Hi,

I want to make a C# program that will show if the pc have a rs232 or not,and if the response is positive to acces it.

Questions:
-can I play with rs232(com1) if it has nothing conected to it(writing/reading)
-where can I start to find informations about programming rs232

In the future I want to connect a circuit with a controller on it made by me and I want to learn how to transmit data through rs232 first.

10x

I dont know about, c#,
but there is definetely in 'c' and c++ on windows and linux.
Linux you can use "outb" for writing to the port and "inb" for reading from the port;

Hi,

I didn't find outb and inb but I found inport and outport commands and I made this program but when I read the port at address 0x3f8(com1 address) it returns 0x0 even though I sent caracter 'C' to the com1 port.

Why it returns 0x0 and not 'C' correspondent in ascii code?

so you are probably programming to windows using Borland(??) compiler ? And in fact the code you posted is C not C#.
Background info such as operating system is very important to know. The functions which <dos.h> provides for i/o port programming are very low level functions. There is no inbuilt flow control or buffering.
What are your assumptions about COM ports i.e. serial i/o ports ?
Why did you expect to get " 'C' corespondent in ascii code " ? COM ports are not loopback-devices so they don't echo the stuff you sent back to you.

This article : http://www.beyondlogic.org/serial/serial1.htm#30
provides very good explanations about serial ports and of their programming in certain pc environments (Part 3). There you can see that using <dos.h> is very low level programming.

I think the easiest way to program for COM ports is in linux where you can access serial ports just like a normal file in /dev/ folder COM1 = ttyS0 etc.. This kind of access is buffered and the behaviour of reading would be in a blocking mode with associated timeout.

You were right,my o.s is windows and I use a turbo C compiler.

I read the article you recomanded and I have seen there that rs232 can be transformed in a loopback device by conecting some pins toghether. I don't know if that is good for motherboard.Now I'm thinking if to do it or not.

Thanks

For RS232 port, they actually have internal ersistors to limit the current. Don't worry........ try to find some technical specifications of RS232 port.




One simple and trivial test u wanna try is to, use a switch and and LED.
Set the switch (the pin u connected to) as the input and set the LED (the pin you connected to) as output. The RS 232 port also has 5V and Ground.

Play around......... its fun. Furthermore you can try connect senros and buzzers. BCD LED......... so many more.

As an alternative to loopback, a system generally has more than two comports, then connect both the commports with RS232 cable. Then for reading open one ttsy and for other another ttsy.

This will help you.