linux下串口程序测试

linux平台下的串口程序网上比比皆是，这里是自己参考资料写的。

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <fcntl.h>#include <termios.h>#include "debug-msg.h"/** if you have a usb serial converter, specify it to 1 */#define USB_SERIAL 0/** * open_port - Open a serial port * * @param port : The port number, eg, open_port(1) will open com1 * * @return Return fd if success, otherwise will return -1 with some msg. */int open_port(int port){ int fd = -1; /* File descriptor for the port, we return it. */ int ret; char device[13] = {0}; /* ??? sizeof("/dev/ttyUSB0")=12 */ if (port < 1 || port > 4) error_ret("Sorry, the port number must be 1~4."); if (USB_SERIAL) sprintf(device, "/dev/ttyUSB%d", port-1); else sprintf(device, "/dev/ttyS%d", port-1); //printf("%s %d/n", device, sizeof(device)); fd = open(device, O_RDWR | O_NOCTTY | O_NDELAY); if (fd == -1) unix_error_ret("Unable to open the port"); /* block */ ret = fcntl(fd, F_SETFL, 0); if (ret < 0) unix_error_ret("fcntl"); ret = isatty(STDIN_FILENO); if (ret == 0) error_ret("Standard input is not a terminal device."); debug_msg("Open the port success!/n"); return fd;}/** * close_port - Close the port * * @param fd : The file description returned by open_port(). * * @return Return 0 if success, return -1 with some msg if error happens. */int close_port(int fd){ if(close(fd) < 0) unix_error_ret("Unable to close the port."); debug_msg("Close the port success!/n"); return 0;}/** * setup_port - Configure the port, eg. baud rate, data bits,etc. * * @param fd : The serial port * @param speed : The baud rate * @param data_bits : The data bits * @param parity : The parity bits * @param stop_bits : The stop bits * * @return Return 0 if everything is OK, otherwise -1 with some error msg. */int setup_port(int fd, int speed, int data_bits, int parity, int stop_bits){ int speed_arr[] = {B115200, B9600, B38400, B19200, B4800}; int name_arr[] = {115200, 9600, 38400, 19200, 4800}; struct termios opt; int ret=-1; int i=0; int len=0; ret = tcgetattr(fd, &opt); /* get the port attr */ if (ret < 0) unix_error_ret("Unable to get the attribute"); opt.c_cflag |= (CLOCAL | CREAD); /* enable the receiver, set local mode */ opt.c_cflag &= ~CSIZE; /* mask the character size bits*/ /* baud rate */ len = sizeof(speed_arr) / sizeof(int); for (i = 0; i < len; i++) { if (speed == name_arr[i]) { cfsetispeed(&opt, speed_arr[i]); cfsetospeed(&opt, speed_arr[i]); } if (i == len) error_ret("Unsupported baud rate."); } /* data bits */ switch (data_bits) { case 8: opt.c_cflag |= CS8; break; case 7: opt.c_cflag |= CS7; break; default: error_ret("Unsupported data bits."); } /* parity bits */ switch (parity) { case 'N': case 'n': opt.c_cflag &= ~PARENB; opt.c_cflag &= ~INPCK; /* ?? */ break; case 'O': case 'o': opt.c_cflag|=(INPCK|ISTRIP); /*enable parity check, strip parity bits*/ opt.c_cflag |= (PARODD | PARENB); break; case 'E': case 'e': opt.c_cflag|=(INPCK|ISTRIP); /*enable parity check, strip parity bits*/ opt.c_cflag |= PARENB; opt.c_cflag &= ~PARODD; break; default: error_ret("Unsupported parity bits."); } /* stop bits */ switch (stop_bits) { case 1: opt.c_cflag &= ~CSTOPB; break; case 2: opt.c_cflag |= CSTOPB; break; default: error_ret("Unsupported stop bits."); } /* raw input */ opt.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); /* raw ouput */ opt.c_oflag &= ~OPOST; tcflush(fd, TCIFLUSH); opt.c_cc[VTIME] = 0; /* time out */ opt.c_cc[VMIN] = 0; /* minimum number of characters to read */ ret = tcsetattr(fd, TCSANOW, &opt); /* update it now */ if (ret < 0) unix_error_ret("Unable to setup the port."); debug_msg("Setup the port OK!/n"); return 0; /* everything is OK! */}</termios.h></fcntl.h></unistd.h></string.h></stdlib.h></stdio.h>

