RTB is a modern BASIC – it has while/until looping constructs and named functions and procedures which can have local variables and be called recursively. It has  simplified colour scheme (or you can use all 24-bits if you like), and the usual point, line and shape drawing primitives as well as some nice turtle graphics commands:

The first problem I faced was that the supplied QEMU for my Debian Squeeze (stable) workstation doesn’t support the right ARM processor emulator, so get and build QEMU from scratch, but first make sure you don’t already have one installed:

dpkg -l | fgrep -i qemu

and if you find anything, then purge it. Now fetch and install QEMU:

cd
mkdir -p rpi/qemu ; cd rpi/qemu
wget http://wiki.qemu.org/download/qemu-1.0.tar.gz
tar zzvf qemu-1.0.tar.gz
cd qemu-1.0
./configure –target-list=arm-softmmu,arm-linux-user
make
sudo make install

with a bit of luck that will just work although the ./configure stage may suggest some packages to install.

The next step is to get, configure and compile a new Linux Kernel. This may be quite daunting if you’ve never done it before, and I offer a few alternatives – the first is to fetch a pre-compiled kernel (easy), then next is to fetch the kernel config file and finally to create your own kernel config file (harder) and compile your own kernel (harder) However, before you compile the kernel, there is a patch you need to apply to it which can be found online in several places, but also on my server as detailed below.

I suggest starting with my pre-compiled kernel, then fetch the config file and patch to compile your own.

cd ~/rpi
wget http://unicorn.drogon.net/rpi/zImage

or if you want to get the kernel .config file:

wget http://unicorn.drogon.net/rpi/config
wget http://unicorn.drogon.net/rpi/linux-arm.patch

You’ll then need to fetch a kernel (I used 3.1.9 here), get the cross compiler tools, compile and install the kernel, etc. I’ll do another article on that, but at it gets close to hardware time, it might not be needed as you will be able to compile a kernel on the Raspberry Pi itself (although it might take all night!)

The final part of the puzzle is to get the Debian SD card image. I used BitTorrent to fetch the file and it’s probably still the best way to get it now. Start at the downloads page on the Raspberry Pi website, or use this direct link to get the torrent file.

You may have read a lot of writings on splitting up that file, working out some magical offsets, etc. but none of that is required at all! This is what’s needed to start QEMU using the supplied Debian image and the kernel you just fetched:

Lets assume you have the zImage kernel and the Debian image in the same directory. Edit this into a little script called (e.g.) go:

qemu-system-arm -M versatilepb -cpu arm1176 -m 192      \       
        -hda debian6-17-02-2012.img                     \       
        -kernel zImage                                  \       
        -append "root=/dev/sda2"                        \       
        -serial stdio -redir tcp:2222::22               \
        -usb -usbdevice host:0403:6001

and run it by typing

sh go

Note the last line – that tells QEMU to use USB device with id 0403:6001 on the host PC and assign it to the emulated CPU. You identify the device with the lsusb command on the host. That device on my workstation is the USB serial port to an Arduino – more on connecting the Raspberry Pi to an Arduino later…

If all goes well, it should look like this:

I can’t claim originality for it all – I’ve picked a lot of this up from online resources, the Raspberry Pi forums and elsewhere – e.g. cnx-software

]]> http://drogon.net/blog/2012/03/raspberry-pi-in-qemu-debian/feed/ 0 http://drogon.net/blog/2012/02/sourdough-again/ http://drogon.net/blog/2012/02/sourdough-again/#comments Mon, 06 Feb 2012 14:02:15 +0000 admin http://drogon.net/blog/?p=250 Continue reading →]]> From the “never stop learning” department…

So… a recent TV series on Channel 4 “The Fabulous Baker Brothers” featuring the wonderful Hobbs House Bakery has made me re-think the way I’ve been making my sourdough bread.

