一开始在网上找资料，最多是《Linux Serial HOWTO 中譯版，
后来发现，其实串口编程的实质就是多串口属性的设置。
而属性也就下面这么几个：
c_cflag Control options
c_lflag Line options
c_iflag Input options
c_oflag Output options
c_cc Control characters
c_ispeed Input baud (new interface)
c_ospeed Output baud (new interface)
关键是理解有那些属性参数可以设置以及是什么意思。
继续找资料。发现下面的经典文章，可以说基本上所有的串口编程的文章都或多或少的参考了这篇文章，《Serial Programming Guide for POSIX Operating Systems》是一定要看的，我读的是5th Edition, 3rd Revision - Updated March 11, 2003.
当把这篇文章看完之后，基本可以解决串口的设置问题了。
下面的是我的程序，一个串口读取，往mysql数据库写数据的程序：
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "mysql.h"
#define BAUDRATE B9600
#define DEVICE "/dev/ttyS0"
#define _POSIX_SOURCE 1
#define FALSE 0
#define TRUE 1
int insertdb(int d1, int d2, int d3, int d4) {
MYSQL connect;
int res, no1, no2, sd1, sd2;
char *query = "INSERT INTO mydata ( stime, sno1, sno2, sdata1, sdata2 ) VALUES ( '%s', %d, %d, %x, %x)";
char *sql, *st1;
struct tm *ptr;
time_t lt;
no1 = d1;
no2 = d2;
sd1 = d3;
sd2 = d4;
lt = time(NULL);
ptr = localtime(<);
st1 = (char *)asctime(ptr);
st1[strlen(st1) -1 ] = '/0';
sql = (char *)malloc(255*sizeof(char));
sprintf(sql, query, st1, no1, no2, sd1, sd2);
/* debug here
printf("%c : ", st1[strlen(st1)]);
printf("%s : %d :",sql, strlen(st1));
return EXIT_SUCCESS;
*/
mysql_init(&connect);
if(mysql_real_connect(&connect, "localhost", "root", "root", "mytest", 0, NULL, 0)) {
printf("connect success!/n");
res = mysql_query(&connect, sql);
if(!res) {
printf("insert success!/n");
} else {
fprintf(stderr, "insert error %d: %s/n", mysql_errno(&connect), mysql_error(&connect));
return EXIT_FAILURE;
}
mysql_close(&connect);
} else {
fprintf(stderr, "connect fail!/n");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
int main(void) {
int fd, res_w, res_r, i, j, k;
struct termios oldtio,newtio;
char inbuf[255];
char cbuf[4];
int buf[4];
res_w = 0;
res_r = 0;
fd = open(DEVICE, O_RDWR | O_NOCTTY ); // | O_NDELAY);
if(fd < 0) {
perror(DEVICE);
exit(-1);
}
tcgetattr(fd, &oldtio);
bzero(&newtio,sizeof(struct termios));
newtio.c_cflag|= (CLOCAL | CREAD);
newtio.c_cflag|=BAUDRATE;
newtio.c_cflag&=~CSTOPB;
newtio.c_cflag&=~PARENB;
newtio.c_cflag&=~CSIZE;
newtio.c_cflag|=CS8;
newtio.c_cflag&=~CRTSCTS;
newtio.c_lflag=0;
newtio.c_oflag=0;
newtio.c_cc[VMIN]=4;
newtio.c_cc[VTIME]=0;
newtio.c_iflag&=~(IXON|IXOFF|IXANY);
cfsetispeed(&newtio, BAUDRATE);
cfsetospeed(&newtio, BAUDRATE);
tcsetattr(fd, TCSANOW, &newtio);
tcflush(fd, TCIFLUSH);
cbuf[0] = 0x00;
//cbuf[1] = 0x00;
j = 0;
for(k = 0; k < 4; k++) {
switch (j) {
case 0:
default:
cbuf[1] = 0x00;
j = 2;
break;
case 2:
cbuf[1] = 0x02;
j = 0;
break;
}
res_w = write(fd, cbuf, 2);
/* debug here
printf("cbuf : %x %x /n", cbuf[0], cbuf[1]);
printf("buf : %x : %x : %x : %x /n", inbuf[0], inbuf[1], inbuf[2], inbuf[3]);
*/
res_r = read(fd, &inbuf, 255);
if(res_r != -1) {
for(i = 0; i < res_r; i++) {
buf[i] = (int)inbuf[i];
buf[i] = buf[i] & 0xff;
//printf(" %x ", buf[i]);
}
printf("/n");
if(insertdb(buf[0], buf[1], buf[2], buf[3]))
printf("insert into db success!");
}
else {
perror("read fail");
exit(-1);
}// if end here
}// for end here
tcsetattr(fd, TCSANOW, &oldtio);
close(fd);
exit(0);
} // main end here