It looks a little like a Microsoft Kinect - a single bar with two embedded cameras. The camera resolution is 720p on each lens.

It clips on easily to a phone via a padded screw clamp. You need to install a dedicate 3D camera app in order to make it work. In the box you get the camera, two USB-OTG cables, a tripod and clamp, and a carrying pouch.

Let's take it for a spin!

Sample shots

Video

As you can see, the 3D effect is prominent.

Video quality is 2560x720. Framerate is variable depending on how fast your phone is. My Nexus 6 managed just 16fps, my S6 got to the slightly better 25fps.

Because the cameras are independent, their exposure and white balance aren't linked. This also means that occasionally one camera may drop a frame or exhibit tearing - while the other side remains unaffected.

The cameras work best in bright light. Too much motion and the JPEG encoding can't keep up. You can stream raw YUYV video off the device - but you need to either lower the framerate or resolution if you want the USB bandwidth to be sufficient.

Audio is aac, 44100 Hz, mono, fltp, 67 kb/s You don't get stereo sound, which is a little bit of a disappointment. There are no microphones in the unit - audio comes from your phone's mic. I've removed the audio from the above videos

3D metadata isn't embedded - this is needed for sites like YouTube to recognise them as 3D videos.

TV Playback

I uploaded a sample video to YouTube - which has native 3D support. I was able to stream the video to my smart TV and watch it using 3D glasses.

Photo

The Svpro app doesn't let you take photos! A bizarre omission. I cheated and used the phone's screenshot tool to capture these. Click for full size.

App

Android doesn't natively support external cameras - so you need to download the Svpro app. It's basic - you can record video and play video. That's it!

No photo capabilities, no resolution or quality settings, no framerate control, no video editing or upload to YouTube.

Worse, the app in the Google Play Store doesn't support Android 7.0 - you need to download it directly from http://www.svpro.cc/app/.

I found that the app would not keep the screen on while I was recording. You may need to adjust your phone's display settings if you want to keep the screen active.

On the positive side, it doesn't ask for crazy permissions - although you will need to grant it USB access.

There are other apps on the play store which you can use, which show how good the Svpro app could be. For example, this is USB Dual Camera:

That's not a perfect app, but it gives you an idea of the potential.

The Svpro app also seems quite slow - which sometimes leads to disappointing video results.

Raspberry Pi Linux support

Although this camera isn't advertised as working on Linux, it is a USB camera - and it works brilliantly!

Running lsusb gives us:

Bus 001 Device 004: ID 1a40:0101 Terminus Technology Inc. 4-Port HUB
Bus 001 Device 005: ID 0ac8:9902 Z-Star Microelectronics Corp.
Bus 001 Device 006: ID 0ac8:9901 Z-Star Microelectronics Corp.

So this is a USB hub with two cameras attached to it! It shows up as /dev/video0 and /dev/video1 - and both cameras work perfectly!

It supports YUV 4:2:2 (YUYV) and MJPG for video capture and, pleasingly, each camera is 1280*720 native. No interpolation!

The Raspberry Pi website has a quick tutorial on capturing images.

You can capture the MJPG directly from the camera. This is the quickest and most efficient way to get 25fps video out of the device - although the filesize is rather large (5MB per second).

avconv -f video4linux2 -input_format mjpeg -i /dev/video0 -t 00:00:05 -c:v copy output.mkv

That will only capture from one of the twin cameras. How do we get both? Here's a lazy way to capture dual USB cameras simultaneously.

avconv -f video4linux2 -input_format mjpeg -i /dev/video0 -t 00:00:05 -c:v copy outputL.mkv & avconv -f video4linux2 -input_format mjpeg -i /dev/video1 -t 00:00:05 -c:v copy outputR.mkv

That worked on my Pi 2 Model B - I'll write a blog post soon explaining other ways to do this.

Technology

At the start of the decade, my mate Ket was building his own 3D cameras. Literally two cameras wired together and mounted next to each other.

It's incredible to think how quickly technology has progressed. For £65 you get a lightweight (50g) and tiny (92mm * 20mm * 20mm) camera pairing. The distance between the cameras is almost identical to the distance between my pupils. The view angle on each lens is 100°. Perfect for stereoscopic viewing.

But pushing all that video over a USB cable is tough. A more practical design may be to place the video processing within the unit - rather than relying on the USB bandwidth and phone speed being sufficient.

Downsides

There are a few little niggles with the Svpro.

• For phones, it is Android only. At the moment the USB OTG functionality only works with Android. So you iPhone users are out of luck.
• Dedicated Android app needed. An app like this needs to be polished, professional, and a joy to use. It isn't.
• 720p is fine for a cheap camera - and matches the resolution of most 3D displays - but a bigger resolution would be welcome.
• Framerate should be higher - although this is partially a limitation of the speed of the USB transfer and of your phone.
• No binaural sound. Audio is recorded from your phone's microphone, so there's no stereo effect.

Those are minor problems. The only other issue I found was that on some devices, it would capture BGR video - the red and blue channels swapped around. Which gave this weird effect: No idea why - I reported it to Svpro and they're looking into it.

To correct it using Linux requires ffmpeg's filter colorchannelmixer

ffmpeg -i in.mp4 -vf colorchannelmixer=rr=0:rb=1:br=1:bb=0 -acodec copy out.mp4

Recording from the Pi didn't exhibit these problems.

Buy it

If you want to get started with a 3D VR Camera - for playback on a Google Cardboard or other VR headset - this is a pretty good device. The app is basic, but the video quality is satisfactory if your phone is fast enough. The 3D effect is perfect. It's also a handy way to add stereo-vision to a Raspberry Pi robotics project.

• The 3D camera is available on Amazon UK for £65.
• You can also get it direct from the manufacturer for around $80.

Most of our domestic energy use is in the evening. So, when I'm out at work I can schedule the tumble dryer, robot vacuum cleaner, and WiFi rice-cooker to consume energy when the sun is shining. The rest is sold back into the grid for my neighbours to use.

Wouldn't it be great to capture that energy and use it to power my lights and games console in the evening? Yes! Enter the Maslow - a 2kWh wall mounted battery designed to capture solar power and put it to use when it is most needed.

The Maslow gobbles up the surplus power and stores it for later use.

I received a subsidised Maslow battery as part of Project ERIC.

Project ERIC (Energy Resources for Integrated Communities) is an initiative bringing solar PV power and smart energy storage to up to 100 homes in Rose Hill, East Oxford. Project ERIC is led by Moixa Technology and Bioregional and is part-funded by Innovate UK.

Installation

It's a relatively svelte box - smaller than a normal domestic boiler - and fits neatly onto my interior wall.

Here it is before installation and without any batteries.

As you can see, the batteries are designed to be replaceable. If they die unexpectedly, or technology leaps ahead, you should be able to keep your existing installation and just swap out the cells for something newer.

A couple of screws - and a bit of swearing - and it was fitted.

Installation took around 3 hours. The battery needs its own RCD in your consumer unit. A few holes had to be drilled in order to get all the wiring hidden away.

The fans on the side run when the batteries are charging or discharging. They're a little louder than a typical PC - and will be easily drowned out by a boiling kettle or rumbling tumble-dryer. You probably wouldn't want this installed in a bedroom or living room - but it's fine for a kitchen or loft.

They're needed for cooling these chunky capacitors.

Down in the bottom of the unit, you'll find the fairly unremarkable control circuitry.

Wait... wait a moment! Is that...? OMG! This thing is RASPBERRY PI POWERED!

Wooo! I think this is the 5th Pi I have controlling something in my home ?

There's a WiFi antenna which runs to the outside of the unit. You can also connect directly to the Pi's Ethernet port if you don't have a strong WiFi signal.

Hidden behind a panel is a full range of blinkenlights.

A mini-USB port is present for debugging purposes, along with some diagnostic LEDs. Apparently there's also Zigbee for controlling smart appliances in the future.

