Bees Not Included

The Doobry Lab - Technical Reference App

2012-01-18T13:24:00.000-08:00

This is a shameless plug for a colleague's recent venture into Android Application development:

"Nautilus [has been] developed to cover a broad range of technical subjects, without getting too bloated with details. It will never cover any one subject in great detail, but will provide the information most commonly requested at your fingertips."

For more information, visit The Doobry Lab or just go straight to the Android App Store

Vim Foo

2012-01-16T12:59:00.000-08:00

My most advanced regular expression to date:

0,$ s:$\d\+$\s\+$\w\+\d\+$:set_location_assignment PIN_\u\u\2 -to HdcSig[\1]

This takes a space-separated-value file of signal names and FPGA pin numbers and generates the tickle assignment statements required by the synthesis tool, Quartus.

Input:

Output:

set_location_assignment PIN_AA1 -to HdcSig[0]
set_location_assignment PIN_A4 -to HdcSig[1]
set_location_assignment PIN_B4 -to HdcSig[2]
set_location_assignment PIN_C9 -to HdcSig[3]

In Summary it:

Extracts a numeric followed by alpha-numeric field and stores them in \1, \2 variables
Adds a line prefix
Capitalises coordinates
Switches order of signal names vs coordinates
Adds some braces

Result: feeling smug :D

Peterborough in January

2012-01-15T14:20:00.000-08:00

Today we made it to Peterborough (just) to watch the Peterborough Phantoms play the Sheffield Steeldogs in the English Premier Ice Hockey League.

Before the ~~match~~ game, we wondered around Peterborough city. Despite being generally quite ugly, there was one redeeming feature, it's Cathedral. Even on an overcast and freezing afternoon its walled grounds were inviting and its architecture both imposing and impressive. Enough words, here are my favourite photos from the Cathedral grounds.

This one isn't actually of the Cathedral or the grounds. It is the market square in the centre of the town. The sky looked too good to pass up the opportunity to photograph it.

You can view the Picasa album here

Man Bench Transformation

2012-01-07T11:14:00.000-08:00

For over a year, the affectionately named 'man bench' has been a bit of an eyesore in our flat. Its some old tool shelving that my Dad lifted from a building site at the end of a job. Our flat is quite small and storage space is at a premium, hence not throwing it out.

More recently I've begun playing the piano more regularly in an attempt to teach myself blues piano. Getting a keyboard stand has been out of the question because there just isn't the room to leave it up all the time. I've been using the ironing board as a temporary stand. It is however, rubbish; it wobbles and cannot be adjusted to a suitable height for playing.

This afternoon I set about transforming the shelving into a sturdy keyboard stand. This involved lowering two of the shelves, sawing off the legs and cutting the top down to the right height.

Here's the before:

From Man Bench Transformation

Here's the during:

From Man Bench Transformation

And here's the after:

From Man Bench Transformation

Domain name at last

2011-12-28T15:30:00.000-08:00

I've finally bought the domain name www.beesnotincluded.com. Links using the old blogspot address will redirect to www.beesnotincluded.com.

Making EE Times more readable

2011-12-28T08:11:00.000-08:00

I enjoy reading some of the technical articles on the EETimes website. This is the best site I have found for professional electronic engineers (excluding the IEEE). Unfortunately, reading anything on the EETimes website is excruciating. There are so many adverts and flash videos that even on a fast computer the pages take ages to load, and scroll latency can be measured in minutes. Sadly, this means I quite often put off visiting the site, even though I'm sure there are interesting articles to be found.

Earlier this year I learned about Readability

I downloaded the app and now find reading EET articles far more inviting and a lot quicker. Here is an example of how much of a difference Readability makes

Try reading this:

http://www.eetimes.com/design/test-and-measurement/4227229/Hunting-noise-sources-in-wireless-embedded-systems

Now try making it readable:

http://www.readability.com/articles/bhwlrpmj

I know neither of these concepts are novel, but for anyone else that was put off reading EETimes by its crappy website design, hopefully this might change your mind.

Replacement sky for overcast photo

2011-12-11T10:11:00.001-08:00

Having recently stayed at the magnificent Down Hall I wanted to take a photograph which did the house and its surroundings justice. Unfortunately it was overcast so my photos were all a bit dull. This was the best I could get:

I wanted to do two things. Remove the tissue from the front lawn and replace the sky with one more fitting. Apparently this is trivial in Photoshop, but I only had access to GIMP. So I found this well written tutorial and followed it. After about half an hour of playing around I produced the following result.

It is a little bit rough and I'm not sure the brightness/contrast of the sky matches the photo too well, but I'm pleased!

Asynchronous behaviour of synchronous counter

2011-12-04T09:04:00.001-08:00

I've written before about performing timing analysis with Altera's FPGA design software, Quartus II. I find Analysing timing for a complex FPGA project far from easy. Distinguishing which timing violations are important and which ones are the result of poorly constrained paths can be tricky. Sometimes a path in your design may report negative slack, but you don't care, because you only latch the signal on every other clock, or perhaps because that path's timing just isn't important to your design.

That being said, once you've identified that a timing violation that does concern the performance of your design it can be tricky to understand what the Timing Analyzer is saying. Typically all you have to go on is a source and destination 'node' in your design and the corresponding clock domains to which the violation concerns. Earlier this week I came across a timing violation which at first glance didn't make any sense.

The analyser flagged a negative slack time from the q[] output of a counter (marked as 'source') to the register 'reg' marked as 'dest' in the diagram below:

This didn't make any sense. There is no combinational logic joining the source to the destination. At least it looks that way on first inspection.

If you consider the behaviour of the synchronous counter, the cout output is dependent upon the direction of the counter. When counting upwards, cout goes high when the counter value is '1111..11' however when counting down, cout goes high when the count reaches '0000...00'. This implies that cout is directly, and combinationally dependent upon updown.

The reason for the timing violation now makes sense, the combinational path joining source to dest now includes 'path_a' and 'path_b' in series, it is as if the path continues from the updown input through to cout output of the counter.

This path includes quite a lot of combinational logic, hence the failure to meet timing requirements. It is these sorts of subtleties that make resolving timing issues far from trivial.

Source: "lpm_counter Megafunction User Guide", Altera, 2007, retrieved 4th December 2011, URL: http://www.altera.com.cn/literature/ug/ug_lpm_counter_mf.pdf

Pumpkin Carving

2011-10-30T08:28:00.000-07:00

From Halloween 2011

Happy Halloween!

Excel can't do maths

2011-10-27T11:53:00.000-07:00

I stumbled upon a little publicised bug in the current version of Excel whereby it displays the wrong trend line equation on scatter graphs.

http://support.microsoft.com/kb/114629

You would expect such a simple and often used function to work but apparently not. I only discovered this after someone tried to use the equation I'd presented to them and complained that it was wrong!

The lesson I've learned is to always double check my maths, regardless of whether I had 'help' from a computer.

Quartus TimeQuest work flow

2011-09-30T13:37:00.000-07:00

As part of my long-lasting DDR2 IP block problems I've learned a little about the TimeQuest timing analyser. This is a program included with Altera's Quartus software which provides post-fit timing information about your design. Once the design is synthesised and the fitter has completed, you can run the TimeQuest tool to find out if your design meets the required set-up and hold timings. This is particularly useful/necessary for high speed circuits such as a DDRAM controller.

The TimeQuest tool is not intuitive. It is very powerful and mostly driven by Tickle scripts so I've outlined the design flow which I've come to learn over the past few days.

Compile your design
Launch the TimeQuest Analyser
Create the Timing Netlist - at this step you can specify the speed grade and the temperature model
Read the sdc file, this is the Tickle file containing the design constraints for your design. This may be generated by an IP block or you may have to create this file for your design. It will typically describe the clocks and derived clocks within your project
Update the timing netlist. This step is Really important. I didn't realize this and as a result I found that my timing reports from the compilation stage disagreed with those produced in the TimeQuest analyser
The final step is to source your timing report tickle script. This will present the setup/hold times for your design

If you don't perform step 5, updating the timing netlist, it is possible to find that the timing report produced as part of the compilation stage drastically disagrees with that produced in the TimeQuest analyser - very confusing.

Hopefully this will help anyone else struggling to verify the timing of their design.

Misleading Quartus Messages

2011-09-30T13:20:00.000-07:00

For the last few weeks I've been struggling to get a closed source IP block from Altera to work. The block is a DDR2 controller for the Cyclone IV range. As part of my debugging I scrutinised all of the Quartus Analysis & Synthesis info and warning messages to try to get to the bottom of the problem (which is still unresolved). One message which stood out was the following:

Info: Instantiated megafunction "Ddr2RamController... with the following parameter:

      Info: Parameter "intended_device_family" = "Cyclone III"

...

Info: Instantiated megafunction "Ddr2RamController... with the following parameter:

      Info: Parameter "intended_device_family" = "Cyclone IV E"

The compiler appears to instantiate some of the Megafunctions for the Cylcone III (which is different from the target device) and some for the Cyclone IV.

I subsequently highlighted this in a service request to Altera.

The official response from Altera is that this is the correct behaviour - despite being incredibly misleading. It turns out that the intended_device_family parameter is only used for simulation purposes, so the fact that it doesn't match the target device is irrelevant. Furthermore the altera docs (PDF page 55) does not allow for this parameter to be set to "Cylcone IV" - presumably, the IP block should behave identically in the Cyclone IV as it does in the earlier Cyclone III.

The result for me is that I'm still no closer to solving my DDRAM issues.

Hopefully this information will prove helpful to others struggling with misleading Quartus info/warning messages.

I originally posted a query about this in the Altera Forums to no avail:

http://www.alteraforum.com/forum/showthread.php?p=129172#post129172

Big Dog

2011-09-23T15:01:00.000-07:00

A friend at work informed me of this US DARPA funded project called Big Dog. Watch the video of this robotic dog in action:

It is made by a US company called Boston Dynamics and they have published some slides and a technical paper about the different technologies and the use of compliant materials within the robot. I'd hate to think what the R&D costs of something this advanced would be. The Big Dog project website has links to the aforementioned presentation and technical paper.My favourite part of the video is when they kick Big Dog on the ice and it stumbles briefly before recovering. The slow motion jumping sequence is very impressive too!

Holiday themed quiz

2011-09-18T10:09:00.001-07:00

As part of our Canadian Thanksgiving celebrations we wrote a holiday themed quiz. Topics range from bizarre holiday customs through to holiday foods and films. The questions, and answers, can be downloaded here:

Holiday Questions

Holiday Answers

If you liked this you may also like:

Pork Timing Diagram

2011-09-18T09:43:00.000-07:00

In preparation for a big Canadian thanksgiving dinner I prepared an ever so slightly nerdy timing diagram for cooking all the ingredients. I started off with the intention of a drawing a Gantt chart but several weeks of staring at DDR2 ram data sheets must have had an effect! The result was remarkably clear and the food turned out O.K so I'd call that a success!

PDF Forms are Evil

2011-09-11T08:38:00.000-07:00

I have to fill out some government forms which are all interactive PDF forms. Some of them even have the ability to save the form data deliberately disabled:

I cannot believe someone at Adobe thought this a good idea. I don't have a printer, so it means printing the stupid form to a postscript file! This doesn't smell like progress to me?

