Automated mains socket power-off for OSMC on a Raspberry Pi

I’ve chosen to replace an ageing mini-PC which I’ve used since 2010 with a new Raspberry Pi 3 B+ running OSMC. It makes for a really capable media centre which can playback newer h.265 HEVC video files at 1080p without any problems, or it can serve 4K files over NFS to a box with a hardware h.265 chip like the Fire TV Box.

This form factor is easy to take on holiday and you can use an old infrared remote control (or Harmony learning remote) with it too.

However, the one thing I’ve struggled with is how to make it easy for my family to use in regard to switching it on and off. The Pi doesn’t have a power button. Some power supplies have an inline rocker switch, which almost fits the bill. I wanted something more automated.

Fortunately I had a spare Energenie power socket from a previous project where I use one to turn off our bass speaker when the TV isn’t on. These power sockets are controlled remotely (over RF) from a Pi which you attach an Energenie control board/shield to.

What I’ve done with the Pi 3 is have it powered through an Energenie socket, and set up a service that executes when it detects OSMC is shutting down. That service will make a quick HTTP call to the Pi with the Energenie controller shield, which will in turn send an RF signal to turn the mains socket off.

 

osmcshutdown

 

Here’s how you can set it up like I have…

Scripts for the Pi running OSMC

First, add a new service script.. create a new file in this folder;

/etc/systemd/system/callenergenie.service

Then enable it with;

sudo systemctl enable callenergenie.service

There are a couple of useful things happening in this service, the After parameter makes sure the code runs before the network code is shut down, and Conflicts parameter is looking for OSMC shutting down.

Now add a helper script… this will make the webserver call as a background task, so control will be given back to the service immediately, rather than it waiting for the wget to complete.

/home/osmc/callenergenie.sh

This calls the PHP script, telling it which socket to turn off, and how long to delay before sending the command, which we’re doing so that the Pi has time to shut down before the power is cut.

Scripts for the Pi with the Energenie shield

This is the PHP script I added to the other Pi which was already configured to be a PHP web server.

/var/www/html/callenergenie.php

To allow PHP to run the script as root, I needed to add the Apache user to the list of sudo-ers.. not that secure tho :( I’d be interested in anyone who knows how to run the Energenie scripts a regular user.. their Python doesn’t like it when it’s not root.

nano /etc/sudoers

www-data ALL=(ALL) NOPASSWD:ALL

The nice thing about the PHP script is that we can actually call it to turn the Pi on remotely too.. so you could configure that into a widget on your phone, or add it to Alexa.

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Basic Automated Testing using FeatherTest for Chrome

There are a fair number of automated testing tools out there like Intern or Puppeteer, but I wanted something super simple and quick to set up to test a variety of pages on a site I develop.

I was making changes to JSON-LD, page metadata, and some of the data that’s sent to Omniture analytics. All the pages types are slightly different, containing things like Documents, Discussions, Blog Posts, landing pages, etc. So I needed to go to a variety of URLs on my local dev environment to see what certain DOM elements got set to, and check the contents of some JavaScript variables.

I’d then need to do the same checks against our Dev, Staging and Production servers to make sure they all looked correct there too.

After a bit of searching I came across FeatherTest which is fed a text file where you use JavaScript/jQuery to define & run the tests.

It’s very easy to set up tests, and the same test script file can be run against whatever site you’re looking at in your browser. For more info go here;

https://xaviesteve.com/5302/feathertest-automated-website-testing-extension-google-chrome/

Typical FeatherTest Script Structure + Syntax

Tip 1 – Preserve Log

The output from FeatherTest goes into the console, so if you’re testing multiple pages, you’ll need to check the ‘Preserve Log’ option, otherwise you’ll lose the output as Chrome navigates between pages.

Tip 2 – Output Formatting

When writing scripts, I’d recommend colouring the console output, and prefixing each line with something easily identifiable. In my case I’m using ‘SUDO – ‘ and colouring the text orange.

You can then simply filter the console to just see your output;

When you’ve filtered the output, you can then save it to a file (right-click, save as..) and format it into shape.

I’ve found this really useful to monitor how my SEO data has improved as I’ve made changes, and to sanity check I’ve not broken anything between releases.

