NAME
ppi —
user-space interface to ppbus parallel
'geek' port
SYNOPSIS
device ppi
Minor numbering: Unit numbers correspond directly to ppbus numbers.
DESCRIPTION
Theppi 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
<dev/misc/ppi/ppi.h>
<bus/ppbus/ppbconf.h>
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. Setting a bit in the control register
drives the corresponding output low.
STROBEAUTOFEEDnINITSELECTINPCD
PPIGEPPA,PPISEPPA- Get and set the address bits of the EPP control register.
PPIGEPPD,PPISEPPD- Get and set the data bits 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; 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.