PDF forms are bad for other reasons too. They only seem to work properly with Adobe's PDF reader, so fat chance of using evince for linux or any other open source reader. Even after installing Adobe Reader for linux (shudders) the form is so unusable that you really have to question what the point of them is?

So in conclusion PDF forms are evil.

A long weekend in Copenhagen

2011-09-10T08:43:00.000-07:00

Copenhagen is a beautiful city and Danes are lovely people.

We recently spent the British August bank holiday in Copenhagen. Arriving early on the Friday morning after an uncomfortable Easyjet flight from Stansted we disembarked in glorious sunshine. Copenhagen airport is, like the rest of Copenhagen, beautifully designed, terrifically efficient (average time through security: 6 minutes) and welcoming. The newly built and still expanding metro service (which incidentally is suicide proof!) takes you straight from the terminal to the city centre in under 15 minutes and for not many Kroner. And from the city centre just about everything is within walking distance.

I'm no travel writer so here is a photo illustrated list of my prevailing thoughts and impressions of this magnificent city:

Copenhagen has a lot of parks and public gardens. You can spend a day just walking around parks if you wanted to. Locals seem to use them too. When the weather was good we saw Danes pitched in parks with crates of Carlsberg/Tuborg. Below is the most beautiful of all the parks, the Botanic Gardens:

From Copenhagen, Summer 2011

Danes do design. The state museum for modern design is a good example of this. I just wish my photography could do it justice:

From Copenhagen, Summer 2011

Even the children's play area is stylish and 'designed':

From Copenhagen, Summer 2011

Herons are a common site in the many parks and gardens. So much so there are statues of them dotted around the city:

From Copenhagen, Summer 2011

These terracotta buildings used to be army barracks but they seem to be domestic dwellings nowadays. I thought they looked stunning and enjoyed photographing them:

From Copenhagen, Summer 2011

This windmill resides at the centre of an active fort, surrounded by a star-shaped moat:

From Copenhagen, Summer 2011

There is a _lot_ of graffiti in Copenhagen, this was one of the less permanent examples:

From Copenhagen, Summer 2011

Danes love their statues. Below is the famous Little Mermaid statue, a frequent victim of political activists. Below that is a statue we found en route which we mistook for the little mermaid. I'm divided as to which one I prefer:

From Copenhagen, Summer 2011

We came across some crazy Danes. Here are some of them:

From Copenhagen, Summer 2011

Just about every famous Danish person in history was called Christian. Here is the city's much loved Hans Christian Anderson, children's author and figurehead for the city:

From Copenhagen, Summer 2011

Copenhagen is a city of canals. This one completely separated the state offices from the mainland. It was frequently circumnavigated by tourist barges not much smaller than the archways of the many bridges that cross it.

From Copenhagen, Summer 2011

Back to more striking architecture and this is the new university library. Its like a glass battleship beached along the canal. Inside it has expansive concrete balconies and stairways at inconvenient angles, curvy passageways and a pretty reasonable cafe.

From Copenhagen, Summer 2011

Christiania is an odd place. It is a self ruling community established in the seventies at a disused military base. It is now a haven for soft drug users, hippies and graffiti artists seeking something approaching immunity from the law. It is a surprisingly popular tourist destination. You are prohibited from running and taking photographs - both activities 'make people nervous'. Below is the entrance to this place.

From Copenhagen, Summer 2011

If you want a beer in Copenhagen you have a choice of Carlsberg or Tuborg. Both are now brewed by Carlsberg brewery and it could be argued are indistinguishable. Drinking out is not cheap in Copenhagen. Even though the brewery is a stone throw from the centre. We took a S-train out of the city to visit it. There is a quaint museum charting the history of brewing in Denmark and an impressive, world record breaking, collection of bottled beer.

From Copenhagen, Summer 2011

As part of the preparations for our visit I compiled a Google map with markers of all the places to visit. Since I don't have a camera with geo-tagging capabilities (yet) I've embedded the map below so I can remember where we went and what we saw (and photographed):

View Copenhagen Trip Aug '11 in a larger map

All my photos from this trip are in this Picasa web album:

99% Invisible

2011-09-10T08:12:00.000-07:00

Its not often that I find a blog which interests me so much that I want to link to it. 99% Invisible is one of them.

It is a collection of well produced, succinct podcasts about design, architecture and engineering. Some of my favourite episodes cover topics such as:

Redesigning the bank statement

Samuel Plimsol's eponymous line

The Great Pyramids

Advice for PCB assembly

2011-08-20T03:36:00.000-07:00

At work I've been developing two new PCBs. These are both eurocard size boards with a high component count and some tricksy BGA and QFN parts. For prototype builds we typically use an external company to assemble the boards. I've been through the process of getting boards assembled several times before, but this current project is by far the most complex and the assembly process has been far from straight forward.

A three working day quote turned into a six day turn-around. Consequently, I've learned a few things about how to manage this process and I want to share what I have learned.

Lesson #1 Make the assembler's life as easy as possible. If you don't, they will make your life as hard as possible. An extra couple of hours of your time spent preparing the data files will speed up the build, reduce the number of component placement mistakes and curry favour with the assembler.

Lesson #2 Supply good assembly drawings. CAD programs are really good at auto-generating this kind of output, but left unchecked they will produce accurate but unhelpful drawings. A good assembly drawing will be a PDF showing each component layer (separately) and all the component designators for that layer. If the board is very compact, enlarge the print so it is more than just a 1:1 print. Use layer colours which are easy to read and which have high contrast.

For prototype builds, it is very unlikely that an assembler will use a pick and place machine to populate the board. It just isn't worth their time. Unless you are supplying parts on reels, the time taken to re-reel components and load the machine is crazy. This means your boards will be placed by hand and so providing clear, human readable drawings is essential.

Lesson #3 Carefully prepare the components This is mainly common sense. If you are getting multiple boards assembled, keep the parts for both in separate boxes. Order spares of inexpensive components. An extra few pounds spent on passive components is preferable over having to leave them off the board or delaying the build to buy more. If you order your components from Digikey, during the checkout process you can enter the component designators corresponding to each part. These will be printed (space permitting) on the component bag label when your order is prepared. This makes it much quicker to find components.

Lesson #4 Check the BOM carefully Again, this is pretty much common sense. Make sure that any no-fit components are removed from the BOM. Failing to do this can mean the assembly is delayed while they look for the missing parts.

Lesson #5 Keep track of your changes This one really caught me out. It is common to purchase components as soon as you have the first draft of the schematic ready. This means you have time to sort out long lead time components while you are revising the design. Inevitably, changes will need to be made to the BOM after this initial order has been placed as issues are discovered during the review/layout stages. If you don't keep track of these changes and order the new parts you will have problems during assembly. One method is to compare the first BOM with the final BOM and spot the differences, but this is tedious and prone to error. It is better to generate an Engineering Change Order (ECO) for each of the changes as you make them. This can be a simple spreadsheet listing the designators affected and the nature of the change. This may sound time consuming but it will save you a lot of lost time later on.

Lesson #6 Get progress updates It is worth checking in on the assembly process every couple of days. A short phone call to check everything is going O.K. may help you spot and resolve parts queries/shortages before they add half a day's delay to your project.

Lesson #7 Remember its a prototype I think most assembly companies acknowledge that during prototype builds there will be problems with the BOM and the odd component shortage. From my experience, they are happy to put the build aside for a day while you fire off a Farnell order to get hold of the missing parts.

This may all seem pretty obvious, but in the hurry to get your prototypes made and meet your next milestone, it is easy to let some of these points slip.

Modelsim fail

2011-08-11T13:22:00.000-07:00

This isn't a blog post about all the things that I think are wrong with Modelsim, nor about the shortcomings of VHDL as a hardware description language. Instead it is a reminder for me (and possibly others) of what to do for when I see this Modelsim error in the future:

Reprinted:

# Fatal error in Process line_78 at C:/.... line 82
#
# HDL call sequence:
# Stopped at C:/... 82 Process line__78
#

I wasted about 15 minutes searching the internet for typical causes of this ambiguous error message and searching line 82 for syntax mistakes. In the end I found out that in this case, the 'fatal error' was caused by trying to write a 17bit vector to a register defined as std_logic_vector(15 downto 0) and therefore only 16bits large. I cannot believe that what must be a common mistake was not picked up by the VHDL compiler (not even as a warning) and also not assigned a more descriptive error message. It was only when running the simulation that Modelsim complains.

To reiterate, the following code will generate a fatal error when you simulate it but will probably compile without generating an error:

signal bees : std_logic_vector(15 downto 0)

...

bees <= X"1234" & '0'; -- 16bits + 1bit = 17bits > length of 'bees'

Peak District in the Summer

2011-08-06T15:23:00.001-07:00

Here are a few of my best photographs from an afternoon walking in the beautiful peak district. We were following the Monsal trail which is an old disused and dismantled branch line. Two stretches of the line pass through some impressively long tunnels and over some spectacularly engineered bridges.

From Monsal Trail, Peak District, UK, August 6, 2011

For all of the photos in this album, go to my Picasa Web Album

Ely in the Summer

2011-07-09T10:30:00.001-07:00

Today we spent the afternoon in Ely, just north of Cambridge and sited on the beautiful river Ouse.

From Ely, Cambridgeshire, UK Jul 9, 2011

I couldn't resist taking a photo of this rude sign.

From Ely, Cambridgeshire, UK Jul 9, 2011

Canada Day

2011-07-02T12:59:00.000-07:00

Friday 1st July was Canada day, which reminded me about last year's Canadian Thanksgiving quiz which I never got around to uploading, despite blogging about the LaTeX foo I used to make it. Well here it is, for anyone who wants to test their knowledge of Canadian geography, history, sports and celebrities.

Here are the questions

Here are the answers

Happy Canada Day!

Inductor selection for Switch Mode Supplies

2011-05-21T13:23:00.001-07:00

Recently at work I have had to design a few switch mode power supply circuits. I haven't had too much experience at designing these before and have so far got away with following recommended circuit topologies in the switcher datasheet. This has generally worked out O.K. but you can end up with an over-specified inductor which has many implications for the performance of the final circuit. Another problem with this approach is that blindly trusting the manufacturers datasheet examples is bound to lead to problems eventually. The design criteria for such circuits are rarely specified beyond output voltage/output current, there is no mention of ripple current/voltage, overshoot, power dissipation...

I set out to get a better understanding of how switch mode power supplies work, and understand the equations which underline their performance. This post is a collection of the resources I found during the learning process.

My starting point was SMPS Technology which has a short tutorial on the basics of switching regulators. This outlines the basic inductor equations and how to apply these to a buck regulator. It offers suggestions on choosing suitable inductor and capacitor values based on simple 'rules of thumb'. Helpfully, it explains the different approaches to controlling switch mode supplies and the effects of each method on stability and overshoot.

