NAME

RPi::LCD - Perl interface to Raspberry Pi LCD displays via the GPIO pins

SYNOPSIS

    use RPi::LCD;

    my $lcd = RPi::LCD->new;

    my %lcd_args = (
        rows  => 2,     # number of display rows, 2 or 4
        cols  => 16,    # number of display columns 16 or 20
        bits  => 4,     # data width in bits, 4 or 8
        rs    => 1,     # GPIO pin for the LCD RS pin
        strb  => 2,     # GPIO pin for the LCD strobe (E) pin
        d0    => 3,     #
        ...             # d0-d3 GPIO pinout numbers
        d3    => 6,     #
        d4    => 7,     # set d4-d7 to all 0 (zero) if in 4-bit mode
        ...             # otherwise, set them to their respective
        d7    => 11,    # GPIO pins
    );

    # initialize the LCD screen

    $lcd->init(%lcd_args);

    my $perl_ver = '5.24.0';
    my $name = 'stevieb';

    $lcd->home; # row 0, col 0

    $lcd->print("${name}'s RPi, on");

    $lcd->position(0, 1); # row 2

    $lcd->print("Perl $perl_ver...");

DESCRIPTION

This module acts as an interface to typical 2 or 4 row, 16 or 20 column LCD screens when connected to a Raspberry Pi.

It is standalone code, but if you access an instance of this class through the RPi::WiringPi library, we'll ensure safe exit upon a crash.

METHODS

new()

Returns a new RPi::LCD object. We check if any RPi::WiringPi setup routines have been run, and if not, we set up in GPIO pin mode.

init(%args)

Initializes the LCD library, and returns an integer representing the handle (file descriptor) of the device. The return is supposed to be constant, so DON'T change it.

Parameters:

    %args = (
        rows => $num,       # number of rows. eg: 2 or 4
        cols => $num,       # number of columns. eg: 16 or 20
        bits => 4|8,        # width of the interface (4 or 8)
        rs => $pin_num,     # pin number of the LCD's RS pin
        strb => $pin_num,   # pin number of the LCD's strobe (E) pin
        d0 => $pin_num,     # pin number for LCD data pin 1
        ...
        d7 => $pin_num,     # pin number for LCD data pin 8
    );

Mandatory: All entries must have a value. If you're only using four (4) bit width, d4 through d7 must be set to 0.

NOTE: In 4-bit mode, connect to pins d4 - d7 on the LCD. These pins act as d0 - d3 when not in 8-bit mode.

home()

Moves the LCD cursor to the home position (top row, leftmost column).

clear()

Clears the LCD display of all data, and return the cursor to the home position.

display($state)

Turns the LCD display on and off.

Parameters:

    $state

Mandatory: 0 to turn the display off, and 1 for on.

cursor($state)

Turns the LCD cursor on and off.

Parameters:

    $state

Mandatory: 0 to turn the cursor off, 1 for on.

cursor_blink($state)

Parameters:

    $state

Mandatory: 0 to stop blinking, 1 to enable.

send_cmd($command)

Sends any arbitrary command to the LCD. (I've never tested this!).

Parameters:

    $command

Mandatory: A command to submit to the LCD.

position($x, $y)

Moves the cursor to the specified position on the LCD display.

Parameters:

    $x

Mandatory: Column position. 0 is the left-most edge.

    $y

Mandatory: Row position. 0 is the top row.

char_def($index, $data)

This allows you to re-define one of the 8 user-definable characters in the display. The data array is 8 bytes which represent the character from the top line to the bottom line. Note that the characters are actually 5 x 8, so only the lower 5 bits are used. The index is from 0 to 7 and you can subsequently print the character defined using the lcdPutchar() call.

Parameters:

    $index

Mandatory: Index of the display character. Values are 0-7.

    $data

Mandatory: See above description.

put_char($char)

Writes a single ASCII character to the LCD display, at the current cursor position.

Parameters:

    $char

Mandatory: A single ASCII character.

print_char($char)

Alias of put_char().

puts($string)

Parameters:

    $string

Mandatory: A string to display.

print($string)

Alias of puts().

AUTHOR

Steve Bertrand, <steveb@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2017 by Steve Bertrand

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.18.2 or, at your option, any later version of Perl 5 you may have available.

cpanm RPi::LCD

perl -MCPAN -e shell
install RPi::LCD