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Device-PiFace-0.01
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Name

Device::PiFace - Perl module to manage PiFace boards

Synopsis

use Device::PiFace;
# OO interface
my $piface = Device::PiFace->new (hw_addr => 0);
$piface->write (value => 0b10000001); # turn pin 0 and 7 on
$piface->write (pin => 4, value => 1); # turn pin 4 on
printf "Status of the inputs: %08b\n", $piface->read;
printf "Input pin 3 is active? %s\n",
       $piface->mask_has_pins ($piface->read, 3) ? "yes" : "no";
# libpifacedigital API
# http://piface.github.io/libpifacedigital/pifacedigital_8h.html
use Device::PiFace ':piface';
pifacedigital_write_reg (0, OUTPUT, $hw_addr);
# libmcp23s17 API
# http://piface.github.io/libmcp23s17/mcp23s17_8h.html
use Device::PiFace ':mcp23s17';
mcp23s17_write_reg (0xFF, GPIOA, $hw_addr, $fd);

Description

This module provides the functions and constants available in libpifacedigital and libmcp23s17. In addition, an OO interface is provided, which makes the module extremely easy to use.

The two libraries specified before are required to install and run this module. Instructions on how this is done are available on the respective webpages.

Methods

Device::PiFace implements the following methods.

new

my $piface = Device::PiFace->new (%options);

Creates a new Device::PiFace instance.

%options may contain the following:

open

my $piface = Device::PiFace->open (%options);

Alias of "new".

close

$piface->close;

This method frees up resources associated with the current instance of Device::PiFace.

It is automatically called when the instance of the class is being destroyed. This means that in most cases it isn't necessary to call this method explicitly.

read

my $val = $piface->read; # read from the register INPUT
$val = $piface->read (register => OUTPUT); # requires :piface_constants
$val = $piface->read (pin => 0);
$val = $piface->read (register => OUTPUT, pin => 0);

Reads a value from a register (by default INPUT). Accepts an hash containing:

WARNING: when register is INPUT, the bits of the resulting value are flipped. This is because on the INPUT register an idle pin is represented with 1, while an active pin is represented with 0 (i.e., 0xFF when no input is active).

write

$piface->write (value => 0xFF); # write to the register OUTPUT
$piface->write (register => OUTPUT, value => 0xFF); # same as before
$piface->write (pin => 0, value => 1); # turns on pin 0

Writes a value to a register (by default OUTPUT). Accepts an hash containing:

enable_interrupts

$piface->enable_interrupts or die 'Something went wrong!';

Enables interrupts on this PiFace board.

Returns 1 on success.

WARNING: pifacedigital_enable_interrupts() returns 0 on success. This method returns 1 on success, and an empty string on failure.

disable_interrupts

$piface->disable_interrupts or die 'Something went wrong!';

Disables interrupts on this PiFace board.

Returns 1 on success.

WARNING: pifacedigital_disable_interrupts() returns 0 on success. This method returns 1 on success, and an empty string on failure.

wait_for_input

my $success = $piface->wait_for_input;
my ($success, $value) = $piface->wait_for_input;
$piface->wait_for_input (timeout => 5000);

Waits for a change of any of the input pins on the PiFace board. Accepts an hash containing:

In scalar context, it returns one of R_SUCCESS, R_TIMEOUT, R_FAILURE ($success).

In list context, it returns $success and the current state of all inputs (the equivalent of a "read" call).

Requires that interrupts are enabled with "enable_interrupts" first.

WARNING: this method blocks until an input pin changes, or the timeout is reached. Be careful.

get_mask

my $mask = $piface->get_mask (@pins);

Returns a mask usable with "write", containing the pins specified in @pins.

NOTE: instead of doing this:

$piface->write (value => $piface->get_mask (qw(1 3 5 7)));

Do this!

$piface->write (value => 0b10101010);

mask_has_pins

my $bool = $piface->mask_has_pins ($mask, @pins);

Checks if $mask contains @pins. Useful to check if a determined set of pins is currently turned on:

printf "Pin 1, 5, 7 active? %s\n",
       $piface->mask_has_pins ($piface->read, qw(1 5 7)) ? "yes" : "no";

NOTE: you can do this by yourself if you have a mask representing the pins to check:

my $bool = ($mask & 0b10000001) == $mask; # pin 0 and 7 turned on?

hw_addr

my $hw_addr = $piface->hw_addr;

Retrieves the hardware address associated with this instance.

fd

my $fd = $piface->fd;

Retrieves the file descriptor returned by pifacedigital_open().

A note about exportable constants and functions

You may export constants/functions either directly (with use Device::PiFace qw(CONST1 func1 ...)) or using "EXPORT TAGS". They are then usable without any prefix.

Otherwise, if you prefer to export nothing, you can refer to constants with

Device::PiFace->CONSTANT_NAME

And to functions with

Device::PiFace::function_name

This approach is useful to reduce namespace pollution, but it is uglier and longer to write.

Export

None by default.

Export tags

Device::PiFace specifies the following export tags:

See also

libpifacedigital, libmcp23s17, http://piface.github.io/

Author

Roberto Frenna (robertof AT cpan DOT org)

Bugs

Please report any bugs or feature requests to https://github.com/Robertof/perl-device-piface.

License

Copyright (C) 2015, Roberto Frenna.

This program is free software, you can redistribute it and/or modify it under the terms of the Artistic License version 2.0.