Wiring

The buttons are simple to wire. This setup uses 3 wires for the 2 buttons. One wire from a ground pin to both buttons, and then one wire each from a GPIO pin (GPIO 20 & 21) and each button.

A simple OctoPrint plugin

Update 2021-01-18: I was having issues with the buttons being triggered erroneously while using the RPi.GPIO Python module..after some research I switched to gpiozero, which still uses RPi.GPIO but adds some additional functionality on top of it. The code is updated below.

I found the simplest way monitor the GPIO state and control OctoPrint was from an OctoPrint plugin written in Python. There are a couple of plugins that include support for physical buttons, but they also have a ton of features and overhead that I don't need or want.

So, I wrote a very simple one that sets up the GPIO pins with software pull-up resistors, adds callbacks for when the buttons are held:

from __future__ import absolute_import, unicode_literals

import subprocess
import gpiozero

import octoprint.plugin

class HWButtonsPlugin(octoprint.plugin.SettingsPlugin):
    def __init__(self):
        super().__init__()
        self.cancel = gpiozero.Button(21, pull_up=True, hold_time=1)
        self.wifi = gpiozero.Button(20, pull_up=True, hold_time=1)

        self.cancel.when_held = self.on_cancel_held
        self.wifi.when_held = self.on_wifi_held

    def __del__(self):
        self.cancel.close()
        self.wifi.close()

    def on_wifi_held(self):
        self._logger.info("Resetting wifi-module. (Hardware button pressed)")
        subprocess.call("/home/taylor/reset_wifi.sh", shell=True)

    def on_cancel_held(self):
        if self._printer.is_operational() and self._printer.is_printing() and not self._printer.is_cancelling():
            self._logger.info("Cancelling print. (Hardware button pressed)")
            self._printer.cancel_print()


__plugin_name__ = "Hardware Buttons"
__plugin_version__ = "1.0.0"
__plugin_description__ = "Actions for hardware buttons wired to RPi GPIO pins."
__plugin_pythoncompat__ = ">=2.7,<4"
__plugin_implementation__ = HWButtonsPlugin()

Some details:

• Subclassing octoprint.plugin.SettingsPlugin is not used at this point. I plan on making the plugin configurable at some point...
• All of the __plugin_* variables are how OctoPrint reads and loads the plugin

Installing the plugin is simple: place the python file in ~/.ocotprint/plugins and restart OctoPrint.

#!/bin/bash
sudo modprobe -r brcmfmac
sleep 1s
sudo modprobe brcmfmac
sleep 1s
sudo iwconfig wlan0 power off