I started my sourdough some 6 months ago (Start of August 2011) after seeing it featured on the River cottage programs. I’ve always liked sourdough since I first tasted it in San Francisco in the early 90′s. I reckon sourdough is the king of breads, yet it’s possibly one of the easiest to make – I’ve been making bread for a great number of years, so when I saw the River cottage sourdough, I thought I’d give it a go, and since last August I’ve been making about one sourdough loaf a week, sometimes more, sometimes less. Always with the same great Shipton Mill flour which I buy locally.

And so-far, so good, however their way seems such a long-winded method, so when I saw the Baker Brothers program, I thought I’d try their method.

Briefly, the River Cottage method involves taking some starter, adding to it a smallish quantity of flour and water, then leaving this “sponge” overnight, then adding more flour (and water & salt) into it, kneading it, letting it rise for 8 hours, then giving it a brief knead again, transfer to a forming basket, let it rise again, but just for an hour or 2 then into the oven.

The (Fabulous) Baker Brothers method removes the overnight sponge step – it’s a good quantity of starter into all the flour, add a bit more water and salt, give it a decent 10+ minute knead, let it rise for 2 hours, then a light knead/shape transfer to the forming basket and let it rise for 8-12 hours, then bake.

And what a difference. It’s risen more than it usually does, the crumb is fluffier and lighter and it has a slightly more intense sour “tang” flavour to it. I’m attributing this to letting the starter get full-contact with all the flour right from the start, so it can get working, and keep on working.

It’s also now trivially easy to get a loaf ready first thing in the morning, as the final 8-12 hour rise can be overnight, then get up only a shade earlier than normal to crank the oven up and bake that loaf!

Fresh Sourdough on my baking "stone" which is really a hand-beaten Kenyan chuppati pan - next to my forming basket

From Starter to Finish - my jar of starter next to the finished bread!

One word: Service.

As in customer service and the whole buying experience making me reluctant to recommend Dualit to any of my friends and I certainly will never buy from them again.

The website (and the machine – see below) is actually quite good. Online manuals and photo guides. No printed manuals with the machine, however – one more thing I was disappointed with.

Another thing I was disappointed with – the ordering process. The website told me that it was in-stock, yet at the very end, after I’d paid for it, I was informed it would take up to 7 working days to be delivered.

Come on! It’s 2011! You have something in-stock and can’t deliver the same (or next) working day? You’re either lying or are just lazy. If I’d known that I’d have to wait for it, I’d have bought it off Amazon (cheaper!) and not wasted my time dealing directly with you.

I was also promised 50 coffee pods with delivery too. Despite one phone call and 2 emails, (which Dualit acknowledged with changes promised) these have yet to arrive. It’s now almost 3 weeks later and I still don’t have them. You told me on Thursday the 1st of December that they had been dispatched. It’s now the 5th of December… Where is my coffee?

On the phone to Dualit on the day of delivery, I was told I had to fill out a voucher and send it in – because they have 3 different types of coffee. There was no voucher with the machine. Worse, there was no indication that I’d need to do this on the website. I could have been left waiting for weeks before I realised that I wasn’t going to get my coffee… (and how many people have?) That means that they must have people phoning the factory all the time! Every time someone buys one of their coffee machines they have to phone the factory to get a voucher. Just how inefficient is that? No-wonder they take 7 working days to deliver stuff – they’re dealing with phone complains all the time! In my email I suggested that since they have 3 different types that they simply send a selection of all three – they have told me that they will take this suggestion on-board, but as yet no change to their website. No indication either that it will take up to 7 working days for delivery. Actually, I lie and notice that there has been an update. It’s now 10 working days.. Looks like if you want a Dualit for xmas then you’re out of luck, so don’t even bother. (Or get it from Amazon)

As for the machine itself? Yes, it makes good espresso coffee, it has simple controls and is easy to use – however it has a bunch of irritations that take the edge off it’s otherwise good ability to make coffee.. The grounds end up as a soggy mess in the filter making it impossible to simply tap out in one nice compacted “cake” which the Gaggia used to produce. (So making more than one large coffee is a PITA) and the steam nozzle is too close to the body of the machine, making the use of a larger milk jug quite tricky (the one supplied is far too small for anything other than a thimble full of milk) Here’s a tip for Dualit and other kitchen equipment manufacturers: As well as producing nice photo shoots for making coffee… How about making one for cleaning it out afterwards!

