I bought a Google Nexus 4 mobile phone. It is a high specification phone at a very good price, especially when purchased in full without a contract, compared with the long term costs of the in-contract price.

The most frustrating thing about the Nexus was actually getting hold of one as due to low stock and high demand it was a couple of months before I was able to place an order. Unfortunately that’s still the case for some of the accessories including the wireless charger which is still not available in the UK. The Nexus 4 uses QI which is a standard for inductive chargers. I found several expensive chargers before I settled on this charger from Clever Gadgets (Amazon marketplace). The title says GMYLE, but the one I received was branded as a PowerQI wireless QI charger. This appears to be in a similar way that other items such as Media centre remote control for the Raspberry Pi which appears to be the same product available under different names through different suppliers.

The wireless charging plate is a little bigger than the Nexus 4 (which is a large smartphone). One of the reviews (also from Clever Gadgets) says it came with a UK adapter to a non-UK plug, but when I bought mine it came with a standard UK transformer plug with no adapter needed. Positioning the phone is fairly straight forward (just above the writing). The phone lays flat which means you can’t easily see the screen unless very close to the phone, but at least it means that the phone is not likely to fall off the chargers. The phone gives an audible beep when the phone is put onto the charger. It can repeat the beeps if the phone position is borderline.

I haven’t done any tests on charging time, but I believe that the charge time is quite a bit longer than through a plug-in charger. As it’s so convenient to put down the phone it spends more time on charge and so is generally not an issue.

As it is designed to work with the QI standard it will work with a few different models of mobile phones and is likely to work with more in future. You can also buy QI wireless charging shields for some other phones, but are almost as expensive as the charger.

This is a reasonable charger and is a good price for a wireless charger.

I have tried three different remote controls on my Linux XBMC and Raspberry Pi RaspBMC / OpenElec media centres. All of these worked well, but each have their own pros and cons.

These are all three generic remote controls and are available from different suppliers with different names, I have used the manufacturer names under which I purchased them from Amazon.co.uk, but these may be listed from other suppliers as Vista MCE Remote, or Windows XP / Windows 7 media centre remote controls.

These all include a USB infra-red (IR) sensor.

Another remote that I haven’t tried is an X-Box remote control. One thing to be aware of is that xbox remote controls are supplied without IR sensors, which will need to be purchased separately.

I tested these using the mouse control and the cursor / back buttons with XBMC on both the Raspberry Pi and a Linux based media centre. I was looking for ease of use with the remote control as well as it’s effective range. I only used the primary controls and some of the function keys may need to be mapped within XBMC.

PC remote – Cheapest and smallest media centre remote control

This remote control is the cheapest I have seen. It is considerably smaller and cheaper than the other remote controls. It is a little larger than a credit card and about as thick as most smartphones, a similar size to remote controls used for in-car DVD players etc. It uses a button style battery.

The USB IR sensor is provided with an extending (rewind) cable, which would be convenient if used for travelling or for use in a car entertainment system, but which is bulky and difficult to position / hide for in-home entertainment systems. The remote control has to be fairly accurately lined up with the sensor for it to work correctly. There is also a more limited range on the remote than the others tested.

The mouse control is a track pad to one side of the remote and is reasonably easy to use. The cursor keys are around a square area. These are fairly easy to see in good light, but not obvious in a dimly lit room. The volume control is clearly marked in blue and the backspace button is directly above which makes it fairly easy to find.

This would be a good remote for use in an in-car entertainment system or for travelling. It is also considerably cheaper than the others, but I think it’s worth spending the extra if looking for a remote for a lounge or bedroom media centre.

Trixes – Alternative media remote control

The second remote fits in at the middle of the price range of these tried (although all three could still be considered at the budget price). It is the size of a standard remote control, but has a budget look and feel to it.

The mouse control is well placed and easy to use. The cursor keys are within a cross shape towards the button of the remote, but with some more buttons above and below and so are not as obvious as the other remote controls tested. The backspace button is not an obvious location (although similar position in relation to the cursor keys as the PC remote it is much easier to find on the PC remote due to the position and colour of the volume keys). The button positioning is something that you can get used to over time, but is not the easiest to navigate around the buttons.

