Serial setup program

os2 · 03-21-2005, 12:08 PM

hi

in c programming (linux), i search a way to read the setting of the serial port (speed, parity...) and change it.

i need also to write to a led display (alpha sign communications protocole)

with bash i do:

Code:

echo -e \\000\\000\\000\\000\000\\001Z00\\002AA LINUX \\004 >/dev/ttyS1

now i need to do it in c programming

any idea?

thanks

ahwkong · 03-22-2005, 06:33 AM

http://www.easysw.com/~mike/serial/serial.html

os2 · 03-22-2005, 09:34 AM

i beginning to write this code:

Code:

#include <sys/ioctl.h>
#include <stdio.h>
#include <stdlib.h>                     /*atoi, system, getenv */
#include <unistd.h>                     /*sleep, close */
#include <dirent.h>                     /*opendir, readdir, closedir */
#include <string.h>
#include <fcntl.h>                      /*open */
#include <sys/stat.h>
#include <sys/errno.h>  

char *ledisplay;
   
/* Opening port one for read and write */
int writeopen(char msg[])
{
    int fd1;
    int wr;
    fd1 = open(ledisplay, O_RDWR | O_NOCTTY | O_NDELAY );
    if (fd1 == -1)
    {
        perror("open_port: Unable to open /dev/ttyS0 - ");
    }
    else
    {
        fcntl(fd1, F_SETFL, 0);
        printf(" Port 1 has been sucessfully opened and %d is the file descriptor\n",fd1);
        wr=write(fd1, msg, sizeof(msg));
        printf(" Bytes sent are %d \n",wr);
        if (wr < 0)
            fputs("write() of n bytes failed!\n", stderr);
        else
            printf(" Stuff has been written into port 1\n");
        close(fd1);
    }
    return (fd1);
} 

int readopen()
{
    int fd1;
    int rd;
    char *buff=NULL;
    fd1 = open(ledisplay, O_RDONLY | O_NOCTTY | O_NDELAY );
    if (fd1 == -1)
    {
        perror("open_port: Unable to open /dev/ttyS0 - ");
    }
    else
    {
        fcntl(fd1, F_SETFL, 0);
        printf(" Port 1 has been sucessfully opened and %d is the file descriptor\n",fd1);
        rd=read(fd1, buff, 100);
        printf(" Bytes recieved are %d \n",rd);
        printf("%s",buff);
        close(fd1);
    }
    return (fd1);
} 

int readRtuConfig()
{
    /* LED_DISPLAY port */
    if(!(ledisplay = getenv("LED_DISPLAY")))
    {
        fprintf(stderr, "%s - Unable to read variable: LED_DISPLAY\n", strerror(errno));
        return -1;
    }
    return 0;
}

int main()
{
    int result;
    char msg[] = {'\0', '\0', '\0', '\0', '\0', '\1', 'Z', '0', '0', '\2', 'A', 'A', ' ', 'T', 'R', 'I', 'P', 'L', 'E', 'X', '\4' };
      
    
    if((result=(readRtuConfig()))!=-1)
    {       
        {
        if((result=(writeopen(msg)))!=-1){
            sleep(3); 
        //readopen();   
        }
        
    }    
    return 1;
}

when i run the program, i get:

Code:

Port 1 has been sucessfully opened and 3 is the file descriptor
 Bytes sent are 4
 Stuff has been written into port 1

that seem ok but on the led display, i see nothing...

surely,
char msg[] = {'\0', '\0', '\0', '\0', '\0', '\1', 'Z', '0', '0', '\2', 'A', 'A', ' ', 'T', 'R', 'I', 'P', 'L', 'E', 'X', '\4' };

is not equivalent to

echo -e \\000\\000\\000\\000\000\\001Z00\\002AA TRIPLEX\\004 >/dev/ttyS2

any idea?

gbonvehi · 03-22-2005, 09:44 AM

Octal numbers in C starts with a 0 (zero) (and a chat is a byte which can be represented in octal).
See this for a reference: http://www.lysator.liu.se/c/bwk-tutor.html (search for Octal there) and this: http://www.csee.umbc.edu/courses/und...C_summary.html

try
declare a string here = "\000\000\000\000\000\001\Z00\002\AA TRIPLEX\004";

or

declare a string here = "\o000\o000\o000\o000\o000\o001\oZ00\o002\AA TRIPLEX\o004";

I don't know C but I guess this should work anyways...

os2 · 03-22-2005, 11:34 AM

Quote:

Originally posted by gbonvehi
Octal numbers in C starts with a 0 (zero) (and a chat is a byte which can be represented in octal).
See this for a reference: http://www.lysator.liu.se/c/bwk-tutor.html (search for Octal there) and this: http://www.csee.umbc.edu/courses/und...C_summary.html

try
declare a string here = "\000\000\000\000\000\001\Z00\002\AA TRIPLEX\004";

or

declare a string here = "\o000\o000\o000\o000\o000\o001\oZ00\o002\AA TRIPLEX\o004";

I don't know C but I guess this should work anyways...

with the first option i get:

Code:

com.c:102:18: warning: unknown escape sequence '\Z'
com.c:102:18: warning: unknown escape sequence '\A'

and nothing is displayed on the led display

with the second option i get

Code:

com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\o'
com.c:106:21: warning: unknown escape sequence '\A'
com.c:106:21: warning: unknown escape sequence '\o'

and nothing is displayed on the led display

gbonvehi · 03-23-2005, 10:33 AM

It may differ on different compilers, it was a generic example.
You'll get an error because neither Z or A are octal numbers, there you should avoid the \ but as I said i don't know C to tell you exactly how to put this, but reading from those page I can see that octal numbers inside strings are escaped with \xxx being the x three numbers.

Maybe: declare a string here = "\000\000\000\000\000\001Z00\002AA TRIPLEX\004";

Edit I did:

Code:

echo -e "\\000\\000\\000\\000\000\\001Z00\\002AA TRIPLEX\\004" > octal.1

and this is what I got in HEX using: bpe octal.1

Code:

ADDRESS      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F   ASCII
-------------------------------------------------------------------------------
0x00000000   00 00 00 00 00 01 5A 30 30 02 41 41 20 54 52 49   ......Z00.AA TRI
0x00000010   50 4C 45 58 04 0A                                 PLEX..

(the latest 0A is a new line character, I'll ignore it but maybe it's necessary)

That means you could try something like:

Code:

    char msg[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x01,0x54,0x30,0x30,0x02,0x41,0x41,0x20,0x54,0x52,0x49,0x50,0x4C,0x45,0x58,0x04};

or

Code:

    char msg[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x01,'Z','0','0',0x02,'A','A',' ','T','R','I','P','L','E','X',0x04};

Where you use "printable" characters when you can.

keefaz · 03-23-2005, 11:34 AM

Did you check the value for sizeof(msg) in your writeopen(char msg[]) function ?