Waiting for response --- Read() and Write C functions are working only for Console Port, not for another serial port on MVME162

[Chris Johns]

AJAI KUMAR MEDHAVI wrote:
>
>
> I have tried Read(..) and Write(...) C functions to read/write from
> Console Port / Serial port1 and Serial port 2 on MVME162-522A CPU Board
> ruuning RTEMS 4.10.2 . But it is only working for console port(serial port
> 1) and not for Serial Port2.
>
>
> I have used following read() and write() functions to read/write from
> Console Port ( Serial Port 1 on CPU Board) :
>
>
> FOR READING FROM CONSOLE PORT  :
>
>     char buf[5];
>
>     memset(buf, 0, sizeof(buf));
>     nbytes = read(0, buf, sizeof(buf));

You could use ...

   nbytes = read(STDIN_FILENO, buf, sizeof(buf));

You are accessing stdin.

>     printf("string read = %s\n", buf);
>
> TO WRITE ON CONSOLE PORT :
>
>     int len;
>     char *respmsg;  (Global variable)
>     rtems_libio_rw_args_t *rw_args_test; (Global Variable)
>
>     respmsg[0]= 69;
>     respmsg[1]= 70;
>     respmsg[2]= 71;
>     respmsg[3]= 72;
>
>
>     rw_args_test->buffer = respmsg;
>     rw_args_test->count = 4;
>
>     len = write(1, respmsg, 4);

and ..

   len = write(STDOUT_FILENO, respmsg, 4);

This is writing to stdout, the same device printf uses by default.

>
>
> The above read(0, buf, sizeof(buf)) and  write(1, respmsg, 4) functions
> are working fine for Console Port (Serial port 1) without using
>
> open("/dev/console", O_RDWR)
>

These are opened for you during initialization.

>
> but following read/write functions for Serial port 2 (tty00 / tty01) are
> not working :
>
> read(1, buf, sizeof(buf));
> write(0, respmsg, 4);
>

You need to use the 'fd' returned by the 'open'. You should also call 
close with the fd when you are finished.

>
> Please advise me on following points :
>
> 1. Whether first parameter in read/write functions corresponds to minor no
> of console driver.
>

I suggest you read the man page for open, read and write. FreeBSD 
provide a suitable resource online. The open man page is ...

http://www.freebsd.org/cgi/man.cgi?query=open&apropos=0&sektion=0&manpath=FreeBSD+9.1-RELEASE&arch=default&format=html

>
> 2. Whether I have to open ports using system call Open(...,...) like
>
>       fd = open("/dev/console", O_RDWR)
>
>     Please note that I have also tried by following :
>
>     static const char                 device0[] = "/dev/tty00";
>     static const char                 device1[] = "/dev/tty01";
>
>     fd0 = open(device0, O_RDWR);
>          rtems_test_assert(fd0>= 0);
>
>     fd1 = open(device0, O_RDWR);
>     rtems_test_assert(fd1>= 0);
>
>
>     nbytes = read(fd0, buf, sizeof(buf));
>     len = write(fd0, respmsg, 4);
>
>
>      nbytes = read(fd1, buf, sizeof(buf));
>      len = write(fd1, respmsg, 4);
>
>      But this method is not working for both Serial port 1 (Console) and
>      Serial port 2.
>

I also suggest you read about 'termios' ...

http://www.freebsd.org/cgi/man.cgi?query=termios&apropos=0&sektion=0&manpath=FreeBSD+9.1-RELEASE&arch=default&format=html

This effects what happens to the data arriving over the serial port. For 
example the serial port may have default to requiring hardware hardware 
handshaking and the signals have not been asserted by the remote device. 
You also need to set the correct baudrate matching the remote device.

>
> 3. When console Major/Minor number comes as 0/0 then following calls are
>     working fine :
>
>
> rtems_io_write(Console_device_major_number,(rtems_device_minor_number)0,
> (void  *)rw_args_test);
>
> rtems_io_write(Console_device_major_number,(rtems_device_minor_number)1,
> (void  *)rw_args_test);
>

I suggest you use the standard functions such as open, read and write 
and not the ones used to implement the standard interfaces.

>
> but on using write functions :
>    write(1, respmsg, 4);
>    write(0, respmsg, 4);
>
> only write(1, respmsg, 4) is working on console port.
>
>
> 4. One more stange thing I wish to share :
>
>     In testsuites\hello\init.c, By putting follwoing I have made hello.ralf
> downloadable file
>
> status = rtems_io_lookup_name("/dev/console",
> &Console_low_level_device_info);
>          if(status == RTEMS_SUCCESSFUL)
>          {
>                  printf("\nrtems_io_lookup_name : successful");
>                  Console_device_major_number =
> Console_low_level_device_info.major;
>                  Console_device_minor_number =
> Console_low_level_device_info.minor;
>                  printf("\n\nConsole Device Major No. : %d",
> (int)Console_device_major_number);
>                  printf("\n\nConsole Device Minor No. : %d",
> (int)Console_device_major_number);
>          }
>
> On running hello.ralf on CPU board, when I get console major/minor number
> 0/0 then rtems_io_read/ rtems_io_write and write(1,respmsg, len) calls
> work fine.
>
> But on next day, when I run same hello.ralf on CPU board, I get Console
> Major/Minor no. different (like -1/-1 or any other values) and
> rtems_io_read/ rtems_io_write gets failed but write(1,respmsg, len)
> however write(0,respmsg, len) is stil not working.
>
> Any idea how same hello.ralf downloadable file is giving different
> major/minor number on next day. (is there any bug in rtems_io_lookup_name)
>

I am sorry but I do not know the answer to this question. They should be 
the same if the BSP has not changed.

>
> Kindly provide an example for using  console driver for read/write on both
> channels (Please note that Minor number for Console, tty00, tty01 are
> 1,0,1 in Console driver for MVME162).
>

May I suggest you google "termios examples". This looks like an 
interesting one to try ...

http://www.tldp.org/HOWTO/Serial-Programming-HOWTO/x115.html

> You also look  rtems-4.10.2\c\src\lib\libbsp\m68k\mvme162\console.c for
> your reference.
>
>
> Here in console.c,  tty00/ttyo1 have not been initialized /open with
> rtems_termios_initialize  / open rtems_termios_open. also tty00/tty01
> read/write functions are not using rtems_termios_read and
> rtems_termios_write. Whether it may be the reason for problem on reading /
> writing on serial port2.
>

The open call will happen when you use the 'open' call with the correct 
path to the tty01.

Chris