The IR sensor supplied is the best of the three remote controls. Although the sensor itself is bigger than the GMYLE infra-red sensor it is black and so looks better stuck to the side of most TVs than the smaller one.

The remote works well and doesn’t need to be pointed as accurately as the PC remote.

GMYLE – Preferred media remote control

The final remote control is the most expensive of those tested, although still only about £4 more than the Trixes remote control. It is the size of a standard remote with a curved side that makes it feel comfortable in the hand. The buttons are all well positioned and intuitive to find. There is a 4-way cursor button above the soft touch mouse. The mouse buttons are above the mouse pad, which is the opposite to most laptop trackpads but which comes quite naturally.

The IR sensor is the smallest of those tested, but is all coloured red which makes it stand out against a black TV outline and does not look as professional as the others. The remote does not need to be pointed at the sensor too accurately and works from a good distance away.

Whilst this remote is still a budget remote and feels like one it is the best feel and looks of all these remote controls.

Summary

My favourite remote is the GMYLE remote. It works well, looks good and makes it easier to find all the buttons.

The PC remote has it’s own advantages due to it’s small size which makes it good for travelling or in car entertainment, but is not recommended for use in the home.

The Trixes remote control fits well price wise and is the best price for a full-size remote control. I would however recommend spending that little bit extra for the GYME remote control.

I recently upgraded the blog import function on my website. This imports the blog posts from WordPress and updates the news section of the PenguinTutor site.

I’ve now redesigned to the menu for the PenguinTutor website. This is to make the website more relevant and easy to find the appropriate content.

The following have been renamed / relocated:

Tutorials >> Learn Linux
Electronics >> Learn Electronics
Raspberry Pi (new section)
Certification >> LPI certification
Software projects >> Projects

I hope to add more project based activities in future.

Connecting the Raspberry Pi to an analogue vga monitor

The Raspberry Pi uses a HDMI output for its video. Ideally this should be connected to a monitor or TV with HDMI input or DVI input (the DVI monitor connection is electrically compatible with HDMI so it just needs the appropriate cable to change the connector type). Unfortunately many of us still have monitors with only VGA connectors, and in fact many cheaper monitors are still sold with only VGA. It is npt possible to connect HDMI direct to a VGA only monitor as the signal needs to be converted from a digital signal to an analogue signal. Fortunately there are converters available and here are two of the ones that I’ve got to work successfully with the Raspberry Pi. Some are expensive, but these are ones that I’ve been able to buy for about £15 or less.

Please ensure that the one you buy is listed as a converter, active converter or “with chip”, and is not just a cable that changes the connector type as some cheaper cables may be. It won’t work if it doesn’t have the required electronic chip to convert the signal from HDMI to VGA.

Neewer HDMI Input To VGA Adapter Converter For PC Laptop

This is the first one I bought which is described as a “Neewer HDMI Input To VGA Adapter Converter For PC Laptop”. I bought this from Amazon marketplace which works fine once connected.

This does not support audio from the HDMI port, so external speakers will also be required to connect to the onboard 3.5mm adapter.

HDMI TO VGA Cable Adapter for PC Laptop Power-Free, Raspberry Pi, MHL support

The second one I purchased also from Amazon.co.uk is HDMI TO VGA Cable Adapter for PC Laptop Power-Free, Raspberry Pi, MHL support. It is branded CAMAC. Looking at the title and description this sounds like this would be an even better one for the Raspberry Pi, but that is not the case. Whilst it does work well with the Raspberry Pi and may work directly with some monitors it is likely that some configuration changes are needed.

The file to edit is /boot/config.txt. If it’s not possible to edit this directly on the Raspberry Pi (as you can’t get video working until this is complete) then you can edit the file in another computer. The file is in partition which is about 56Mb formatted as a FAT partition accessible on any computer. Edit the file called config.txt

The following two lines need to be uncommented by removing the ‘#’ at the start of the line.

hdmi_force_hotplug=1
hdmi_drive=2

The Raspberry Pi should be able to work with most vga monitors. If it still doesn’t work then you may also need to look at the hdmi_safe and the hdmi_mode entries.