Network and API

As part of the Project ERIC trial, I've agreed to have my battery's energy usage monitored.

The Maslow collects details of usage every minute, these data are then combined to provide an overview of what our village is consuming and producing:

I also get access to a personalised dashboard - which will hopefully show more details soon!

There's nothing really to control on the battery - it just sits there doing its job. There is an API, more details in a future blog post!

Cost

Because I'm on a trial of this hardware, the total cost of the Maslow battery and installation was £600 (including VAT@ 20%).

What do you get for that?

A typical mobile phone battery holds around 0.015kWh. My electric car has a battery capacity of 19kWh. My house's idle usage overnight (lights, chargers, servers, devices on standby) is around 100 Watts. So a typical night (2200 - 0600) will use around 1kWh.

My electricity costs me 13.08p / kWh - sign up to Ovo Energy and we both get a £25 Amazon voucher.

So, assuming the battery is fully charged once during the day and then fully discharged overnight, how long before the device pays for itself?

£600 / (£0.1308 * 2) ~= 2,300 days.

2,300 / 365 = 6 years 4 months.

At the unsubsidised price of £2,000 the repayment period is around 21 years. That's essentially the guaranteed lifetime of most solar-power systems. It also assumes that energy prices stay static.

Of course, the solar panels don't always generate enough - let alone enough surplus - to fill the battery:

Edent's Solar Panels

@Edent_Solar
Automated

Pretty grim. @edent's solar panels generated ~1.42kWh, earning £0.25
FAQ: shkspr.mobi/blog/solar-gra…
#edentSolar pic.x.com/92wikj4nuy

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There's no doubt the Maslow is an expensive "lifestyle" product. It's for saving the planet rather than fattening the wallet. Built in to the cost of a typical home it could be a real game-changer in how energy is used in this country.

As an aside, the UK Government pays me for every kWh the solar panels generate. They don't measure the actual amount I export. So the Maslow doesn't reduce the Feed In Tariff (FIT) payments.

Features

OK, other than offsetting my grid usage, what does this big ol' box do?

• Powering DC lighting. I decided not to go for this option. I already have energy efficient bulbs, so the extra cost for replacement didn't make sense for my needs.
• DC Power Circuitry. I've not yet installed this, but it should let me charge USB devices without needing to do a costly AC/DC conversion.
• Works during a power-cut. For safety reasons, the Maslow won't power normal household sockets during a power-cut, but it will allow you to use the aforementioned USB sockets and LED lighting. Handy in an emergency
• WiFi for monitoring usages. Which of course means…
• An API available for HACKING!

Alternatives

There are number of alternatives to this sort of technology.

• Divert to immersion heater. I currently have a Solar iBoost which heats up my water and reduces my gas usage.
• Build it yourself! If you have lots of spare batteries and are a qualified electrician.
• Car storage. At the moment, I've been using my electric car to store surplus electricity - but I'm not always at home during the day. I can't "reverse the polarity" and feed back from the car into the house.
• Tesla Powerwall - the elephant in the room!

Tesla battery has the cachet of the Tesla brand - but hasn't yet been released to the UK public. At around US$3,000 for a 7kWh model, the cost/power ratio is pretty good - but it is significantly larger in size to the Maslow.

The Tesla is only generally available in the USA, so it will be very interesting to see what their price is for the UK market. The Maslow is designed for typical UK use, which may be different from Tesla's focus - UK houses don't tend to have air conditioning, for example.

Final Thoughts

I've only just had the batteries installed - but it's obvious that the Maslow provides a vital way to reduce peak grid usage from domestic properties. Even if it is a little costly.

I'm delighted to be part of such an innovative trial - I'd love to see every home in the UK generating and storing their own energy.

It's a testament to the success of the Raspberry Pi. Anyone with £30 to spare can pick one up and start hacking. Want to build an IoT fishtank? Start with a Pi. Need to monitor air pollution? Start with a Pi. Have a vague idea...? You get the picture.

The only problem with the Pi is the age-old complaint about just how user-friendly the command-line is. I've spent a lot of time with kids and adults who are familiar with computers - but utterly stumped when it comes to the CLI. Trying to get an LED to illuminate when you press a button using Python can be an exercise in frustration. It just doesn't match the mental models that people have on how computers should work.

Programming a Pi for IoT tasks should be as simple as coding a game in Scratch. A visual, drag-and-drop interface with instant feedback.

That's where Cayenne comes in handy. It's a free app which you can install on your Pi in about 5 minutes. If you install their mobile app, your phone will automatically find the Pi (if you're on the same WiFi network) and you can configure it directly. Cayenne offers five main areas of functionality.

A GUI for your GPIO

Once set up, you get this delightful web interface which will allow you to assign and monitor your GPIO pins. A couple of clicks and you're all set. No Python to mess with or external libraries to load.

It also means connecting up sensors and output devices becomes a breeze. Wire them in, tell Cayenne what and where they are. Done.

Which means...

Dashboard All The Things!

You instantly get a dashboard showing your Pi, its stats, and all its sensors.

It's a beautiful HTML5 representation of everything going on in your device - and it allows you to...

IFTTT For Your Pi

Even if you're already an accomplished programmer - sometimes it's just easier to do things in a visual manner. The If-This-Than-That style of webservices has totally revolutionised how people make complex interactions. Cayenne finally makes it simple to get started with IoT on Pi. If the light is shining, turn on the fan.

Scheduling

This is a brand new feature - and a most welcome one. Anyone who has accidentally typed
crontab -d rather than crontab -e will know just how frustrating it is to manage scheduled tasks on the Pi!

Cayenne will give you a simple, graphical way to turn your home into a smart-home. Once you've connected devices, you can schedule actions to happen as and when you need them. Set security cameras to come on at specific times, start your slow-cooker as you come home from work, or get the lights to switch off after you leave for work.

Phone Access

And, everything is accessible over your phone! You can monitor, configure, and adjust your Pi via your iPhone - with Android coming soon.

Get Cayenne

The Cayenne software is free - although you will need to register an account with them first. There's a comprehensive set of documentation and several introductory videos if you want to explore all the power it provides.

There's an active developer community, and the team behind the project are keen to find out how they can improve the app.

Right, I'm off to track down my missing Pi and put it to work!

Terence Eden is on Mastodon

@edent

If you hurry down to WHSmith in Oxford, there are still a few @TheMagP1 copies left.

---

Terence Eden is on Mastodon

@edent

Replying to @edentIn related news, @summerbeth is the best wife of them all!
#PiZero pic.x.com/utsf2m13jo

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Ok, so what can I do with a wafer-thin Linux box? I had thought of turning it into a simple door sensor, or perhaps wiring it in to a lightswitch, or swallowing it to see if I would get super powers. Then it struck me - turn it into a games console!

Now, don't get me wrong, this has been done many times before - but I think I've come up with a unique twist. Build it directly into the controller!

My original plan was to buy some USB NES controllers - they're about the right size, but with only two buttons I'd be restricted to playing, well, old NES games. Also, buying new plastic stuff... nah! Reduce, Reuse, Recycle!

Long term readers will remember that I turned my original Xbox into a Linux running media centre. I still have the original (giant) controllers, my brilliant wife suggested that there was probably enough space in one to fit the Pi Zero.

Terence Eden is on Mastodon

@edent

Replying to @edentIt's probably too late to start soldering, isn't it? x.com/edent/status/6…

Terence Eden is on Mastodon

@edent

Replying to @MrPJEvansOoh! The #PiZero just about squeezes inside a gutted original Xbox controller.

Inspired by @MrPJEvans pic.x.com/vlesbizfgg

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Terence Eden is on Mastodon

@edent

Replying to @edentRight, time to load an OS into my games controller ☺ pic.x.com/xqyup3i3dm

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Let's Go!

Getting Started

WARNING! Playing around with electric items can be dangerous. You risk damaging yourself or, worse, breaking your toys. Proceed with caution.