Tip 3 – Variable access

Some of the test scripts I’ve written needed access to variables defined in the scope of the main window.. FeatherTest can’t normally access these variables, so we need a helper function.

The helper function either needs baking into your site’s JavaScript, or you can inject it using an extension like TamperMonkey. Using TamperMonkey means you can use it on whatever site you want, not just ones where you’re able to install the function on.

My code adds an event listener that you can call from FeatherTest which you can request variable values from.

e.g.

window.postMessage({ "action": "variable", "value": "myVar.hierarchy"}, window.origin);

This is the TamperMonkey/GreaseMonkey script I use;

FeatherTest Script – Example 1 – DOM Lookup

Pulling data out of the DOM is straightforward;

FeatherTest Script – Example 2 – Variable Access & JSON-LD

To access variables we’ll use the TamperMonkey function I posted above. We can also pull out any JSON-LD splats and present them quite nicely in the console output.

 

17 Extensions to help the transition from Firefox to Chrome

I’m finally done with Firefox. When I first started using Firefox, the add-ons were a game-changer & I loved how much extra functionality they added to my day-to-day work.

Today, Chrome dominates the market, is waaay faster, and at the end of 2017 Mozilla is changing the add-on framework so some of the ‘classic’ add-ons I use will cease to work.

The final straw was seeing how fast Chrome way for general browsing and content creation; so much snappier than Firefox. Maybe that’s down to an ageing Firefox user profile.. but, IMO, Chrome is the future.

To ease my transition from Firefox to Chrome I’m using a bunch of extensions that give me the features I’ve grown used to. I thought I’d list out what I’m using so that others might benefit from knowing they’re out there & how useful they can be.

Adblock Plus
Blocks adds. I’d tried uBlock.. but found it breaking a bunch of sites.. so back to this one I’ve used for years in Firefox.

Akamai debug headers
Makes it simple to see what’s happening with websites fronted by the Akamai CDN.

Awesome Screenshot
Full-page screenshots

Cookie Inspector
Enables editing + adding of Cookies (I guess one day the Chrome devs will add this into the core app.. one day).

Downloads Router
Routes certain file types to certain folders. Bit of a faff to set up, but I find it useful for filing downloads into set folders.

Fauxbar
The Chrome omnibar isn’t great for finding URLs I had open hours/days ago (Firefox was brilliant). This sorts out that problem & does a pretty good job at indexing everything nicely.

In addition to that, it gives you a neat menu bar with shortcuts to a whole bunch of things; bookmarks, extensions, apps, options, etc. The configurable tiles for sites is super-handy too.

HostAdmin App
Quick and easy host file editor.. especially useful if you’re using proxy exceptions to speed up access to certain internal sites, and want to be able to configure or toggle the entries easily.

LastPass
Excellent cross-device password manager.

ModHeader
Modify browser headers. Useful for testing things like GeoIP.

Open IE
Adds in a context menu to open the current URL or link in other browsers (IE, Firefox, Opera, etc). Need an external helper program installing in Windows.

Page Monitor
Monitor web pages for changes.. works best when you set the Advanced option to look at a particular part of the page using CSS selectors.

Proxy SwitchyOmega
Set up multiple proxies and easily switch between them via the toolbar button.

SimpleUndoRecents
This will give you a button where you can undo the accidental closing of a tab. (TabMixPlus did something similar in Firefox).

Tampermonkey
Lets you run scripts against web pages each time you load the page.. essentially allowing you to alter the page after it renders. Super handy for removing or adding elements to the page. This extension is the equivalent to Greasemonkey on Firefox.

The Camelizer
Nothing to do with work.. but essential all the same. Lets you see the price history for products on Amazon.. and set alerts for price fluctuations.

Web Developer
Handy tools for developers.

Xmarks Bookmark Sync
Synchronise bookmarks between multiple browsers on multiple PCs.. even has version history in case you delete bookmarks by accident.

 

Honorary mention..

An extension called Postman would have made this list a few months ago.. but it’s moved to a stand-alone application for Windows + Mac. It’s another essential bit of kit for developers; if you’ve not checked it out, go take a look.