Having read this tutorial through a few times, I was keen to understand where these rules of thumb had come from and what the implications of following them were. After a trawl of switching regulator manufacturer's websites, I came across a National Semiconductors Application Note 1197. This is an expertly written document which explains how to select an appropriate inductor for your application. As well as showing how to choose a starting value for your inductor, it explains how to calculate the RMS current, Peak current, energy handling capability and saturation current required for you application. Furthermore, it shows how you can take the parameters from an Inductor datasheet and calculate the power losses due to core losses and copper losses and therefore work out the temperature rise.

Another good resource for selecting an Inductor is the Coilcraft website. Their Inductor Selector for DC-DC converter circuits is a pretty good starting point. Once you have chosen an inductor, they also provide an inductor loss calculator.

If you want to be even more lazy you can try the National Semiconductor WEBENCH tool, which will not just select an inductor but will design the whole switch mode circuit for you, including sourcing all the components! I tried using this for the last switch mode circuit I designed to see how good it was. I was sceptical that it would do a good job. The circuit topology it suggested was pretty much the one from the datasheet with some important exceptions. It suggested an output capacitor with a large ESR which would have given poor voltage ripple. It violated the maximum resistance for the feedback resistors and it missed of the soft start capacitor. In conclusion, don't trust it to get everything right just yet!

Farnell Box Ticker

2011-05-16T12:28:00.000-07:00

Frequent users of the Farnell website may, like me, get annoyed at having to continually tick the 'in stock', 'RoHs' and 'Exclude extended range' check boxes while searching for parts. Unfortunately, these check boxes do not seem to stay checked beyond a single search, even if you log in it will not save your preferences.

Using Greasemonkey to tick Farnell Search Boxes

So I set about writing a greasemonkey script to automatically tick these boxes when the page loads. Just in case I later decided I did want to pay £16 to ship a resistor across the Atlantic, I decided to add a keyboard short cut to invert the selection.

It turns out that greasemonkey is really annoying. User scripts execute in a sandbox, which means you can't access elements on the page or in the DOM as you would in say Firebug or a script running on the page itself. There is quite a lot of documentation out there about all these quirks, but even simple things like changing the value of a checkbox becomes a real headache.

After spending an evening getting to grips with Greasemonkey and refreshing my Javascript foo, I thought I had it cracked. So much so that I uploaded my efforts and boasted about it on Twitter. Then I took a closer look and discovered that all my script actually achieved, was graphically ticking the boxes on the Farnell search page and not actually affecting the search.

A little more time spent inserting breakpoints into the Farnell application script and I found the function that needed to be called to affect the search. For this, Firebug was essential! From the DOM tab, you can right click on an element and select 'Break on attribute change'.

Installing the script

The working script can be downloaded from userscripts, it is called: Farnell Box Ticker or you can directly install it by clicking this link

Unlike many scripts, this does not use the potentially unsafe 'Unsafe Window' work-around. Instead it relies on the fact you can type javascript directly into the URL box in your browser like thus: javascript:alert('beesnotincluded"');

Using the script

Once installed, this script will run on all of the farnell domains (hopefully). On the non-parametric search pages, the Stock,ROHS,Extended items boxes will automatically be ticked. For parametric searches, these boxes cannot be automatically ticked, because they are generated dynamically after the page has loaded. You can however, use the CTRL+E shortcut to toggle the state of these boxes on these pages.

Bug reports welcomed :s

Alternatives to amazon downloader

2011-04-28T14:37:00.000-07:00

I'll keep this short, because I've just spent in excess of an hour trying to get Amazon's official, propitiatory downloader for linux Fedora 13 to work. The problem is that Amazon's binary is dynamically linked to old versions of C++ Boost libraries which are not part of Fedora 13 or beyond. Trying to install the old libraries and all their dependencies is a nightmare.

The solution is Pymazon. It works, its open source, its python (so installing it is a child's play) and best of all it is better than Amazon's official offering.

Also Clamz exists but I've not used it so cannot vouch for it.

Inverted Pendulum Part I

2011-04-16T11:15:00.000-07:00

Foreword (no technical content)

For the best part of a year, I've been hoarding an old Dell Deskjet 720. As printers go, this was a pretty crappy printer. The ink cartridges or 'cash cows' as I like to call them, were only officially available through Dell and therefore very expensive. The Lexmark driver (for it was actually a Lexmark at heart) was closed source and buggy and the print quality was poor. All of these are probably explained by the fact Dell were giving them away free when I bought my first computer about 6 years ago. Here is what it is supposed to look like:
I had been toying with the idea of taking it apart and making something out of the parts but didn't really come up with any good ideas. There are already lots of projects such as RepRap which use printer parts to make rapid prototyping machines or similar CAMs. I don't really have the space or need for any of these at the moment so the printer went un-hacked.

Earlier this week I came across this project - a self balancing one wheeled robot. This reminded me of the inverted pendulum lab experiment which I'd done during my time at Southampton University. Labs generally weren't much fun, but I remember enjoying this one so I set about making an inverted pendulum out of printer carriage and some other parts.

Step 1: Tear-down
So far this has been the most fun part. I'm not sure how people can make those really long winded videos/slide shows of incrementally taking apart their newly bought I phone. Once I started disassembling the printer I soon forgot about photographing anything which is why there is a large gap in the photo sequence below:

This part was quite interesting. Most desktop inkjet printers use aqueous inks. Aqueous inks are volatile and if a print head is left exposed to the air for long (which could be a matter of minutes for some inks) then the water will evaporate from the nozzle plate leaving the less volatile pigments to block up the nozzles. In commercial inkjet printers, a lot of money and effort is spent trying to prevent the nozzles from drying up and becoming blocked between prints. In this Dell printer, there are two suction cups (one for black, one for colour) which are pressed up against the nozzle plate when the carriage reaches the extreme of its travel. Below is a close up of this mechanism. When the printer is switched on, the carriage moves left, pushing the suction cups down and out of the way.

The right end of the transport is shown below. The carriage, which by this time has been stripped down as much as possible, travels along the heavily greased steel dowel.

At the opposite end, a 24V DC motor is coupled to the drive belt. The belt was surprisingly easy to remove. The cog at the other end of the printer is mounted on a spring loaded assembly which makes it easy to remove and fit the belt.

I decided to leave the paper feed rollers in place, since I may find a use for them later. They too are spring loaded, so it is possible to feed fat media, such as a bare PCB through the mechanism without breaking anything.

A stepper motor which I currently know very little about drives the paper feed mechanism.

Step 2: The electronics

Not shown in these picture is a self contained 30V 0.4A power supply which fits into the back of the printer. It has two rectangular contacts which mate with the large steel contacts shown in the right of the picture below. This is the main print controller board which I have spent a little time inspecting. There is a Lexmark IC in the centre of the board which doubtlessly does the grunt of the data processing. The rest of the board is made up of a 1K Atmel EEPROM chip, two switch mode power supplies, a status LED, ribbon cable to carriage, stepper motor controller and DC motor controller. In the top left of the board is a photointerrupter which, coupled with a plastic flange, acts as the product detect, to notify the print controller that the leading edge of the paper has arrived at, or a known distance from, the print head.

The second and much smaller board is mounted behind at the rear of the carriage. It is linked by a flexi-pcb. This board has a single IC marked SC90105 which is about all I could deduce. I couldn't find a datasheet for the part so I can only guess at what it is for. Since this board connects directly to the electrical contacts of the printer cartridge, I'd guess that this is a shift register with high current outputs for driving the individual nozzles. I'm more used to working with industrial inkjet print heads, which are much different.

The black plastic block on the right is an optical, quadrature linear encoder. It has a slot through which the linear strip passes. The strip is printed with black bars to interrupt the photo beam inside the sensor. This is the part I'm most interested in, as I need to be able to track the position of the carriage in order to keep the pendulum near the centre of the transport.

Before disassembling the electronics any further, I powered up the electronics, outside of the printer confines, from my bench power supply. I was forced to power it at my power supplies limit of 20V, instead of the 30V it is designed for, but fortunately this was not a problem since I was only interested in the logic level signals. More of a problem was the 1mF capacitor on this board which caused my power supply to current limit for the best part of a minute while it charged up.

I concentrated on the encoder, trying to work out the pin out by viewing the signals on a scope whilst moving the linear strip. Once I acquired some extra hands, this was easy. The part has few markings and none that correspond to a data sheet. For this reason I post the pin out below:

The pitch of the encoder connector is not quite 0.1" so I was forced to straighten the right angle connector to lengthen the contacts enough to fit into standard strip board. The result was fairly neat and is shown below.

I did a quick test to check that the encoder could still travel unhindered along the rail.

The outputs of the encoder are either low voltage CMOS 3V3 or NPN/PNP. I'm not sure which yet. Now I have abstracted the encoder from the rest of the printer I can hook it to an MSP430 microprocessor and begin work on decoding the quadrature encoder outputs. I've done this on an FPGA before but not on a microcontroller. Should be pretty straight forward though. The board on the left is an old IO board from the Student Robotics project circa 2006.

Its been a while since I've done any electronics and some of my tools were showing signs of neglect. It turns out that an old Brillo pad is a great stand-in for a proper soldering iron sponge. The impregnated soap makes a difference from the usual soldering smell.

Thriplow Daffodil Weekend

2011-03-26T10:16:00.001-07:00

Thriplow Daffodil weekend is this weekend. Sam and I went along on an otherwise overcast and chilly Saturday. It turned out to be a lovely afternoon.

LaTeX Quiz

2010-10-03T09:37:00.000-07:00

I wanted to create a quiz for a Canadian Thanksgiving party and I decided to use Latex and the Beamer Presentation package to create a PDF slide show of questions. This worked pretty well, but I wanted to create a second PDF file with the answers shown next to each question to aid with marking. Rather than copying all the files and risk the question PDF becoming out of date with the answer PDF, I decided to create some new Latex commands to dynamically insert the answers depending on presence of command line compile option.

The following code...


%Question/Answer Commands
\usepackage{color}
\usepackage{ifthen}
\newcounter{q_num}
\setcounter{q_num}{1}
\newcommand{\question}[1]{Question \arabic{q_num}: #1\stepcounter{q_num}}
\ifthenelse{\equal{\showanswers}{true}}
{%: Show the answers
 \newcommand{\answer}[1]{\textcolor{red}{Answer: #1}}
}
{%: Don't show the answers
 \newcommand{\answer}[1]{}
}

...defines the following latex commands:

\question{<question-text>} - This appends a question number to the start of each question. The question number is incremented automatically.

\answer{<answer-text>} - The answer text is only visible when \showanswers is defined as true.

An example Question/Answer slide would look like:


\begin{frame}{}
\question{What is brown and sticky?}
\answer{A stick}
\end{frame}

If \showanswers is defined as false, the output would be:


Question 1: What is brown and sticky?

