use warnings;
use strict;

use RPi::Const qw(:all);
use RPi::I2C;

use constant {
    ARDUINO_ADDR    => 0x04,
    READ_REGISTER   => 0x05,
    WRITE_REGISTER  => 0x0A,
};

my $device = RPi::I2C->new(ARDUINO_ADDR);

for (0..9){
    my (@bytes_read, $value);

    $device->write_byte(HIGH, WRITE_REGISTER);

    @bytes_read = $device->read_block(2, READ_REGISTER);
    $value = merge(@bytes_read);

    print "$value\n"; # 1023

    $device->write_byte(LOW, WRITE_REGISTER);

    @bytes_read = $device->read_block(2, READ_REGISTER);
    $value = merge(@bytes_read);

    print "$value\n"; # 0
}

sub merge {
    return ($_[0] << 8) & 0xFF00 | ($_[1] & 0xFF);
}