I’ve more or less given-up on the coffee pods – probably just as well as I have my own coffee beans anyway, but it would have been nice to play with the pods rather than the beans I normally use. Of-course by not giving me the pods I’ve now absolutely no incentive to buy them, so you’ve lost there, Dualit. I could have been a good customer – there is some nice kitchen kit on the Dualit website and I’m sure it’s all perfectly good, but because of my experiences with your ordering process, I’m simply going to look elsewhere in the future.

UPDATE: 10th Dec 2011 – The coffee pods arrived!

So the coffee finally arrived. An outer box, an inner box, one lightweight jute bag and 50 foil pouches containing the pods.

It’s not the best of coffee I have to admit. Despite being their espresso brand, I find it rather weak and insipid. There’s no indication of origin either. At £65 +P&P for a pack of 50 pods, I do think it’s rather a lot to pay for the convenience of not having to slop out the soggy grounds. I won’t be buying any from Dualit (nor anyone else for that matter)

My starter seems to have settled in and each loaf is getting better than the next. It’s going to be hard to beat number 4 though!

Sourdough loaf number 3

Number 1 was 100% wholemeal flour – and it really was a bit too heavy, so after that I switched to some malted grannary flour with sunflower and pumpkin seeds which has a really nice flavour. I’m feeding the starter with what’s left of the wholemeal, so it’s got a little bit of everything. Eventually, the starter will be fed with whilte flour. Still using the organic stuff from the Shipton Mill. (And one day I want to make one with as much white flour as possible – just because!)

Number 4 cooling on the rack

Number 4 after some essential quality control!

The now weekly process starts with getting the starter out of the fridge on a Friday or Saturday afternoon, leaving it to come up to room temperature after a brief stir to wake it up! Then I take 200g of the starter and put it into the mixing bowl, then add in more flour and water to make the “sponge”. The starter gets another 100g of flour and 100g of water added and both are left overnight (with some clingfilm over the bowl)

In the morning, more flour and water added to the mixing bowl with a good teaspoon of salt, kneaded up and left to rise – this typically takes a good 4-5 hours. It’s a lot slower than commercial yeast. After that, another kneading and turning into the forming bowl – for me that’s a colander lined with some muslin and flour to stop it sticking. This is left to rise again, then we have the tricky part… Turning this out onto the baking tray without disturbing it too much, a few slashes on the top and into a hot oven – which has an old baking tray at the bottom which then gets a mug of boiling water poured into it which creates a bit of steam and creates a good crust (or at least I understand that’s what it’s doing – I might try one without this just to see!)

About half way through cooking, I take it off the baking sheet and put it directly on the next shelf down to help cook through, and that’s it. A loaf of tasty sourdough just ready to have butter spread thickly on… (Or, since we’re in Devon, clotted cream and strawberry jam!)

I’t's still a little bit of trial and error with the quantities, but I’m slowly working out the exact quantities to make it easier to get it consistent. I might even publish my recipe when done!

Look it up in Wikipedia if you like, but in simple terms, sourdough is made from Lactobacillus bacteria and naturally occurring yeasts. The Lactobacillus gives it an acidic nature which acts as a natural preservative and gives it a tangy/sour taste and the yeasts help it rise.

Once I returned from SF, I found it almost impossible to get sourdough bread so quietly forgot about it – until recently! Now, there are artisan bakeries popping up who’re making the stuff, and people like Hugh Fearnly-Whittingstall showing it in TV, but the few I’ve had recently, while good, have lacked that real “tangy” taste I remembered from the breads I had in SF.

