Linux und RS485 Zähler auslesen.

#include "stdio.h"     

#include "string.h"    

#include "unistd.h"    

#include "fcntl.h"     

#include "errno.h"     

#include "sys/types.h"

#include "sys/stat.h"

#include "stdlib.h"

#include "stdarg.h"

#include "termios.h"

#include "linux/serial.h"  

#define TIOCSRS485 0x542F

int main(void) {

    char txBuffer[10];

    char rxBuffer[10];

    int fd;

    struct termios tty_attributes;

    struct serial_rs485 rs485conf;

    if ((fd = open("/dev/ttyS0",O_RDWR|O_NOCTTY|O_NONBLOCK))<0) {

        fprintf (stderr,"Open error on %s\n", strerror(errno));

        exit(EXIT_FAILURE);

    } else {

        tcgetattr(fd,&tty_attributes);

        // c_cflag

        // Enable receiver

        tty_attributes.c_cflag |= CREAD;        

        // 8 data bit

        tty_attributes.c_cflag |= CS8;          

        // c_iflag

        // Ignore framing errors and parity errors. 

        tty_attributes.c_iflag |= IGNPAR;       

        // c_lflag

        // DISABLE canonical mode.

        // Disables the special characters EOF, EOL, EOL2, 

        // ERASE, KILL, LNEXT, REPRINT, STATUS, and WERASE, and buffers by lines.

        // DISABLE this: Echo input characters.

        tty_attributes.c_lflag &= ~(ICANON);     

        tty_attributes.c_lflag &= ~(ECHO);      

        // DISABLE this: If ICANON is also set, the ERASE character erases the preceding input  

        // character, and WERASE erases the preceding word.

        tty_attributes.c_lflag &= ~(ECHOE);     

        // DISABLE this: When any of the characters INTR, QUIT, SUSP, or DSUSP are received, generate the corresponding signal. 

        tty_attributes.c_lflag &= ~(ISIG);      

        // Minimum number of characters for non-canonical read.

        tty_attributes.c_cc[VMIN]=1;            

        // Timeout in deciseconds for non-canonical read.

        tty_attributes.c_cc[VTIME]=0;           

        // Set the baud rate

        cfsetospeed(&tty_attributes,B300);     

        cfsetispeed(&tty_attributes,B300);

        tcsetattr(fd, TCSANOW, &tty_attributes);

        // Set RS485 mode: 

        rs485conf.flags |= SER_RS485_ENABLED;

        if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) {

            printf("ioctl error\n");

        }

        txBuffer[0]='A';

        write(fd,txBuffer,1);

        // Read a char

        if (read(fd,&rxBuffer,1)==1) {

            printf("%c",rxBuffer[0]);

            printf("\n");

        }   

    }   

    close(fd);  

    return EXIT_SUCCESS;

}