Linux基础串口编程

Linux串口的编程，过程也是配置像停止位、奇偶校验位、波特率和数据位。像打开文件一样打开串口设备，然后配置上面说的几个参数。串口的写用标准的Linux系统调用write，读用read。其中还有一些配置，在代码中在详细阐述，下面直接贴代码：首先用一个serial.cfg的配置文件来指定串口的参数，后面就直接更改配置文件来修改参数。我们把这个配置文件放置在/etc/下面DEV=/dev/tq2440_serial2
SPEED=115200
DATABITS=8
STOPBITS=1
PARITY=N这里的设备文件用已经有的串口驱动生成的设备节点。定义头文件Serial.h，定义表征串口的结构体#ifndef SERIAL_PORT_H
#define SERIAL_PORT_H#define TRUE 1
#define FALSE 0#define z_U32 unsigned int
#define z_U8 unsigned char#define SERIAL_NAME_LEN 32
extern int serial_config（）;
extern int set_speed（int fd）;
extern int set_other_parm（int fd）;typedef struct z_Serial_port { z_U8 serial_name[SERIAL_NAME_LEN];
z_U32 serial_baud;
z_U8 data_bits;
z_U8 stop_bits;
z_U8 parity;}HI_Serial_port;extern z_Serial_port get_current_serial（）;
#endif接下来当然是serial.c文件咯，实现串口的各个参数的设置/*
** author: z
** CopyRight: z
** funtion: serial port Interface
** Date: 2014
*/#include <stdio.h> /**/
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <ctype.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include "pthread.h"#include "serial_port.h"#define CFG_FILE "/etc/serial.cfg"//放置配置文件的地方
#define DEBUG 1
#define ERROR -1
#define OK 1/*Serial Port Struct*/
z_Serial_port serial_port ;int speed_array[] = {B230400, B115200, B57600, B38400, B19200, B9600, B4800,
B2400, B1200, B300, B38400, B19200, B9600, B4800,
B2400, B1200, B300};
int name_array[] = {230400, 115200, 57600, 38400, 19200, 9600, 4800,
2400, 1200, 300, 38400, 19200, 9600, 4800,
2400, 1200, 300};//得到当前的串口结构体 z_Serial_port get_current_serial（）{
z_Serial_port current_serial;
memset（current_serial.serial_name, 0, sizeof（current_serial.serial_name））; strncpy（current_serial.serial_name, serial_port.serial_name, sizeof（current_serial.serial_name））;
current_serial.serial_baud = serial_port.serial_baud;
current_serial.data_bits = serial_port.data_bits;
current_serial.stop_bits = serial_port.stop_bits;
current_serial.parity = serial_port.parity;
if（DEBUG）{
printf（"current_serial.serial_baud = %d ", current_serial.serial_baud）;
printf（"current_serial.data_bits = %d " , current_serial.data_bits）;
printf（"current_serial.stop_bits = %d ", current_serial.stop_bits）;
printf（"current_serial.parity = %c ", current_serial.parity）;
}
return current_serial;
}//读取串口的配置文件，并将配置填充到结构体 int serial_config（）
{
FILE *serial_fp;
char read_buf[20] = {0};
char temp[20];
char parity; /*read serial config from file*/
serial_fp = fopen（CFG_FILE, "r"）;
if（serial_fp == NULL）{
printf（"Can"t open serial config file "）;
return ERROR;
}
memset（serial_port.serial_name, 0 ,sizeof（serial_port.serial_name））;
fscanf（serial_fp, "DEV=%s ", serial_port.serial_name）;

