RS232 return values

0
bytes written: 3
***************
buf1:
[0]: h [1]: * [2]: þ
buf2:
[0]:  [1]: ‚ [2]: 
buf3:
[0]:  [1]:  [2]:
0
bytes written: 3
***************
buf1:
[0]: ? [1]: P [2]:

buf2:
[0]: 0 [1]: 2 [2]:

buf3:
[0]: 0 [1]: 0 [2]:

0
bytes written: 3
***************
buf1:
[0]: ? [1]: P [2]:

buf2:
[0]: 0 [1]: 2 [2]:

buf3:
[0]: 0 [1]: 0 [2]:

0
bytes written: 3
***************
buf1:
[0]: 0 [1]: 2 [2]:

buf2:
[0]: 0 [1]: 0 [2]:

buf3:
[0]: ? [1]: P [2]:

/*Function Prototypes*/
int initSerial(char*);
void getCurPos(int);
void flush(int);


int main()
{
        int fd = 0, input;

        fd = initSerial("/dev/ttyS0");

        while(scanf("%i", &input) == 1)
        {
                if(input == 0)
                {
                        getCurPos(fd);
                }
                else if(input == 999)
                {
                        close(fd);
                        return 0;
                }
                else if(input == 555)
                {
                        flush(fd);
                }
        }
        return 0;
}

/*
 *      FUNCTIONS
 *                                                                                                                                           */

/**
   * initialize serial port
   *
   *
   * @param device_name - string for device to init
   *
   * @return int - file descriptor
   *
   * @todo
   */
int initSerial(char* device_name)
{
        int fd;

        fd = open(device_name, O_RDWR|O_NDELAY);

        if(fd != -1)
        {
                struct termios options;

                tcgetattr(fd, &options);

                /*set to 9600 7bit even parity, no flow control*/
                cfsetispeed(&options, B9600);
                cfsetospeed(&options, B9600);

                options.c_cflag |= (CLOCAL | CREAD);
                options.c_cflag |= PARENB;
                options.c_cflag &= ~PARODD;
                options.c_cflag &= ~CSTOPB;
                options.c_cflag &= ~CSIZE;
                options.c_cflag |= CS7;
                options.c_cflag &= ~CRTSCTS;

                tcsetattr(fd, TCSANOW, &options);
                ioctl(fd, TCFLSH, 2);
        }

        return fd;
}
/* end initSerial() */

/**
   * get position of motor
   *
   *
   * @param file_desc - serial port to send commands
   *
   * @return int - integer of point
   *
   * @todo
   */
void getCurPos(int file_desc)
{
        int j, num_written = 0, num1 = 0, cur_pos = 0;
        char buf1[3];
        char buf2[3];
        char buf3[3];
        static const char command[] = "?P
";

        /* send "?P
" */
        num_written = write(file_desc, command, 3);
        printf("bytes written: %i
", num_written);

        /* sleep 20msecs */
        usleep(2000);

        /* read */
        num1 = read(file_desc, buf1, sizeof(buf1));
        num1 = read(file_desc, buf2, sizeof(buf2));
        num1 = read(file_desc, buf3, sizeof(buf3));

        printf("***************
");
        printf("buf1:
");
        for(j=0;j<sizeof(buf1);j++)
        {
                printf("[%i]: %c ", j, buf1[j]);
        }
        printf("
");

        printf("buf2:
");
        for(j=0;j<sizeof(buf2);j++)
        {
                printf("[%i]: %c ", j, buf2[j]);
        }
        printf("
");

        printf("buf3:
");
        for(j=0;j<sizeof(buf3);j++)
        {
                printf("[%i]: %c ", j, buf3[j]);
        }
        printf("
");


}
/* end getCurPos() */

void flush(int file_desc)
{
        printf("flusing buffer
");
        ioctl(file_desc, TCFLSH, 2);
}

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Compiled on Apr 12 2005, 08:56:47.

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?p
02
00
?p
02
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02
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02
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02
00
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+
?p
38
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38
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