serial.c

能够很完善的在LINUX下进行串口编程

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <termios.h>

#include <sys/ioctl.h>
#include <linux/serial.h>

#include "serial.h"
#include "debug.h"

static int tty_bauds[] = {
	0,	50,	75,	110	,134,
	150,	200,	300,	600,	1200,
	1800,	2400,	4800,	9600,	19200,
	38400,	57600,	115200,
};

static int tty_speeds[] = {
	B0,	B50,	B75,	B110,	B134,
	B150,	B200,	B300,	B600,	B1200,
	B1800,	B2400,	B4800,	B9600,	B19200,
	B38400,	B57600,	B115200,
};

static int serial_open(struct serial_t* tty)
{
	int fd;
	
	fd = open(tty->device,O_RDWR | O_NOCTTY | O_NONBLOCK);
	if(fd < 0){
		printf("SERIAL: can't open serial %s: %s\n",
				tty->device,strerror(errno));
		return -1;
	}

	tty->fd = fd;	

	printf("SERIAL: success open serial %s(fd=%d)\n",tty->device,fd);
	return 0;
}

static int serial_close(struct serial_t *tty)
{
	int retval;

	if(tty->fd <= 0)
		return -1;

	retval=close(tty->fd);
	if(retval < 0){
		printf("SERIAL: failed to close serial %s : %s\n",
				tty->device,strerror(errno));
		return -2;
	}

	tty->fd = 0;

	printf("SERIAL: success close serial %s\n",tty->device);

	return 0;	
}

/*get serial's current attribute*/
static int serial_get_attr(struct serial_t *tty)
{
	if(tcgetattr(tty->fd,&tty->options) != 0){
		eprintk("SERIAL: can't get serial's attribute\n");
		return -1;
	}

	return 0;
}

/*update serial's attrbute*/
static int serial_attr_update(struct serial_t *tty)
{
	tcflush(tty->fd,TCIFLUSH);/*handle unrecevie char*/

	if((tcsetattr(tty->fd,TCSANOW,&tty->options)) < 0){
		return -1;
	}

	return 0;
}

//设置为特殊的波特率，比如B28800
int serial_set_special_baud(struct serial_t *tty,int baud)
{
	struct serial_struct ss,ss_set;

	cfsetispeed(&tty->options,B38400);
	cfsetospeed(&tty->options,B38400);
	serial_attr_update(tty);
	
	if((ioctl(tty->fd,TIOCGSERIAL,&ss))<0){
		printf("BAUD: error to get the serial_struct info:%s\n",strerror(errno));
		return -1;
	}

	ss.flags = ASYNC_SPD_CUST;
	ss.custom_divisor = ss.baud_base / baud;

	if((ioctl(tty->fd,TIOCSSERIAL,&ss))<0){
		printf("BAUD: error to set serial_struct:%s\n",strerror(errno));
		return -2;
	}

	ioctl(tty->fd,TIOCGSERIAL,&ss_set);
	printf("BAUD: success set baud to %d,custom_divisor=%d,baud_base=%d\n",
			baud,ss_set.custom_divisor,ss_set.baud_base);

	return 0;
}

static int serial_init_baud(struct serial_t *tty)
{	
	int index;

	if(serial_get_attr(tty) < 0)
		return -1;

	/*enable recevier and set local mode*/
	tty->options.c_cflag |= (CLOCAL | CREAD);

	for(index = 0; index < sizeof(tty_bauds)/sizeof(tty_bauds[0]); index++){
		if(tty->baud == tty_bauds[index]){
			cfsetispeed(&tty->options,tty_speeds[index]);
			cfsetospeed(&tty->options,tty_speeds[index]);
			
			if(serial_attr_update(tty) < 0)
				return -2;

			printf("SERIAL: set baud to %d\n",tty->baud);
			return 0;
		}
	}

	printf("SERIAL: %d is a no standard baud,called to set the special baud!!!\n",tty->baud);
	if((serial_set_special_baud(tty,tty->baud))<0)
		return -2;

