readComData-noSelectFn

int open_com_device() {
//based on: http://www.cmrr.umn.edu/~strupp/serial.html#2_1
    struct termios serial_opts;

    /* Open modem device for reading and writing and not as controlling tty
    because we don't want to get killed if linenoise sends CTRL-C.*/


    fd = open("/dev/ttymxc0", O_RDWR | O_NOCTTY /*| O_NDELAY*/ );

    if (fd <0) {
        DEBUG_SERIAL(printf("error in opening serial device \n"));
        exit(-1);
    }

    tcgetattr(fd, &serial_opts);
    cfsetispeed(&serial_opts, ACM_BAUD);
    cfsetospeed(&serial_opts, ACM_BAUD);
    serial_opts.c_cflag |= ( CLOCAL | CREAD );
    //next 4 options are for 8n1
    serial_opts.c_cflag &= ~PARENB;
    serial_opts.c_cflag &= ~CSTOPB;
    serial_opts.c_cflag &= ~CSIZE;
    serial_opts.c_cflag |= CS8;
    //enable raw input
    serial_opts.c_lflag &= ~( ICANON | ECHO | ECHOE | ISIG );
    //disable "&= ~(..." software flow control. ( To enable |= and remove the ~ )
    serial_opts.c_iflag &= ~( IXON | IXOFF | IXANY );
    //ignore parity and CR LF chars
    serial_opts.c_iflag |= ( IGNPAR | ICRNL );
    //enable raw output
    serial_opts.c_oflag &= ~OPOST;
    //c_cc
    serial_opts.c_cc[VTIME]=10*SERIAL_TIMEOUT_SEC; //in deci-seconds
    serial_opts.c_cc[VMIN]=1;
    if (tcsetattr(fd, TCSANOW, &serial_opts)==-1){
        DEBUG_SERIAL(printf("SERIAL: tcsetattr set failed!\n"));
    }
    return SUCCESS;
}

int ch_C_cc(const unsigned int c_cc_arrayIdx, const unsigned int value){
//change termios c_cc[VTIME] or c_cc[VMIN]
    struct termios opts;

    if (tcgetattr(fd, &opts)==-1){
        DEBUG_SERIAL(printf("SERIAL: tcgetattr set failed errno %d, %s!\n",errno,strerror(errno)));
        return -1;
    }

    if (c_cc_arrayIdx==VTIME)   opts.c_cc[VTIME]=10*value; //in deci-seconds
    else if (c_cc_arrayIdx==VMIN)   opts.c_cc[VMIN]=value;
    else DEBUG_SERIAL(printf("SERIAL: c_cc invalid array index!\n"));

    if (tcsetattr(fd, TCSANOW, &opts)==-1){
        DEBUG_SERIAL(printf("SERIAL: tcsetattr set failed errno %d, %s!\n",errno,strerror(errno)));
        return -1;
    }
    return 0;
}

int readComData(const int toReadBytes, char *serDataBuf){
    unsigned int idx=0; //index of the serDataBuf
    int remainingBytes=toReadBytes, readBytes=0, totalReadBytes=0;
    DEBUG_SERIAL(printf("SERIAL: DATA will read DATA bytes %d\n",toReadBytes));

    ch_C_cc(VMIN,0);
    while (remainingBytes>0){
        readBytes=read(fd,&serDataBuf[totalReadBytes],remainingBytes);
        if ((readBytes<remainingBytes) && (readBytes!=0)){
            DEBUG_SERIAL(printf("SERIAL: DATA read %d bytes and a total of %d .\n",readBytes,totalReadBytes));
            remainingBytes-=readBytes;
            totalReadBytes+=readBytes;
        } else if (readBytes==-1) {
            DEBUG_SERIAL(printf("SERIAL: errno num: %d, string: %s\n",errno,strerror(errno)));
            ch_C_cc(VMIN,1);
            return ERROR;
        } else if ((readBytes==0) && (totalReadBytes<toReadBytes)) {
            DEBUG_SERIAL(printf("SERIAL: No DATA have been read. Prob Timeout @ byte %d. exiting fn\n",totalReadBytes));
            ch_C_cc(VMIN,1);
            return SERIAL_TIMEOUT;
        } else {
            DEBUG_SERIAL(printf("SERIAL: All remaining DATA have been read %d .\n",toReadBytes));
        }
    }//end while
    ch_C_cc(VMIN,1);

    return SUCCESS;
}