fscanf（serial_fp, "SPEED=%s ", temp）;
serial_port.serial_baud = atoi（temp）; fscanf（serial_fp, "DATABITS=%s ", temp）;
serial_port.data_bits = atoi（temp）; fscanf（serial_fp, "STOPBITS=%s ", temp）;
serial_port.stop_bits = atoi（temp）; fscanf（serial_fp, "PARITY=%s ", temp）;
serial_port.parity = temp[0]; if（DEBUG）{
printf（" Serial Dev = %s ", serial_port.serial_name）;
printf（" Serial Speed = %d ", serial_port.serial_baud）;
printf（" Serial DataBits = %d ", serial_port.data_bits）;
printf（" Serial StopBite = %d ", serial_port.stop_bits）;
printf（" Serial Parity = %c ", serial_port.parity）;
}
fclose（serial_fp）;
return OK;
}/*
* Set Baudrate
* 设置波特率，fd是打开设备节点的句柄
* */
int set_speed（int fd）
{
struct termios option;
struct termios old_option;
int i = 0; //get the old option
tcgetattr（fd, &old_option）;// termios是所要操作的结构体 for （i = 0; i < sizeof（speed_array）/sizeof（int）; i++）{
if（serial_port.serial_baud == name_array[i]）{
tcflush（fd, TCIOFLUSH）;
cfsetispeed（&option, speed_array[i]）;
cfsetospeed（&option, speed_array[i]）; if（tcsetattr（fd, TCSANOW, &option）！= 0）{//配置立即生效
printf（"set serial baudrate failed "）;
return ERROR;
}else{
tcflush（fd, TCIOFLUSH）;//清空输入输出队列
if（DEBUG） printf（"set serial baudrate sucessed "）;
return OK;
}
}
}
}/*
* Set Other Paramters
*设置其他的参数
* */
int set_other_parm（int fd）
{
struct termios options;
struct termios old_options; if（tcgetattr（fd, &old_options）！= 0）{
printf（"Failed to getattr "）;
return ERROR;
}
options.c_cflag |= （CLOCAL|CREAD）;
options.c_cflag &= ~CSIZE; /*set Date Bits*/
switch （serial_port.data_bits）{
case 7:
options.c_cflag |= CS7;
break;
case 8:
options.c_cflag |= CS8;
break;
default:
options.c_cflag |= CS8;
break;
} /*Set Parity Bites*/
switch （serial_port.parity）{
case "n":
case "N":
options.c_cflag &= ~PARENB;
options.c_iflag &= ~INPCK;
break;
case "o":
case "O":
options.c_cflag |= （PARODD|PARENB）;
options.c_iflag |= INPCK;
break;
case "e":
case "E":
options.c_cflag |= PARENB;
options.c_cflag &= ~PARODD;
options.c_iflag |= INPCK;
break;
default:
options.c_cflag &= ~PARENB;
options.c_iflag &= ~INPCK;
break;
printf（"default parity none parity "）;
} /*Set Stop Bites*/
switch （serial_port.stop_bits）{
case 1:
options.c_cflag &= ~CSTOPB;
break;
case 2:
options.c_cflag |= CSTOPB;
break;
default:
options.c_cflag &= ~CSTOPB;
}
if（serial_port.parity ！= "n" || serial_port.parity ！= "N"）{
options.c_iflag |= INPCK;
}
options.c_cc[VTIME] = 0;//Timeout parma 超时时间的设置
options.c_cc[VMIN] = 0;//read x bite return 读到多少个字节才进行操作，这里设置为0 options.c_iflag |= IGNPAR|ICRNL;
options.c_oflag |= OPOST;//原始模式，有两种模式，若不是原始模式的话，则会在后，才会输出
options.c_iflag &= ~（IXON|IXOFF|IXANY）;
tcflush（fd, TCIFLUSH）;
if（tcsetattr（fd, TCSANOW, &options）！= 0）{
printf（"set serial other parma failed "）;
return ERROR;
}
return OK;
}到这里，基本的参数就配置完毕了，这里需要注意VMIN和VTIME的配置和原始模式的配置。接口写好了，写个测试的程序来进行测试就好，测试程序写的比较丑，见谅，哈哈：#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>#include "serial_port.h"int main（int argc, char *argv[]）
{
int ret;
int fd;
unsigned char data[50]; z_Serial_port serial_p; printf（"Configing serial from local file... "）;
ret = serial_config（）;
if（ret ！= 1）{
printf（"Failed to config serial "）;
return -1;
}
serial_p = get_current_serial（）;
fd = open（serial_p.serial_name,O_RDWR, 0）;//以读写的方式打开
printf（".opening. %s ", serial_p.serial_name）;
if（fd == -1）{
printf（"Can"t open tty "）;
return -1;
}
// set speed
if（set_speed（fd） < 0）{
printf（"set speed Failed "）;
return -1;
}
if（fcntl（fd, F_SETFL, O_NONBLOCK） < 0）{
printf（"fcntl failed "）;
return -1;
}
if（isatty（STDIN_FILENO）==0）
{
printf（"not a terminal device "）;
}else
printf（"isatty success！ "）;
//set other parma like stopbites etc.
if（set_other_parm（fd） < 0 ）{
printf（"set other parm failed "）;
return -1;
}
//write data
int i;
char buff[512];
char buff21[] = "Hi Babby！"; int nread,nwrite = 0;
int nx;
printf（"fd = %d ",fd ）;
nx = write（fd,buff21,sizeof（buff21））;
printf（"nx=%d ",nx）;
while（1）
{
if（（nread = read（fd,buff,512））>0）
{
buff[nread] = "";
//write（fd,buff,nread）;
printf（" recv:%d ",nread）;
//printf（"%s",buff）;
printf（"%d",buff[0] ）;
printf（"%d",buff[1] ）;
printf（"%d",buff[2] ）;
printf（"%d",buff[3] ）;
printf（" "）;
}

}
return 1;
}搞个MakeFileCC=arm-linux-gcc
SEND_EXEC=serial_sendall:serial_port.c serial_port.h serial_send_msg.c
$（CC） -o $（SEND_EXEC） serial_port.c serial_send_msg.c
#chmod 777 $（SEND_EXEC）
clean:
rm -rf *.o serial_send哈哈，完成，接下来就是测试了。这里将电路板中的TXD2和RXD2短接，即自发自读，串口打印“Hi Babby！”嘿嘿，搞定。后面会搞一个GSM模块玩玩。也是串口发送AT指令来通信的。到时候调通了在进行相关的分析。本文永久更新链接地址：http://www.linuxidc.com/Linux/2016-01/128025.htm