测试函数如下：

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <pthread.h>#include <signal.h>#include "debug-msg.h"#include "serialport.h"pthread_t write_tid; /**< write thread */pthread_t read_tid; /**< read thread */char *buf = "Are you going to die? "; /**< The data we write to the port. *//** data we receive */char tmp[512];/** * write_port_thread - A thread that write data to the port * * @param argc : Here means the port(specified by the fd). * * @note * This is only a test, not the @e really one. */void *write_port_thread(void *argc){ int ret; int fd; int i = 3; fd = (int)argc; //while (i--) while (1) { debug_msg("writing... "); ret = write(fd, buf, strlen(buf)); if (ret < 0) pthread_exit(NULL); write(fd, "/r/n", 2); debug_msg("write: %d/n", ret); sleep(1); } pthread_exit(NULL);}/** * read_port_thread - Thread that read data from the port * * @param argc : Here means the port(specified by the fd). * * @note * This function has not tested yet. */void *read_port_thread(void *argc){ int num; int ret; int fd; fd = (int)argc; while ((num = read(fd, tmp, 512)) > 0) { debug_msg("read: %d/n", num); tmp[num+1] = '/0'; printf("%s/n", tmp); } if (ret < 0) pthread_exit(NULL); debug_msg("read: %d/n", ret); pthread_exit(NULL);}/** * sig_handle - Handle the INT signal. * * @param sig_num : The signal. * @note * This function is not used. */void sig_handle(int sig_num){ debug_msg("catch signal %d/n", sig_num); exit(0);}int main(void){ int fd; int ret; //signal(SIGINT, sig_handle); fd = open_port(1); /* open the port(com1) */ if (fd < 0) exit(0); ret = setup_port(fd, 115200, 8, 'N', 1); if (ret<0) exit="" ret="pthread_create(&write_tid," null="" write_port_thread="" if="" 0="" unix_error_exit="" write="" thread="" error="" 0="" ret="pthread_create(&read_tid," null="" read_port_thread="" if="" 0="" unix_error_exit="" read="" thread="" error="" pthread_join="" null="" null="" close_port="" return="" 0=""> </0)></signal.h></pthread.h></unistd.h></string.h></stdlib.h></stdio.h>

另外那个头文件是我经常使用的，现在还在不断更新、修改中，也放到这里吧：

#ifndef _DEBUG_MSG_H#define _DEBUG_MSG_H#include <stdio.h> /* perror() */#include <string.h> /* strerror() */#include <errno.h> /* errno *//*** * Print the error msg is one thing * but print the msg is another!! *//** * @def error_exit * @brief A macro that prints the @a error msg and exit. */#define error_exit(error) / do{ / fprintf(stderr, "%s/n", error); / exit(0); / } while(0)/** * @def error_ret * @brief A macro that prints the @a error msg and return -1. */#define error_ret(error) / do{ / fprintf(stderr, "%s/n", error); / return -1; / } while(0)/** * @def unix_error_exit * @brief A macro that prints the @a error msg(with errno) and then exit. * I put 'unix' before the 'function' name because I am using 'errno'. */#define unix_error_exit(error) / do{ / fprintf(stderr, "%s Info[%d]:%s/n", / error, errno, strerror(errno)); / exit(1); / } while(0)/** * @def unix_error_ret * @brief A macro that prints the @a error msg(with errno) and then return -1. * I put 'unix' before the 'function' name because I am using 'errno'. */#define unix_error_ret(error) / do{ / fprintf(stderr, "%s Info[%d]:%s/n", / error, errno, strerror(errno)); / return -1; / } while(0)/* error handle ,detail version *//* it can show the file,function and the line *//** * @def unix_print_error * @brief A macro that prints the @a error msg(with errno) and then exit. * I put 'unix' before the 'function' name because I am using 'errno'. * This error handle(detail version) can show the @p file, @p function * and @p line where the @a error happens. * @note I do not often use this 'function' in my program. */#define unix_print_error(error) / do { / fprintf(stderr, "Oh God!/nFile:%s Line:%d Function:%s:/n", / __FILE__, __LINE__, __func__); / perror(error); / exit(0); / } while(0)/* DEBUG=0 will show nothing */#ifndef DEBUG#define DEBUG 1 /**< we debug all the time */#endif/** * @def debug_msg * @brief A macro that prints the debug msg, as the same with @a printf. * */#if DEBUG > 0#define debug_msg(fmt, ...) / fprintf(stdout, fmt, ##__VA_ARGS__)#else#define debug_msg(fmt,...)#endif /* DEBUG */#ifndef TRACE#define TRACE 1 /**< we trace all the time */#endif/** * @def debug_trace * @brief A macro that traces the @p file, @p function and @p line. * */#if TRACE > 0#define debug_trace(trace) / fprintf(stdout, "%s File:%s Line:%d Func:%s./n", / trace, __FILE__, __LINE__, __func__)#else#define debug_trace(trace)#endif#endif /* _DEBUG_MSG_H */</errno.h></string.h></stdio.h>

测试如下：

虚拟机fc9，使用物理串口(可以在vm中设置的)，在tty1上运行该程序，在tty2上运行minicom，短接串口线2、3脚，可以看到在minicom中输出了程序发送的字符串。实际环境中没有测试，因为开发板上只有一个串口。

也可以参考这篇文章：http://www.latelee.org/programming-under-linux/90-serialport-programming.html

完整代码下载地址：serialport-latelee.org.tar.bz2

(如不能下载，请到http://www.latelee.org/programming-under-linux/90-serialport-programming.html页面下载，支持原创，从你做起。)

木草山人

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