MIA…

That covers all but one of the Firefox add-ons I used to use. The one I still miss is Locationbar2, which I simply can’t find an equivalent for in Chrome.

It essentially makes each part of a site’s URL a clickable link.. which is super handy for quickly moving through a site’s structure.

If anyone spots something suitable, hit me up in the comments.

Home Automation Project – Raspberry Pi Heating Controller – Part 1

pi-controlI’m going to build a home automation project which connects a Raspberry Pi to control my central heating. I wasn’t particularly happy ripping out all the existing controls, and wanted to piggyback onto them.. which helps if the Pi ever fails (I’ve still got the old controls to fall back on).

I also didn’t want to mess with the existing heating control board, so bought a duplicate unit (British Gas UP2) from eBay for about £12.. I can perfect the project on that, and install it when I’m ready.

This set of videos goes through each step of the project.. starting off with opening the control board, an overview of what I want to do, and testing out the changes.

Opening up the Control Panel

This was a bit tricky.. it wasn’t quite obvious which plastic clips needed pushing in to pull the board out.. if you were doing this on your actual panel (not an eBay-bought duplicate) then this video should help work out what you need to do to get into it without damaging anything.

 

Project Overview

Next up, I’ll quickly go over what I intend to do to piggyback onto the control board. There’s a project here which did exactly what I wanted to do. He’s not using a PiFace 2 like I intend to use, and he wants to be able to control the hot water as well, but everything else is the same.

 

Safety First – Masking off the High Voltage Area

In this second video, I’ll show how I’m masking off the high voltage area of the board to make it a bit safer when I’m testing things out. Obviously most of the time the board is off, but this helps keep things safer when it is on without the cover.

 

Identifying Solder Points

Luckily this blog gave me a good starting point, but it wasn’t clear where to get the status of the central heating.. I used a multimeter to find a spot which changed voltage when the system was on, and this diagram shows you what I found;

pi-heat-3

Soldering

Since I only needed 4 wires for this project (2 for the switch, and 2 for the system state), I took an old USB cable, cut the ends off, stripped the wires and soldered it to the board without much trouble.

pi-solder

Soldering Complete!

This shows the control board after the soldering has been completed.. it’s pretty simple soldering; the only tricky part was finding the points to connect to for the system state (on/off). I’ve stuck down some of the wires so that they don’t catch or get stuck underneath the control boards buttons.

 

Testing the Wiring

Now that I’ve done the soldering, I’m testing out the wiring.. seeing whether connecting the two wires for the switch turns the central heating on, and when it is on, whether we get voltage on the other two wires to indicate the system state.

 

Controlling from Software

I’ve now hooked it up to the Pi Face 2 board, which can be controlled with a few lines of Python to simulate a button press, and detect the state of the system.

With these basics in place, the rest of the control software can be written to do scheduling, bring in temperature readings, and allow the system to be controlled remotely.

Controlling Power Sockets using a Raspberry Pi

The subwoofer we had in our home cinema setup died a few weeks ago, so I did my research and found a nice replacement. The only thing I didn’t spot was the fact it never goes into standby if there’s no signal (unlike the old one). I tried using some eco plugs which turn off peripherals when the TV was turned off.. but it learns the TV remote signals, and completely turns the TV off as well.. meaning that you have to hit the power button twice to turn the TV back on; that doesn’t work well with the Harmony all-in-one remote we use.

What I decided to do was buy an Energenie socket, which can be switched on/off wirelessly from a Raspberry Pi. The kit comes with 2 sockets and a transmitter to attach to the GPIO headers on the Pi, and costs about £20.

