serial_connect.c

主要用于无线传感网络的编写的书籍.对于初学者有着很大的用处

#include <stdio.h>   /* Standard input/output definitions */
#include <string.h>  /* String function definitions */
#include <unistd.h>  /* UNIX standard function definitions */
#include <fcntl.h>   /* File control definitions */
#include <errno.h>   /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */

#include "../../debug/debug.h"   /* includes definitions for dbprintf */

#include "serial_connect.h"

/* see serial_connect.h for description */

int g_serial_connect_port_open = SERIAL_PORT_CLOSED;

int openSerialPort(char *serial_port_filepath) 
{
  struct termios options;
  int serial_port_fd;

  if (g_serial_connect_port_open != SERIAL_PORT_CLOSED) {
    return g_serial_connect_port_open;
  }

  if ((serial_port_fd = open(serial_port_filepath, O_RDWR | O_NOCTTY | O_NDELAY)) == -1) {
    dbg(DBG_PHYSICAL, CRITICAL, "FATAL ERROR: open_port: Unable to open %s\n", serial_port_filepath);
    serial_port_fd = -1;
    return -1;
  }

  fcntl(serial_port_fd, F_SETFL, 0);
  tcgetattr(serial_port_fd, &options); // get the current options for the port

  cfsetispeed(&options, B57600);  // set input baud rate to 57600
  cfsetospeed(&options, B57600);  // set output baud rate to 57600
  options.c_cflag |= (CLOCAL | CREAD); // enable the receiver and set local mode

  /* setting character size, not a straighforward thing */
  options.c_cflag &= ~CSIZE; /* Mask the character size bits */
  options.c_cflag |= CS8;    /* Select 8 data bits */


  /* setting up parity: also not straightforward: options available are:
     No parity (8N1): 
     options.c_cflag &= ~PARENB
     options.c_cflag &= ~CSTOPB
     options.c_cflag &= ~CSIZE;
     options.c_cflag |= CS8;
    
    
     Even parity (7E1): 
     options.c_cflag |= PARENB
     options.c_cflag &= ~PARODD
     options.c_cflag &= ~CSTOPB
     options.c_cflag &= ~CSIZE;
     options.c_cflag |= CS7;
     
     
     Odd parity (7O1): 
     options.c_cflag |= PARENB
     options.c_cflag |= PARODD
     options.c_cflag &= ~CSTOPB
     options.c_cflag &= ~CSIZE;
     options.c_cflag |= CS7;
     
     
     Space parity is setup the same as no parity (7S1): 
     options.c_cflag &= ~PARENB
     options.c_cflag &= ~CSTOPB
     options.c_cflag &= ~CSIZE;
     options.c_cflag |= CS8;
 
    I want no parity for MICA2 */
  options.c_cflag &= ~PARENB;
  options.c_cflag &= ~CSTOPB;
  options.c_cflag &= ~CSIZE;
  options.c_cflag |= CS8;

#ifdef CNEW_RTSCTS
  options.c_cflag &= ~CNEW_RTSCTS; // disable hardware flow control (to enable, remove the negation and change to |=)
#endif

  options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);  // make sure no processing is done on data: instead of "canonical" I want "raw"

  /* Control input processing: the c_iflag
     INPCK Enable parity check 
     IGNPAR Ignore parity errors 
     PARMRK Mark parity errors 
     ISTRIP Strip parity bits 
     IXON Enable software flow control (outgoing) 
     IXOFF Enable software flow control (incoming) 
     IXANY Allow any character to start flow again 
     IGNBRK Ignore break condition 
     BRKINT Send a SIGINT when a break condition is detected 
     INLCR Map NL to CR 
     IGNCR Ignore CR 
     ICRNL Map CR to NL 
     IUCLC Map uppercase to lowercase 
     IMAXBEL Echo BEL on input line too long  */
  options.c_iflag &= ~(INPCK | IXON | IXOFF | ICRNL | INLCR | IMAXBEL | IGNBRK | ISTRIP);
  options.c_iflag |= (IGNPAR | IXANY | IGNCR);

  options.c_oflag &= ~OPOST; // for raw output, mask OPOST bit and all other flags (there are many) are ignored


  /* NOTE: c_cc character array defines the bytecodes for various control characters: we don't care about them since we
     masked the OPOST bit above */

  /* timeouts: NOTE: Timeouts are ignored in canonical input mode or when the NDELAY option is set on the file via open or fcntl.
     The VMIN and VTIME elements of the c_cc character array, are important since they
     control how timeouts and minimum number of chracters work.
     VMIN = minimum number of characters to read: if 0, then VTIME is taken as maximum time per character
     VTIME = time to wait for first character if VMIN != 0, otherwise it specifies the time (in tenths of seconds) to wait for 
             incoming characters (set it to 0 if you want to block indefinitely)  */
  options.c_cc[VMIN] = 0;
  options.c_cc[VTIME] = BYTETIMEOUT;

  /* Set the new options for the port...
     TCSANOW: moke changes NOW, regardless of Tx or Rx state of port
     TCSADRAIN: Wait until all transmission has finished to make changes
     TCSAFLUSH: flush the input and output buffers, then make the change */
  tcsetattr(serial_port_fd, TCSAFLUSH, &options);
  g_serial_connect_port_open = serial_port_fd;
  tcflush(serial_port_fd, TCIOFLUSH);
  return serial_port_fd;
}

int closeSerialPort(int serial_port_fd) {
  if (g_serial_connect_port_open == serial_port_fd && g_serial_connect_port_open != SERIAL_PORT_CLOSED) {
    close(serial_port_fd);
    return SUCCESS;
  }
  return FAILURE;
}

int flushInputPort(int serial_port_fd) {
  tcflush(serial_port_fd, TCIFLUSH);
  return SUCCESS;
}

int flushOutputPort(int serial_port_fd) {
  tcflush(serial_port_fd, TCOFLUSH);
  return SUCCESS;
}