Again there is no audio support. There is another adapter made by the same manufacturer that has audio support built-in, but I haven’t tried that one with the Raspberry Pi.

Although this adapter states it is for the Raspberry Pi and sounds promising from the description the other adapter works better with other the Raspberry Pi.

One of the things I’ve been doing recently is a school project with my children using the Raspberry Pi. My daughter has written the program in Scratch, but I needed to find a way to get it to autoplay. This should have been fairly straight forward using an appropriate autostart file and Scratch presentation mode, except for the fact it was accessing the GPIO port. When you use Scratch with another programming language (in this case it’s Python to interface with the GPIO) then it provides a pop-up informing the user: Remote sensor connections enabled. Easy enough to click through if you have a mouse and monitor attached, but this project was designed to not use the mouse and even the monitor is optional. These are the steps required to allow Scratch to communicate with the GPIO, for Scratch to launch into autostart “presentation mode” and so that this all happens without any human interaction required.

Allow Scratch to communicate with the Raspberry Pi GPIO

Although Scratch is not aware of the GPIO ports on the Rasbperry Pi, it does have the ability to communicate with other programs. Therefore it is possible to have a python program that runs in the background that acts as an interface to the GPIO ports. There are a couple of sources that can help in this regard.

The Scratch Wiki has details of how Scratch can communicate with a Python application:
Scratch Wiki: Communicating between Scratch and Python.

Then there is a choice of two projects that provide the ability for python to talk to the Raspbery Pi GPIO. RPI:GPIO or WiringPi.

Fortunately cymplecy (simplesi) has already done the hardwork and provided step-by-step instructions on getting this installed:

Scratch GPIO install instructions.

Running Scratch as autostart in presentation mode

I needed Scratch to run in presentation mode which is their name for running the application in fullscreen mode. This achieved by using the presentation option on the scratch command, but we also need to start the scratch handler first.

If you are using the CympleCy we first need to run the following:
sudo ps aux | grep 'python.*scratch_gpio_handler.py' | grep -v grep | awk '{print $2}' | xargs sudo kill -9
sudo python /home/pi/simplesi_scratch_handler/scratch_gpio_handler.py &

The first line stops an existing handler if currently running, the second starts it up again. If running on startup (I’ll come to that later) then the first line isn’t required.

Then Scratch is started in presentation mode using the following:

scratch presentation /home/pi/Documents/Scratch/scratchApp.sb

Note that the default directory that Scratch uses is called “Scratch Projects”. Unfortunately the space make it complicated to add this to a script (it’s not as simple as just escaping the space as there are different places that it needs to be escaped in different ways”), so I instead put it into a different directory without a space in the name.

To make this easier this can be put into a single script

#!/bin/bash
sudo ps aux | grep 'python.*scratch_gpio_handler.py' | grep -v grep | awk '{print $2}' | xargs sudo kill -9
sudo python /home/pi/simplesi_scratch_handler/scratch_gpio_handler.py &
scratch presentation /home/pi/Scratch/scratchApp.sb


Then create autostart script

Created the directory (if it doesn’t already exist)
mkdir /home/pi/.config/autostart

Add a file ending with .desktop (eg scratchApp.desktop) with the following

[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
Exec=/home/pi/Scratch/scratchApp.sb
Icon=scratch
Terminal=false
Name=Program name
Comment=About the program
Categories=Application;Education;Development;
MimeType=application/x-scratch-project

This will then run whenever you login (ie. assuming GUI autostart and auto-login is enabled then whenever you boot the Raspberry Pi).

Dealing with the Remote sensor connections pop-up

We now have the program working in presentation mode, but as mentioned earlier there is a pop-up message “Remote sensor connections enabled” that stops it running until you have clicked OK. This is something that needs to be turned off within the Scratch application, which is one of the hidden settings within Scratch.

After lauching Scratch shift left-click on the R in the Scratch logo (top left) and choose “turn fill screen off”. Click on the white area to the right or bottom of the screen and choose “Open” and “Browser”. Navigate to the section Scratch-UI-Panes -> ScratchFrameMorph -> menu/button actions -> enableRemoteSensors and remove the line:

Dialogboxmorph Inform: 'Remote Sensor Connections Enabled' Localized

This can be seen in the screen shot below.