Equipment

1. Raspberry Pi Zero (£5).
2. Original large-sized Xbox Controller (£variable).
3. USB OTG cable (65p).
4. 2A USB power supply (£5).
5. Mini HDMI adapter (80p) or Mini HDMI cable (£5).
6. MicroSD card (£5).
7. The usual assortment of screwdrivers, knives, wire-strippers, and nerves of steel!

Right, remember this big brute?

The Pi nestles neatly between the triggers, so it should fit.

Open it up:

I removed the chunky memory card holder. I left in the physical slots as a wedge to hold the Pi.

After unscrewing all the cross-head screws, we can see how well it fits.

Nifty!

Ah, but can you spot the problem?

The Pi is blocking that strut. Only one thing to do...

The plastic was soft enough that a penknife made short work of this.

As you can see, the inside of the controller has lots of room.

In order to connect the controller to the Pi, we need to do some wire stripping. The Xbox controller uses bog-standard USB wiring, but has a proprietary plug. So, chop the ends of that and wire it into a USB OTG cable.

I suppose I could have just wired in a regular USB plug, or bought an Xbox USB adapter. But where's the fun in that?

One thing to note, you'll need to insulate the bottom of the Pi against all the contacts on the controller. For this quick hack, I'm using some of the cardboard packaging. Not exactly sustainable from a long term POV! Nor is the BluTak used to hold everything into place.

So, the controller's cable loops back into itself and plugs into the Pi. The Pi takes in power and outputs over HDMI.

It would have been great if HDMI also supplied the power - but I don't think that's possible. There is enough space inside the controller for a USB battery pack should you want a more portable solution.

And... errr... that's it really!

Emulation

The good folks at RetroPie have a pre-built image which contains everything you need in order to run a variety of emulators. It even includes some built in shareware games.

We want the build for the Raspberry Pi version 1. It automagically detected the Xbox controller, and after a few clicks I was playing Doom!

Terence Eden is on Mastodon

@edent

OMG! I'VE ONLY GONE AND BLOODY DONE IT!
#PiZero hidden in an Xbox controller playing DOOM!
x.com/edent/status/6… pic.x.com/b9irxokxg7

Terence Eden is on Mastodon

@edent

Replying to @edentRight, time to load an OS into my games controller ☺ pic.x.com/xqyup3i3dm

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The Raspberry Pi Zero is, without exaggeration, a marvel.

When I was a kid, computers were unreasonably expensive. I remember reading this passage from The Demon Headmaster series of books:

I felt so angry that the computer revolution was restricted to those whose parents or schools could afford such luxuries. The Pi is (almost) cheap enough to give away with cornflakes. Sure, the sundry items cost a little bit more - but this puts powerful computers within the reach of everyone.

The size is also... It's almost too small! If you lose one in your home, it's probably cheaper to buy another than waste an hour looking for it. That also means it can sneak into unexpected places - I can see kids hiding these in games controllers, hair brushes, or flick knives. Add a battery pack and a mesh-networking module and you've got a communications infrastructure that a school cannot censor.

Interesting times ahead!

Update! Well, that went better than expected. You can read what people have to say about the project at:

• Hacker News
• Heise (German)
• der Standard (Geman)
• Make Magazine
• Geek Times (Russian)
• Hackaday
• LifeHacker
• Xatak (Spanish)
• IT Pro
• Wired

David Bower

@rddave

Mini-bot had great fun playing on @edent's hacked Xbox @Raspberry_Pi #PiZero with @LinuxUserMag #PiParty pic.x.com/zzmcfnsuew

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It's been ages since I did any real electronics. Most of my work involves software and pre-assembled bits of kit. I thought that it was time I reacquainted myself with the joys of electricity :-)

Because I'm fundamentally lazy, I purchased the all-in-one Raspberry Pi 2 kit from Vilros.

Lots of LEDs, some buttons, a nice case, all the cables, resistors, and all sorts of bits and bobs. Including a breadboard!

What's A Breadboard?

I remember - from school - that a breadboard is a.... thing... that lets you... electricity?

Honestly, it wasn't until I saw this diagram from Adafruit that it all finally clicked into place:

Aha!

The kit comes with a T-Shaped Cobbler which fits onto the breadboard and means you have a neatly labelled system with fewer wires running about the place.

I followed a sample tutorial on how to wire in an LED to be permanently on. Basically +3.3v → long leg of LED. Short leg of LED → 330Ω resistor → Ground.

Ok, that was easy. Now lets make it flash on command!

The wiring is fairly similar, but we use a controlable GPIO pin instead.

GPIO pin 21 → long leg of LED. Short leg of LED → 330Ω resistor → Ground.

Here's what it looks like:

And here's the Python code to switch it on, then off.

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
led = 21
GPIO.setup(led, GPIO.OUT)
# Switch on
GPIO.output(led, 1)
# Switch off
GPIO.output(led, 0)

Wooo!

Ok, so, next thing - how to get information in to the Pi?

I was confused about exactly how the push switch worked - why were their four pins?

I read the O'Reilly Raspbery Pi Tutorial and became enlightened.

So, lets create a thingumy which lights up an LED when a button is pressed.

The LED will be the same as the above. The button will be wired as: GPIO pin 19 → Button A. Button B → Ground.

And the code is:

import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)

# Pin 19 will sense for button pushing
button = 19
GPIO.setup(button, GPIO.IN, pull_up_down=GPIO.PUD_UP)

# The LED
led = 21
GPIO.setup(led, GPIO.OUT)

while True:
    input_state = GPIO.input(button) # Sense the button
    if input_state == False:
        print('Button Pressed')
        time.sleep(0.2)
        # Switch on LED
        GPIO.output(led, 1)
    else :
        # Switch off LED
        GPIO.output(led, 0)

I'm not entirely sure why if input_state == False: is the logic for the button being pressed. Seems like it ought to be True, no? Anyway, there's a long discussion about all the ways sensors can be read on the raspberry-gpio-python pages.

Well, there you have it. An utterly simple guide to getting started. I just hope future-me finds this useful!

So, I plugged it into my Raspberry Pi, loaded up the Scratch programming environment, and created a fruit and veg interface. See for yourself!

The scripts themselves are very simple. The MakeyMakey in its default state, acts like a USB keyboard - so it will send up, down, left, right, and the space key. So, it's really easy to use with Scratch's "Key ___ Pressed" sensor.

Download Scratch from MIT (available for Linux, Windows, Mac).

You can grab yourself a Raspberry Pi on Amazon

You can buy a MakeyMakey from Amazon for around £40

You can buy bananas and spring onions from any reputable green-grocer. Be sure to ask if they're electrically conductive.

Thanks to the OpenRightsGroup for sending me the MakeyMakey.

All this has happened before...

We started with mainframes on which we had to time-slice. Then we got powerful personal computers. Now we're back to spooling up instances of cloud computers.

...and all this will happen again

We used to have individual websites. Upon which we ran whatever services we wanted - mail, FTP, finger, anything.

Where are we now? We run these services - or similar - on mainframes. Whether it's Facebook, MySpace, Instagram, or Path - we're back to storing all our data and connections with 3rd parties.

Into The Future With Confidence!

At the moment we're stuck in an era of restricted data portability. Theoretically we can extract our data from Twitter et al - but we're totally at the mercy of those who run the services.

Compare Twitter to Email. If Twitter goes down - that's it. Game over. No more Twitter. All those connections lost in the wind.

If Google decided to shut down Gmail, it would be a blow - but email would continue working.

We need to be using protocols - not services. The reason email, http, ftp, can't be switched off is that anyone can use them for any purpose. They are not at the whim of any owner.

This is the future.

• A LAMP stack running...
• ...Federated Services...
• ...based on open standards which can...
• ...communicate over mesh networks...
• ...protected and authenticated by strong cryptography
• All running on hackable hardware.

Most of those requirements can run happily on an Android phone right now.

