readComData2

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]=60; //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 timeval_subtract(struct timeval *result, struct timeval *x, struct timeval *y){
//Subtract the `struct timeval' values X and Y,
//storing the result in RESULT.
//Return 1 if the difference is negative, otherwise 0.
    int nsec=0;

    // Perform the carry for the later subtraction by updating y.
    if (x->tv_usec < y->tv_usec) {
        nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
        y->tv_usec -= 1000000 * nsec;
        y->tv_sec += nsec;
    }
    if (x->tv_usec - y->tv_usec > 1000000) {
        nsec = (y->tv_usec - x->tv_usec) / 1000000;
        y->tv_usec += 1000000 * nsec;
        y->tv_sec -= nsec;
    }

    // Compute the time remaining to wait. tv_usec is certainly positive.
    result->tv_sec = x->tv_sec - y->tv_sec;
    result->tv_usec = x->tv_usec - y->tv_usec;

    // Return 1 if result is negative.
    return x->tv_sec < y->tv_sec;
}

int asciiToHex(char *aChar){
// Convert ASCII HEX values, to plain HEX
    if ((*aChar & 0xF0) == 0x30)
        *aChar = *aChar - 0x30; // Number
    else if (*aChar>='A' && *aChar<='F')
        *aChar = *aChar - 0x37; // Upper-case letter
    else if (*aChar>='a' && *aChar<='f')
        *aChar = *aChar - 0x57; // Lower-case letter
    else {
        DEBUG_SERIAL(printf("Invalid hex stream (nibble: 0x%0X)\n",*aChar));
        pthread_mutex_unlock(&serial_lock_mutex);
        return ERROR;
    }
}

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;
    DEBUG_SERIAL(else                   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,timeoutCounter=0; //index of the serDataBuf
    int remainingBytes=toReadBytes, readBytes=0, totalReadBytes=0;
    struct timeval difftime,begintime,endtime;

    DEBUG_SERIAL(printf("SERIAL: DATA will read DATA bytes %d\n",toReadBytes));
    ch_C_cc(VMIN,0);
    while (remainingBytes>0){
        gettimeofday(&begintime);
        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)) {
            gettimeofday(&endtime);
            if (timeval_subtract(&difftime,&endtime,&begintime)==1) {
                printf("SERIAL: time diff was negative\n");
                printf("SERIAL: time diff is tv_sec=%d , tv_usec=%d\n",difftime.tv_sec,difftime.tv_usec);
            } else {
                printf("SERIAL: time diff is tv_sec=%d , tv_usec=%d\n",difftime.tv_sec,difftime.tv_usec);
            }
            DEBUG_SERIAL(printf("SERIAL: No DATA have been read. Timeout @ byte %d, timeout counter %d.\n",totalReadBytes,timeoutCounter));
            if (timeoutCounter>MAX_RETRIES) {
                ch_C_cc(VMIN,1);
                return SERIAL_TIMEOUT;
            } else {
                timeoutCounter++;
            }
        } else {
            DEBUG_SERIAL(printf("SERIAL: All remaining DATA have been read %d .\n",toReadBytes));
        }
    }//end while
    ch_C_cc(VMIN,1);

    return SUCCESS;
}