Then click with the centre mouse button (or Ctrl and left button) and choose Accept (s).

You can now remove the white space in Scratch by shift left click on the R in Scratch logo and choose Turn Fill screen on. Finally shift left click on the logo again and choose “save image for end-user”

A feature of the Raspberry Pi is that it uses very little power for a computer. Admittedly it takes a lot more power than a micro-controller (such as an Arduino), but it’s still low enough to consider running it from batteries.

I first did some testing with using a battery powered Raspberry Pi to help users on the Raspberry Pi forum, but I’ve since been looking at my own battery powered Raspberry Pi project.

The power for the Raspberry Pi needs to be around 5v. The normal supply voltage range for USB is from 4.75 to 5.25 which is the target voltage. It so happens that this is 4 times standard battery voltages for rechargeable batteries which are rated at 1.2v per battery. In the case of normal disposable batteries each battery is 1.5v, which gives a total of 6 volts which is over the allowed voltage. I haven’t tried exceeding the voltage, but a small amount should be OK; there is a TVS (transient voltage suppressor) diode at the input so as long as connecting through the micro-USB port then the worst case it should trip the input fuse. If providing power through the GPIO then you should look at adding a 1.3A fuse to provide the same protection. Another reason for only using rechargeable batteries is how quickly the batteries run flat…

I first tried running the Raspberry Pi using 4 x NiMh AA batteries each rated at 2100mAh (high capacity rechargeable batteries). This gives about 5.2v fully charged (note the initial voltage is higher than the rated voltage).

To test the running time the power was connected to the Pi through the GPIO (nothing else connected) and a crontab job running to record the uptime every minute. Voltage dropped to about 5v when powered up and slowly decreased over time. The Pi was still running when the voltage dropped to less than 4.25V – although I expect it would not have been able to power most USB devices before that point was reached. The Raspberry Pi ran on batteries for about 3 hours 30 minutes before it failed.

I then tried with Ethernet connection (still no monitor / keyboard – after all if you can power a monitor you probably have a better power source than AA batteries). I also added a cron job on another machine to probe the Pi at 1 minute intervals (simulate remote monitoring application). I measured the current this time which peaked at about 430mA, ran normally at between 360mA and 400mA.
The network connection remained active for about 2 hours 15 minutes and the Pi continued to work without networking for a further 25 minutes.

For my next test I used D-size batteries. I looked to get high capacity rechargeable batteries to aim for longest uptime. I bought some High capacity 5000mAh D-cell batteries from Maplin. These batteries have a good power to price ratio, but even so cost more than a Model A Raspberry Pi. There are even higher capacity batteries available, but they are considerably more expensive.

It’s worth noting that D-size batteries are much bigger and heavier than the other battery types. In this case the 5000mAh provided by the D-size batteries is more than the equivalent smaller C-size batteries, but that is not the case for all brands and types of batteries. So if size and weight are a requirement you may want to consider C-size instead.

I tested these by connecting the supply to the GPIO connector as before. This was done using an Adafruit cobbler (break-out connector) connected to a breadboard.

Whilst I previously stated it’s less likely you’d want to have a monitor connected when running on battery that’s exactly what I need for this particular project which is intended to work stand-alone, but with the option to connect to a monitor or TV. I therefore had the Raspberry Pi connected to a monitor via a HDMI powered HDMI to VGA convertor and standard wired keyboard and mouse. In this case I achieved an uptime of 5 hours.

If you are in a situation where you need to run off batteries then chances are going to be no Ethernet. With the model A the lack of Ethernet will save some power. I’m still waiting on my model A to arrive, but I will look at a comparison of how long the Model-A can operate.

Standard rechargeable batteries can be used for powering the Raspberry Pi. Obviously any additional peripherals will take more power from the batteries. If size and weight is an issue then AA batteries are available in reasonably high capacity for a relatively short period of time. Larger C or D batteries can be used to provide a longer running time, but with increased weight and size. If a longer run-time is required then it will need bigger or more specialist batteries.

See the guides and blog posts relating to the Raspberry Pi. Also see the Linux Tutorials for more information on using Linux.

