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 0 int 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 speed cfsetispeed(&Opt, B115200); cfsetospeed(&Opt, B115200); //set databits Opt.c_cflag &= ~CSIZE; Opt.c_cflag |= CS8; //set parity Opt.c_cflag &= ~PARENB; Opt.c_iflag &= ~INPCK; //set stopbits Opt.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; }