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Man Pages


Manual Reference Pages  -  PPI (4)

NAME

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

CONTENTS

Synopsis
Description
Programming Interface
Examples
Bugs

SYNOPSIS


.Cd device ppi

Minor numbering: unit numbers correspond directly to ppbus numbers.


.In dev/ppbus/ppi.h
.In dev/ppbus/ppbconf.h

DESCRIPTION

The ppi driver provides a convenient means for user applications 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 uint8_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. Setting 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 register.
PPIGECR, PPISECR
  Get and set the contents of the ECP control register.
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;         uint8_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.

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