Subj : Re: reading com port
To   : wanes98
From : Jeff Silverman
Date : Sun Aug 22 2004 07:32 am

On Sat, 21 Aug 2004 23:11:46 -0400, wanes98 wrote:

> Hello
> I am connecting a device to one of the com port of the PC
> is there any code or directin on how to start.
> I might be using C programming for this project
> thanks
> wanes

There is a lot of material on this subject.  I recomend the Linux Serial
How-to for starters.

First of all, the serial ports are /dev/ttySx where x varies from 0 to 3
in a standard PC configuration (you can have hundreds of serial ports on a
PC if you want to go to an oddball configuration).

You can change the baud rate and other characteristics of a serial port
with the setserial command.

If you just want to read data from a serial port into a program, you can
do that very easily using redirection:

program < /dev/ttyS0

or

program < /dev/ttyS0 > /dev/ttyS1

for example.

If you have to have asynchronous I/O or if you want to avoid having your
program hang waiting for a character, then you have to either use threads
or multiple processes or you can use the select(2) system service call. 
My recommendation is that if you can avoid asynchronous I/O, then avoid
asynchronous I/O, because it is challenging to debug.  Be wary also of the
"Deadly embrace" problem, where both your program and the remote device
are waiting for the other.

I hope this is helpful.


Jeff

.