Linux

I had just configured my grub .........
title Fedora Core NEW (2.6.18-1.2798.fc6xen)
root (hd0,0)
kernel /xen.gz-2.6.18-1.2798.fc6
module /vmlinuz-2.6.18-1.2798.fc6xen ro root=LABEL=/ xencons=xvcX
module /initrd-2.6.18-1.2798.fc6xen.img

and after restarting my system......when I does........

[root@arun TestReadport0]# dmesg | grep tty
serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
0000:05:04.0: ttyS1 at I/O 0x1100 (irq = 18) is a 16550A
0000:05:04.0: ttyS2 at I/O 0x1108 (irq = 18) is a 16550A
[root@arun TestReadport0]#

So here I think my device working correctly..........
1st is serial port on board....
and second & third one my new device
05:04.0 Serial controller: Timedia Technology Co Ltd PCI2S550 (Dual 16550 UART) (rev 01) (prog-if 02 [16550])
Subsystem: Timedia Technology Co Ltd Unknown device 4037
Flags: stepping, medium devsel, IRQ 18
I/O ports at 1100 [size=32]

After that I connected my cable loop backed into my ports........
my program is showing that it is opening serial port correctly but not sending any data ...
its happening why?????
any solution????????

Did you use a null-modem or similar to swap the TX(etc) and RX(etc) wires over?

Why do you not test

(a) by connecting to another working machine?

(b) by using a known working piece of software such as minicom at both ends?

yes I had used Null modem cable........

(a) by connecting to another working machine?
and I had not tested on another system...because another system is far away...and my team member is working on another module......on that system..

(b) by using a known working piece of software such as minicom at both ends?
because I dont know how to use that....I had tried earlier but not able to understand that minicom...

If you are writing communications software demand another machine to assist development/testing.

If you don't work with some known software/test harness you are totally in the dark until something suddenly starts working.

Please find a terminal emulator you can use, once you know the hardware/devices are configured then you can test your software.

this is the line that my minicom is showing me at the bottom of my terminal.....
CTRL-A Z for help | 9600 8N1 | NOR | Minicom 2.1 | VT102 | Online 00:10

but my another minicom is showing offline???
why so and no transfer of data??????whay so...........
please provide me some knowledge......how to use...I am going in dark....
why it is not receving data ???????????

every port is showing opening correctly..........
then also not recieving data??????
what's happening???????

Configure the terminal using

ctrl+A Z O Serial-Port-Setup

set the port name and baudrate,

set parity to none, handshaking to none, bits to 8bits

If you have this running on either end and you type at one end and nothing is happening then you are, what we call "not connected".

So you have to go through the process of confirming that your device name does really map to the 9 or 25 pins sticking out of the back of your machine.

And you also have to try with null-modem, or what ever combination of 9 or 25 pin dongles you have.