I'm enjoying playing with my Raspberry Pi - but I also have an eye on these "<a href="https://web.archive.org/web/20121026041709/http://www.chinavasion.com/china/wholesale/Home_Audio_Video/Digital_TV/Android_4.0_Mini_PC_-_Android_Media_Player_Internet_TV_1.0_Ghz_CPU_1080p_Playback_4GB_Built-in_Memory/>Android on a stick" system. Thinking Thumb Drives. Ready and waiting to do our bidding....

This is loosely based on The Byte Brothers Go to a Getaway, by Lois and Floyd McCoy. My well-thumbed copy was printed in 1984. I'm not sure when I got it, but I remember being around 8 or 9 when I first started writing programs in BASIC. Sadly, BASIC is as outdated as the Lascaux Cave Paintings, so I've written this in more friendly Python.

My hope is that people will write a bunch of interesting mystery stories (using these characters or their own) release them as Creative Commons, then we can put out a book AND SAVE THE WORLD!

Ahem...

Without further ado, I present to you the first adventure of "The Python Pals"!
This work is licensed under a Creative Commons Attribution 2.0 UK: England & Wales License.

The Morse Code Mystery

The Beachcombers

The waves crashed angrily on the beach, and the rain seemed to come in from all directions. A sudden gust blew a thin drizzle straight down Poppy's collar. "This weather is foul," she spat. "Just five more minutes," yelled Penny.

Poppy collapsed herself until she was eye level with her friend Penny. Even though Penny was the shorter of the two, she was hunched down on the beach anxiously glancing at the shoreline.

"Penny, what are we doing here? It's cold, wet, and most importantly," she paused for dramatic effect, "We're going to miss the Food Network's 'Marzipan Marathon'!" Her friend giggled - neither of them could stand those TV cookery channels - but they had agreed there was something oddly compelling about watching a man trying to eat his body weight in cake. "There!" Yelled Penny, pointing a little way down the shoreline. "I told you that interesting stuff gets washed up here when there's a storm. Grab it!"

Penny was used to being bossed around by Poppy. Despite being the older of the two friends, she was always being treated like Poppy's younger sister - so she relished in the chance to bark orders at her.

Penny scooped up the large square of blue canvas a spun around. "Please can we go in now?" she whined, "It's cold and wet and..."

Before she could even finish her sentence, Poppy exclaimed "Look! Look at the cloth!"

They both stared at the raggedy square of canvas. It was peppered with strange white marks.

"Let's get home and work out what this is," said Poppy. With that, she snatched the cloth from Penny, and started sprinting away toward her parent's home.

"That just what I was about to say!" yelled Penny, as she slowly trudged up the beach.

Pi Power

"Will you be wanting some soup, girls?" asked Poppy's mum, Ada. She had gotten used to both of them storming in and expecting to be fed. "No time Ada, thanks," said Penny breathlessly, "We've got to work out what this is."

"Hmmm, looks like old fashioned Morse Code to me," said Ada after a moment's cursory examination of the cloth. "Where on Earth did you find..."

"Can we get some soup and croutons, and maybe some cheese. Do we have any crisps?" yelled Poppy as the girls bolted upstairs.

They flipped on the Raspberry Pi. It had been a birthday present from Poppy's dad. One of the few things she had left to remember him by. Just as Linux was quickly booting up, there was an enormous crack of thunder which shook the whole house. The lights flickered, then went off.

A second later they were back on, but there was a strange burning smell.

"Oh no! Cried Penny, "The router!"

Where their Internet router had been was a smouldering lump of twisted plastic and metal.

Poppy said a word which, if her mother had overheard her would have meant an instant reduction in pocket money. "How will we find out what 'Morse Code' is if we can't get online?"

The girls sat, stunned. No Internet. No Facebook. More importantly, no Wikipedia!

They looked at their phones but, as always they didn't have any credit.

Poppy looked around the room forlornly. The little study had been Poppy's dad's work area before he... Well. Just before. As she scanned the shelves looking for something which might help - even an old fashioned dial-up modem would do.

Penny suddenly chirruped, "Pops, what's the 'Encyclopedia Britannica'?" Pointing to an imposing set of books on a shelf. "No idea," sniffed Poppy despondently. "Only, and I know it was your dad's, but 'encyclopedia' sounds a bit like 'Wikipedia' and I wondered..." "Of course! Quick, which one of the books has 'M' printed on the side?" Poppy smiled. It was rare to see her smile these days, and Penny relished cheering her friend up.

They plucked the dusty volume from the shelf and opened it up more-or-less at random. Its musty smell filled the room and they began flicking through the yellowing pages. "Where's the search function on this thing?" joked Penny. "Möbius, Moomins, Mormon, Morse!"

There, laid out in the pages of the encyclopedia was a guide to Morse Code.

The girls flipped on the Pi and waited for it to boot.

"The most important thing to consider when programming," said Poppy doing her very best imitation of Mr Cartwright their inexcusably dull IT teacher. "...is planning!" said Penny, finishing her friend's sentence.

"We want a program which will let us type in each letter of Morse Code and then show us the English translation."

Penny grabbed the keyboard. She knew that she would be doing most of the typing while Poppy did most of the pointing out of her mistakes. Apparently, this was known as "pair programming" according to Mr Cartwright. She didn't think much of it.

"First," said Poppy, "Let's define a dictionary of English and Morse Code."

Penny's hands darted across the keyboard as her friend read the dots and dashes from the book.

morse = {  '.-'  :'A', '-...':'B', '-.-.':'C', '-..' :'D', '.'   :'E',
           '..-.':'F', '--.' :'G', '....':'H', '..'  :'I', '.---':'J'
        }

You can program the rest of the dictionary yourself.

Poppy sighed, "Why on Earth have you bothered to line up all the letters?" "It helps me think," said Penny defensively, "I like it neat. Besides, Python doesn't care how I space things like that." "Fine! Let's do a quick test to see if it works," said Poppy. "Right, I'll ask the user to type a single letter of Morse Code. Then it's really easy to look it up in the dictionary," said Penny.

get_code = raw_input('Type a Morse Character ')
print morse[get_code]

She ran the program. As expected it asked her to type in a code. She hit the sequence ".-" and hit enter.

She was rewarded with a glowing "A" on the screen.

"Good start," said Poppy. "But it's going to be a pain to type in every Morse character, then hit enter, then try to string the letters together."

Penny thought for a moment. She knew she could come up with something clever.

"How about we read in the string we type in, then break it up based on where the spaces are?" She said tentatively. Poppy looked confused, "What do you mean, Pen?"

Penny ran Python directly so she could show what she was thinking

Python 2.7.3 (default, Aug  1 2012, 05:14:39)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

At the prompt she typed

>>> "This is a test".split()

"If I'm right, the .split() function will give us an list of all the word."

She gently thumbed the enter key.

['This', 'is', 'a', 'test']

"Yes!" Shouted both girls simultaneously.

"So now we will have each Morse Letter in a list, then we want to look it up in the dictionary." "That's right. Luckily it's super simple to do something on every item in a list - look,"

Penny typed directly into Python again.

>>> list_of_words = "This is a test".split()
>>> for item in list_of_words:
... print item

But this time, when she hit enter, an error message popped up!

  File "", line 2
    print item
        ^
IndentationError: expected an indented block

This time it was Penny's turn to swear.

"Wipe that grin off your face! Yes, spacing and indentation are important in Python. But generally it's fine if I line up my code just how I like it."

She tried again. This time hitting the spacebar as hard as she thought it could stand.

>>> list_of_words = "This is a test".split()
>>> for item in list_of_words:
...    print item

This time, the result was a lot more satisfactory.

...
This
is
a
test
>>>

"Getting there," muttered Poppy under her breath. They swiftly changed the last few lines of their code to read:

get_code = raw_input('Type in the Morse Code ')

code_list = get_code.split()

for item in code_list:
   print morse[item]

"Ok," said Penny, "Let's see what this mysterious blue cloth says on it..."

