NAME
    RPi::HCSR04 - Interface to the HC-SR04 ultrasonic distance measurement
    sensor on the Raspberry Pi

SYNOPSIS
        use RPi::HCSR04;

        my $trig_pin = 23;
        my $echo_pin = 24;

        my $sensor = RPi::HCSR04->new($trig_pin, $echo_pin);

        my $inches = $sensor->inch;
        my $cm     = $sensor->cm;
        my $raw    = $sensor->raw;

        ...

DESCRIPTION
    Easy to use interface to retrieve distance measurements from the HC-SR04
    ultrasonic distance measurement sensor.

    Requires wiringPi to be installed.

TIMING WITHIN A LOOP
    This software does no timing whatsoever; it operates as fast as your
    device will allow it.

    This often causes odd results. It's recommended that if you put your
    checks within a loop, to sleep for at least two milliseconds (`0.02').
    You can use `select(undef, undef, undef, 0.02);', or `usleep()' from
    Time::HiRes.

VOLTAGE DIVIDER
    The HC-SR04 sensor requires 5V input, and that is returned back to a Pi
    GPIO pin from the `ECHO' output on the sensor. The GPIO on the Pi can
    only handle a maximum of 3.3V in, so either a voltage regulator or a
    voltage divider must be used to ensure you don't damage the Pi.

    Here's a diagram showing how to create a voltage divider with a 1k and a
    2k Ohm resistor to lower the `ECHO' voltage output down to a safe
    ~3.29V. In this case, `TRIG' is connected to GPIO 23, and `ECHO' is
    connected to GPIO 24.

METHODS
  new
    Instantiates and returns a new RPi::HCSR04 object.

    Parameters:

        $trig

    Mandatory: Integer, the GPIO pin number of the Raspberry Pi that the
    `TRIG' pin is connected to.

        $echo

    Mandatory: Integer, the GPIO pin number of the Raspberry Pi that the
    `ECHO' pin is connected to.

  inch
    Returns a floating point number containing the distance in inches. Takes
    no parameters.

  cm
    Returns a floating point number containing the distance in centemetres.
    Takes no parameters.

  raw
    Returns an integer representing the return from the sensor in raw
    original form. Takes no parameters.

REQUIREMENTS
    * wiringPi must be installed.
    * You must regulate the voltage from the `ECHO' pin down to a safe 3.3V
    from the 5V input. See VOLTAGE DIVIDER for details.

AUTHOR
    Steve Bertrand, `<steveb at cpan.org>'

LICENSE AND COPYRIGHT
    Copyright 2017 Steve Bertrand.

    This program is free software; you can redistribute it and/or modify it
    under the terms of either: the GNU General Public License as published
    by the Free Software Foundation; or the Artistic License.

    See http://dev.perl.org/licenses/ for more information.