So I decided to make my own.

Patience. Plenty of patience is what you need to make sourdough. You will not make a loaf of sourdough in under 24 hours, and you need at least a week, preferably more to make sure your starter is healthy!

I made the mistake of starting with 100% wholemeal flour – something the local artisan baker subsequently advised against, but it did work and it was (is!) edible, if a little doughy and heavy.

To make good bread needs good ingredients, so some stoneground wholemeal flour from Shipton Mill was obtained, and off I went. Mixed some with water, left it outside on a warm evening with a cloth tied over it to hopefully allow some natural yeasts to invade, let it rest in a warm place, add more flour and water a day later, take some out add more in, and so on for a week. I was somewhat dubious, but there was definitely action happening – plenty of bubbles (CO2 hopefully!) and a definite aroma of alcohol (as brewers would recognise!) – yeast basically eats sugars (carbohydrates in the flour in this instance), burps CO2 and pees alcohol – meanwhile the Lactobacillus is also digesting the carbohydrates and producing lactic acid – which gives the sour flavour and acts as a preservative. The production of CO2 is really what we’re after – that’s what makes the bread rise and gives it its springy texture! I did have a bit of separation of the flour and water, but I suspect that’s because I used heavier wholemeal flour – I’m currently weaning the starter off wholemeal to plain white flour, so hopefully that’ll change in time.

So, after the first week or so, making a loaf still takes a day and a half! The first stage is to make the “sponge” by mixing a portion of starter with more flour and water, making a thinnish paste and leave it overnight – hopefully producing a frothing mass in the morning! Into this, add salt, more flour and knead – for a good 10 minutes! (although next time I might just use the K-Mix!) Leave to rise, knead again, turn into a forming basket (I used a colander and a floured cloth), leave to rise again, gently turn out onto a floured baking tray, a few signature slashes on-top and into a hot oven. A bit of steam helps it rise and form a nice crust, so I have a baking tray in the bottom which I poured some boiling water into.

Simples!

Or maybe it would have been, had I used a lighter flour, however the resulting loaf was edible, although it’s a touch undercooked, it’s good in the toaster with fresh farmhouse butter, or even clotted cream! And the one thing I wanted was definitely there; a real tangy sourdough taste! (So hurrah for the local Devon yeasts )

The first loaf

The starter – not bubbling too much as I’d just added some more flour into it. It’ll sit in the airing cupboard now until tomorrow, but as I’m probably not going to make another loaf until next weekend, it might go in the fridge.

In the 24-hours from Friday 2pm until Saturday 2pm (18th Feb). Just short of £16,000 was raised!

The phones and setup were provided by Bluegrass Computer Services, backed up by us here at Drogon Systems.

We handled about 550 calls during the time, although most seemed to come in between 9am and 10am on the Saturday, keeping the volunteers on the phones very busy indeed! It seems that’s a very popular time for BBC Radio Devon listeners.

So how did we do it?

It was all VoIP because that’s what we do here at Drogon Systems! We now have the best part of 5 years experience using VoIP, so it was 2nd nature to us. Originally it was going to be hosted by BBC Radio Devon, but was changed rather late in the day, so with the flexibility of VoIP we were able to make it happen without any fuss. Bluegrass installed a 2nd ADSL line at the Devon Air Ambulance Trust HQ in Pinhoe, Exeter and re-provisioned some Linksys VoIP phones left-over from another project and we supplied the back-end infrastructure to plumb their phones via the Internet to the PSTN. And thanks to Magrathea, we also managed to get a nice charity phone number for them to use too (03030 400 400) We also provided a backup set of phones, just in-case (which weren’t needed in the end and just got in the way!)

