Linux C 配置串口
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参考技术A配置串口需要包含头文件
其中最核心的配置结构体为:
如何获取该结构呢?我们操作串口跟操作文件一样,也是调用 open() 函数来打开串口,
这样我们就能够得到一个文件描述符 fd ,然后就可以调用 tcgetattr() 函数来获取上述配置结构体了。
Linux 串口默认的配置为:波特率 9600,数据位 8 位,无奇偶校验,停止位 1 位,无 CTS/RTS 。
以下介绍一些常用的配置项:波特率、奇偶校验、数据位、停止位、硬件控制流。
相关接口:
Linux 将串口的波特率分为了输入波特率和输出波特率,不过最常用的场景是将两者设置成一样。
cfgetispeed() 函数获取输入波特率, cfgetospeed() 函数获取输出波特率。 cfsetispeed() 函数设置输入波特率, cfsetospeed() 函数用于设置输出波特率,当然 cfsetspeed() 函数扩展为同时设置输入和输出波特率。
上述接口中的 speed_t 是一系列波特率的标志位,例如常用的 115200 波特率就为 B115200,参考下述选项:
设置奇偶校验位可以通过修改 termios 结构体中的 c_cflag 成员来实现,若无校验,则将 PARENB 位设为 0;若有校验,则 PARENB 为 1。之后再根据 PARODD 来区分奇偶校验, PARODD 为 1 表示奇校验, PARODD 为 0 表示偶校验。例如设置无奇偶校验位:
设置数据位可以通过修改 termios 结构体中的 c_cflag 成员来实现,CS5、CS6、CS7 和 CS8 分别代表数据位 5、6、7 和 8。不过在设置数据位之前,需要先用 CSIZE 来做屏蔽字段,清楚这几个标志位,例如设置数据位为 8 位:
设置停止位可以通过修改 termios 结构体中的 c_cflag 成员来实现, CSTOPB 位为 1 表示 2 位停止位, CSTOPB 位为 0 标志 1 位停止位。例如设置停止位为 1 位:
设置硬件控制流可以通过修改 termios 结构体中的 c_cflag 成员来实现, CRTSCTS 为 1 表示使用硬件控制流,为 0 表示不使用硬件控制流。例如使能硬件控制流:
当然,最后还需要用 tcflush() 抛弃存储在 fd 里的未接收的数据。
再利用接口 tcsetattr() 函数将配置信息写入文件描述符 fd :
这样整个串口最常用的用法就配置完成了。
具体的配置使用可以参考我的项目 HCI-Middleware 里的 hci_transport_uart_linux.c 文件。
参考:
Linux C Serial串口编程
1,Linux 下打开串口设备,信号模型 读写程序
2,串口读写的IO复用Select模型
3, Linux 下打开串口设备,读写程序
1,Linux 下打开串口设备,信号模型 读写程序
[email protected]:/tmp/serial# cat main.c #include<stdio.h> #include<stdlib.h> #include<string.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() { 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[] = "1234567890123456789012345678901234567890"; int n= write(fd,buf,strlen(buf)); printf("字符串实际长度%zd \n", strlen(buf)); printf("成功写入%d \n", n); char buff[512]; int nread; while(1) { if((nread = read(fd, buff, 512))>0) { printf("Len: %d:",nread); buff[nread] = ‘\0‘; printf("%s \n",buff); } } close(fd); return 0; } [email protected]:/tmp/serial# gcc -Wall main.c && ./a.out open /dev/ttyUSB0 succesfully 字符串实际长度40 成功写入40 Len: 32:12345678901234567890123456789012 Len: 8:34567890 ^C [email protected]:/tmp/serial#
2,串口读写的IO复用Select模型
[email protected]:/tmp/serial# cat main.c #include<stdio.h> #include<stdlib.h> #include<string.h> #include<unistd.h> #include<sys/types.h> #include<sys/stat.h> #include<sys/signal.h> #include<fcntl.h> #include<termios.h> #include<errno.h> #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 () { 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 str[] = "1234567890123456789012345678901234567890"; int n= write(fd,str,strlen(str)); printf("字符串实际长度%zd \n", strlen(str)); printf("成功写入%d \n", n); 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; } [email protected]:/tmp/serial# gcc -Wall main.c && ./a.out open /dev/ttyUSB0 succesfully 字符串实际长度40 成功写入40 received SIGIO signale. received SIGIO signale. nread=32,12345678901234567890123456789012 received SIGIO signale. nread=8,34567890 ^C [email protected]:/tmp/serial#
3, Linux 下打开串口设备,读写程序
[email protected]:/tmp/serial# cat main.c #include<stdio.h> #include<stdlib.h> #include<string.h> #include<unistd.h> #include<sys/types.h> #include<sys/stat.h> #include<sys/signal.h> #include<fcntl.h> #include<termios.h> #include<errno.h> #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 () { 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 str[] = "1234567890123456789012345678901234567890"; int n= write(fd,str,strlen(str)); printf("字符串实际长度%zd \n", strlen(str)); printf("成功写入%d \n", n); 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= %02d,%s\n",nread, buf); memset(buf, 0 , sizeof(buf)); } } } } close (fd); return 0; } [email protected]:/tmp/serial# gcc -Wall main.c && ./a.out open /dev/ttyUSB0 succesfully 字符串实际长度40 成功写入40 nread= 32,12345678901234567890123456789012 nread= 08,34567890
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