If \showanswers is defined as true, the output would be:


Question 1: What is brown and sticky? Answer: A stick

There are many ways to go about defining \showanswers. For example you could just define it in your main .tex file:


\newcommand{\showanswers}{true}

Or you could pass it as a command line argument which is what I chose to do using a makefile:


questions:
 pdflatex --jobname=questions '\newcommand{\showanswers}{false}\input{quiz.tex}'
answers:
 pdflatex --jobname=answers '\newcommand{\showanswers}{true}\input{quiz.tex}'
#where quiz.tex is the latex file containing quiz questions

This will produce two PDFs one called questions.pdf and one called answers.pdf. Only the second one will have the answers visible

Linux Shutdown / Login Issues

2010-07-27T11:44:00.000-07:00

I frequently use the shutdown command with a time delay to act as a basic 'sleep' function so I can listen to music before I fall asleep. Last night I scheduled a shutdown for 20min but 18min in I prematurely shutdown the computer, without cancelling the scheduled shutdown process. When I booted up the computer the next day I was unable to login despite using correct details: 'Authentication Failure'. I was also prevented from shutting down the system from the login screen. I switched to a different screen (tty2 etc.) and logged in as root after which I was presented with a message that the system was to shutdown in 2min. Attempts to cancel the shutdown using:


% shutdown -c

...didn't work as it couldn't identify the process id to cancel. Logging out and in again a few minutes later revealed the same 2min message. Unsure what to do I read the shutdown man page which revealed that during the last 5min of scheduled shutdown, logins are prevented. This explained the symptoms. I searched the process list but there was no trace of the shutdown utility running. Googling the symptoms revealed nothing so I tried scheduling a(nother) restart (from within root terminal) with a delay of 0min to see if this would clean up / overwrite any left over/corrupt system files:


% shutdown -r now

Fortunately, this worked. I couldn't find evidence of anyone else encountering this problem, so I figured I'd note down the solution here. Essentially I've learned that if you set up a scheduled shutdown, its safest to cancel it explicitly using the shutdown -c command, instead of hoping it will cancel itself when you pull the power.

Spell Checking on Fedora 13

2010-06-16T04:53:00.001-07:00

I recently installed Fedora 13 after spending over a year with Fedora 11. So far my only disappointment is with the spell checking. Despite ticking the English (UK) option in the install it did not install the correct spell checking libraries by default. Furthermore, I found it hard to find information on how to install the UK spell checking option manually. A lot of information is outdated, suggesting installing gnome-spell. This package is now retired [1] and has been replaced with enchant. So in order to get spell checking set up in Fedora 13, i had to install the following packages:

aspell

aspell-en

enchant-aspell

The english dictionaries now appear for use in gnome applications such as Evolution.

Its a shame that the correct language dictionaries still aren't installed by default.

[1] https://fedorahosted.org/rel-eng/ticket/115

Flat hunting in Cambridge

2010-06-09T07:51:00.001-07:00

Here are a few pictures from a recent trip to Cambridge to look for flats.

Monkey World

2010-05-22T09:41:00.001-07:00

Time for a non-geeky blog post. Sam & I went to Monkey World on what could be the warmest day in England this year :s

Video of Formica bouncing off the walls

2010-05-13T10:07:00.000-07:00

A video demonstrating the bump sensors we built onto the expansion board:

Formica Expansion Board Complete

2010-05-11T10:35:00.000-07:00

It's been a while since I've written about this project. This is because the deadline is rapidly approaching and there is still a considerable amount to do. First, here is the final thing:

View from front

View from top

The main problem we are experiencing is trying to get pictures out of the chip quick enough. At the moment we can only manage 4.6fps which is quite poor. Despite increasing the speed of the SPI link, the chip itself is holding us up the process. In returns 'invalid data' if you read it any faster than we are doing so at present.

The second problem we're having is a mechanical one. With the rather large eyes at the front, most of the robot's weight is *not* over the rear wheels, so we loose traction and consequently directional and speed control is proving tricky.

The final presentation is on Thursday and the demonstration some time next week. Busy days.

Formica Expansion boards have vision ... almost!

2010-04-29T11:08:00.000-07:00

Today was the fourth day of assembling and testing our Formica Expansion Boards. The final set of components arrived, enabling us to finish assembling all the boards. We spent the morning getting all of the bump sensor to work. These consist of a pair of piezo transistors, a rectifier, filter and Schmitt trigger. The conditioned analogue piezo signal and the digital signal from the Schmitt trigger are connected to the MSP430. This will allow the possibility of doing something clever with the analogue signal in software to deduce something about the nature of the collision. I'd like to see texture recognition based on this principle at some stage, although this is beyond the scope of our project.

The final, assembled expansion pack will look very similar to the ones in the photos below:

This eye sensor are not soldered on yet, because we are still prototyping how to make the aperture. The picture below has this chip soldered on it and we successfully read a pixel dump from it earlier today. Unfortunately the PCB footprint for one of the capacitors on the eye PCB was wrong, which meant 3v3->GND shorts were really easy to induce while soldering.

In order to manufacture the antennas in a sane and reproducible way, Tom constructed a jig to make them:

First signs of life in Formica Expansion Board

2010-04-27T13:50:00.000-07:00

Today we gained access to some surface mount soldering tools which ECS recently purchased. This meant we could solder on some of the more complex components such as the MSP430s. Particularly enjoyable was using the hot tweezers to rapidly solder on annoyingly small capacitors and resistors.

Below is a photo of the first signs of life from one of our expansion boards.

Unfortunately, while I was designing the board layout I reordered the programming pins (GND, DIO, CLK). This means that the programming adapters I have had to make to program Student Robotics boards are incompatible (GND, CLK, DIO). To get around this I made yet another adapter board. This lead to a rather unpleasant situation involving too many adapters. Here is a photo of the horror:

I think it is time I address this!

Ducklings on Campus

2010-04-26T08:16:00.001-07:00

First spotting of Southampton university ducks:

Formica Expansion Boards Arrive!

2010-04-26T07:55:00.000-07:00

As part of a final year group project I have been working to develop an expansion board for the Formica Robots. Over the Easter holidays I spent a considerable amount of time designing the PCB for the project. This is the first PCB which I have fully designed and had manufactured, so it was quite exciting. The boards arrived at the end of last week and so today (Monday) was the first chance I had to look at them and see if they work.
Here is the stack of ten boards fresh from PCB Train:

The white card behind them is a standard business card, which gives you some idea of how tiny these things are. These were then promptly cut with a PCB guillotine to separate the eyes from the expansion board:

Two eyes will stand vertically at the front of each expansion board, as the following mock up demonstrates:

The first problem experienced during construction is that the reverse of the inductor (shown in photo below) has a lot of exposed contact area. This is fine, except there is some ground plane and some signal lines routed directly under it on the board. To get around this I experimented with electrical tape stuck to insulate these tracks from the inductor.

LESSON #1: If you decide not to get a solder mask, be sure that you have not routed signals underneath components such as inductors, which have exposed conductive surfaces.

I have so far assembled only the DC-DC convert sub-circuit, due to the majority of the components being held captive by `stores' (My departments woefully inefficient system for ordering parts). Nonetheless, what has been built, works. This surprised me! The photo below shows the current state of assembly:

Pybill

2010-04-24T13:14:00.000-07:00

The task of working out who owes who what amongst my flatmates was getting pretty complicated. There are always circular debts and bills being split amongst different groups of people. For these reasons I set about writing a program to do this for us. I have name it Pybill. It is written in Python and can be downloaded from gitorious:

git clone git://gitorious.org/pybill/pybill.git

Or visit the project page: http://gitorious.org/pybill

The program takes a csv file (bills.csv) as an input with the format:


#comment
payee, amount, debtors

The program then outputs the minimum number of cheques required to settle all of the bills. Each person is identified by a single character and groups can be defined similarly. At present these are hard coded at the start of the pybill.py code, although I will change this to be a second CSV file soon. I am still in the process of testing the program but am confident that the algorithm to work out the payments is correct.

There are other freeware/shareware (mainly for windows) which claim to do this, along with many more websites which promise to do the same. However if you don't want all the guff that they come with, or want a simple file based solution then this may be useful.

First Barbecue of the Year

2010-04-23T03:03:00.000-07:00

Last night my flatmates and I had our first barbecue of the year. This was the first time we used the home made barbecue that has lived in our back garden since we moved in. The barbecue itself is made from an oil drum, some door knobs off an old set of draws, an upturned shopping trolley and some chains taken off the plugs in the bathroom. We had nothing to do with the design! Of particular merit was the use of the sides from the shopping trolley as the grill.

Unfortunately, whilst it was a really good barbecue, the base of the oil drum rusted through and the legs of the shopping trolley came through it. It now has a sort of tilt to it which it didn't have before.

Playing with fire

Warmth

Hot stuff

If I've said it once, I've said it fifty times. What this barbecue needs is *more* paraffin!

Burning sticks

Shopping trolley barbecue

Good times

My trident of fire

Long exposure fun

The tilt

Duck's Guide to 2010

2010-04-21T10:02:00.001-07:00

Dizzy Duck

Power Tool Duck

Public service announcement duck

Scaffold duck

duck-on-a-stick

Technobooth Duck

Duck, Over!

Hacker Duck

George Duck

Ramp Duck

Duck at Home

I hate my CAPS_LOCK key...

2010-03-26T04:49:00.000-07:00

...so I disabled it, using xmodmap. Since I'm a Vi user, hitting the Caps Lock key accidentally is really annoying as it is mapped to all sorts of crazy functions. Since I never use it for its prescribed function, (even outside Vi) I remapped it to be a second Escape key using the following code in my ~/.Xmodmap file:


remove Lock = Caps_Lock
keysym Caps_Lock = Escape

Source: http://www.peterbe.com/Disable-Caps-Lock-in-Linux

Programming puzzle

2010-02-24T07:25:00.000-08:00

What does this code do?


int main(void)
{
 int a = 123456;
 int b = 654321;
 
 printf("a = %d\nb = %d\n", a, b);

 a = a ^ b;
 b = b ^ a;
 a = a ^ b;

 printf("a = %d\nb = %d\n", a, b);
}

Last night my flatmate posed a programming puzzle and I solved it with the code above. Turning the problem on its head, what does the above code do?

Answer (highlight): Swaps a and b without using temporary
variable

PS: I expect this problem is as old as time itself...

Canada Day #17

2010-01-12T15:37:00.000-08:00

Today we went to the nearest town to where we were staying, Okotoks (oh-co-toks). It has a river which was, of course, frozen at this time of year. You can walk for what seemed like many miles along the river bank and even see deer along its edge. Also, for good measure, I've included a motel sign which amused me.

Canada Day #16

2010-01-12T15:28:00.000-08:00

This evening we went to a Calgary Flames game which was as much a theatrical performance as it was a sporting event. As a result I enjoyed it immensely and found it far more entertaining than any football match I've watched before. There was light and sound displays, not to mention fire, mascots and pee-wee hockey. Here are some mediocre pictures, since my attention was on the ice and not my camera! The opponents were the LA Kings.

Canada Day #16

2010-01-12T13:44:00.000-08:00

Today we went into `down town' Calgary. This was exciting for many reasons. Firstly I imagined it being like New York, given that It has some pretty big sky scrapers. Secondly It has a huge observation tower which we were going to ascend.

Here is the tower itself.

And here is the view through the glass floor at the top :s

These are a selection of my best photos taken looking down on Calgary.

The following two photos are of street level Calgary. The over ground tunnel is called a 'plus fifteen' as in plus fifteen feet above street level.