In my subwoofer scenario I basically want it switched on when the TV is on, and off when the TV is off. The TV has a Chromecast plugged into it which is visible on my local network. If you’ve got a Smart TV on your network, maybe that’ll be visible in the same way. So when the TV/Chromecast appear on the network, we know to switch on the power socket.

energeniesockets

Here’s the small Energenie transmitter attached to the GPIO headers on my B+.. it’s pretty tiny and the case I’ve got still fits over the top. Notice the small hole where you can attach an aerial.. if you want extra range, then you’ll need to solder one on.. I added a 135mm wire, since the range I got out of it just wasn’t enough to get from the dining room cupboard to the living room.

energeniepi

 

To put this together, we can use the Raspberry Pi Network Spy code I wrote in my previous blog posts on element14;

Raspberry Pi Network Spy – Part 1 – Initial Setup + d/b Schema
Raspberry Pi Network Spy – Part 2 – D/b Setup + PHP for the scanner

All we need is a new PHP page that’ll call one of the functions we’ve already written.. we need a list of the MAC addresses that are currently visible on the network, then check whether the Chromecast is there. Once we know whether the TV/Chromecast is on or off, we then call a Python script that will turn the Energenie socket on/off.

Here’s the PHP;

arp-chromecast.php

The Python script could follow the Energenie example script, but there’s actually an even more simple Python package which I’ve used in this project. To install it I did the following;

sudo apt-get install python-pip
sudo pip install energenie

Then I wrote this helper Python script (which we’ll call from PHP) that accepts a couple of parameters, like this callenergenie.py [on|off] [switch_number];

callenergenie.py

from energenie import switch_on, switch_off
import sys

if len(sys.argv)==1:
print ‘Please specify arguments like this callenergenie.py [on|off] [switch_number]’
print ‘eg. callenergenie.py on 1’
print ‘eg. callenergenie.py off 2′
else:
on_or_off = sys.argv[1]
which_switch = int(sys.argv[2])

if (on_or_off==’on’):
print ‘Switching on ‘, which_switch
switch_on(which_switch)

if (on_or_off==’off’):
print ‘Switching off ‘, which_switch
switch_off(which_switch)

Now that we’ve written the PHP & Python, all we need to do is run the PHP every minute to scan the network and do the switching. We’ll do this using another cron job;

crontab -e

*/1 * * * * sudo /usr/bin/php /var/www/arp-chromecast.php

Using Wireshark and MITM to explore a STB

I’ve recently bought a new Freeview HD box from 3view. It has a whole host of features and can be considered a “connected” device. As with most high-end set-top-boxes (STB) it pulls software firmware updates from the web, and I was interested to see where it went to get these updates & how it knew they were available.

I know about using tools to sniff network traffic, but have only done this to sniff traffic coming directly out of the PC I’m running the capture software on. Buying this 3view box gave me more of an inventive to expand my knowledge & figure out how to capture the traffic from other devices.

It was actually relatively easy. I decided to do a Machine in the Middle (MITM) ‘attack’ which was documented over at the Wireshark wiki.

In my case I didn’t have 2 network cards, but did have a laptop with one network card, and a wireless card. In Windows XP I bridged the NIC to the Wireless adapter, then plugged in a cross-over cable that linked the 3view box to my laptop. Then, after a bit of messing about with IP addresses it started working.. my 3view box was accessing my wireless router via my laptop.

Now that all the traffic from the 3view box was going via my laptop, all I then needed to do was fire up Wireshark & take a look at the packets.

Intercepting the traffic allowed me to see where the box was going for it’s updates, and the User Agent. That’s been documented over at the 3viewer community website I set up for 3view owners.

http://3viewer.elementfx.com/

QR Code Bookmarklet

QR Codes are a useful way of getting data to your mobile phone using it’s built-in camera. They’re basically 2D barcodes that can carry things like URLs and contact details. On Android I’d recommend using the app called Barcode Scanner to read QR Codes.

There were instances where I wanted to open up a webpage with a long URL on my phone & didn’t want to go through the hassle of copying and pasting it into one of those online QR Code generators.

This bookmarklet for Firefox and newer versions of IE lets you create a QR Code for the page you’re on.. it’ll default to the current page, but you can also override this with something else (like a URL from your clipboard, or whatever).

Add a new bookmark to your toolbar, and set the URL to the code below (I’d have put the proper link on here but WordPress disables the Javascript);

javascript:var%20sCode=prompt('Enter%20URL%20to%20encode',window.location);void(window.open('http://chart.apis.google.com/chart?cht=qr&chs=300x300&chl='+encodeURIComponent(sCode),'Qr%20code','top=100,left=200,width=350,height=350,status=yes'));