–

Update:

My model A Rasberry Pi has now arrived and the uptime running on batteries is much better than the model B.
I’ve not done a proper scientific comparison as I needed to test it in the project. So for the purpose of this test there was nothing connected to the HDMI port, but there was a USB powered MP3 player speaker connected to the USB port and the 3.5mm audio output. I also rebooted the Pi part way through the test as I needed to make some minor changes and test the startup script. Total uptime on a single charge was 21.5 hours, over 4 times longer than the model B.

As I said this is not a fair comparison, but it should be accurate enough for an approximate guide. I does show that the model A uses considerably less power than the model B.

During last year I entered into the PA Consulting Raspberry Pi competition. The aim to “Make the world a better place” using the Raspberry Pi computer. My entry was the Kidsafe family Internet filter proxy. I reached the final which was held last week. I had a great day meeting the staff at PA Consulting and a few familiar names, in particular Clive Beale from the Raspberry Pi Foundation.

I had already had the idea to create my own filter to protect my own children on the Internet and to protect my own bank balance from App purchases. I decided this needed to be a dedicated server so that it could filter traffic from my daughters tablet as well as PCs but the cost of a dedicated PC (in terms of always on power as well as purchase price) would have been high. With the availability of a low cost, low power computer in the form of the Raspberry Pi I decided that this could be a viable solution. This was something I was considering when I first heard about the competition and so was a good fit.

I had an initial version working quite quickly, but after initial testing decided that the technique used was too limited. I therefore started again using a more sophisticated back-end and a much more ambitious design. I realised that this was going to be difficult to meet the timescales of the competition I’d entered it in, but had the initial release and introductory video created just in time for the closing date for the competition. I then continued to work on the project, fixing some critical bugs and managing to get the dashboard in the week prior to the final.

On the day of the final I setup a demonstration environment (using two additional Pis as webservers) and gave a 5 minute demonstration to the judges. The biggest challenge on the day was how to explain several months worth of work into a 5 minute demonstration. There were some difficult questions from the judges which certainly got me thinking and I am going to incorporate some of those ideas into a future version. Essentially whilst I’ve been thinking about ways to make the proxy easier to install and ensuring that you don’t have to install anything on the clients, I think I also need to look at ways of making the clients easier to configure. Perhaps this could be achieved using a client side configuration app which would be optional so as not to require anything to be installed on the client (although perhaps a challenge getting it on a IPad due to the app store requirements).

Whilst the rest of the judging was going on we had a tour of some of the facilities at PA Consulting. The engineering section was fascinating, it would be many a hobbyists dream to have access to some of the machines they had including a colour 3D printer and a Stereo-lithography machine.

I also got a chance to look around some of the school entries which is more about what the Raspberry Pi is all about. They had clearly put a lot of time and effort into the projects. One thing that was evident was that most of these were entries from private schools and was mentioned in a blog post from Rory Cellan-Jones (Technology correspondent for the BBC and one of the Judges) The life of Pi – clever ideas with a tiny computer. One thing I will say is that there had clearly been a huge amount of time and effort gone into the projects that made it to the final which may have restricted the number of schools.

I later spoke with Clive Beale whose job, as Director of Educational Development for the Raspberry Pi Foundation, is to look at ways that children from all walks of life can get involved in programming computers. I’ve already started to teach my daughter Scratch and was interested in ways that I and others like me could be involved. After talking to Clive I’m now looking at applying to become a STEM Ambassador and hopefully passing some of this on to other children.

At the end the winners were announced and unfortunately my project didn’t win, although I did get a Raspberry Pi and case as a runner up prize (my 6th Raspberry Pi). There were some great projects and a great deal of credit goes to the winners. I had a great time at the competition. I still think it’s early days for the Raspberry Pi at the moment, but now appreciate even more what the aims of the foundation are and hopefully in the future I can help in some way with getting children excited about technology and learning computer science.

PA Consulting – Raspberry Pi Competition Winners

Congratulations to the Raspberry Pi foundation as the Pi is now 1 Year old today! The $25 (or $32 for the model B) computer that has been a run-away success.