...  ---  ...  -...  ---  .- -  ...  .-  -.  -.-  ---  -.  ..  ...  .-..  .-  -.  -..

They checked and double checked what they had typed in.

"Ready?" said Poppy. "Let's do it!" said Penny as she hit the enter key.

Saving The Day

"Well done you two," said the Mayor. "Without your help, that sailor would have been stuck there a long time."

Penny and Poppy both grinned. It had all been such a rush, they'd gone from running their code, to screaming for Poppy's mum, to calling the coastguard, to seeing a shipwrecked sailor being rescued. They had been interviewed for TV and the clip had hundreds of YouTube likes.

There was even a Facebook page dedicated to thanking them!

The Mayor had decided that such fine upstanding citizens deserved a reward - and had invited them to a special event in the town hall.

"Who would have thought two girls would know Morse Code?" They Mayor said, "Did you learn that at school?"

Penny fixed him with a steely glare, "No. We taught ourselves."

The Mayor peered over his glasses, "But surely you had help from someone? An older brother perhaps?"

Poppy knew the look on Penny's face and answered before her friend lost her temper, "I think you'll find," she said sweetly, "that women don't need help from boys!"

Poppy felt Penny's hand slip in to hers. She started to chuckle as her hand was squeezed in firm but measured bursts.

-  ....  .-  -  ...  .--  ....  -.--  -.--  ---  ..-  .-  .-.  .  --  -.--  -...  .  ...  -  ..-.  .-.  ..  .  -.  -..

THE END

What Next

• Write your own story - using these character or ones you've created.
• Make the Python simple and readable - explain as you go.
• If there's enough interest, I'll gather them all up, maybe on a central site.
• Perhaps, if people like them, we can release a (free) ebook?
• Oh, and feel free to criticise my storytelling abilities or coding deficiencies!

That's The Power Of Love

The first thing to say is use a powered USB hub! I had lots of problems getting the modem working when it was plugged directly into the Pi. A 3G signal takes more power than the Pi's USB sockets can supply.

In the above image, you can see that the Raspbery Pi is plugged into the mains - via a 1.8A plug. The USB cable has two male ends. The black plug goes directly into the Pi for data. The red plug goes into the mains via a 1A plug (an Amazon Kindle adapter).

I used a USB Y Cable to supply power and data.

I also tried plugging both plugs into the Pi - that didn't work either. You need a separate powered hub.

Rather than use two plugs, I'm going to try to find a mains plug with two USB sockets. Each socket needs to supply at least 1A. Something like this looks like it should do the trick.

Or, you can use a cable like this.

Put one male USB plug into the PI and the other into a power supply. The dongle fits into the female USB socket.

P-p-p-p-pick Up A PPPD

In order to get our network connected, we need to install the ppp package.

sudo apt-get install ppp

If You Think I'm Sakis, And You Want My Body...

I tried using wvdial and numerous other ways to connect to 3G. None of them worked reliably. In the end, I turned to sakis - the All-In-One script for connecting 3G modem.

Sakis says it is:

"The easiest way to have your 3G/UMTS/GRPS connection up and running."

I can't argue with that!

Installation is very simple:

First, download the latest version. The Raspberry Pi runs on an ARM processor, so this is the version we download.

wget "http://www.sakis3g.org/versions/latest/armv4t/sakis3g.gz"

The script is compressed. Unzip it.

gunzip sakis3g.gz

Finally, we want to make the file executable so that we can run it.

chmod +x sakis3g

Running sakis is quite straightforward. It has a basic GUI which will work even if you're just using the command line.

sudo ./sakis3g --interactive

Sakis has a fairly comprehensive list of connection details - it should find yours automatically and present you with this screen.

If it doesn't know your connection settings (if you're on GiffGaff for example) you can manually enter them.

All being well, after a few seconds, you should see this screen.

You can now exit sakis. You will stay connected.

To check the details of your connection, run the following command:

sudo ./sakis3g connect info

You'll get back something like this:

K3565 connected to giffgaff (23410).
Connection Information

Interface: P-t-P (ppp0)

Connected since: 2012-07-13 07:36
Kilobytes received: 2
Kilobytes sent: 2

Network ID: 23410
Operator name: giffgaff
APN: giffgaff.com

Modem: K3565
Modem type: USB
Kernel driver: option
Device: /dev/ttyUSB0

IP Address: 10.136.6.52
Subnet Mask: 255.255.255.255
Peer IP Address: 10.64.64.64
Default route(s): 10.64.64.64

That's it! You can now access the Internet via your 3G modem.

Surfin' Safari

One last tip for you! There's no need to start your window manager to surf the web. There's a brilliant lo-fi web browser called Lynx.

You install it by typing:

sudo apt-get install lynx

You run it by typing:

lynx http://www.bbc.co.uk/news

(or whatever website you want to visit).

So, that should be everything you need to get the Raspberry Pi connected over a USB 3G dongle. Have fun!

Here is how to use Python to send an SMS from the Raspberry Pi via a 3G USB dongle.

In order to talk to the dongle, we need to install pyserial

wget http://pypi.python.org/packages/source/p/pyserial/pyserial-2.6.tar.gz
gunzip pyserial-2.6.tar.gz
tar -xvf pyserial-2.6.tar
cd pyserial-2.6
sudo python setup.py install

Save this file as sms.py - make sure you change the phone number and message!

# This is pyserial which is needed to communicate with the dongle
import serial

# Set up the connection to the dongle
dongle = serial.Serial(port="/dev/ttyUSB0",baudrate=115200,timeout=0,rtscts=0,xonxoff=0)

# This sends the command to the dongle
def sendatcmd(cmd):
    dongle.write('AT'+cmd+'r')

# put the dongle into text mode
sendatcmd('+CMGF=1')

# Set the telephone number we want to send to
sendatcmd('+CMGS="+447700900123"')

# Set the message we want to send
dongle.write('Sending from python')

# Pass the CTRL+Z character to let the dongle know we're done
dongle.write(chr(26))

# Close the connection
dongle.close()

Run the file by typing

python sms.py

An SMS should be sent!

SMSC

The SMSC is the the message centre through which an SMS is sent. This is how to discover the SMSC of your SIM

AT+CSCA?

Should generate this as the output.

+CSCA: "+447802002606",145

SMS Modes

To see which modes your mobile supports, you can use the "AT+CMGF=?" command. You will get a response with the supported SMS formats 0: PDU mode, 1: Text mode

Putting It All Together

My previous program calculated the PDU which needed to be sent to the dongle.

This program asks the user for the destination phone number, message, and whether they want to send a flash SMS or regular SMS. It gets the SMSC from the dongle, calculates the PDU values, then sends them to the dongle.

Then - hopefully! - an SMS will be sent :-)

The source is on GitHub.

# This Python file uses the following encoding: utf-8
"""
© 2012 Terence Eden

Adapted from http://rednaxela.net/pdu.php Version 1.5 r9aja
Original JavaScript (c) BPS & co, 2003. Written by Swen-Peter Ekkebus, edited by Ing. Milan Chudik, fixes and functionality by Andrew Alexander.
Original licence http://rednaxela.net/pdu.php "Feel free to use this code as you wish."