We had 6 stations, each with 2 phones – the main one connected to the ADSL line Bluegrass provisioned for the task and a backup phone connected to the offices existing ADSL line just in-case. The credit card terminals were also connected to the LAN, so that made for some interesting wiring on the table and the meeting room in the DAAT office did look a bit “Heath Robinson”, but it all worked very well indeed.

Saturday morning took us rather by surprise and did see a small number of people queue for a little over 10 minutes before their call was answered,  but once they got 6 people answering the phones the process speeded up somewhat and it all it went rather well!

Behind the scenes was a hosted call answering and queuing system (hosted in the Drogon Server bunker in Sheffield) The server there did the hard work of connecting the callers telephones to the volunteers phones via the queuing system – callers got some nice music and the voice of Richard Digance from BBC Radio Devon while the team of volunteers took callers details and donations. 550 calls isn’t a big amount by any traditional call centre standards (and it’s a fraction of what we handle anyway), but it was a nice little setup and example of what can be done at relatively short notice.

Volunteers taking calls for the DAAT Charity Phone-In

Well done to the team taking the calls, and everyone else involved!

Footnote: What’s an 03 number?

03 numbers were introduced by Ofcom early in 2007. They are defined as non-geographic number with no revenue share – unlike 084x, 087x numbers where the operator does get revenue from each call placed to them. They should be billed at the same rate as regular 01 and 02 numbers with calls to them coming from any inclusive minute call plans you may have. 03 numbers where the 3rd digit is a zero (030…) are designated for charity or NGO use.

Here at Drogon, we can queue calls to any number – we’re not restricted to 084x or 087x numbers at all.

Over the next few weeks, I’m going to write some articles here telling you about IPv6, why it’s important and what it will mean. I’ll start with what’s happening to IPv4…

But before that – what’s an IP address again? An IP (Internet Protocol) address is a number that uniquely identifies a site or device connected to the Internet. This could be your home broadband connection, a website, or your fridge/freezer… Since we’re good at remembering names, not numbers, we normally use a system called DNS – Domain Name Service that does the name to number translation for us, so it’s quite rare to see an actual IP address.

What is IPv4?

IPv4 is the current version (i.e. version 4) of the Internet Protocol. It uses a 32-bit number to hold an IP address which gives the potential for just over 4,300,000,000 different IP addresses. If we write them, we usually put down 4 decimal digits separated by dots. E.G. 195.10.225.68. You can see why using names is sometimes easier, even if longer to type – that IP address is unicorn.drogon.net. IPv6 still uses names, but the underlying numbers are bigger – much bigger!

Due to the way IPv4 addresses were carved-up in the early days (mid-1980′s) not all these 4.3 billion addresses are usable, however even if they were, it would only put off the inevitable – we are running out of IPv4 addresses.

What will happen when we run out?

Well, be reassured that the Internet will not stop, grind to a halt or have anything else disastrous happen. Things will keep on going as they are, but we might see a slow-down of new sites appearing, or a slow-down of new Internet connections happen – as the existing providers struggle to clean-up unused ones, recycle old, and so on. Eventually there will come a point when we’re well and truly out of IPv4 addresses.

When will we run out of IPv4 addresses?

IP addresses are allocated in a hierarchy. At the top there is IANA – they hand out big allocations to local registries who then hand out smaller allocations to ISPs and so on. There are five local registries across the globe. E.G. RIPE manages Europe.

As of January 20, 2011, only seven of the 255 allocation blocks remain available, or less than 3% of the IPv4 address space… APNIC will be allocated 2 of these blocks in the next few days then the remaining 5 blocks will be allocated to each of the local registrys soon after that, and then IANA will have no more to hand out. The local registrys will tighten up on allocations and there will be a squeeze… How long it will take before we’re properly out is anyones guess. It could be a year, or more or less.

Enter IPv6

IPv6 will give us the potential for 2^128 unique addresses. That’s about 3.4×10^38. That’s a very big number. It’s not new either – it was defined in 1995 – some 15 years ago at the time of writing this post and more or less adopted as a standard round about the year 2000.

