Linux串口的編程，過程也是配置像停止位、奇偶校驗位、波特率和數據位。像打開文件一樣打開串口設備，然後配置上面說的幾個參數。串口的寫用標准的Linux系統調用write，讀用read。其中還有一些配置，在代碼中在詳細闡述，下面直接貼代碼：
首先用一個serial.cfg的配置文件來指定串口的參數，後面就直接更改配置文件來修改參數。我們把這個配置文件放置在/etc/下面
DEV=/dev/tq2440_serial2
SPEED=115200
DATABITS=8
STOPBITS=1
PARITY=N
這裡的設備文件用已經有的串口驅動生成的設備節點。
定義頭文件Serial.h，定義表征串口的結構體
#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
接下來當然是serial.c文件咯，實現串口的各個參數的設置
/*
** 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};
//得到當前的串口結構體
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\n", current_serial.serial_baud);
printf("current_serial.data_bits = %d\n" , current_serial.data_bits);
printf("current_serial.stop_bits = %d\n", current_serial.stop_bits);
printf("current_serial.parity = %c\n", current_serial.parity);
}
return current_serial;
}
//讀取串口的配置文件，並將配置填充到結構體
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\n");
return ERROR;
}
memset(serial_port.serial_name, 0 ,sizeof(serial_port.serial_name));
fscanf(serial_fp, "DEV=%s\n", serial_port.serial_name);
fscanf(serial_fp, "SPEED=%s\n", temp);
serial_port.serial_baud = atoi(temp);
fscanf(serial_fp, "DATABITS=%s\n", temp);
serial_port.data_bits = atoi(temp);
fscanf(serial_fp, "STOPBITS=%s\n", temp);
serial_port.stop_bits = atoi(temp);
fscanf(serial_fp, "PARITY=%s\n", temp);
serial_port.parity = temp[0];
if(DEBUG){
printf(" Serial Dev = %s\n", serial_port.serial_name);
printf(" Serial Speed = %d\n", serial_port.serial_baud);
printf(" Serial DataBits = %d\n", serial_port.data_bits);
printf(" Serial StopBite = %d\n ", serial_port.stop_bits);
printf(" Serial Parity = %c\n", serial_port.parity);
}
fclose(serial_fp);
return OK;
}
/*
* Set Baudrate
* 設置波特率，fd是打開設備節點的句柄
* */
int set_speed(int fd)
{
struct termios option;
struct termios old_option;
int i = 0;
//get the old option
tcgetattr(fd, &old_option);// termios是所要操作的結構體
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\n");
return ERROR;
}else{
tcflush(fd, TCIOFLUSH);//清空輸入輸出隊列
if(DEBUG) printf("set serial baudrate sucessed\n");
return OK;
}
}
}
}
/*
* Set Other Paramters
*設置其他的參數
* */
int set_other_parm(int fd)
{
struct termios options;
struct termios old_options;
if(tcgetattr(fd, &old_options) != 0){
printf("Failed to getattr\n");
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\n");
}
/*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 超時時間的設置
options.c_cc[VMIN] = 0;//read x bite return 讀到多少個字節才進行操作，這裡設置為0
options.c_iflag |= IGNPAR|ICRNL;
options.c_oflag |= OPOST;//原始模式，有兩種模式，若不是原始模式的話，則會在\n後，才會輸出
options.c_iflag &= ~(IXON|IXOFF|IXANY);
tcflush(fd, TCIFLUSH);
if(tcsetattr(fd, TCSANOW, &options) != 0){
printf("set serial other parma failed\n");
return ERROR;
}
return OK;
}
到這裡，基本的參數就配置完畢了，這裡需要注意VMIN和VTIME的配置和原始模式的配置。
接口寫好了，寫個測試的程序來進行測試就好，測試程序寫的比較丑，見諒，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...\n");
ret = serial_config();
if(ret != 1){
printf("Failed to config serial\n");
return -1;
}
serial_p = get_current_serial();
fd = open(serial_p.serial_name,O_RDWR, 0);//以讀寫的方式打開
printf(".opening. %s\n", serial_p.serial_name);
if(fd == -1){
printf("Can't open tty\n");
return -1;
}
// set speed
if(set_speed(fd) < 0){
printf("set speed Failed\n");
return -1;
}
if(fcntl(fd, F_SETFL, O_NONBLOCK) < 0){
printf("fcntl failed\n");
return -1;
}
if(isatty(STDIN_FILENO)==0)
{
printf("not a terminal device\n");
}else
printf("isatty success!\n");
//set other parma like stopbites etc.
if(set_other_parm(fd) < 0 ){
printf("set other parm failed\n");
return -1;
}
//write data
int i;
char buff[512];
char buff21[] = "Hi Babby！";
int nread,nwrite = 0;
int nx;
printf("fd = %d\n",fd );
nx = write(fd,buff21,sizeof(buff21));
printf("nx=%d\n",nx);
while(1)
{
if((nread = read(fd,buff,512))>0)
{
buff[nread] = '\0';
//write(fd,buff,nread);
printf("\nrecv:%d\n",nread);
//printf("%s",buff);
printf("%d",buff[0] );
printf("%d",buff[1] );
printf("%d",buff[2] );
printf("%d",buff[3] );
printf("\n");
}
}
return 1;
}
搞個MakeFile
CC=arm-linux-gcc
SEND_EXEC=serial_send
all: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，接下來就是測試了。這裡將電路板中的TXD2和RXD2短接，即自發自讀，串口打印“Hi Babby！”嘿嘿，搞定。後面會搞一個GSM模塊玩玩。也是串口
發送AT指令來通信的。到時候調通了在進行相關的分析。