Python version © 2012 Terence Eden - released as MIT License
***
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
***

Note - this is my first Python program - I am quite happy to be corrected on True Pythonic Style etc. :-)
"""

"""
This program allows the user to craft a PDU when sending an SMS.
The user enters the destination number, the message, the class, and the SMSC.
The program generates the commands needed to instruct a modem to deliver the SMS.
"""

# This is pyserial which is needed to communicate with the 3G USB Dongle http://pyserial.sourceforge.net/
import serial


# Array with the default 7 bit alphabet
# @ = 0 = 0b00000000, a = 97 = 0b1100001, etc
# Alignment is purely an attempt at readability
SEVEN_BIT_ALPHABET_ARRAY = (
    '@', '£', '$', '¥', 'è', 'é', 'ù', 'ì', 'ò', 'Ç', 'n', 'Ø', 'ø', 'r','Å', 'å',
    'u0394', '_', 'u03a6', 'u0393', 'u039b', 'u03a9', 'u03a0','u03a8', 'u03a3', 'u0398', 'u039e',
    '€', 'Æ', 'æ', 'ß', 'É', ' ', '!', '"', '#', '¤', '%', '&', ''', '(', ')','*', '+', ',', '-', '.', '/',
    '0', '1', '2', '3', '4', '5', '6', '7','8', '9',
    ':', ';', '< ', '=', '>', '?', '¡',
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
    'Ä', 'Ö',
                                                                     'Ñ', 'Ü', '§', '¿',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
    'ä', 'ö',
                                                                     'ñ', 'ü',
    'à')


def semi_octet_to_string(input) :
    """ Takes an octet and returns a string
"""
    out = ""
    i=0
    for i in range(0,len(input),2) : # from 0 - length, incrementing by 2
        out = out + input[i+1:i+2] + input[i:i+1]
    return out


def convert_character_to_seven_bit(character) :
    """ Takes a single character.
Looks it up in the SEVEN_BIT_ALPHABET_ARRAY.
Returns the position in the array.
"""
    for i in range(0,len(SEVEN_BIT_ALPHABET_ARRAY)) :
        if SEVEN_BIT_ALPHABET_ARRAY[i] == character:
            return i
    return 36 # If the character cannot be found, return a ¤ to indicate the missing character


def send_AT_command(cmd) :
    """ Send a command to the dongle
"""
    dongle.write(AT_COMMAND+cmd+'r')


def get_SMSC_from_dongle() :
    """ Interogate the dongle and get the SMSC number
"""

    print "Asking the SIM for the SMSC"
    # find the SMSC
    send_AT_command('+CSCA?')

    # read the output, print it to screen. Stop when "OK" is seen
    while True:
        output = dongle.readline()
        print output

        # find the response about the SMSC
        if output.startswith("+CSCA:") :
            first_quote = output.find('"') + 1 # zero based index, first quote
            last_quote = output.rfind('"') # last quote
            SMSC_number = output[first_quote:last_quote] # Extract the string between the "
            print "The SMSC number is " + SMSC_number
            return SMSC_number

        if output.startswith("OK"):
            break
        if output.startswith("ERROR"):
            break



# Set the initial variables
FIRST_OCTET = "0100" # MAGIC
PROTO_ID = "00" # MORE MAGIC
data_encoding = "1" # EVEN MORE MAGIC
message_class = "" # Message Class. 0 for FLASH, 1 for normal
SMSC_number = "" # The message centre through which the SMS is sent
SMSC = "" # How the SMSC is represented once encoded
SMSC_info_length = 0
SMSC_length = 0
SMSC_number_format = "81" # by default, assume that it's in national format - e.g. 077...
destination_phone_number = "" # Where the SMS is being sent
destination_phone_number_format = "81" # by default, assume that it's in national format - e.g. 077...
message_text = "" # The message to be sent
encoded_message_binary_string = "" # The message, as encoded into binary
encoded_message_octet = "" # individual octets of the message
AT_COMMAND = "AT" # Commands sent to dongle should start with this
AT_SET_PDU = "+CMGF=0" # Command to set the dongle into PDU mode
SEND_CHARACTER = chr(26)

# Set up the connection to the dongle
dongle = serial.Serial(port="/dev/ttyUSB0",baudrate=115200,timeout=0,rtscts=0,xonxoff=0)

# Get the user inputs. No error checking in this version :-)
get_destination_phone_number = raw_input("Which phone number do you want to send an SMS to? (e.g. +447700900123) : ")
get_message_text = raw_input("What message do you want to send? : ")
get_message_class = raw_input("For FLASH SMS, type 0. For regular SMS, type 1 : ")

# TODO Error check & sanitize input
destination_phone_number = get_destination_phone_number
message_text = get_message_text
message_class = int(get_message_class)
SMSC_number = get_SMSC_from_dongle() #get_SMSC_number

# Set data encoding
data_encoding = data_encoding + str(message_class)

# Get the SMSC number format
if SMSC_number[:1] == '+' : # if the SMSC starts with a + then it is an international number
    SMSC_number_format = "91"; # international
    SMSC_number = SMSC_number[1:len(SMSC_number)] # Strip off the +

# Odd numbers need to be padded with an "F"
if len(SMSC_number)%2 != 0 :
    SMSC_number = SMSC_number + "F"

# Encode the SMSC number
SMSC = semi_octet_to_string(SMSC_number)

# Calculate the SMSC values
SMSC_info_length = (len(SMSC_number_format + "" + SMSC))/2
SMSC_length = SMSC_info_length;

# Is the number we're sending to in international format?
if destination_phone_number[:1] == '+' : # if it starts with a + then it is an international number
    destination_phone_number_format = "91"; # international
    destination_phone_number = destination_phone_number[1:len(destination_phone_number)] # Strip off the +

# Calculate the destination values in hex (so remove 0x, make upper case, pad with zeros if needed)
destination_phone_number_length = hex(len(destination_phone_number))[2:3].upper().zfill(2)

if len(destination_phone_number)%2 != 0 : # Odd numbers need to be padded
    destination_phone_number = destination_phone_number + "F"

destination = semi_octet_to_string(destination_phone_number)

# Size of the message to be delivered in hex (so remove 0x, make upper case, pad with zeros if needed)
message_data_size = str(hex(len(message_text)))[2:len(message_text)].upper().zfill(2)

# Go through the message text, encoding each character
for i in range(0,len(message_text)) :
    character = message_text[i:i+1] # get the current character
    current = bin(convert_character_to_seven_bit(character)) # translate into the 7bit alphabet
    character_string = str(current) # Make a string of the binary number. eg "0b1110100
    character_binary_string = character_string[2:len(str(character_string))] # Strip off the 0b
    character_padded_7_bit = character_binary_string.zfill(7) # all text must contain 7 bits
    # Concatenate the bits
    # Note, they are added to the START of the string
    encoded_message_binary_string = character_padded_7_bit + encoded_message_binary_string


# Reverse the string to make it easier to count
encoded_message_binary_string_reversed = encoded_message_binary_string[::-1]

# Get each octet into hex
for i in range(0,len(encoded_message_binary_string_reversed),8) : # from 0 - length, incrementing by 8
    # Get the 8 bits, reverse them back to normal, if less than 8, pad them with 0
    encoded_octet = encoded_message_binary_string_reversed[i:i+8][::-1].zfill(8)
    encoded_octet_hex = hex(int(encoded_octet,2)) # Convert to hex

    # Strip the 0x at the start, make uppercase, pad with a leading 0 if needed
    encoded_octet_hex_string = str(encoded_octet_hex)[2:len(encoded_octet_hex)].upper().zfill(2)

    # Concatenate the octet to the message
    encoded_message_octet = encoded_message_octet + encoded_octet_hex_string

# Generate the PDU
PDU = str(SMSC_info_length).zfill(2)
        + str(SMSC_number_format)
        + SMSC
        + FIRST_OCTET
        + str(destination_phone_number_length)
        + destination_phone_number_format
        + destination
        + PROTO_ID
        + data_encoding
        + str(message_data_size)
        + encoded_message_octet

# Generate the AT Commands
AT_CMGS = "+CMGS=" + str((len(PDU)/2) - SMSC_length - 1)

# Show the commands
print AT_COMMAND + AT_SET_PDU
print AT_COMMAND + AT_CMGS
print PDU

# Send the commands to the dongle
send_AT_command("") # Send an initial AT
send_AT_command(AT_SET_PDU) # Send the command to place the dongle in PDU mode
send_AT_command(AT_CMGS) # Send the command showing the length of the upcoming PDU, should prompt for input ">"
dongle.write(PDU) # Send the PDU
dongle.write(SEND_CHARACTER) # Submit the PDU
dongle.close() # Close the connection

The source is on GitHub.

