattr( fd,&oldtio) != 0) {
perror("SetupSerial 1");
return -1;
}
bzero( &newtio, sizeof( newtio ) );
newtio.c_cflag |= CLOCAL | CREAD;
newtio.c_cflag &= ~CSIZE;
newtio.c_oflag &= ~(ONLCR | OCRNL); //
newtio.c_iflag &= ~(IXON | IXOFF | IXANY); //
switch( nBits )
{
case 7:
newtio.c_cflag |= CS7;
break;
case 8:
newtio.c_cflag |= CS8;
break;
}
switch( nEvent )
{
case 'O':
newtio.c_cflag |= PARENB;
newtio.c_cflag |= PARODD;
newtio.c_iflag |= (INPCK | ISTRIP);
break;
case 'E':
newtio.c_iflag |= (INPCK | ISTRIP);
newtio.c_cflag |= PARENB;
newtio.c_cflag &= ~PARODD;
break;
case 'N':
newtio.c_cflag &= ~PARENB;
break;
}
switch( nSpeed )
{
case 2400:
cfsetispeed(&newtio, B2400);
cfsetospeed(&newtio, B2400);
break;
case 4800:
cfsetispeed(&newtio, B4800);
cfsetospeed(&newtio, B4800);
break;
case 9600:
cfsetispeed(&newtio, B9600);
cfsetospeed(&newtio, B9600);
break;
case 115200:
cfsetispeed(&newtio, B115200);
cfsetospeed(&newtio, B115200);
break;
default:
cfsetispeed(&newtio, B9600);
cfsetospeed(&newtio, B9600);
break;
}
if( nStop == 1 )
newtio.c_cflag &= ~CSTOPB;
else if ( nStop == 2 )
newtio.c_cflag |= CSTOPB;
newtio.c_cc[VTIME] =5; //测试时该大一点
newtio.c_cc[VMIN] = 0;//set min read byte!
tcflush(fd,TCIFLUSH);
if((tcsetattr(fd,TCSANOW,&newtio))!=0)
{
perror("com set error");
return -1;
}
printf("set done!\n");
return 0;
}
int open_port(int fd,int comport)
{
/* fd 打开串口 comport表示第几个串口 */
char *dev[]={"/dev/ttySAC0","/dev/ttySAC1","/dev/ttySAC2"};
long vdisable;
if (comport==1)
{ fd = open( "/dev/ttySAC0", O_RDWR|O_NOCTTY|O_NDELAY);
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttySAC0 .....\n");
}
else if(comport==2)
{ fd = open( "/dev/ttySAC1", O_RDWR|O_NOCTTY|O_NDELAY);

if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttySAC1 .....\n");
}
else if (comport==3)
{
fd = open( "/dev/ttySAC2", O_RDWR|O_NOCTTY|O_NDELAY);
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttySAC2 .....\n");
}
if(fcntl(fd, F_SETFL, 0)<0)
printf("fcntl failed!\n");
else
printf("fcntl=%d\n",fcntl(fd, F_SETFL,0));
if(isatty(STDIN_FILENO)==0)
printf("standard input is not a terminal device\n");
else
printf("isatty success!\n");
printf("fd-open=%d\n",fd);
return fd;
}

//我的应用函数
unsigned char uart_cmd(unsigned char *buffer,int tx, int rx)
{
int fd;
int i;
int nread=0;
int nwrite=0;
unsigned char mybuffer[520],buffer1[520];
if(( fd=open_port(fd,3)) < 0)//使用开发板的con2
{
perror("open_port error");
return -1;
}

if(( i=set_opt(fd,115200,8,'N',1) ) < 0)
{
perror("set_opt error");
return -1;
}

if(( nwrite=write(fd,buffer,tx)) != tx)
{
perror("write error");
return -1;
}
printf("nwrite=%d\n",nwrite);

for(i=0;i<rx;i++)//read only one byte once,loop for rx times!
{
if((nread=read(fd,mybuffer+i,1)) != 1)
{
perror("read error");
return -1;
}
}
mybuffer[rx]='\0';

strncpy(buffer,mybuffer,rx+1);

close(fd);
return 0;
}