Re: regarding serial ports

From: emb in linux (haranath.t_at_gmail.com)
Date: 11/16/05

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    Date: 15 Nov 2005 20:37:15 -0800

    hai
    if input is j,k,l
    then output: j ΃Žÿw˜öÿ¿±„ À@0²‚Ôõÿ¿˜öÿ¿±„
    À@0²˜I@øS@I@Ôõÿ¿@öÿ¿HH@΃
    k
    ƒŽÿw@Îöÿ¿±„ À@0²˜‚Ôõÿ¿Îöÿ¿±„
    À@0²˜I@S@˜I@õÿ¿@öÿ¿HH@Îöÿ¿±„ À@0²ƒ
    l
     if if check for read==0 also i didn't got any difference.

          with regards

           emb in linux.
    Rune Christensen wrote:
    > emb in linux wrote:
    > > hai all,
    > > Here i want to communicate with two serial ports interactivelly.(i.e)If
    > > i send a byte to com1 i have to receive in com2 correpondingly.Here I
    > > am getting the subsequent bytes but in between i am getting some junk
    > > charecters too.(For that i have connected a null modem cable in
    > > between com1 and com2.)
    > >
    > > For clear Understanding i am giving my transmitting and receving code.
    > >
    > > // Transmitting 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 */
    > >
    > > int
    > > main()
    > > {
    > > int fd,c,i;
    > > struct termios options;
    > > char c, buff[10];
    > > fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY );
    > > if (fd == -1)
    > > perror("Unable to open /dev/ttyS0\n");
    > > else
    > > {
    > > fprintf(stdout,"enter any byte");
    > > fgets(buff,sizeof(buff),stdin);
    > > fcntl(fd, F_SETFL, 0);
    > > tcgetattr(fd, &options);
    > > cfsetispeed(&options,B115200);
    > > cfsetospeed(&options,B115200);
    > > options.c_cflag |= (CLOCAL | CREAD);
    > > options.c_cflag &= ~PARENB;
    > > options.c_cflag &= ~CSTOPB;
    > > options.c_cflag &= ~CSIZE;
    > > options.c_cflag |= CS8;
    > > options.c_cflag |=(ICANON | ECHO | ECHOE);
    > > options.c_oflag |=OPOST;
    > > tcsetattr(fd, TCSANOW, &options);
    > > while((c=fgetc(stdin)!=EOF)
    > > {
    > > buff[i]=c;
    > > if(write(fd,buff,1)<0)
    > > fprintf(stderr,"Write() failed!\n");
    > > i++;
    > > fputc(buff,stdout);
    > > }
    > > close (fd);
    > > }
    > > return (0);
    > > }
    > >
    > > output:
    > > enter any byte:a
    > > enter any byte:b
    > > enter any byte:c
    > > it will close whenever we give ctrl+d
    > >
    > > //Receiving
    > >
    > >
    > > #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 */
    > >
    > > int main()
    > > {
    > > int fd,i=0;
    > > char buff[10];
    > > struct termios options;
    > > fd = open("/dev/ttyS1", O_RDWR | O_NOCTTY );
    > > if (fd == -1)
    > > perror("Unable to open /dev/ttyS1\n");
    > > else
    > > {
    > > fcntl(fd, F_SETFL, 0);
    > > tcgetattr(fd, &options);
    > > cfsetispeed(&options,B115200);
    > > cfsetospeed(&options,B115200);
    > > options.c_cflag |= (CLOCAL | CREAD);
    > > options.c_cflag &= ~PARENB;
    > > options.c_cflag &= ~CSTOPB;
    > > options.c_cflag &= ~CSIZE;
    > > options.c_cflag |= CS8;
    > > options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
    > > options.c_oflag &= ~OPOST;
    > > options.c_cc[VMIN]=1;
    > > options.c_cc[VTIME]=10;
    > > tcsetattr(fd, TCSANOW, &options);
    > > fprintf(stdout,"In server\n");
    > > while(1)
    > > {
    > > if (read(fd,buff,10)<0)
    > > fprintf(stderr,"Read() failed!\n");
    > > fputs(buff,stdout);
    >
    > Your problem could be that you don't test if read(..) == 0 and nothing
    > has been read.
    >
    > > }
    > > close (fd);
    > > }
    > > return (0);
    > > }
    > >
    > > output:a
    > > [JUNK ----------------------->]b
    > > [JUNK------------------------->]c
    >
    > Could you show me the junk?
    >
    > > here i want to clear the buffer after receiving 1st byte.so that i can
    > > put that function in loop.Is there any function to do that?
    > > Hope i explaned clearly.If you have any guide other than posix
    > > standard,please give me the url.
    > > Thanks in advance.
    > >
    > >
    > > With Regards
    > >
    > > emb in linux.
    > >
    >
    >
    > Rune Christensen
    > Engineer

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