Date: Fri, 4 Apr 2003 09:45:06 +0200 From: "Daan Vreeken [PA4DAN]" <Danovitsch@Vitsch.net> To: Dtseven@gmx.at Cc: FreeBSD-questions@FreeBSD.org Subject: Re: LPT1 Port in ASM or C Message-ID: <200304040945.06653.Danovitsch@Vitsch.net> In-Reply-To: <200304040931.34722."Dtseven@gmx.at"> References: <200304040931.34722."Dtseven@gmx.at">
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On Friday 04 April 2003 09:31, Dtseven@gmx.at wrote:
> Hi all!
> I want to know how I can control the lpt1 port in asm or C.
> I'm a newbie.
> Any help would be greatly appreciated.
There are two ways to do that.
1. Directly poke around with the ports
2. open /dev/lpt0 and communicate with that
I have never looked at the second way, but I can tell you how to do it th=
e=20
first way :)
In FreeBSD to have direct port-access you application needs to open /dev/=
io
Once it has done that, it can directly write to any port it wants.
Opening /dev/io should look something like :
FILE *IO;
IO =3D fopen("/dev/io","rw");
And then you can write/read ports with this little piece of assembly :
void outp(unsigned short Port, unsigned char Data)
{
unsigned char D =3D Data;
=20
__asm __volatile("outb %0,%%dx" : : "a" (D), "d" (Port) );
}
unsigned char inp(unsigned short Port)
{
unsigned char Data =3D 0;
=20
__asm __volatile("inb %%dx,%0" : "=3Da" (Data) : "d" (Port) );
return Data;
}
With the following command you should create a nice 1-0-1-0 bit pattern o=
n the=20
parallel port :
outp(0x378,0xaa);
I have some example code (that does much more than controlling the port) =
here:
http://danovitsch.dnsq.org/cgi-bin/gpl/cat.cgi/lampd/v1.0?lampd.c
grtz & good luck,
Daan
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