In the afternoon we went to Calgary Zoo which housed some pretty hardy animals, since most were outside all year round:

At night time during the festive period, the zoo is adorned with lights in a spectacle known as `zoo lights'

Canada Day #15

2010-01-12T13:34:00.000-08:00

So, I fell somewhat behind with uploading photos from my trip to Canada. The ordering of the days therefore is slightly dubious. Anyway, Today we went to Big Rock, just outside of Okotoks, Alberta, Canada. Its special because it is believed to have been carried down from the Rockies by a glacier that once crept over these lands. It stands out in an otherwise rock-less flat expanse of pastures. I liked it anyway!

There really is nothing else around this rock, just a small car park

Here it is a little bit closer up

And here is me posing in front of the rock

Canada Day #14

2009-12-29T08:31:00.000-08:00

Today we went horse riding in the garden. The horse was called Freckles.

This is Sam riding Freckles...

a...and this is me looking every bit the Cowboy!

Canada Day #12

2009-12-25T16:24:00.001-08:00

today is Christmas day. After waking early to help Sam get the breakfast ready (a dish termed 'wife saver' due to the fact it can be prepared in advance). We then settled down to open our personalised stockings. Mine can be seen below:

Tucker took it all in his stride:

He even joined in the festivities:

And here are some of my presents:

And here are some more:

Here is the full ensemble:

And here is the evil cat in a box:

This is what happens when you tease a cat with ribbon:

Here is by far the most entertaining gift of the day (My blackjack prize!):

Here it is once I assembled it:

And now in motion:

Canada Day #11

2009-12-24T15:29:00.000-08:00

Today is Christmas eve. We spent the morning in Okotoks collecting groceries for tomorrow and ingredients for gingerbread men today.

Step 1: Attack counter with rolling pin

Step 2: Continue attacking with a rolling pin

Step 3: Arrange into whimsical shapes. Bake.

Step 4: Look smug whilst icing the shapes

Step 5: Enjoy

Actual recipe: http://homecooking.about.com/od/cookierecipes/r/blcookie15.htm

Canada Day #10

2009-12-23T19:13:00.000-08:00

Today we went to a friend's for breakfast. Not just any breakfast though; this was a Canadian feast including crispy bacon, Canadian style pancakes and maple syrup. Before lunch we travelled from the South of Calgary to the North for the Olympic Oval Christmas skating. For $2 we got to skate around the Olympic ice rink and watch Santa Clause drive the Zamboni (the machine that cleans the ice). There were carollers and free cookies too.

We hired ice skates and managed just over one hour of injury-free skating. There are photos but not on my camera, so I can't post them just yet!.

In the evening we went to a Chinese restaurant. After taking our orders they asked "would you like full size or half size - you can take away what you don't eat". Needless to say we opted for the full size option and still have it in the fridge!

Canada Day #9

2009-12-23T19:09:00.000-08:00

Today we went to the cinema and watched 'The Men Who Stare at Goats'. We went to see it at the 'cheap theatre' which shows old films for $3, that's £1.88. No photos from today!

Canada Day #8

2009-12-21T18:45:00.000-08:00

Today we played 5 - Pin Bowling at the Chinook `Moll'. This is identical to 10 - Pin bowling with the following exceptions:

There are only 5 pins
The balls are much smaller
You get three bowls per turn

The result is that it is a lot harder to get a clean strike, but it is still as much fun. Also I won :)

Canada Day #7

2009-12-21T18:33:00.000-08:00

So I went to my first ever ice hockey game (don't call it a match, people look at you strangely). This was a fairly gentle introduction to the game since it was an over 35s league. The rules were fairly simple to pick up and I found it surprisingly entertaining to watch compared to football, rugby, cricket ... any sport. The `rink' was surprisingly small when you consider many thousands of people cram into stadiums to watch these games.

For me the most surprising thing about ice hockey is that there is nowhere that is out of bounds. Players can play the puck behind the goal if they like. This means there are very few interruptions to the game, making it far more exciting to watch.

The team we were supporting was the Mustangs, and they were playing the Bonavista Breakers. The Mustangs lost convincingly.

Canada Day #6

2009-12-19T18:40:00.001-08:00

This is Banff Springs Hotel, the most expensive and beautiful hotel in the town. Although new by British standards, compared to the rest of the town and little of Canada I have seen, this hotel looks ancient.
Sam and I stopped to have our photo taken at the back of the hotel. It was lightly snowing whilst the photo was taken.

This picture shows both the bronze statue of the mounted policeman or `mountie' as they are affectionately known, the rear of the Banff Springs Hotel and the Rockies in the background.

The rear of the hotel overlooks a magnificent golf course, and of course the river. A small section of which was cleared to form this natural skating rink. The small vehicle on the ice is clearing the fallen snow off of the ice and polishing it ready for the skaters waiting in the foreground. A small log fire was started over which hot-dogs were being prepared.

This is the Bow Falls. During the spring and summer this is a thunderous waterfall carving its way through the mountains. Today it was frozen almost completely. An equally impressive sight. The ice was at least 8'' deep at the edges, with a narrow strip of free flowing water in the centre, about 3-4' wide.

These are just some of the trees that line the fairway of the golf course. Deer tracks were clearly visible in the snow between the trees.

Protrusions out of the surface of the frozen river were noticeable. In the photo below, near the centre of the river, it is interesting how the entire sheet of ice appears to have been `lifted'.

A similar protrusion is visible here, where water has frozen whilst flowing over rocks in the riverbed.

The ice was thick enough to walk right out into the middle of the river.

Looking back along the river the Banff Springs Hotel was just as imposing.

Approximately 15 minutes after leaving Banff you arrive in Canmore, which is another ski resort, although not quite as spectacular as Banff!

These ducks weren't deterred by the ice.

The three peaks in the photo below form the ``Three sisters''

We weren't quite sure what the kid in this photo was doing. Unfortunately we did not have time to stay and see just how he falls into the river

The water could not have been any clearer.

Canada Day #5

2009-12-19T18:17:00.001-08:00

Today was a lazy day. An initial failed attempt to walk to Banff (hot) springs was foiled by the low morning temperatures which forced us to divert to the warm shopping centre or `moll' as the locals call it. The helpful local in the picture below told me some more about the town of Banff:

"Banff was founded in 1876 by a Canadian brown fighting bear called Bam Bam. He had grown tired of defecating in the woods and decided that he not only needed warm bathroom facilities but a full shopping experience including tourist T-shirts, Starbucks and Steak houses. News spread quickly of the town and over the years the town's name was shortened to Banff"

It later transpired that the integrity of the aforementioned local was brought into doubt.

All of the street names appeared to be named after local fauna.

At the end of the day we retreated to `Dairy Queen' - this is the McDonalds of the milkshake/ice-cream world. The bucket in the photo below was only a `regular' size.

Canada Day #4

2009-12-19T18:13:00.001-08:00

We travelled to Banff (pronounced: Bamph) by coach on Friday morning. Banff is a famous ski resort in the Rockies and is almost completely surrounded by beautiful mountains. The view below is from one end of Banff looking along the high street. It was taken on the bridge across the river, most of which was frozen.

This is another photograph of the main Banff shopping street, this time taken from the other end.
The bin in the foreground below is bear-proof. The person walking next to it is not.
This is a church or at least it looks like a church. Needless to say, we didn't cross the road for it - pretty nonetheless.
This is another mountain picture

Canada Day #3

2009-12-16T16:52:00.001-08:00

The bear before I restrained itThe bear after I restrained it
An expensive horse
A place for horses
Bleachers (seats) in the snow

Canada Day #2

2009-12-16T16:45:00.001-08:00

It's like a Windows wallpaper
Me with a cat (Roper)
Geronimo - like a horse, only smaller
Geronimo - Mo to his friends
This is what Santa looks like in Canada

Canada Day 1: The view from the front window

2009-12-15T07:27:00.000-08:00

GDP Week 9 (of 10)

2009-12-02T16:42:00.001-08:00

Wow. There is exactly one week left before the submission of my 4th year Group Design project. This beast has taken over my last 9 working weeks and I'm now on the final straight - the group report. I have spent the last three days doing nothing but report writing and it has got me thinking:

How did I ever write group reports before I started using Linux?

During a typical report writing session I use:

LaTeX - I really can't imagine the horrors of having to collaboratively edit a single Word document, whilst simultaneously dealing with formatting, referencing, fighting with the formatting toolboxes.

GIMP - Sometimes you just have to Print Screen to get graphical data out of dreadful software; when this happens GIMP is your friend!

Subversion - I am still amazed that in fourth year there are students emailing zip files to each other instead of using some kind of versioning tool.

GNU Plot - This is quite possibly the most enjoyable piece of GNU software to use. It produces stunningly simple graphs without forcing you to play `hunt the properties option' whenever you want to tweak a setting. If you have ever used Open Office Spreadsheet for graphs you will understand why GNU Plot is so good!

Multiple Desktops - My flatmates joke about me having 8 virtual desktops...I need every one of them, especially when report writing

Ninja Cats

Now that the LaTeX document takes about 30 seconds to compile, I thought what would be great, is if while it was compiling, a python script randomly selected youtube videos of Ninja Cats were played to me. I spent about 10 minutes trying to make this a reality before realising I only have a week before the hand-in. Why doesn't this feature exist already?

GDP Week 6

2009-11-19T05:39:00.001-08:00

Been a little busy with GDP so I thought I'd take a moment to explain what my group's Project is and how it is going. At the moment the military use two AA Alkaline Batteries to power troops personal role radios (PRRs). The PRR provides short range (500m) communications between soldiers and is a replacement to hand signals. The manufacturer, Selex Communications, worked hard to get the battery life up to 24 hours, which is impressive, considering most missions are approximately 3 hours long.

The problem with using disposable batteries is that they present a logistical nightmare. Surplus batteries must be carried for each mission and used batteries must be collected at the end. Standard procedure is to always replace the batteries in the PRR before every mission, regardless of previous use. The military have expressed a strong dissatisfaction with lithium-ion batteries, on the grounds that they are slow to charge and their state of charge is unpredictable/unreliable.

Our brief was to research and present an alternative technology which could be retrofit into the PRR. Ideally it would have competing capacity and be of comparable size. Importantly it must overcome the failings of present Li-Ion technology. Bring on the Ultracapacitor:

The beasts we are using are Philips 50F 2.3V capacitors from Farnell. We also have some MAXIM 100F 2.5V Capacitors to play with. They are pretty chunky, and present some problems in themselves, namely:

Interfacing the PRR (xV to 3V)

Fast Charging circuit (T ~ 60s)

Cell Monitoring

The last point is interesting and of most importance. The caps are damaged if taken above their working voltage of 2.3V or 2.5V. Because of their low energy density, many ultracapacitors, connected in series and parallel will be required to replace the AA Batteries. This makes it easy for unbalanced cells to exceed their working voltage during normal use. Over Voltage Protection (OVP) circuitry is required, and that forms my part of the project. I have just finished the final design of my circuit which is capable of detecting the OVP condition, isolating the capacitor and bypassing the charging current. I hope to blog more about it soon.

Fireworks

2009-11-05T12:53:00.000-08:00

And this is what it did to the stand!