The aim - to be able to send an SMS via a 3G USB dongle. The problem - the way SMS needs to be encoded is hideously complicated.

For example, suppose you want to send "This is a very simple message :-)" to the phone number +447700900123.

This is the command that you need to send to your dongle:

AT+CMGS=42
079144872000626001000C9144770009103200112154747A0E4ACF416190BD2CCF83E6E9369C5D06B5CBF379F85C06E95A29

WHAT? THE? JUDDERING? FUCK?!

I found an excellent JavaScript PDU tool - which I have adapted. Also of great help was Lars Pettersson's PDU explanation and Jeron's discussion of the SMS PDU. I would have been totally lost without them.

Python is already pre-installed on the Raspberry Pi - which is handy. So here is a tool I whipped up which will generate the above gibberish.

Running the program should show this:

Which phone number do you want to send an SMS to? (e.g. +447700900123) :
What message do you want to send? :
For FLASH SMS, type 0. For regular SMS, type 1 :
Which SMSC will you use? (e.g. +447802002606) :

And will output this:

AT+CMGS=60
079144872000626001000C91447700091032001035493328FFAE83D0617B19442E8FDFE432194447A7E72C50FE5D07A1C3F632E8FE7683C2A0B3BC1CA683E0F2B4BE1C02

The source is on GitHub - or please find in below for your edification and delight.

This is my first outing in Python, so I'm sure I've made a few syntactic and stylistic mistakes. Any corrections gratefully received.

# This Python file uses the following encoding: utf-8
"""
© 2012 Terence Eden

Adapted from http://rednaxela.net/pdu.php Version 1.5 r9aja
Original JavaScript (c) BPS & co, 2003. Written by Swen-Peter Ekkebus, edited by Ing. Milan Chudik, fixes and functionality by Andrew Alexander.
Original licence http://rednaxela.net/pdu.php "Feel free to use this code as you wish."

Python version © 2012 Terence Eden - released as MIT License
***
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
***

Note - this is my first Python program - I am quite happy to be corrected on True Pythonic Style etc. :-)
"""

"""
This program allows the user to craft a PDU when sending an SMS.
The user enters the destination number, the message, the class, and the SMSC.
The program generates the commands needed to instruct a modem to deliver the SMS.
"""

# Array with the default 7 bit alphabet
# @ = 0 = 0b00000000, a = 97 = 0b1100001, etc
# Alignment is purely an attempt at readability
SEVEN_BIT_ALPHABET_ARRAY = (
    '@', '£', '$', '¥', 'è', 'é', 'ù', 'ì', 'ò', 'Ç', 'n', 'Ø', 'ø', 'r','Å', 'å',
    'u0394', '_', 'u03a6', 'u0393', 'u039b', 'u03a9', 'u03a0','u03a8', 'u03a3', 'u0398', 'u039e',
    '€', 'Æ', 'æ', 'ß', 'É', ' ', '!', '"', '#', '¤', '%', '&', ''', '(', ')','*', '+', ',', '-', '.', '/',
    '0', '1', '2', '3', '4', '5', '6', '7','8', '9',
    ':', ';', '< ', '=', '>', '?', '¡',
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
    'Ä',                                                                  'Ö', 'Ñ',                     'Ü', '§', '¿',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
    'ä',                                                                  'ö', 'ñ',                     'ü',
    'à')


def semi_octet_to_string(input) :
    """ Takes an octet and returns a string
    """
    out = ""
    i=0
    for i in range(0,len(input),2) : # from 0 - length, incrementing by 2
        out = out + input[i+1:i+2] + input[i:i+1]
    return out


def convert_character_to_seven_bit(character) :
    """ Takes a single character.
    Looks it up in the SEVEN_BIT_ALPHABET_ARRAY.
    Returns the position in the array.
    """
    for i in range(0,len(SEVEN_BIT_ALPHABET_ARRAY)) :
        if SEVEN_BIT_ALPHABET_ARRAY[i] == character:
            return i
    return 36 # If the character cannot be found, return a ¤ to indicate the missing character

# Set the initial variables
FIRST_OCTET = "0100" # MAGIC
PROTO_ID = "00" # MORE MAGIC
data_encoding = "1" # EVEN MORE MAGIC
message_class = "" # Message Class. 0 for FLASH, 1 for normal
SMSC_number = "" # The message centre through which the SMS is sent
SMSC = "" # How the SMSC is represented once encoded
SMSC_info_length = 0
SMSC_length = 0
SMSC_number_format = "81" # by default, assume that it's in national format - e.g. 077...
destination_phone_number = "" # Where the SMS is being sent
destination_phone_number_format = "81" # by default, assume that it's in national format - e.g. 077...
message_text = "" # The message to be sent
encoded_message_binary_string = "" # The message, as encoded into binary
encoded_message_octet = "" # individual octets of the message

# Get the user inputs. No error checking in this version :-)
get_destination_phone_number = raw_input("Which phone number do you want to send an SMS to? (e.g. +447700900123) : ")
get_message_text = raw_input("What message do you want to send? : ")
get_message_class = raw_input("For FLASH SMS, type 0. For regular SMS, type 1 : ")
get_SMSC_number = raw_input("Which SMSC will you use? (e.g. +447802002606) : ")

# TODO Error check & sanitize input
destination_phone_number = get_destination_phone_number
message_text = get_message_text
message_class = int(get_message_class)
SMSC_number = get_SMSC_number

# Set data encoding
data_encoding = data_encoding + str(message_class)

# Get the SMSC number format
if SMSC_number[:1] == '+' : # if the SMSC starts with a + then it is an international number
    SMSC_number_format = "91"; # international
    SMSC_number = SMSC_number[1:len(SMSC_number)] # Strip off the +

# Odd numbers need to be padded with an "F"
if len(SMSC_number)%2 != 0 :
    SMSC_number = SMSC_number + "F"

# Encode the SMSC number
SMSC = semi_octet_to_string(SMSC_number)

# Calculate the SMSC values
SMSC_info_length = (len(SMSC_number_format + "" + SMSC))/2
SMSC_length = SMSC_info_length;

# Is the number we're sending to in international format?
if destination_phone_number[:1] == '+' : # if it starts with a + then it is an international number
    destination_phone_number_format = "91"; # international
    destination_phone_number = destination_phone_number[1:len(destination_phone_number)] # Strip off the +

# Calculate the destination values in hex (so remove 0x, make upper case, pad with zeros if needed)
destination_phone_number_length = hex(len(destination_phone_number))[2:3].upper().zfill(2)

if len(destination_phone_number)%2 != 0 : # Odd numbers need to be padded
    destination_phone_number = destination_phone_number + "F"

destination = semi_octet_to_string(destination_phone_number)

# Size of the message to be delivered in hex (so remove 0x, make upper case, pad with zeros if needed)
message_data_size = str(hex(len(message_text)))[2:len(message_text)].upper().zfill(2)

# Go through the message text, encoding each character
for i in range(0,len(message_text)) :
    character = message_text[i:i+1] # get the current character
    current = bin(convert_character_to_seven_bit(character)) # translate into the 7bit alphabet
    character_string = str(current) # Make a string of the binary number. eg "0b1110100
    character_binary_string = character_string[2:len(str(character_string))] # Strip off the 0b
    character_padded_7_bit =  character_binary_string.zfill(7) # all text must contain 7 bits
    # Concatenate the bits
    # Note, they are added to the START of the string
    encoded_message_binary_string = character_padded_7_bit + encoded_message_binary_string


# Reverse the string to make it easier to count
encoded_message_binary_string_reversed = encoded_message_binary_string[::-1]

# Get each octet into hex
for i in range(0,len(encoded_message_binary_string_reversed),8) : # from 0 - length, incrementing by 8
    # Get the 8 bits, reverse them back to normal, if less than 8, pad them with 0
    encoded_octet = encoded_message_binary_string_reversed[i:i+8][::-1].zfill(8)
    encoded_octet_hex = hex(int(encoded_octet,2)) # Convert to hex

    # Strip the 0x at the start, make uppercase, pad with a leading 0 if needed
    encoded_octet_hex_string = str(encoded_octet_hex)[2:len(encoded_octet_hex)].upper().zfill(2)

    # Concatenate the octet to the message
    encoded_message_octet = encoded_message_octet + encoded_octet_hex_string

# Generate the PDU
PDU = str(SMSC_info_length).zfill(2)
        + str(SMSC_number_format)
        + SMSC
        + FIRST_OCTET
        + str(destination_phone_number_length)
        + destination_phone_number_format
        + destination
        + PROTO_ID
        + data_encoding
        + str(message_data_size)
        + encoded_message_octet

# Generate the AT Commands
AT_CMGS = (len(PDU)/2) - SMSC_length - 1
AT_COMMAND = "AT+CMGS=" + str(AT_CMGS)

# Show the commands
print AT_COMMAND
print PDU

The source is on GitHub.

