com2show.c

嵌入式liunux系统中的串口测试程序

/*
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <termios.h>
#include <fcntl.h>

const char *com2 = "/dev/ttyS1";

static struct termios newtios, oldtios;		/* terminal settings */
static int saved_portfd = -1;           /* serial port fd */

/* cleanup atexit handler */
static void reset_tty_atexit(void)
{
	if(saved_portfd != -1){
		tcsetattr(saved_portfd, TCSANOW, &oldtios);
	}
}

/* cleanup signal handler */
static void reset_tty_handler(int signal)
{
	if(saved_portfd != -1){
		tcsetattr(saved_portfd, TCSANOW, &oldtios);
	}
	_exit(EXIT_FAILURE);
}

static int open_port(const char *portname)
{
	struct sigaction sa;
	int portfd;

	printf("opening serial port: %s\n", portname);

	/* open serial port */
	if((portfd = open(portname, O_RDWR|O_NOCTTY)) < 0){
		printf("open serial port %s fail\n", portname);
		return portfd;
	}

	/* get serial port params, save away */
	tcgetattr(portfd, &newtios);
	memcpy(&oldtios, &newtios, sizeof newtios);

	/* configure new values */
	cfmakeraw(&newtios);            /* see man page */
	newtios.c_iflag |= IGNPAR;      /* ignore parity on input */
	newtios.c_oflag &= ~(OPOST|ONLCR|OLCUC|OCRNL|ONOCR|ONLRET|OFILL);
	newtios.c_cflag = CS8|CLOCAL|CREAD;
	newtios.c_cc[VMIN] = 1;         /* block until 1 char received */
	newtios.c_cc[VTIME] = 0;        /* no inter-character timer */
	
	/* 115200 bps */
	cfsetospeed(&newtios, B115200);
	cfsetispeed(&newtios, B115200);

	/* register cleanup stuff  */
	atexit(reset_tty_atexit);
	memset(&sa, 0, sizeof sa);
	sa.sa_handler = reset_tty_handler;
	sigaction(SIGHUP, &sa, NULL);
	sigaction(SIGINT, &sa, NULL);
	sigaction(SIGPIPE, &sa, NULL);
	sigaction(SIGTERM, &sa, NULL);

	/* apply modified termios */
	saved_portfd = portfd;
	tcflush(portfd, TCIFLUSH);
	tcsetattr(portfd, TCSADRAIN, &newtios);

	return portfd;
}

static void close_port(int portfd)
{
	tcsetattr(portfd, TCSANOW, &oldtios);
	close(portfd);
	saved_portfd = -1;
}

int main(int argc, char *argv[])
{
	fd_set fds;
	int portfd;
	int retval;
	unsigned char c;

	if((portfd = open_port(com2)) < 0)
		return -1;
	
	while(1){
		FD_ZERO(&fds);
		FD_SET(portfd, &fds);

		retval = select(portfd + 1, &fds, NULL, NULL, NULL);
		if(FD_ISSET(portfd, &fds)){
			if(read(portfd, &c, 1) == 1)
				putchar(c);
		}
		fflush(NULL);
	}
	
	return 0;
}