Automata & Useless Machines

2009-11-03T09:33:00.000-08:00

Back in design and technology class during GCSE I made an automata of a flying pig. It had angle wings that flapped and floated around a little, whilst the clouds moved in the background. The word 'shoddy' would aptly describe it. My woodworking skills were, and I can only assume still are, poor. Whilst always backed up with plenty of enthusiasm, my creations generally looked better in my mind than in reality. I think it has something to do with a lack of patience.

I completely forgot about all of this until about fifteen minutes ago, when I stumbled upon this construction on the hack-a-day website. This then lead me on to a Youtube binge of useless machines and inspired automata. I think I'm envious of just about every one of these machines. They are clearly a labour of love. Here were my personal highlights. For those cautious of entering the same Youtube binge, its too late.

Automata

Simple but brilliant - Flipping Pancakes

Adorable - Marching Penguins

Sad - An Afternoon in the park

Bizarre - Drifting Apart

Useless machines

Art? - Unplugger

Hot? - Banana Fan

Spinning - Its the things you can't change that change you

Halloween

2009-11-01T05:21:00.000-08:00

GDP

2009-10-27T16:40:00.001-07:00

Lunch break Post

2009-07-15T05:17:00.000-07:00

With 12 minutes left of my lunch break, I'll keep this short.

Fedora 11: I've finally got around to updating to Fedora 11. It broke my ALSA driver and there were loads of problems with the fedora 11 repositories. However I fixed this and I can begin poking around to see what has actually changed. CTRL+ALT+Backspace no longer works and the Sound controller has changed - this is all I've gleamed so far!

MythBuntu: My house mates and I have hacked together a media PC in our lounge on which we've installed MythUbuntu (My pleas for Fedora went unheard) and we're currently configuring it the way we want it. Rich sorted out Wii remote control which is a pleasure to use, particularly fast forwarding, which involves twisting your wrist! We're yet to install a DVB-TV tuner and get proper PVR functionality, but time is our only enemy at the moment.

Musical Houses

2009-06-28T13:13:00.000-07:00

If a rolling stone gathers no moss, after two years in the same house I'm practically covered in moss. It's musical houses time and the fact that I'm only changing the last two letters of my postcode, doesn't stop it from being a pain. The icing on the top of this metaphorical cake of pain is that I start my new job tomorrow in Christchurch, UK. The nice people at PGDT offered me a three month placement during which I hope to experience some real world engineering, with all the fun pressures that it entails.

The last few days have consisted of packing a considerable amount of my own stuff (and student robotics kit) as well as doing a practice drive to my new work, since getting up at 5.30 is bad enough without dealing with getting lost as well. In addition, I've been trying to work on some Student Robotics hardware - I2C isolation in particular - however the university labs, out of term, are only accessible during working hours. My working hours. This could be the last straw before I actually buy some tools - in particular, a scope and power supply.

With my bedtime adjusted by -3 hours, its off to bed!

PS: I'm currently testing Zemanta which helps to make blog writing easier by automatically suggesting tags, suggesting suitable open source photos/images to enrich your posts, and automatically making phrases such as: ice cream actually link to relevant pages on wikipedia, google maps etc. It integrates seemly into the page, so once installed you could be fooled into thinking it was part of Blogger or Wordpress. Its still got some way to go though.

Surface mount soldering onto Stripboard (2)

2009-06-26T04:24:00.000-07:00

Following yesterday's post Surface Mount Soldering onto Stipboard I adapted the technique to work with sixteen pin SO package chip. The results are satisfactory although I cannot believe this approach will scale beyond 16 pin. I'll find out later if the circuit works...

Surface mount soldering onto Stripboard

2009-06-25T11:09:00.000-07:00

While working on prototyping a circuit to electrically isolate and level translate an I²C bus, I had to work with SMD-only chips. I stumbled upon this post on Make and decided to give it a try. The process requires little more than:

Knife

Stripboard

SMD Solder paste

The principle is simple enough: the prototype tracks are twice as wide as the pads on the chip, so cut then in half lengthways and use fine wire (or judicious application of solder) to connect the chip's pins to the header pins. The result is a unit which can be plugged into a breadboard.

This approach is great for 8 pin devices, however a different approach is required for anything bigger - more on this later when I have to wire up a 16 pin device.

Here are some photos of the finished article:

It helps if you use two sets of headers which are the same length :O

Anything but revision....

2009-05-26T11:19:00.001-07:00

After a day of group revision our minds wandered from Radio Comms and Analogue electronics and onto cool things to make for our house next year. The result is still in the 'wild ideas' stage but essentially its a teas made system, without all the automated kettle rubbish. Essentially when you go to make a cup of tea, a 'Tea?' request is sent to everyone's computers, besides which is a `tea button'. After the offer of tea you have ~15 seconds to hit the button to confirm you want tea/coffee. A small lcd readout near the kettle alerts the tea maker to the number of teas/coffees required. The kettle boils and when it is lifted from its stand the 'tea ready' signal is relayed back to those who ordered tea.

Its all explained here:

Bees Not Included

2009-05-18T13:27:00.001-07:00

..is the new name for this blog. Courtesy of Sloganize which incidentally is a good way to waste half an hour.

EVAs

2009-05-08T06:32:00.000-07:00

Last night, Student Robotics was awarded an Excellence in Volunteering Award (EVA) for Best Student-Led Project.

"The EVAs are a celebration and acknowledgement of volunteering in SUSU. From dropping the beats live on air, to digging flower beds and running societies, SUSU has a diverse and inspirational volunteering movement." source

The award ceremony was held at Southampton Guildhall and featured performances from a range of societies including Comedy Club, Jazz Dance, Showstoppers and Ballroom & Latin Dance Society.

Well done to everyone who has helped out in the society over the years and made it into on of the best!

Rob + Chicken

2009-05-03T12:19:00.000-07:00

This is a response to Rob's blog post:

Rob + Chicken

Batch Image Editing using Script-Fu & GIMP

2009-04-25T07:25:00.000-07:00

I have a large number of bitmap images which i need to include in a latex document. I didn't want to manually scale the images and save them to PNG format so I looked for ways of automating GIPM. Script-Fu is the language/interface for GIMP. It is unlike any other language I have used before and so it took me a little time to work out what was going on.

The script below, when saved to ~/.gimp-2.6/scripts/ directory can be used to convert any image file to a PNG and scaling it in the process to 150px by 150px.


(define (chris infile outfile)
 (let* ((image (car (gimp-file-load RUN-NONINTERACTIVE infile infile)))
         (drawable (car (gimp-image-get-active-layer image))))
 (gimp-image-scale image 150 150)
 (file-png-save-defaults 0 image drawable outfile outfile)
 )
)

To run it from the terminal:


gimp -i -b '(chris "infile.bmp" "outfile.png")' -b '(gimp-quit 0)'

EDIT

Or to run this automatically on all bitmap files within a directory use this bash script:


#!/usr/bin/env bash

for myfile in *.bmp
do
 echo Converting $myfile...
 gimp -i -b "(chris \"$myfile\" \"$myfile.png\")" -b  "(gimp-quit 0)"
done

References

[1] http://www.lemur.com/dmm/culch/scriptsfu/index.html
[2] http://www.gimp.org/tutorials/Basic_Batch/

Student Robotics Competition 2009

2009-04-23T01:59:00.000-07:00

After a year of hard work and preparation the second ever Student Robotics competition happened last Sunday at Southampton University. A film of the event has already been edited and does a far better job of describing the event than I can. This will appear on the srobo.org site as soon as I encode it into something which isn't half a gigabyte. Instead I want to dedicate this blog post to look forward to the next competition.

Meeting

The first meeting after the competition is usually the most fun as everyone, regardless of their technical involvement has ideas and suggestions of how we can make SR better. Yesterday's meeting was no exception and at least 3 whiteboards of ideas were generated. The criticism which has captivated my imagination is that the was a distinct lack of competitive spirit on the day. This manifested itself as:

Limited interaction between teams
General calmness on the day, no frantic hacking or code writing
Poor team images - some teams didn't have names or proper flag

Whilst the more technical failures of the day can be solved with a palette of probes and debugging equipment, this problem requires a different approach. It was reassuring to hear everyone's wide-ranging ideas for how to make this better but it is clearly a difficult question to answer.

Ideas

Here are some of my favourite suggestions from yesterday's meeting:

Online blogs for every teams - Students are encouraged to take loads of photos and blog about their progress. There is an award (publicised from the start) for the best online presence and we try to push this as being almost as coveted as first prize (like First)
Robot Showcase - At the start of the competition, each team exhibits their robot in the arena to intimidate other teams and encourage competitism.
SR Points - Teams can score points before the competition day by achieving certain milestones. This could be for being the first to post X blog posts or the first to demonstrate a working ball launcher or for helping another team solve their technical problem. Points could also be awarded for posting helpful responses in forums
Kickstart reminders - When we have the `year in an hour' build session at Kickstart, we take photos of progress after each `month' and then during the year when students log in they are first presented with a picture of their progress for the equivalent month. For most teams this will be an incentive to work harder!

Fostering a strong online community is clearly a difficult task, you need only look at the comments on youtube for evidence of this - however we are in a good position to do so, since we have a large group of sixth form students with a common interest in robotics and hopefully a desire to win.

PWM & JIO Boards V2 (SR)

2009-03-14T18:40:00.000-07:00

[The following post is mirrored from: chris-sr.blogspot.com

It has taken me approximately three days of soldering, de-soldering, and then flashing to get through all of the mods on the JointIO and PWM Boards but now they are all done. This means they will be shipped from Monday of this week onwards. Which leaves the teams with just about enough time to program their robots.

Here is a photo of the individual boards:

JointIO Board

PWM Board

Jointio & PWM Boards

Third Year Project - CAT Scanning Results

2009-03-02T04:24:00.000-08:00

Here is an exciting before and after pair of images demonstrating the CAT scanning ability of the program written for my Third Year Project. The original images is of 'Lena' which as explained in this wikipedia article is a common test image for image processing techniques. The resolution of the scan is only set to 25% of the maximum at the moment, because of the time taken to process, but i'll look into improving this next!

The Original File: Lena

The CAT Scan Output file

Fixing ALSA Driver

2009-02-10T10:40:00.000-08:00

Since buying my Dell Studio laptop back in December, I had not got around to fixing the Advanced Linux Sound Architecture (ALSA) bug. The bug manifested itself in a variety of guises, as the bug report lists, but for me it meant that:

The front, built-in speakers were always on

The headphone jacks (there are two) were mute unless phones were inserted at boot-time

Unplugging the headphones immediately caused them to stop working

This was really annoying, but then so are exams, so I neglected to fix it.

Today however, I grabbed the latest snapshot of the driver source from: http://www.alsa-project.org/snapshot/ and compiled it from source, installed it, rebooted. Now full functionality is restored, the headphones work fully and the front speakers can be controlled independently of the master volume.

Whilst this may not seem particularly impressive, this is the first time I've ever successfully compiled from source and installed any part of the linux kernel.

I hope the fixed ALSA driver gets included into the next kernel release very soon.

