#  You may distribute under the terms of either the GNU General Public License
#  or the Artistic License (the same terms as Perl itself)
#  (C) Paul Evans, 2017 -- leonerd@leonerd.org.uk

package Device::Chip::PCF8574;

use strict;
use warnings;
use base qw( Device::Chip::PCF857x );

our $VERSION = '0.02';

=encoding UTF-8

=head1 NAME

C<Device::Chip::PCF8574> - chip driver for a F<PCF8574>


This L<Device::Chip> subclass provides specific communication to a
F<NXP> or F<Texas Instruments> F<PCF8574> attached to a computer via an I²C

The reader is presumed to be familiar with the general operation of this chip;
the documentation here will not attempt to explain or define chip-specific
concepts or features, only the use of this module to access them.



=head2 addr

The I²C address of the device. Can be specified in decimal, octal or hex with
leading C<0> or C<0x> prefixes.


=head1 METHODS

The following methods documented with a trailing call to C<< ->get >> return
L<Future> instances.


=head2 write

   $chip->write( $val )->get

Sets the value of the GPIO pins, as an 8-bit integer.

Pins set low will sink current suitable for signalling or driving an LED. Pins
set high will source current via a weak current-source to act as a pull-up for
an active-low input signal, such as a button.


=head2 read

   $val = $chip->read->get

Reads the current logic levels on the GPIO pins, returned as an 8-bit
integer. Pins of interest as inputs should have previously been set to high
level using the L</write> method.


use constant PACKFMT => "C";
use constant READLEN => 1;

=head2 as_adapter

   $adapter = $chip->as_adapter

Returns a new object implementing the L<Device::Chip::Adapter> interface which
allows access to the GPIO pins of the chip as if it was a GPIO protocol
adapter. The returned instance supports the following methods:

   $protocol = $adapter->make_protocol( 'GPIO' )



use constant DEFMASK => 0xFF;
use constant GPIOBITS => {
   map { +"P$_", ( 1 << $_ ) } 0 .. 7

=head1 AUTHOR

Paul Evans <leonerd@leonerd.org.uk>