Archives for category: Raspberry PI


I am happy to announce the 2nd edition of Raspberry Pi Home Automation with Arduino is now released.

Raspberry Pi Home Automation with Arduino 2nd edition It’s available from all good bookstores and Amazon of course. After much editing and refinement here is a taster of what the book covers:

  • Arduino Uno
  • Raspberry Pi
  • Cooking Hacks Arduino to Pi bridge shield
  • Relays
  • Temperature sensors
  • Water sensors
  • Motor shields
  • Humidity sensors
  • Pressure sensors (FRS)
  • Networking
  • Python
  • C++ and Arduino sketches

Sadly we didn’t end up with space to cover the YUN this time round.

Things have been a little quiet as of late due to me being busy.

The various projects have been progressing nicely in the background and I’ll be getting their progress written up into blog posts as soon as time permits.

In the interim here is a quick update on where things are at:

Wireless thermostat

My Arduino YUN has arrived. This is going to be the perfect piece of equipment for completing my WiFi thermostat project. It takes away the need to worry about hooking up a separate wireless shield. I’ll just need to attach one of my touch screen shields to it and hook up a relay and thermistor and it will be ready to go.

My next wireless thermostat post will go into more detail on this.

Ethernet Thermostat

The Ethernet thermostat is almost complete. The next post on this will detail each component I used, how to set it up and will also discuss connecting it to baseboard heaters and the types of relay needed.

Thermostat controller

The Java based thermostat controller running on the Pi is coming along nicely. The next posts on this will tie in with my earlier post on parallel computing.

The controller is going to leverage Hadoop which is running on other devices in my home to process temperature data. Expect a guide to setting up Hadoop on the Raspberry Pi and also a further look at MPI for C based applications that can also leverage spare processing capacity.

There will also be code uploaded to BitBucket which you can download and use as a base for your projects.


Upcoming reviews

I have some upcoming reviews on the Arduino YUN, the Pebble smart watch and Mint floor sweeper.




In a previous post I touched on the fact we would be examining HPC (High Performance Computing), parallel processing and Hadoop in relation to Home Automation.

As our home network grows with multiple devices, tablets, microprocessors and similar running on it we reach a point where we have many CPU’s which are often sitting dormant. Being able to leverage this spare computational power for working on other tasks in our home poses an interesting challenge.

One method we can use in the case of multiple Raspberry Pi units is to use applications that run using MPI (Message Passing Interface). The MPI provides us with a set of base routines and functionality for communicating between multiple CPU’s.

Originally written with C and Fortran in mind, there are many libraries for languages including Python and Java that allow us to implement MPI based applications.

MPI has eight basic concepts, these are:

Communicator – An object that connects groups of processes in the MPI session.

Point-to-point basics – Allows process to process communication

Collective basics – Performs communication amongst all processes in a process group

Derived datatypes – Used for dealing with datatypes in MPI applications

One-sided communication – A set of operations used for dealing with scenarios where synchronization would be an inconvenience for example the manipulation of matrices and calculating matrix products.

Collective extensions –  For example non-blocking collective operations (A combination of non-blocking point-to-point functionality with collective basics) which can help reduce the over-head on communications.

Dynamic process management –  The ability for an MPI process to help with the creation of new processes or establish communication between MPI processes.

MPI-IO – The abstraction of the I/O management on parallel systems to the MPI

These eight concepts can help us to decide what functionality we wish to use in our home automation applications that implement MPI.

To give an example of how this may be useful in the home let’s look at the following example.

Redundant media unit and thermostat controller

In this scenario we have a thermostat controller running on a Raspberry Pi that calculates various temperature data and adjusts the thermostats, blinds and similar as needed. This thermostat controller for example may also use weather data to decide whether a device that acts as a damp/water sensor should be switched on or off based upon predicted rain fall levels.

Over time as we store more historical data and get weather streams via the web we have an ever increasing amount of data to work with. More data should hopefully provide more precision. However working with more data also means we are crunching more numbers and thus placing an ever increasing burden on the CPU of the Raspberry Pi.

We can optimize our code and database in order to help tackle performance issues, however this will only get us so far.

Now let’s imagine we have a second Raspberry Pi running XMBC in our home, which we use on occasions to watch streamed TV from the web. This Raspberry Pi may be sitting idle for much of the day, so it would be great if we could leverage it’s CPU to crunch our weather data while it is sitting dormant.

This is where using MPI can help. A program written using MPI can check if the media unit is being used and if not set its CPU to work on processing temperature data.

Using the eight basic concepts of MPI we can write an application that will handle the communication between the thermostat controller and XMBC RPi and pass calculations back and forth.

This model also allows us to add further devices to our network that can be used by the thermostat controller for parallel processing.


Our thermostat controller is being written in Java and will run on Tomcat, therefore in the next post on MPI we will look at its Java implementation and how we can use this in our code.

We will explore the techniques used for writing distributed applications and look at a scalable model that allows for the addition of extra devices to the network.


We are now going to look at the first step of building the controller system for our home automation system using the Raspberry Pi as the “brains”.

