Linux平臺上的串口通訊API很簡單，也很適用，使用C語言實現。我特別覺得它的讀數據函數很好用，因為使用了select機制，可以很容易的做讀數據超時。代碼簡單，不說了，自己下載了看就明白了。
/**
* @file serialport.c
* @brief serial port API implementation
* @author Deng Yangjun
* @date 2007-1-9
* @version 0.1
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <assert.h>
#include "serialport.h"
#ifdef __cplusplus
extern "C" {
#endif
#define MAX_DEV_NAME 256
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, };
/**
* @brief set speed of the serial port
* @param fd [in] file description of the serial port
* @param speed [in] speed that want to set value in speed array
* @return error code
*/
int set_serial_port_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)
return status;
else
return 0;
}
tcflush(fd,TCIOFLUSH);
}
//invalid baud rate
assert(FALSE);
}
/**
* @brief set serial port control flag
* @param fd [in] file description of the serial port
* @param databits [in] data bits, it's value is 7 or 8
* @param stopbits [in] stop bits, it's value is 1 or 2
* @param parity [in] parity char, it's value is onef of 'N','E','O','S'
* @return error code
*/
int set_serial_port_ctrl_flag(int fd,int databits,int stopbits,int parity)
{
struct termios options;
int result = tcgetattr(fd,&options);
if(result != 0){
return result;
}
/*8N1*/
options.c_cflag &= ~CSIZE; /* Mask the character size bits */
switch (databits)
{
case 7:
options.c_cflag |= CS7;
break;
case 8:
options.c_cflag |= CS8;
break;
default:
assert(FALSE);
break;
}
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); /* Set odd checking*/
options.c_iflag |= INPCK; /* Disnable parity checking */
break;
case 'e':
case 'E':
options.c_cflag |= PARENB; /* Enable parity */
options.c_cflag &= ~PARODD; /* Set event checking*/
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:
assert(FALSE);
break;
}
//set stop bits
switch (stopbits)
{
case 1:
options.c_cflag &= ~CSTOPB;
break;
case 2:
options.c_cflag |= CSTOPB;
break;
default:
assert(FALSE);
break;
}
/* Set input parity option */
if (parity != 'n') {
options.c_iflag |= INPCK;
}
options.c_cc[VTIME] = 150; // 15 seconds
options.c_cc[VMIN] = 0;
options.c_cflag &= ~CRTSCTS;//disable hardware flow control;
options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);/*raw input*/
options.c_oflag &= ~OPOST; /*raw output*/
tcflush(fd,TCIFLUSH); /* Update the options and do it NOW */
result = tcsetattr(fd,TCSANOW,&options);
if ( result != 0)
{
return result;
}
return 0;
}
/**
* @breif open serial port device
* @param dev [in] name of the device
* @return file description of the device
*/
static int open_dev(const char *dev)
{
int fd = open( dev, O_RDWR | O_NOCTTY | O_NDELAY );
if (fd != -1 ){
fcntl(fd, F_SETFL,0); //set to block
}
return fd;
}
/**
* @breif open serial port
* @param port_num [in] number of the serial port, from 0~255
* @return file description of the serial port
*/
int open_serial_port(int port_num)
{
assert(port_num > -1 && port_num < 256);
char dev[MAX_DEV_NAME]={0};
// dev/ttyS0 = serial port 0
sprintf(dev,"/dev/ttyS%d",port_num);
return open_dev(dev);
}
/**
* @brief write serial port data
* @param fd [in] file description of serial port
* @param buffer [in] write data buffer
* @param size [in] write data buffer size
* @return write data count,return -1, occur error
*/
int write_serial_port(int fd,unsigned char *buffer, size_t size)
{
int writecount = write(fd,buffer,size);
return writecount;
}
/**
* @brief read N data from serial port in time out
* @param fd [in] file description of the serial port
* @param buffer [in] read data buffer
* @param size [in] read data buffer size
* @param readcount [in,out] at last read (readcount) size data.
* set it equal to 0, read random count data.
* it will return received data count.
* return -1, the serial port closed
* return N, count of the serial port received
* @param timeout [in] read N count data's time out
* @return return 0 : time out\n
* return -1 : error\n
* return N: received data count\n
*/
int read_serial_port(int fd, unsigned char *buffer,size_t size, size_t *readcount,
struct timeval *timeout)
{
assert(size >= *readcount);
fd_set inputs;
int result; //select result
int nread; //totla read count
int iread; //ont time read count
int maxfd;
maxfd = fd + 1; //NOTE
nread = 0 ;
FD_ZERO(&inputs);
FD_SET(fd, &inputs);
do {
result = select(maxfd, &inputs,(fd_set *)NULL, (fd_set *)NULL, timeout);
switch(result)
{
case 0: //time out
case -1: //error
return result;
default:
if(FD_ISSET(fd,&inputs)) {
ioctl(fd,FIONREAD,&iread);
if(iread == 0) {
*readcount = -1; //port closed
return TRUE;
}
int count = 0;
if(*readcount != 0) {
//only care buffer size
count = min(iread, size - nread);
}
nread += read(fd, buffer+nread, count);
}
else {
assert(FALSE);
}
}//end of switch
}while((*readcount != 0) && (nread < *readcount));
//receive random data, return data count
if( 0 == *readcount) {
*readcount = nread;
}
return TRUE;
}
/*
* @brief close serial port
* @param fd [in] file description of the serial port
*/
void close_serial_port(int fd)
{
close(fd);
}
#ifdef __cplusplus
} /* extern "C" */
#endif
posted on 2007-08-24 09:31
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