readdata.c - updated

#include <stdio.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <errno.h>

void main(void)
{
    int fd;
    fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY); //FileDescriptor fd = ttyUSB0 (CP2102)

    if (fd<0) {
        printf("Failed to open ttyUSB0\n");
        close(fd);
        return; //Wenn ttyUSB0 nicht geöffnet werden konnte, return
    }

    struct termios SerialPortSettings;
    tcgetattr(fd, &SerialPortSettings);

    //Baudrate setzen 9600 bps
    cfsetispeed(&SerialPortSettings, B9600);
    cfsetospeed(&SerialPortSettings, B9600);

    SerialPortSettings.c_cflag &= ~PARENB; //No Parity
    SerialPortSettings.c_cflag &= ~CSTOPB; //1 Stopbit
    SerialPortSettings.c_cflag &= ~CSIZE; //Clear Mask
    SerialPortSettings.c_cflag |= CS8; //Databits = 8
    SerialPortSettings.c_cflag &= ~CRTSCTS; //Turn off hardware flow control
    SerialPortSettings.c_cflag |= CREAD | CLOCAL; //Turn on rx

    SerialPortSettings.c_iflag &= ~(IXON | IXOFF | IXANY); //Turn off software flow control
    SerialPortSettings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG); //Set Non-Cannoncial

    SerialPortSettings.c_oflag &= ~OPOST;

    if((tcsetattr(fd,TCSANOW,&SerialPortSettings)) != 0) { //Set attributes
        printf("Failed to set attributes!");
        close(fd);
        return;
    }

    char write_buffer[2];
    write_buffer[0] = 'C';
    write_buffer[1] = '\n';
    int bytes_written = 0;

    bytes_written = write(fd,write_buffer,sizeof(write_buffer));

    printf("\n  %s written to ttyUSB0",write_buffer[0],write_buffer[1]);
    printf("\n  %d Bytes written to ttyUSB0", bytes_written);

    close(fd);
}