	return 0;
}

static int serial_init_databit(struct serial_t *tty)
{
	if(serial_get_attr(tty)<0)
		return -1;

	tty->options.c_cflag &= ~CSIZE;
	switch(tty->databit){
		case 5:	tty->options.c_cflag |= CS5;break;
		case 6:	tty->options.c_cflag |= CS6;break;
		case 7:	tty->options.c_cflag |= CS7;break;
		case 8: tty->options.c_cflag |= CS8;break;
		default:
			eprintk("SERIAL: unsupported databit %d\n",tty->databit);
			return -2;		
	}

	if(serial_attr_update(tty) < 0)
		return -3;

	printf("SERIAL: set databit to %d\n",tty->databit);
	return 0;
}

static int serial_init_parity(struct serial_t *tty)
{
	if(serial_get_attr(tty)<0)
		return -1;

	/*ignore framing and parity error*/
	tty->options.c_iflag = IGNPAR;

	switch (tty->parity){
 		case 'n':
		case 'N':
			/* Clear parity enable */
  			tty->options.c_cflag &= ~PARENB;
			/* Enable parity checking */
  			tty->options.c_iflag &= ~INPCK;
  			break; 
 		case 'o':  
 		case 'O':
			/* 设置为奇校检*/ 
  			tty->options.c_cflag |= (PARODD|PARENB);
			/* Disnable parity checking */
  			tty->options.c_iflag |= (INPCK|ISTRIP);
  			break; 
 		case 'e': 
 		case 'E': 
			/* Enable parity */
  			tty->options.c_cflag |= PARENB;   
			/* 转换为偶效验*/
  			tty->options.c_cflag &= ~PARODD;
			/* Disnable parity checking */
  			tty->options.c_iflag |= (INPCK|ISTRIP);    
  			break;
 		default:  
  			eprintk("SERIAL: unsupported parity %c\n",tty->parity);   
 			return -2; 
 	}

	if(serial_attr_update(tty) < 0)
		return -3;

	printf("SERIAL: set parity to %c\n",tty->parity);

	return 0;
}

static int serial_init_stopbit(struct serial_t *tty)
{
	if(serial_get_attr(tty)<0)
		return -1;

	switch(tty->stopbit){
		case 1: 
			tty->options.c_cflag &= ~CSTOPB;break; 
 		case 2: 
			tty->options.c_cflag |= CSTOPB;break;
		default:
			eprintk("SERIAL: unsupported stopbit %d\n",tty->stopbit);	
			return -2;		
	}

	if(serial_attr_update(tty) < 0)
		return -3;

	printf("SERIAL: set stopbit to %d\n",tty->stopbit);

	return 0;
}

int serial_init(struct serial_t *tty)
{

	/*set default databit:8,parity:N,stopbit:1*/
	if(tty->databit == 0)
		tty->databit=8;
	if(tty->parity == 0)
		tty->parity='N';
	if(tty->stopbit == 0)
		tty->stopbit=1;

/*	//FIXME:这里是直接设置的，没有使用
	//设置无奇偶校验8N1
	tty->options.c_cflag &= ~CSIZE;
	tty->options.c_cflag  ?= CS8;
	tty->options.c_cflag &= ~PARENB;
	tty->options.c_cflag &= ~CSTOPB;
	tty->options.c_cflag &= ~CSIZE;
	tty->options.c_cflag  ?= CS8;

	//终端为本地连接，忽略MODEM的状态线
	tty->options.c_cflag  ?= CLOCAL;
	tty->options.c_cflag  ?= CREAD;

	//设置波特率
	cfsetispeed(&tty->options,B115200);
	cfsetospeed(&tty->options,B115200);
*/

