Need help in serial port interfacing

Hi,

I am using a Mini2440 board running Qtopia OS. I want to use with it a GPS
receiver for navigation purposes. The GPS receiver comes with a serial
interface, hence I have been trying to write a code to receive data from
one of its serial ports.

The code attached here is supposed to send some data from the tx of a port
and read that data from the rx of the same port. I cross compile this code,
run in my board and get this output - 

Attempting 

That's it. The serial port becomes unresponsive after this. Can anyone tell
me what could be wrong with my code? 

Thank you.

To run thttpd with PHP and access the serial port using 
php_serial.class.php I have to place this in my /etc/profile.environment
file:

chmod 666 /dev/ttySAC1

Curious why you only get "Attempting" rather than "Attempting to open
serial port"?

HTH

davef

@davef
Did you try the code? Are you getting the proper output? Or at least the
full string "Attempting to open serial port"?

Tarin,

I haven't run your code.

I would suggest a simple printf statement only containing the phrase
"Attempting to open serial port" and see if that works.

Perhaps, printf is falling over.

Dave

1) which serial port are you using
 line 26: const char *device = "/dev/ttySAC2";
 line 35: perror("open_port: Unable to open /dev/ttySAC1 - ")
2) Is this source really the base of your program?
 serial.c:15:6: warning: return type of 'main' is not 'int'
 serial.c: In function 'main':
 serial.c:18:2: warning: implicit declaration of function 'open_port'
 serial.c: In function 'open_port':
 serial.c:27:17: warning: unused variable 'out'
 serial.c:27:9: warning: unused variable 'sd'
 serial.c:84:1: warning: control reaches end of non-void function
 serial.c:78:10: warning: 'in' may be used uninitialized in this function
3) did you check if the serial port is not used by another program in your
   Qtopia environment  
4) How did you connect your GPS receiver electrically to the serial ports
  (ttySAC1 or ttySAC2)?

@Dave

I have tried running a code with only printf. And it works properly. The
problem lies somewhere in the serial part of the code.

@Juergen Beisert 
1) which serial port are you using
 line 26: const char *device = "/dev/ttySAC2";
 line 35: perror("open_port: Unable to open /dev/ttySAC1 - ")

Line 35 doesn't matter. Its just a print statement. There are 3 port
drivers in my board - ttySAC0,1,2. I tried all the three and none of them
is working. 

Also, don't look at those warnings. I keep commenting/uncommenting various
parts of my code while debugging, so those warnings are just due to that.

1 of the 3 ports is being used in connecting my board to my pc but the
other 2 ports must be free. And I tried all the 3 ports in the code and
none of them is working. 

I didn't connect my GPS receiver yet. As I have already mentioned in my
first post, I was trying to send data from the tx of a port and receive
data from the tx of the same. I was thinking planning on shorting their rx
tx pins to check the output. But since the code is not running in the first
place, I didn't do the shorting part.

Your program works as expected if I comment out the stdio manipulations.

$ /usr/bin/serial

Attempting to open serial port

In open_port
read = 34968
read = 34968
read = 34968
read = 34968

Your stdio manipulation is completely broken, even the strace command
cannot help, because your manipulation forces a logout.

Comment out the stdio manipulation? What do you mean by that? Exactly
commenting what?

I just commenting out this block in your file (in open_port() ):

  [...]
#if 0
  memset(&stdio,0,sizeof(stdio));
        stdio.c_iflag=0;
        stdio.c_oflag=0;
        stdio.c_cflag=0;
        stdio.c_lflag=0;
        stdio.c_cc[VMIN]=1;
        stdio.c_cc[VTIME]=0;
        tcsetattr(STDOUT_FILENO,TCSANOW,&stdio);
        tcsetattr(STDOUT_FILENO,TCSAFLUSH,&stdio);
        fcntl(STDIN_FILENO, F_SETFL, O_NONBLOCK)
#endif
  [...]

This manipulation will confuse the system. On my Mini2440 is forces a
logout.

Ohh but that fails my purpose of writing from the port. Now the code can
only read. I referred to this
http://en.wikibooks.org/wiki/Serial_Programming/termios#Example_terminal...
while writing the code. And according to the wiki, it should work. What do
you could be the reason that it's confusing the system and forcing it to
logout or behave weird?

But you do a "read(fd,&input,1)" and "write(fd,&input,1);" on your serial
port. You should extend your program using select() to wait for chars.