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RPi::ButtonWatcher zef:patrickb last updated on 2021-04-09



RPi::ButtonWatcher - A button push event supplier


use RPi::Wiring::Pi;
use RPi::ButtonWatcher;

die if wiringPiSetup() != 0;

# Takes WiringPi pin numbers.
my $watcher = => ( 4, 5, 6 ), edge => BOTH, PUD => PULL_UP);
$watcher.getSupply.tap( -> %v {
    my $e = %v<edge> == Edge.RISING ?? 'up' !! 'down';
    say "Pin: %v<pin>, Edge: $e";


This library provides a supplier of GPIO pin state changes.

Read/write access to /sys/class/gpio/export and /sys/class/gpio/gpioXX/ is required for this library to work. This usually means the user running the code has to be in the gpio group.

This module uses polling to detect state changes. A polling interval of 0.1 seconds is usually fast enough for normal button pushes.

The Sysfs interface is documented here:



Do initialize WiringPi before using this class using wiringPiSetup!

Takes the following parameters:

A list of WiringPi pin numbers to watch.

The edges to listen for.

* `Edge.RISING`

Triggered when a button is released.

* `Edge.FALLING`

Triggered when a button is pressed.

* `Edge.BOTH`

Triggered on both, button presses and releases.

Time in seconds to sleep between polls. Faster means more responsive, but also more system resource eating. Defaults to 0.1 (100ms).


Returns a supply that can be tapped. The supply will emit hashes with two entries:

The WiringPi pin number that was triggered.

Either Edge.RISING or Edge.FALLING.