Is it interesting to control GPIO pins in a way that's compatible not only with RPi? #25

kosilin · 2021-03-16T22:06:18Z

kosilin
Mar 16, 2021

Hello!

May be the following could be useful for someone...

I've set up OctoPrint onto my Banana Pi M2 Zero SBC and wanted to use any plugin
that can control GPIO pins. But the results of my investigation were very sad -
I didn't found anything that can work not only on RPi!

So, as I want to change this sorrowful world and due to this fact I'd improved source code
of OctoLight plugin enabling it to work with any modern SBC that's using mainline kernel.
It's quite easy! The thing is to reject using RPi GPIO library and switch to libgpiod.

Yeah, of course there are some little inconveniences related to this manner, but they are
reaaly piece of cake.

So, at first step we need 'gpio' user group:

sudo groupadd gpio

Second, it's neccessary to append this group to OctoPrint's service account ('pi' in my case):

sudo usermod -aG gpio pi

Third, we must assign proper user group and access rights to '/dev/gpiochip' devices at OS boot.
I'm doing it with help of udev:

sudo su -c 'cat <<EOF > /etc/udev/rules.d/99-gpio.rules
SUBSYSTEM=="gpio",GROUP="gpio",MODE="660"
EOF'

Fourth, it would be nice to install libgpiod itself and also its utilities:

sudo apt install gpiod

Fifth, In OctoPrint virtual python environment run:

pip install gpiod

At this point we are ready to use libgpiod in OctoPrint server environment.

As for me, I'd just installed OctoLight plugin and replaced octoprint_octolight/__init__.py
with following text (Voila! It works!):

# -*- coding: utf-8 -*-
from __future__ import absolute_import, unicode_literals

import octoprint.plugin
import flask
import gpiod

class OctoLightPlugin(
		octoprint.plugin.StartupPlugin,
		octoprint.plugin.TemplatePlugin,
		octoprint.plugin.SimpleApiPlugin,
		octoprint.plugin.SettingsPlugin,
		octoprint.plugin.RestartNeedingPlugin
	):

	light_state = False

	def get_settings_defaults(self):
		return dict(
			light_pin = 16,
			inverted_output = False
		)
	
	def get_template_configs(self):
		return [
			dict(type="navbar", custom_bindings=False),
			dict(type="settings", custom_bindings=False)
		]

	def on_after_startup(self):
		self.light_state = False
		self._logger.info("--------------------------------------------")
		self._logger.info("OctoLight started, listening for GET request")
		self._logger.info("Light pin: {}, inverted_input: {}".format(
			self._settings.get(["light_pin"]),
			self._settings.get(["inverted_output"])
		))
		self._logger.info("--------------------------------------------")

		# Setting the default state of pin
		chip =  gpiod.chip ('/dev/gpiochip0')
		self._light_line = chip.get_line (int (self._settings.get(["light_pin"])))

		config = gpiod.line_request()
		config.consumer = "OctoLight"
		config.request_type = gpiod.line_request.DIRECTION_OUTPUT

		if bool(self._settings.get(["inverted_output"])):
			config.flags = gpiod.line_request.FLAG_ACTIVE_LOW

		self._light_line.request (config)
		self._light_line.set_value (0)

	
	def on_api_get(self, request):
		self.light_state = not self.light_state
		
		# Sets the light state
		self._light_line.set_value (self.light_state)

		self._logger.info("Got request. Light state: {}".format(
			self.light_state
		))

		return flask.jsonify(status="ok")
	
	def get_update_information(self):
		return dict(
			octolight=dict(
				displayName="OctoLight",
				displayVersion=self._plugin_version,

				type="github_release",
				current=self._plugin_version,

				user="gigibu5",
				repo="OctoLight",
				pip="https://github.com/gigibu5/OctoLight/archive/{target}.zip"
			)
		)

__plugin_pythoncompat__ = ">=2.7,<4"
__plugin_implementation__ = OctoLightPlugin()

__plugin_hooks__ = {
	"octoprint.plugin.softwareupdate.check_config":
	__plugin_implementation__.get_update_information
}

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Is it interesting to control GPIO pins in a way that's compatible not only with RPi? #25

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Is it interesting to control GPIO pins in a way that's compatible not only with RPi? #25

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kosilin Mar 16, 2021

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kosilin
Mar 16, 2021