	/*init serial*/
	if(serial_open(tty)<0)
		goto error;
	if(serial_init_baud(tty)<0)
		goto error;
	if(serial_init_databit(tty)<0)
		goto error;
	if(serial_init_parity(tty)<0)
		goto error;
	if(serial_init_stopbit(tty)<0)
		goto error;

	//FIXME：这里已经解决第一次打开不能读的问题

/*
	//设置非加工方式输入
	tty->options.c_iflag  ?= IGNPAR;
	tty->options.c_lflag &= ~( ICANON  ? ECHO  ? ISIG  ? IEXTEN  ? ECHOE );
	tty->options.c_iflag &= ~INPCK;
	tty->options.c_iflag &= ~ICRNL;
	tty->options.c_iflag &= ~INLCR;
	tty->options.c_iflag &= ~ISTRIP;
	tty->options.c_iflag &= ~IXON;
	tty->options.c_iflag &= ~BRKINT;
*/

	//输入参数
	tty->options.c_iflag &= ~(IGNBRK|BRKINT|ICRNL|INPCK|ISTRIP|IXON|INLCR|IGNCR);   
	//选择原始输入(非加工方式输入),不回送字符  
	tty->options.c_lflag &= ~(ICANON|ECHO|ECHOE|ISIG|IEXTEN);

	//非加工方式输出
	tty->options.c_oflag &= ~(OPOST);
	//阻塞字节数和等待时间
	tty->options.c_cc[VMIN] = 1;
	tty->options.c_cc[VTIME] = 0;

	serial_attr_update(tty);

	/*设置串口读写为阻塞模式*/
	fcntl(tty->fd,F_SETFL,0);
	//非阻塞方式
	//fcntl(tty->fd, F_SETFL, FNDELAY);

	return 0;
error:
	serial_close(tty);
	return -1;
}

int serial_send(struct serial_t *tty,const char *buf,int length)
{
	 int ret,nleft;
	 const char *ptmp;

	 ret = 0;
	 nleft = length;
	 ptmp = buf;

	 while(nleft > 0) {
		ret = write(tty->fd,ptmp,nleft);
	  	if(ret > 0){
	   		nleft -= ret;
	    		ptmp += ret;
	  	}
	  	/*usleep(100);*/
	}
	
	/*
	if(!nleft){
		if(length == 1){
			printf("SERIAL: success send a char,value=%d\n",*buf);
		}else
			printf("SERIAL: success send string %s\n",buf);
	}else 
		printf("SERIAL: WARING,request send %d,but %d not send!!!\n",length,nleft);
	*/
	 
	return length - nleft;
}

int serial_recv(struct serial_t *tty,char *buf,int length)
{
	int ret,left,bytes;

	left = length;

	while(left > 0)
	{
  		ret = 0;
  		bytes = 0;

		/*wait util have a key press*/
		ret = read(tty->fd,buf,left);
		if(ret > 0){
			left -= ret;
			if(length!=1) buf += ret;
		}

		/*usleep(100);*/

		/* 非阻塞式读取按键，会消耗很大CPU。
  		ioctl(tty->fd, FIONREAD, &bytes);
  		if(bytes > 0){
  			ret = read(tty->fd,buf,left);
		}
  	
  		if(ret >0){
   			left -= ret;
   			if(length!=1)buf += ret;
  		}

  		//usleep(100);
		*/
 	} 

 	return length - left;
}

//只能一下读取刚好的数据，比如需立即读取8个字符，如果没有就返回错误
//没有阻塞的读取，就是没有数据来的话就要立即返回了，而不是等待数据的到来
int serial_recv_noblock(struct serial_t *tty, char *buf, int length)
{
	int bytes;

	ioctl(tty->fd, FIONREAD, &bytes);
	if(bytes <length){
		//printf("SERIAL: request recv %d chars noblock,but can only %d !!!\n",length,bytes);
		return -1;
	}

	return read(tty->fd,buf,length);
}

int serial_remove(struct serial_t *tty)
{
	return serial_close(tty);
}