Date: Fri, 23 Feb 2001 11:55:44 -0600 From: Lucas Bergman <lucas@slb.to> To: Greg Hormann <ghormann@ns.kconline.com> Cc: questions@freebsd.org Subject: Re: Direct Access to Parallel Port Message-ID: <20010223115544.B28130@billygoat.slb.to> In-Reply-To: <Pine.BSF.4.05.10102222016410.18380-100000@hormann.tzo.cc>; from ghormann@ns.kconline.com on Thu, Feb 22, 2001 at 08:26:33PM -0500 References: <Pine.BSF.4.05.10102222016410.18380-100000@hormann.tzo.cc>
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> I need to control some solid state relays (SSRs) from my old P75.
> In the past, I've used dos, Qbasic, and Parallel port to control up
> to 8 SSRs. (Just by sending 0-255 to the correct I/O address, I can
> turn on/off pins 2-9.)
>
> Anyway, I'd like to convert this DOS box over to FreeBSD so that I
> can make changes remotely. How difficult would it be to send a byte
> out to the I/O address of the parallel Port on a FreeBSD box?
Not difficult, if you know C. The "official" (and more Unixly
correct) way to do this is through the existing ppi interface; see
ppi(4). Be warned, though, that ioctl()'s are slow. If this is a
problem, you can always do stuff like
void
port_out_byte(unsigned port, unsigned char byte)
{
asm volatile("outb %0,%1" : : "a"(byte), "id"((unsigned short)(port)));
}
from a C program. Then `port_out_byte(0x378,0xa5)' would send the
byte 0xa5 to port 0x378.
> Secondly, Anybody ever worked on a driver for digital I/O boards?
Maybe, but I definitely haven't. :)
Lucas
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