Guitar Effects Mods

2009-02-01T09:56:00.001-08:00

I don't play the guitar, but my flatmate does. He has a collection of electric guitar effects peddles and has recently expressed an interest in modifying one of his less favoured peddles to improve the sound. This interest was further motivated by an ebook which he received at Christmas detailing common mods made to a number of popular effects peddles.

So yesterday afternoon was spent taking apart the peddle apart, making some simple changes to it and then seeing if it made a difference. After reading the instructions for the mod, I was a little sceptical as to the difference it would make to the sound. The changes involved replacing one of the capacitors with a beefier one and replacing two diodes with three diodes (one was replaced with two in series). In addition, and at the insistence of my flatmate, the LED colour was changed, so that it was obvious that the peddle had been modified.

After a couple of hours wrestling with a horribly constructed PCB, we were finished. The unit worked first time, however neither of us were sure if our changes had made a significant difference to the sound. The aim was to make the distortion effect more 'responsive' and 'thicker'. Whilst my flatmate was certain there was a difference, I am less convinced. Despite this, I learned a few interesting things about this area of electronics:

Guitar effects peddles are remarkably easy to modify. There appears to be a lot of information including schematics and suggested modifications to be found on the internet.

Some effects peddles are custom made for bands and cost a phenomenal amount.

The design of such peddles seems to be a black art. The results are very subjective and I have no idea how one would go about designing to specification such a device. If I played the guitar then I would be tempted to build from scratch a simple effects peddle which allowed you to tweak component values quickly - as I suspect this is how most peddles are designed. Although this is entirely un-researched!

Shuffle

2009-01-09T19:33:00.000-08:00

The Problem: I have a 2Gb Creative Stone Plus MP3 player which I listen to a lot. I have close to 20Gb of music on my laptop. Every three or so days I exhaust the songs on my player and I want to replace them with different ones. This takes a while and requires sifting through folders of songs, remembering which ones I've listened to recently.

The Solution: I have written a python program to automatically replace all of the albums on my player with new ones from my library. It first generates two text files listing all the album folders on both the player and in my library. Each entry on the player is cross-checked with the library. If it exists in the library it is automatically delete from the player. If it can't be found in the library, it is left on the player, in case these are new files yet to be copied across. Once old albums have been received, a random number generator is used to pick new albums from the main library. If the selected album was previously on the player, another album is selected. New albums are continually copied across until a copy operation fails - signalling that the player is full.

Shortcomings: The program is highly customised to my machine. This will change - I want to make this into a proper command line program with some more features. Eg. supporting histories longer than 1, and allow user to 'teach' the program which albums it prefers. This is long term. Once the program code is respectable, I'll publish it here. This has been something I've been meaning to do for a long time - I have loads more ideas for features and improvements.

Interim Report - Done

2009-01-08T14:14:00.000-08:00

I've finally completed my interim report for third year project after days spent sweating over it. To be sure i don't submit the wrong copy, (its subversioned but still): MD5(report.pdf)= c08757d27d53e16f51afc031d2b6d1d5 -relief :D

Dell Studio

2008-12-22T11:44:00.000-08:00

After aprox 9 months using my EEE PC I have upgraded to a proper laptop. Whilst my EEE PC was handy in lectures for following slides and for watching BBC iplayer it was not really up to much else (viewing PCB layouts on 7in of screen is almost impossible). This was really apparant last week when i had to work on the Student Robotics hardware. I was forced to use it as not much more than a dumb terminal from which I could shell into the SR server, Rob's desktop computer and the slug in order to get anything done. This was really painful and so I bought a Dell Studio laptop which has 15in screen amongst other benefits.

It arrived three days ago with Vista preinstalled. I subsequently shrunk the Windows partition to make way for Fedora 10. I decided to make the switch from Ubuntu to Fedora for no significant reason other than change - and to simplify setting up the MSP430 tool chain. So far so good.

Setting up dual boot was considerably easier this time. This is because I cheated and used a third party windows bootloader tool to set it up. Although there are undoubtedly 'better' ways of doing this, I found EasyBCD really simple to use. There are even Fedora specific instructions for how to do the install. My first attempts at dual booting Ubuntu/XP a year ago, required at least two reinstallations of the MBR (mainly becuase i didn't know what i was doing) so this tool was a welcome change.

Servo Board V2 Firmware

2008-11-30T15:55:00.001-08:00

I have spent today fighting gdb and gdb-proxy in an attempt to update the firmware for the PWM board (Servo board). I spent the first two hours going 'aargh' because msp430-gdb kept issuing me with missing data stack errors and empty symbol tables. Eventually from looking at last years code i was able to view work out what was wrong. Weirdly, adding a static variable into my code (which was only assigned to once) was enough to solve my problem, however this makes no sense why.

The reason the firmware needed upgrading is because we have put a beefier MSP micro-controller on the board, subsequently the board layout has changed. Once I got my head around both the motor controllers i2c routines and the old pwm firmware i began merging bits of code together. After a suitable amount of time, anger, coffee, realisation of how stupid i was being and more coffee, I managed to get the new board to seep all the servo pins back and forth, demonstrating that this part of the board works.

Enjoy the video - I did!

Some Photos:

The new servo board. The two LEDs indicate both power supplies are connected. The third LED which isn't illuminated, should be, however due to some primate-like soldering skills, there appears to be a short.

The servos in motion.

The MSP430 programmer. I mounted it on an old credit card to make the wiring a little more secure. Despite it looking horrible, it actually works surprisingly well. Honest.

Tongue Extraction

2008-11-29T08:54:00.000-08:00

I have just completed my first ever Dynamic Programming project for Intelligent Algorithms module COMP3032. The task was to extract a contour which corresponds to the human tongue shown in the ultrasound image shown below:

The first step was to narrow the search area by applying some boundary conditions. The red points in the image above represent these conditions. The region is extracted by joining up the points and sampling along the lines. Next an energy functional was defined to describe a 'good contour'. An optimal contour will be smooth and have high intensity. The end result is shown below (Note: pixel values have been inverted i.e. negative image):

The contour is a good representation of the tongue and because the energy functional places equal emphasis on smoothness and intensity, it is not affected by the noise (high intensity pixels near the centre of the search area). With a week left before the deadline I hope to improve the computation time and experiment with changing the various parameters.

Trouble in Ambridge

2008-11-23T10:58:00.000-08:00

My Dad likes the Archers, so does my mum. Up until about 5 years ago, My dad would record the omnibus onto cassette for playing in the car during commutes to work and back, likewise my mum would listen to it in the house on the hi-fi. Then my dad bought a car without a tape player, so I taught him how to record the omnibus using his computer (connected to the hifi with a line-in cable), this worked but required editing the audio file in Audacity which my dad never got on well with.

Finally earlier this year my Dad entered the 21st Century and began downloading the archers podcast from the BBC website. This was by far the simplest and quickest way. This was until the company my Dad works for banned multimedia content downloading on the company network. The only other connection in the house is dial-up so i promised to develop a work around.

I have written a python script which parses the RSS feed for the archers podcast, extracts the .mp3 links, downloads them to a temporary directory, compresses them into a single zip file which, with the help of a bash scrip, gets uploaded to my University web space for my dad to download every Saturday. The script is shown below, but the reason I blog about this is because for the first time in my linux lifetime, I have written a script to do a task in less time that it would have taken to just do it manually! (hence time to blog)

The only remaining task is to get the script to trigger automatically every Saturday without me having to remember. But Google calendar reminders will suffice for the time being!


import feedparser
import urllib
import os
import zipfile

ARCHERS_XML_URL = "http://downloads.bbc.co.uk/podcasts/radio4/archers/rss.xml"
TEMP_ADDRESS = "/tmp/archers/"

feed = feedparser.parse(ARCHERS_XML_URL)

shows = feed["entries"]
episodes = []

for show in shows:
 mp3_url = str(show["links"][0]["href"])
 print "Retrieving: "+mp3_url
 fname = os.path.basename(mp3_url)
 try:
  f = urllib.urlretrieve(mp3_url, TEMP_ADDRESS+fname)
  episodes.append(TEMP_ADDRESS+fname)
 except IOError:
  print "Couldn't retrieve file: "+mp3_url
 
 urllib.urlcleanup()

all = zipfile.ZipFile(TEMP_ADDRESS+"archers.zip", 'w')
for file in episodes:
 try:
  all.write(file)
  print "added "+file+" to zip archive archers.zip"
 except:
  print "Faile to write "+file+" to zip archive archers.zip"
all.close()
all = zipfile.ZipFile(TEMP_ADDRESS+"archers.zip", 'r')
if all.testzip() == None:
 print "succesfully wrote episodes to zip file"
else:
 print "failure writing episodes to zip file" 
all.close()
print "end"

*tex Pain

2008-10-27T07:41:00.001-07:00

I've just finished writing my first report in Latex. I have also just experience Bibtex, the referencing package. The idea seems simple; keep the reference details and main content separate; and let Bibtex process it and pump out a correctly formatted bibliography.

The reality is that you will spend hours chasing horrible error messages from Bibtex about undefined references due to the minefield of possible syntax errors. The lesson is, use a proper latex editor in combination with some form of reference organiser to remove some of the pain.

Having said all this, i will definitely be using Latex in the future, primarily because it prevents me from getting distracted with formatting whilst writing the report. The end result is also much prettier.

2D CAT scan emulation software

2008-10-13T16:26:00.000-07:00

A draft of the brief for my 3rd Year Project:

Recently the principles of CAT scanning have been transferred to non-medical applications. Examples of this include using GPS satellites to map weather in the ionosphere as well as scanning for oil and gas reservoirs. Typically in these environments it is not possible to move the scan points nor to scan the target from all angles. With such restrictions it is possible that large, important structures may not be resolved by the scanning process.

The objective of this project is to write a software tool to emulate the scanning, interpolation and processing stages of computer aided tomography. This tool will then be used to study the effects of restricting the number and position of scan-lines on the final reconstructed image.

The inputs to the program will be:

A bitmap of arbitrary size and colour depth that will be used to represent the 2D object being scanned.

A text file fully describing the position and orientation of the scan points.

The program will output:

The raw scan data

The reconstructed image

The reconstructed image after image processing

A measure of the similarity of the target and scan image

The program will have the following variables:

Position and number of scan lines

Absorption model – additive/integral

Image manipulation techniques – applied after interpolation

Target/Image comparison techniques – a selection of methods to evaluate the accuracy and resolution of the scan output

Batch processing

The goal of this project is to design an appropriate set of test images and scan configurations to be processed by the emulation software. Theses tests should highlight the circumstances that lead to important data within the target image being lost as a result of the scanning process. The results may then be used to comment on the suitability and effectiveness of CAT scanning in a range of real-world non-medical applications.

A Better Timetable

2008-10-09T03:51:00.000-07:00

The Problem:

The university timetable (at Southampton University) is rubbish. A flat PDF with cryptic course codes and building/room numbers which require at least two other resources to translate into any sort of geographical location. If you are in a hurry (which i usually am when looking at a timetable) not only is it extremely irritating having to log in to various portals (none as exciting as Narnia) just to get at some pretty simple info.

The Solution:

A web based timetable which integrates all the info in one place. The steps involved:

Upload the rubbish PDF file downloaded from university website.

