ppi(4)

NAME

ppi - user-space interface to ppbus parallel 'geek' port

SYNOPSIS

device ppi
Minor numbering: unit numbers correspond directly  to  ppbus
numbers.
#include <dev/ppbus/ppi.h>
#include <dev/ppbus/ppbconf.h>

DESCRIPTION

The ppi driver provides a convenient means for user applica

tions to
manipulate the state of the parallel port, enabling easy

low-speed I/O
operations without the security problems inherent with the

use of the
/dev/io interface.

PROGRAMMING INTERFACE

All I/O on the ppi interface is performed using ioctl()

calls. Each command takes a single u_int8_t argument, transferring one byte

of data.
The following commands are available:

PPIGDATA, PPISDATA

Get and set the contents of the data register.

PPIGSTATUS, PPISSTATUS

Get and set the contents of the status register.

PPIGCTRL, PPISCTRL

Get and set the contents of the control register.

The following
defines correspond to bits in this register. Set

ting a bit in
the control register drives the corresponding output

low.
STROBE
AUTOFEED
nINIT
SELECTIN
PCD

PPIGEPP, PPISEPP

Get and set the contents of the EPP control regis

ter.

PPIGECR, PPISECR

Get and set the contents of the ECP control regis

ter.

PPIGFIFO, PPISFIFO

Read and write the ECP FIFO (8-bit operations only).

EXAMPLES

To present the value 0x5a to the data port, drive STROBE low

and then
high again, the following code fragment can be used:

int fd;
u_int8_t val;

val = 0x5a;
ioctl(fd, PPISDATA, &val);
ioctl(fd, PPIGCTRL, &val);
val |= STROBE;
ioctl(fd, PPISCTRL, &val);
val &= ~STROBE;
ioctl(fd, PPISCTRL, &val);

BUGS

The inverse sense of signals is confusing.

The ioctl() interface is slow, and there is no way (yet) to

chain multiple operations together.

The headers required for user applications are not installed

as part of
the standard system.

BSD January 2, 1998

BSD