I’m celebrating by ordering my 5th one exactly a year after my first. Hopefully delivery should be a lot quicker this time – ETA 1 week rather than several months.

What a great success story – now over 1 Million sold, most running Linux – it’s a great way of people learning about Linux and hopefully about the philosophy behind the open source operating system.

Whilst, like me, many are adults enjoying the Pi as it allows them to create projects that were too expensive / too difficult to achieve before, the main aim is educating children. My 7 year old daughter has her own Pi (included in the 5) and my 5 year old son will be getting one soon (with lots of hand holding).

I’ve created some Pi projects already, am teaching my daughter to program with Scratch, been a technical reviewer for a book, I’m entered into a competition (more about that in the next few weeks) and have some more plans for the future. Whilst some of these I may have done eventually it’s the Raspberry Pi and the great community that has gathered around it that has given me the motivation to get so involved.

These are still very early days and it’s when the Raspberry Pis start to get into the classroom that the educational side is going to really take off. It’s going to be an interesting second year.

• More information on the Raspberry Pi

I’ve reviewed a number of Linux books through my website, but this was a review of a completely different kind. During the latter half of last year I’ve been spending some of my spare time as the Technical Reviewer for a book on the Raspberry Pi.

One thing I’d like to do in the future is to write my own book. I enjoy writing and have a good grasp of the technical skills, but I’ve been trying to improve my writing skills. This was one of the reasons I first started blogging nearly 8 years ago. So when Apress approached me earlier in the year I jumped at the chance to be involved in a book as a way of understanding a little more about the steps involved in getting a book published and as another way of establishing my own “brand” (inspired by the book Career Warfare).

I can’t really take much credit for the book as I only had a tiny part compared with the work that the two authors have put in, but it is good to know that I’ve had some part into putting it together. Being a technical reviewer involved reading through each chapter, following the instructions on the Raspberry Pi and commenting on any potential issues.

For obvious reasons I’m not going to post a review of the book, but as a quick summary the book is about learning Linux using the Raspberry Pi. It covers various Linux topics from the basics of getting started, the way Linux works and how to administer the Pi remotely. There are also some fun projects including creating your own web server and using the Raspberry Pi as a media centre.

There are other books available on the Raspberry Pi, although I’ve not seen any to actually compare.

You can buy the hardcopy book from the usual book shops (including Amazon), but as someone frustrated by DRM in ebooks (having multiple devices with different operating systems) if you are looking for an ebook then I suggest buying direct from the publisher where the ebook is DRM free.

Learn Raspberry Pi with Linux – from Apress

Yesterday I had my first proper attempt at teaching my 7 year old daughter programming.

This is done using the Raspberry Pi with Scratch and the Official Raspberry Pi Programming Manual produced by Computing at Schools.

Biggest problem we found was that due to the bedroom TV being wall mounted it was at the wrong height / position for working on as a computer screen. Will need to work on a proper solution in future, but managed for now creating a temporary table and pointing the TV down.

First I updated the SD card to a dual-boot option using BerryBoot so that we didn’t have to swap out SD cards from the XBMC media player she’s been using the Raspberry Pi for so far (more on BerryBoot in future as it’s quite useful).

We only had a small time to work through the programming, but then it’s perhaps better done in small regular chunks rather than trying to teach it all at once. So far we got the Scratch cat to say “Hello World” and change the amount of time it’s displayed for.

She was enthusiastic about it, enjoyed what we did and is looking forward to our next session. She’s even trying to think about what games she may be able to create thinking about the features in the games she plays on her Android tablet.

For me it was a different experience to what I’m used to. As with many parents I have helped my daughter to learn new skills and help with school work, but not structured teaching in the same way as I’m trying to with using the Raspberry Pi Manual. I’ve also provided training to adults and children in a more structured environment (work and volunteer related). Teaching your own child using this manner is something different. Perhaps it’s because I’ve already introduced her to Scratch running on a Linux laptop (whilst waiting for my first Pi to arrive and before the educational manual was available), but the hardest thing so far is trying to keep on-topic.

We’re both looking forward to the next session which is certainly a good sign.

Check back in future to see how it goes – or follow my updates on Facebook, Twitter or Google+

Guides and blog posts on the Raspberry Pi