🚀 go-pugleaf

In article <johnr.703398126@wambenger>, johnr@cs.uwa.oz.au (John Redman) writes:
> This is probably a very basic kind of thing to
> ask, but --
> 
> 	How do I go about reading and sending
> 	information from/to serial and parallel
> 	ports?
Actually it is not a very basic kind of thing, but rather a very good question.
Working with either port is rather tricky.  Lets consider the parallel port
first.  The parallel port, as setup up by default on the PC, has 12 output
pins and 5 input pins (if I remember correctly).  Depending on the chip 
used in your PC and how it is setup, you might be able to redefine which pins
are input and which are output.  The serial port has essential a transmit
pin, a receive, and a couple signal pins.
The tricky part now is recovering the information from the ports.  The easiest
method is to constantly poll the port and see if a new byte has arrived.
This unfortunately sucks up some CPU time and also precludes high speed
data transfer.  The preferred method to use is to set-up an interrupt service
that gets called whenever a incoming byte is recevied.  Transmitting is usually
pretty easy.  You stick the byte to be transmitted and that is it.  If you
want high speed communication (especially on a serial port), you might have
to setup an interrupt service that feeds the port whenever a byte has been
transmitted.  Thus the ideal setup is to double buffer the port you want to
use.
If you want information on the parallel port, a good person to talk to is
fdeck@grumpy.helios.nd.edu.  I've done some work, but I haven't gotten my
double buffering code to work yet so I wouldn't be the best person to talk 
to.

-james dishaw
JDISHAW@POMONA.CLAREMONT.EDU