serial port in linux

vishnu anand · 12-20-2011, 01:18 AM

can any one explain me with example about the serial port programming in linux??
first i want to configure a port and thn write a file to port and thn again read the file from the port..please explain with example

TB0ne · 12-20-2011, 08:46 AM

Quote:

Originally Posted by vishnu anand

can any one explain me with example about the serial port programming in linux??
first i want to configure a port and thn write a file to port and thn again read the file from the port..please explain with example

Spell out your words. And Google can explain it with an example, did you bother to look???

First hit in Google:
http://www.easysw.com/~mike/serial/serial.html

michaelk · 12-20-2011, 11:08 AM

How to send/receive data via the serial port really depends on what is connected on the other end. We need more information.

Satyaveer Arya · 12-20-2011, 02:23 PM

Hello vishnu,

First you have to open serial port.

The code to open serial port 1 on a PC running Linux:

Code:

#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 */

    /*
     * 'open_port()' - Open serial port 1.
     *
     * Returns the file descriptor on success or -1 on error.
     */

    int
    open_port(void)
    {
      int fd; /* File descriptor for the port */


      fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
      if (fd == -1)
      {
       /*
	* Could not open the port.
	*/

	perror("open_port: Unable to open /dev/ttyS0 - ");
      }
      else
	fcntl(fd, F_SETFL, 0);

      return (fd);
    }

Then you write data to the port:

Code:

n = write(fd, "ATZ\r", 4);
    if (n < 0)
      fputs("write() of 4 bytes failed!\n", stderr);

The write function returns the number of bytes sent or -1 if an error occurred.

Then read data from the port and then close the port.

Satyaveer Arya · 12-20-2011, 02:33 PM

I'm attaching a Linux serial test program which requires the command parameters to be entered on the command line when the program is started. This program will send output typed on the computer keyboard after the program is started, through the serial port specified.

This program will allow a user to communicate from one computer to another using two serial lines. It is intended only as a test for the serial connection allowing any possible serial setting. This program is named com when compiled. To use it, the following is an example command line:

Quote:

com /dev/ttyS0 38400 8 1 0 4

This line works for com1 at 38400 baud, 8 data bits. I make it a file, call it "fcom1" and put it in my system path and invoke it as a script program.

Find the attachment.