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linux串口接收数据，目前有三种方法： 一：循环读取数据。 二：通过软中断方式，使用信号signal机制读取串口，这里需要注意的是硬件中断是设备驱动层级的，而读写串口是用户级行为，只能通过信号机制模拟中断，信号机制的发生和处理其实于硬件中断无异。 该方法问题。 异步通知的方式释放SIGIO信号实现应用层到内核的访问，现在发现当SIGIO信号释放时，应用程序的sleep会被中断。 SIGIO本来就是利用内核的软中断实现的，不想影响你的sleep，那么你就用多路复用IO的方式。 也就是第三种方式 三：多路复用IO。通过select系统调用，在没有数据时阻塞进程，串口有数据需要读时唤醒进程。 1.循环读取。 #include #include #include #include #include #include #include #include #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("This program updates last time at %s %s\n",__TIME__,__DATE__); 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[] = "fe55aa07bc010203040506073d"; write(fd,&buf,26); char buff[512]; int nread; while(1) { if((nread = read(fd, buff, 512))>0) { printf("\nLen: %d\n",nread); buff[nread+1] = '\0'; printf("%s",buff); } } close(fd); return 0; }2.通过signal机制读取数据 #include #include #include #include #include #include #include #include #include #define FALSE -1 #define TRUE 0 #define flag 1 #define noflag 0 int wait_flag = noflag; int STOP = 0; int res; 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); } void signal_handler_IO (int status) { printf ("received SIGIO signale.\n"); wait_flag = noflag; } int main () { printf ("This program updates last time at %s %s\n", __TIME__, __DATE__); printf ("STDIO COM1\n"); int fd; struct sigaction saio; fd = open ("/dev/ttyUSB0", O_RDWR); if (fd == -1) { perror ("serialport error\n"); } else { printf ("open "); printf ("%s", ttyname (fd)); printf (" succesfully\n"); } saio.sa_handler = signal_handler_IO; sigemptyset (&saio.sa_mask); saio.sa_flags = 0; saio.sa_restorer = NULL; sigaction (SIGIO, &saio, NULL); //allow the process to receive SIGIO fcntl (fd, F_SETOWN, getpid ()); //make the file descriptor asynchronous fcntl (fd, F_SETFL, FASYNC); set_speed (fd, 115200); if (set_Parity (fd, 8, 1, 'N') == FALSE) { printf ("Set Parity Error\n"); exit (0); } char buf[255]; while (STOP == 0) { usleep (100000); /* after receving SIGIO ,wait_flag = FALSE,input is availabe and can be read */ if (wait_flag == 0) { memset (buf, 0, sizeof(buf)); res = read (fd, buf, 255); printf ("nread=%d,%s\n", res, buf); // if (res ==1) // STOP = 1; /*stop loop if only a CR was input */ wait_flag = flag; /*wait for new input */ } } close (fd); return 0; }3. 多路IO复用。 #include #include #include #include #include #include #include #include #include #define FALSE -1 #define TRUE 0 #define flag 1 #define noflag 0 int wait_flag = noflag; int STOP = 0; int res; 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); } void signal_handler_IO (int status) { printf ("received SIGIO signale.\n"); wait_flag = noflag; } int main () { printf ("This program updates last time at %s %s\n", __TIME__, __DATE__); printf ("STDIO COM1\n"); int fd; fd = open ("/dev/ttyUSB0", 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[255]; fd_set rd; int nread = 0; while(1) { FD_ZERO(&rd); FD_SET(fd, &rd); while(FD_ISSET(fd, &rd)) { if(select(fd+1, &rd, NULL,NULL,NULL) < 0) { perror("select error\n"); } else { while((nread = read(fd, buf, sizeof(buf))) > 0) { printf("nread = %d,%s\n",nread, buf); printf("test\n"); memset(buf, 0 , sizeof(buf)); } } } } close (fd); return 0; }
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