So why aren’t use using it? Who knows. Lazyness, lack of knowledge, fear of the unknown are just some reasons I can think of right now, and I’m hoping that in time I’ll be able to help with some of these. Keep reading these articles to find out more!

]]> http://drogon.net/blog/2011/01/are-you-ready-for-ipv6/feed/ 0 http://drogon.net/blog/2011/01/geek-yoghurt/ http://drogon.net/blog/2011/01/geek-yoghurt/#comments Sun, 09 Jan 2011 22:29:28 +0000 admin http://drogon.net/blog/?p=148 Continue reading →]]> And now for something completely different…

Not the usual run of the mill posting from me, but today I’ve made 2 pints of yogurt as we seemed to have a surplus of milk this weekend.

The geek part was using my infra-red laser pointer thermometer to keep an eye on the milk temperature. (A tip I picked up from watching the chef in the Riverford Field Kitchen!)

It’s trivially easy to make too – you need milk and some live yoghurt to use as a starter. Gently heat the milk to just under boiling point (not more than 85C), chill it to 45C (pan in bath of cold water), stir in a few tablespoons of live yoghurt, pour it into a warmed thermos flask and leave for 7 hours. Chill overnight in the fridge and voila. A pint of something that costs over a pound in shops for 50p and a few minutes of work in the kitchen. It will last 1-2 weeks in the fridge too – an ideal way to preserve spare milk!

Of-course you do need some live yoghurt to start with – which does beg the question – where did the first live yoghurt come from? Well for us, we almost always have some, so it’s easy – the fridge! Our milk comes in bottles and is  unpasteurised from Scorriton Farm and it seems to make really nice yoghurt! (And Kefir too – and I always have a surplus of Kefir grains if anyone local wants them!)

Managing these servers is relatively straightforward, but recent expansions have required a small re-think of how we work…

Until relatively recently, we’ve ignored the cloud or virtual servers – much preferring to use a real, physical server – you know where you are with a real server! However, our latest product is a hosted version of our popular in-office based PBX, so trying to host dozens of these poses a challenge – not only in hosting costs, but additional infrastructure required, so enter server virtualisation which arguably is the core of “The Cloud”.

“The Cloud” is a term that seems to be used to cover a multitude of applications – from a simple remote hosted service to 1000′s of servers all working together on big scientific applications and even to distributed or remote data storage. We like to think that our cloud is just a means to enable us to better manage and utilise available resources and give us additional and more efficient recovery mechanisms from hardware failures and so on.

Taking a single server and carving it up into many virtual hosts is something that’s been going on for many years – right since the days of putting many web sites on the same IP address. Server virtualisation takes this one step further and provides servers-inside-servers. Advantages? Many – you can take one of these servers and migrate it to different hardware – sometimes completely transparently!

This give the hosting company the ability to better manage resources – we can move a virtual server onto new hardware should it be required (e.g. faster CPU, more memory), they can use it to enhance disaster recovery should a servers hardware before unreliable or fail, and probably as important, can ultimately require less physical servers to host everything on.

Less servers means less infrastructure costs – which leads to less energy used which can arguably be considered “green”. However from our point of view, it allows for a simple model of server hosting and facilitating. The base servers can be identical (or as near identical as required), the virtual servers then do the customisations as required.

There is a down-side… The virtualisation mechanisms do require additional learning for the administrators and a lot of testing required! However in our opinion, it’s well worth it.

The Drogon Cloud is actually two clouds. A cloud of VoIP servers and a separate cloud of LAMP servers. The VoIP servers have a somewhat different requirement to LAMP servers, so are maintaned separately from them.

The maintenance and running of them is very similar though, and the strategy we’re adopting is to always have at least one spare server of each type, so if a server fails then we have the option of migrating the individual virtual servers on that server to other servers, or we can migrate everything to the spare server.

So, it’s all gone cloudy, but for once, this is a good thing!