Linux串口编程

之前一直在纠结这个怎么做，其实就是一个读写文件的流程，需要配置下串口的参数。

不过有意思的地方更在于，一，串口是可以作为终端的，linux终端tty是很有意思的，二，串口的配置涉及缓冲区设计，这点又和C语言的缓冲区息息相关，很多公司也喜欢考这样的C语言问题。

参考文献为：http://www.ibm.com/developerworks/cn/linux/l-serials/index.html

                        http://book.51cto.com/art/200711/59766.htm#book_content

                        http://book.51cto.com/art/200711/59758.htm

其中，IBM的源码为：

#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<sys/types.h>#include<sys/stat.h>#include<fcntl.h>#include<termios.h>#include<errno.h>#define FALSE -1#define TRUE 0int speed_arr[] = { B38400, B19200, B9600, B4800, B2400, B1200, B300,B38400, B19200, B9600, B4800, B2400, B1200, B300, };int name_arr[] = {38400,  19200,  9600,  4800,  2400,  1200,  300, 38400, 19200,  9600, 4800, 2400, 1200,  300, };void set_speed(int fd, int speed){  int   i;   int   status;   struct termios   Opt;  tcgetattr(fd, &Opt);   for ( i= 0;  i < sizeof(speed_arr) / sizeof(int);  i++) {     if  (speed == name_arr[i]) {           tcflush(fd, TCIOFLUSH);           cfsetispeed(&Opt, speed_arr[i]);        cfsetospeed(&Opt, speed_arr[i]);         status = tcsetattr(fd, TCSANOW, &Opt);        if  (status != 0) {                perror("tcsetattr fd1");          return;           }          tcflush(fd,TCIOFLUSH);       }    }}int set_Parity(int fd,int databits,int stopbits,int parity){ struct termios options; if  ( tcgetattr( fd,&options)  !=  0) { perror("SetupSerial 1");     return(FALSE);  }options.c_cflag &= ~CSIZE; switch (databits) {   case 7:options.c_cflag |= CS7; break;case 8:     options.c_cflag |= CS8;break;   default:    fprintf(stderr,"Unsupported data size\n"); return (FALSE);  }switch (parity) {   case 'n':case 'N':    options.c_cflag &= ~PARENB;   /* Clear parity enable */options.c_iflag &= ~INPCK;     /* Enable parity checking */ break;  case 'o':   case 'O':     options.c_cflag |= (PARODD | PARENB); options.c_iflag |= INPCK;             /* Disnable parity checking */ break;  case 'e':  case 'E':   options.c_cflag |= PARENB;     /* Enable parity */    options.c_cflag &= ~PARODD;    options.c_iflag |= INPCK;       /* Disnable parity checking */break;case 'S': case 's':  /*as no parity*/       options.c_cflag &= ~PARENB;options.c_cflag &= ~CSTOPB;break;  default:   fprintf(stderr,"Unsupported parity\n");    return (FALSE);  }  switch (stopbits){   case 1:    options.c_cflag &= ~CSTOPB;  break;  case 2:    options.c_cflag |= CSTOPB;     break;default:     fprintf(stderr,"Unsupported stop bits\n");   return (FALSE); } /* Set input parity option */ if (parity != 'n')   options.c_iflag |= INPCK; tcflush(fd,TCIFLUSH);options.c_cc[VTIME] = 150; options.c_cc[VMIN] = 0; /* Update the options and do it NOW */if (tcsetattr(fd,TCSANOW,&options) != 0)   { perror("SetupSerial 3");   return (FALSE);  } return (TRUE);  }int main(){printf("STDIO COM1\n");int fd;fd = open("/dev/ttyS0",O_RDWR);if(fd == -1){perror("serialport error\n");}else{printf("open ");printf("%s",ttyname(fd));printf(" succesfully\n");}set_speed(fd,115200);if (set_Parity(fd,8,1,'N') == FALSE)  {printf("Set Parity Error\n");exit (0);}char buf = 'c';write(fd,&buf,1);close(fd);return 0;}

51cto的这本书讲解较为详细，对每项参数有详细解释：

#include<stdio.h>#include<stdlib.h>#include<fcntl.h>#include<unistd.h>#include<errno.h>#include<termios.h>#include<sys/types.h>#include<sys/stat.h>int main(){printf("COM1 test program\n");int fd;fd = open("/dev/ttyS0",O_RDWR);if(fd == -1){perror("serialport error\n");}else{printf("open %s succesfully\n", ttyname(fd));}struct termios Opt;int status;tcgetattr(fd, &Opt);//set speedcfsetispeed(&Opt, B115200);cfsetospeed(&Opt, B115200);//set databitsOpt.c_cflag &= ~CSIZE;Opt.c_cflag |= CS8;//set parityOpt.c_cflag &= ~PARENB;Opt.c_iflag &= ~INPCK;//set stopbitsOpt.c_cflag &= ~CSTOPB;tcsetattr(fd, TCSANOW, &Opt);status = tcsetattr(fd, TCSANOW, &Opt);if(status != 0){perror("tcsetattr fd1");return;}char buf = 'd';write(fd, &buf, 1);close(fd);return 0;}