In order to host web applications, write data to our temperature database and host a method for serving the data stored in the DB via http we are going to need to install a number of tools.

For calculating the temperature and communicating with the thermostats we are going to use Java and setup a Java based web server. Following from this we will once again look at HTSQL and setup an HTSQL server for reading the temperature data from our database. We will also in later posts consider using Hadoop for a scalable parallel based controller capable of handling lots of data.

Having built the controller, we will then need to re-visit the post on Postgres and build out our database.

In part one of this post we will look at installing Java Apache Tomcat.

Setting up Apache Tomcat

Apache Tomcat provides us with a web server that can run Java based applications, distributed through WAR file.

Before we install the WAR file we should setup a new user on our Raspberry Pi. Tomcat will then run under this user, and we can lock down the user so it can only perform certain tasks.

To add a user run the following command from the RPi shell:

useradd controller
passwd <password>

This will create a new user on the system. Under the home directory you will see a list of the user on your RPi. New directories can be added here using the mkdir command. You should create a home directory for your new user controller

mkdir controller

Ownership of the directory can be changed using the chown command, for example:

chown controller:users /home/controller

Now we have a user who will be used for running our controller code and servers under.

Our next step is to install Java on the Raspberry Pi.

Installing Java

We will start by installing the latest version of Java onto our Raspberry Pi. The first command we should run is to remove the existing version installed. Keeping your version of Java up-to-date is important as security patches are released that address underlying security flaws.

To remove your existing Java version run the following from the command line:

sudo apt-get purge openjdk*

Once this is complete we can run the following commands to install Java

 sudo apt-get update
 sudo apt-get install openjdk-7-jdk

In the above command we have installed the Java Development Kit version 7. You should install the latest version, a list can be found at the following URL:

Once you have installed Java run the clean up command:

sudo apt-get clean

You now have the latest version of Java running on your Raspberry Pi. If you need a basic guide to the language you can read IBM’s introduction guide:

Installing Tomcat

We now need to install the Tomcat web server onto the Raspberry Pi. You can read more on Tomcat at the Apache Tomcat website at the link below:

Let’s start by downloading the tar.gz for the web server.

From the command line on your RPi run the following command, make sure you are located in the controller directory under /home:


As with installing Java you should replace the version number above with the latest version.

Once wget has finished running you should be find a .tar.gz file located in the controller directory.

We can untar/unzip the file as follows:

tar xzf apache-tomcat-7.0.39.tar.gz

Now change directory into the conf folder located in the new apache tomcat folder created when untar/unzipping

cd apache-tomcat-7.0.39/conf

We can now add our controller user to the configuration so they can start and stop the server.

Open the tomcat-users.xml and add the following:

<user username="controller" password="raspberry" roles="manager-gui"/>

Save the file. We can now test that Tomcat runs.

Navigate to the bin directory e.g.

cd ../bin

then run

sudo sh

This will start your Tomcat server.

Tomcat by default runs on port 8080 of the localhost. In the next post we will take a look at the management console and explain how it works and look at further configuration of our Tomcat server.

Just a quick update.

1.) Exams are done, so plenty of time to work on various projects.

2.) In the coming weeks I’ll be doing an interview with Marco of Open Home Automation.

3.) Wrapping up the controller module on the Raspberry Pi

4.) Completing the Ethernet and wireless thermostats

5.) A review of the Mint robot sweeper

6.) A closer look at Nest

7.) Baseboard heaters and wireless thermostats

8.) HPC with the Raspberry Pi


Raspbmc Upgrade

For those of you who have been using Raspbmc you will be aware that was an update on the 22nd of Feb.

A lot of people seem to have had problems with the update starting, then hanging with a screen that says:

“Relax CMBG will restart shortly”

I have attached a screen shot of this below:




I fixed the problem using the following steps.

Note you will need to also download any 3rd party plugins again or copy the zip files if your Raspberry Pi if you still have them on there.

Start by backing up your Raspbmc settings. You can do this by shelling into your Raspberry Pi and taring the settings.

tar -czf xbmc-backup.tar.gz .xbmc

Copy the tar file to another machine. For example you can open a fresh shell into the Raspberry Pi and secure copy (scp) the file to your local machine

scp <user>@<ip address>:/path/to/backup .

Next head over to the Raspbmc website’s download page.

You can find the instructions here to re-install Raspbmc.

Once the instillation is complete, copy your tar file containing the settings back up to the Raspberry  Pi.

Running the following command will then untar the settings and re-load them.

sudo initctl stop xbmc && tar -xzf xbmc-backup.tar.gz && sudo initctl start xbmc

Finally you will need to setup your 3rd party plugins again.

Raspbmc book

Sam Nazarko the creator of Raspbmc also has a book out on the subject, you can check it out on the Packt Publishing website.

I slightly belated happy Birthday to the Raspberry Pi, which turned one year old on Feb the 29th.

You can read more over at the Raspberry Pi foundations website:




Get every new post delivered to your Inbox.

Join 25 other followers