In order to actually send the SMS, you will need to put the modem into PDU mode, this is done by the command

AT+CMGF=0

So, as per my earlier post on sending SMS, the complete sequence is

AT+CMGF=0
AT+CMGS=60
07914487...

Then press CTRL+Z to send.

A few weeks ago, I won a Raspberry Pi at the #OTA12 hackday. It arrived on Friday, so I thought I would turn it into an SMS server using the incredible FrontlineSMS.

0. Setting up the Pi

This is the easy part. Follow the excellent guide on the eLinux wiki. Essentially, download the Debian image, extract, and dd it onto an SD card.

The hardest part was finding a full sized SD! In the end, I found an old adapter and stuck in a 2GB micro SD card.

1. First Boot

My first boot was a failure. Nothing appeared on the screen. So, I switched off the power, unplugged every lead, plugged them back in, and powered it on. Success!

The first thing I did was ensure the operating system was up to date.

Check for updates:

sudo apt-get update

Then, apply those updates

sudo apt-get upgrade

This took a few minutes.

Finally, set up SSH or VNC if you plan on using the machine remotely.

2. Dongle Hardware

FrontlineSMS maintains a list of USB dongles which work with its service. I used a Vodafone branded Huawei E220. Sold as Vodafone K3565 The Raspberry Pi only has 2 USB slots - the dongle was slim enough not to interfere with the other USB cable, but it did mean I could only run either a keyboard or a mouse without using a hub. It's recommended that you use a powered USB hub - although my keyboard and mouse didn't seem to draw too much power.

3. Frontline SMS

Downloading Frontline SMS via the commandline (using v1.6 because v2 isn't ready for Linux yet)

wget http://frontlinesms.com/download/secure/FrontlineSMS-distribution-1.6.16.3-linux_i686-dist.zip

Unzip

unzip FrontlineSMS-distribution-1.6.16.3-linux_i686-dist.zip

Run

cd FrontlineSMS-distribution-1.6.16.3
./FrontlineSMS.sh

Gave an error - FrontlineSMS requires Java.

4. Installing Java

The Java install takes about 140MB of disk space. After downloading and extracting FrontlineSMS, I only had about 220MB of free space. I deleted the FrontlineSMS zip file and had 234MB free. Just about enough room!

sudo apt-get install openjdk-6-jdk

Wait several minutes and you'll be good to go.

5. Running for the First Time

Frontline SMS requires a GUI.

Running a GUI is as easy as typing

startx

The resolution was set at the slightly odd dimensions of 1264*672 - which meant there was a large black border around the screen.

Open a terminal (Start, Accessories, LXTerminal, then type

cd FrontlineSMS-distribution-1.6.16.3
./FrontlineSMS.sh

After several minutes of waiting, FrontlineSMS started!

However, no matter what I tried, I couldn't get FrontlineSMS to detect the dongle. The OS could see it fine (using "lsusb" and "dmesg"), but it just didn't appear to be detected by FrontlineSMS.

A delve into the commandline, showed this error:

librxtxSerial.so: cannot open shared object file: No such file or directory
(Possible cause: can't load IA 32-bit .so on a ARM-bit platform)
thrown while loading gnu.io.RXTXCommDriver

6. Installing the Correct Libraries

We need to load the correct (ARM) version of rxtx.

sudo apt-get install librxtx-java

Find where the install process has dumped it

find . -name "librxtxSerial.so"

It should show you two location - the first being where the correct version is, the second where the FrontlineSMS version is.

./usr/lib/jni/librxtxSerial.so
./home/pi/Desktop/FrontlineSMS-distribution-1.6.16.3/librxtxSerial.so

All we need to do is overwrite the incorrect version.

cp /usr/lib/jni/librxtxSerial.so /home/pi/Desktop/FrontlineSMS-distribution-1.6.16.3/

Then, run

./FrontlineSMS.sh

And, after some warnings and waitings, you should see

Hey Presto! FrontlineSMS up and running on a Raspberry Pi!

(Oh! I finally worked out how to do screenshots! install scrot and run "scrot -d 10" to take a screenshot after 10 seconds.)

7. Manually Sending an SMS

Running FrontlineSMS via Java on a 700MHz ARM device is very slow. It is possible to talk directly to the dongle and manually tell it to send SMS.

First, I installed picocom.

sudo apt-get install picocom

To find out where the dongle has been installed, type:

dmesg

Which will give an long output, which should contain some text like this like this:

option 1-1.2:1.1: GSM modem (1-port) converter detected
usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
option 1-1.2:1.0: GSM modem (1-port) converter detected
usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1

The dongle installs itself in two places - ttyUSB0 & 1. It's the first one we want.

Connect by issuing this command

picocom /dev/ttyUSB0 -b 115200 -l

Which will give you the output

port is        : /dev/ttyUSB0
flowcontrol    : none
baudrate is    : 115200
parity is      : none
databits are   : 8
escape is      : C-a
noinit is      : no
noreset is     : no
nolock is      : yes
send_cmd is    : ascii_xfr -s -v -l10
receive_cmd is : rz -vv

Terminal ready

From now on in, we're typing commands directly into the dongle. You cannot press the delete key! Copy & paste, or be careful when typing!

First, to make sure everything is working, we type

AT

We should see this response

OK

Next, set the dongle to text mode

AT+CMGF=1

Again, the response should be

OK

Let's send our first SMS!

AT+CMGS="+447700900123"

This will not say "OK", rather, it will prompt us to type a message

> 

Type your message, so the screen looks like

> This is a test

DO NOT HIT ENTER. Instead, hit CTRL and Z at the same time.

You should see a response like

+CMGS: 193

OK

The number is the "sent items" reference. Within a few moments, the SMS should have been received.

You can send an SMS to the dongle. To check for messages, type the command

AT+CMGL="ALL"

You should see all the messages in the inbox

+CMGL: 0,"REC READ","+447700900000",,"12/06/19,13:53:19+04"
Received
+CMGL: 1,"REC READ","+447700900321",,"12/06/23,17:16:29+04"
Testing
+CMGL: 2,"REC UNREAD","+447700900555",,"12/06/23,23:27:48+04"
This is another test

To quit picocom, hold down CTRL, then hold down A, then hold down X.

Useful Links

A collection of links I found useful when writing this blog post

• http://designbuildtestrepeat.wordpress.com/2008/04/29/huawei-e220-on-linux-for-sms/
• http://www.diafaan.com/sms-tutorials/gsm-modem-tutorial/
• http://www.shapeshifter.se/2008/04/30/list-of-at-commands/
• http://raspberrypi.homelabs.org.uk/raspberrypi-the-arduino-development-tool/
• http://developer.vodafone.com/labs/opensource/linux- connection-manager/operating-systems/ubuntu-linux-setup/
• For unlocking Huawei modems