Adding IoT Capabilities

Lakka is an emulation environment designed to run console and arcade emulators in a kiosk-style setup. The underlying operating system for Lakka is a Linux distribution named LibreELEC that uses read-only access to the filesystem via squashfs. The following is a quick and possibly reliable method to add IoT capabilities via python and subscrbing to an MQTT topic.

pip can be installed with:

wget -c https://bootstrap.pypa.io/get-pip.py

and then by executing:

python get-pip.py

which will perform a local install of pip.

Next, the default PATH must be adjusted to take the local pyton binaries into account. This is done by editing .profile and adding:

#!/usr/bin/sh
 
export PATH=~/.local/bin:/usr/bin:/usr/sbin

and then saving the file.

A re-log is necessary to take the new path into account.

After logging in, install paho MQTT with:

pip install paho-mqtt

which will create a local install of paho MQTT.

The file from the code section (mqttSwitch.py) should be placed at /storage/system/mqttSwitch/mqttSwitch.py after which the file should be made executable, for instance, by issuing chmod +x /storage/system/mqttSwitch/mqttSwitch.py. The file /storage/.config/autostart.sh should either be created or edited in order to add the following line for mqttSwitch.py:

/usr/bin/python /storage/system/mqttSwitch/mqttSwitch.py --daemon

mqttSwtich.py

#!/usr/bin/env python
###########################################################################
##  Copyright (C) Wizardry and Steamworks 2019 - License: GNU GPLv3      ##
###########################################################################
 
import yaml, subprocess, os, argparse, signal, sys
import paho.mqtt.client as mqtt
from os import path
from daemonize import Daemonize
 
with open(os.path.join(os.path.dirname(sys.argv[0]), 'config.yml'), 'r') as ymlfile:
    cfg = yaml.load(ymlfile, Loader=yaml.FullLoader)
 
# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, flags, rc):
    print 'Connected with result code: ', str(rc)
 
    # Subscribing in on_connect() means that if we lose the connection and
    # reconnect then subscriptions will be renewed.
    #client.subscribe("$SYS/#")
    client.subscribe('arcade-engine/#')
 
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
    if str(msg.payload) == 'shutdown':
        os.system('systemctl poweroff')
 
def main():
    client = mqtt.Client()
    client.on_connect = on_connect
    client.on_message = on_message
 
    client.connect(cfg['mqtt']['host'], cfg['mqtt']['port'], 60)
 
    # Blocking call that processes network traffic, dispatches callbacks and
    # handles reconnecting.
    # Other loop*() functions are available that give a threaded interface and a
    # manual interface.
    client.loop_forever()
 
def daemon():
    try:
        if path.exists(cfg['pid']):
            with open(cfg['pid'], 'r') as pid_file:
                pid = pid_file.read()
                os.kill(int(pid), signal.SIGHUP)
            os.remove(cfg['pid'])
    except Exception, e:
        print 'Unable to kill previous process: ', str(e)
        return
 
    daemon = Daemonize(app='mqttSwitch', pid=cfg['pid'], action=main)
    daemon.start()
 
parser = argparse.ArgumentParser()
parser.add_argument('--daemon', action='store_true', help='run as a daemon')
parser.add_argument('--foreground', action='store_true', help='run as a daemon')
args = parser.parse_args()
 
if(args.daemon):
    daemon()
elif(args.foreground):
    main()
 
parser.print_help()