The file is processed on the server and converted into a database table format

All user-identifiable information is stripped from the pdf

The user then selects a memorable identifier that identifies their timetable, there is no need for a password (cannot link student number/name with timetable)

The user or someone the user has shared their timetable with goes to the site eg. http://www.better-ttable.com/?table=funkymonkey

The page then shows the 'now & next' lectures. Each one shows the building number and name and on click highlights the building on the map

you can browse the weeks timetable and add extra lectures (tutorials etc.) and 'week specific' events (non recurring)

There is a mobile version of the site adapted for the small screen

I just wish i had time to actually do this :-( , perhaps sell it to the uni when it becomes a roaring success

This is not just Sardines On Toast ...

2008-09-16T06:38:00.001-07:00

Here's something that I made up this lunchtime, and it tasted good so I thought I'd share it.

Ingredients

Bread

Tin of Sardines

Sun-dried Tomatoes (paste)

Worcestershire Sauce

Basil

What to do

Lightly toast the bread under a grill for just over a minute on each side

Remove the bread and spread a thin layer of sun-dried tomatoes on each slice

Return to the grill for a minute

Meanwhile, remove the bones from the sardines and break them up gently with a fork (keep as much of the sauce as possible

Sprinkle some chopped up basil onto the bread and then add the sardines

Sprinkle some more basil on top and return to the grill for another minute

Add Worcestershire sauce to taste, eat immediately

Your Thoughts?

2008-08-19T08:13:00.001-07:00

A (virtual) penny for your thoughts...

Diving into C++

2008-08-19T07:54:00.000-07:00

My first C++ script to practice string manipulation, standard input/output and formatting. It compiles with GCC using g++ [name.c] -o [name] under linux. ~~Note that to meet ANSI C compliances, it is necessary to use not in the preprocessor directives, hence library function calls are prefixed with 'std::'.~~ Using the 'using namespace std;' statement removes the need to prefix iostream objects/methods with 'std::' - similar to C#.


//*******************************************************
// Copyright (c) Christopher Cross 2008
// Format Name to fit within 
// confines of Envelope window
// (An example of C++ string/cin/cout manipulation)
//*******************************************************

#include 
#include 
#include 

#define INCOME_TAX 40
#define FORENAME_LENGTH 30
#define SURNAME_LENGTH 30
#define ENVELOPE_LENGTH 15

void fitOnEnvelope(char * first, char * last);

using namespace std;

int main(void)
{ 
 char firstName[FORENAME_LENGTH];
 char lastName[SURNAME_LENGTH];
 
 cout << "Enter First Name:" << endl;
 cin.get(firstName, 15);
 cin.get();
 cout << "Enter Last Name:" << endl;
 cin.get(lastName, 15);
 cin.get();
 fitOnEnvelope(firstName, lastName);
 return 666;
}

void fitOnEnvelope(char * first, char * last)
{
 int size = strlen(first) + strlen(last);
 char border[4] = "***"; 

 if(size < (ENVELOPE_LENGTH - 1))  //allow for \0
 {
  cout  << setw(ENVELOPE_LENGTH) 
    << setiosflags(ios::right) 
    << first << " " << last << endl;
 }
 else 
 { 
  char abbrev[ENVELOPE_LENGTH-3];  //allow for wspace, period, \0
  strcpy(abbrev, last);
  cout  << setw(ENVELOPE_LENGTH) 
    << setiosflags(ios::right) 
    << first[0] << ". " << abbrev << endl;
 }
 return;
}

Hack, Anyone?

2008-08-03T05:32:00.000-07:00

Here's an easy and pointless hack. You will need:

Poor quality PC speakers

Strong elastic band

No headphones nearby

You can see where this is going...

Dolby 2.0?

Reading List

2008-08-02T15:33:00.000-07:00

In an attempt to become more cultured I have compiled a list of books I want to read this year:

One Flew Over the Cuckoo's Nest - by Ken Kesey

Crime and Punishment - by Fyodor Dostoyevsky

Lady Chatterly's Lover - by D.H.Lawrence

Wuthering Heights (Signet Classics) - by Emily Bronte

Of Mice and Men - by John Steinbeck

Dr. Jekyll & Mr. Hyde - by Robert Louis Stevenson

Old Curiosity Shop - Charles Dickens

The Turn Of The Screw - Henry James

Emma - Jane Austen

The Grapes of Wrath - John Steinbeck

Three Men in A Boat - Jerome K. Jerome

On The Road - Jack Kerouac

Alice in Wonderland - Lewis Carroll

The Picture of Dorian Gray - Oscar Wilde

The Communist Manifesto - Karl Marx

The Time Machine - H.G. Wells

The Invisible Man - H.G. Wells

The Day of the Triffids - John Wyndham

A Clockwork Orange - Anthony Burgess

A Tale of Two Cities - Charles - Dickens

Subterraneous - Jack Kerouac

Death of a Salesman - Arthur Miller

Treasure Island - Robert Louis Stevenson

The Illiad of Homer - Homer

War and Peace - Leo Tolstoy

I've Missed You Blighty

2008-08-01T14:45:00.000-07:00

For the past 35 days I have been interralining around Europe, stopping at major cities and sleeping in cheap hostels. I have seen 1.5Gb of tourist stuff and eaten an unhealty amount of Salami and Ice Cream (although never at the same time - thats just silly). Now I am back, and I have never been so glad to be back in England. Whilst my travels were fun and educational (travelling really does broaden the mind), they were nonetheless tiring and exhaustive.

My contact with the outside world has been limited. Very limited. I had a mobile phone with a UK only SIM and a collective total of 90min of internet cafe time. Despite my undeniably unhealthy addiction to the internet and my computer I missed neither whilst away. Even being unaware of the latest headlines and tabloid playthings was of no concern to me. Now that I am back in the country (still devoid of a permenant internet connection and my computer) the usual distractions are creeping back into my daily routine.

My travel photos are available, unfortunately on Facebook only (i love flickr, but I only have time to upload to one site, and I've got fbook-only friends to please). They can be found here: Part III, Part II, Part I. But what have I actually learnt from this trip??

It is possible to eat Ice Creams every day for 35 days continuous and not put on weight

Europe is expensive

The Interrail pass does not always work out cheaper than buying tickets ad hoc. Hefty reservation fees soon add up, especially in Italy, Greece and on sleeper trains

The leaning tower of Pisa is tiny - There is nothing else to do in Pisa

Florence is dull and I cannot imagine it not being 'overcast'

The Berlin TV Tower is overprice for what it is

European trains sometimes have splitting carriages. Always check that you are in the correcct car before the journey.

Greecians are not all friendly

Venice, in places, smells

I like Oscar Wilde

Sleeper trains are termed sarcastically (I do not sleep well on them)

Prague is very much 'hyped'

Salvidor Dali, before the Prage Castle

apt-get install linux

2008-06-05T16:35:00.000-07:00

I have an EEE PC. However until last week something just wasn't quite right. Here's a story about my tenuous relationship with Linux.

My experience with Linux is very much a love hate one. I'd love to love Linux, but Linux just isn't making this easy for me. My first experience with it was only a little over a year ago when I eagerly launched a live CD - at the time, I wasn't really sure what that was - but I must admit it was impressive. Gutsy Gibbon ran like a panther compared to XP, which, constrained within the confines of a Dell Dimension 3000, was (and still is) just 'putting on a brave face'.

Eager to release Ubuntu from the limitations of its live CD, but cautious of upsetting the fragile but dependably unreliable XP, I concluded the way forward was to install it on an external hard drive. Don't do this. I did and it worked for a day. The problem was, of course, unquestionably due to my naivity in thinking I knew what I was doing. Because the bootloader 'Grub' was installed on the external drive, a delicate 'ballet' of switching things on was required to get beyond the boot menu. Eventually even this failed and XP came to the rescue by rebuilding the MBR.

Knocked slightly by this, I sat in the familiar but uncomfortable gardens of XP which always booted, rarely crashed and talked to every piece of hardware I owned. Over time and with every unresponsive window and XP 'quirk' my resentment towards Windows grew. One night, with a still-warm CD of Gutsy I slowly built up the confidence to repartition my internal drive and do a fresh install of Linux. All went to plan and as the days went on Windows made its way further and further down the Grub boot order.

And then along came Hardy Heron. Brilliant! An overnight upgrade later and then bye bye Linux. First it takes an age to log in, then parts of the desktop are missing, and finally I can't get past the splash screen. Undeterred and giddy with the success of installing Ubuntu, I bravely entered the 'Fail safe terminal' where I diagnosed the fault to lie with Gnome. Convinced with my prognosis and inspired by forum posts I sudo apt-get'ed my way to reinstalling Gnome. Don't do this. It doesn't work. Apparently apt-get remove gnome; apt-get install gnome; isn't big, and certainly isn't clever.

Xandros on the EEE PC

Crawling back to XP, I dismissed Linux as 'not for me'. Then along came the EEE PC, with Xandros pre-installed. Dressed up to look like XP, Xandros is poor visually, but more importantly, poor functionally. The package repository was pathetically small and restrictive. Nonetheless I messed around in terminal apt-getting myself around, hoping to find programs to do the jobs I wanted. This all ended when I typed apt-get upgrade which filled the internal solid state drive and locked up the PC, nothing would load.

Puppyeee on the EEE PC

I though puppeee linux (EEE spinoff from puppy Linux) was the temporary solution, it was. Wireless worked, keyboard almost worked, it was incredibly responsive and it looked a little rough around the edges. Incidentally, to date it is the only linux distro to make it to the end of its natural life without being broken by me.

Bored of the steep learning curve of puppy and envious of the gnome desktop I installed eeeXubuntu onto my eee. The process was educational but about 5 days longer than the tutorial I was following implied. XFCE window manager is a great gnome substitute and is lightweight enough to be usable with such a small device.

eeeXubuntu on the EEE PC

My dependence on Linux has grown and grown since fixing the EEE and now even my trusty dell is running Ubuntu Hardy Heron.

Run Forrest Run

2008-06-02T10:24:00.001-07:00

Spontaneous run #1:
Running in the rain :: The best way to get over an electromagnetism exam (click to view route)

Err, yeah, I got lost OK? - Deal with it! (Isn't that the plough constellation)

Student Robotics Blog

2008-04-28T02:37:00.000-07:00

As well as this blog, I have also started a blog dedicated to Student Robotics activities, electronics and ideas. It is at: http://chris-sr.blogspot.com

Setting up Windows Mobile for SQL CE

2008-04-28T02:18:00.000-07:00

My battle against Windows Mobile 5 continues. Set back initially by its limited support for databases, i was forced to adapt my (poorly written) code to use SqlCe which doesn't even fully support the SQL dictionary.

With some - even if limited - database implementation I hoped to move from the VS Emulator to the actual device. Predictable this was not easy. Despite SqlCe .sdf file capabilities and even a program already on the device to open such files - my program refused to run.

Missing libraries. Installing these librarys was more painful than it should have been. Originally i hoped that the compiler and linker would copy all necessary code into the executable file. After all the program ran in the emulator fine. Unable to find an installer for just SqlServerCe which would run on the device itself, i manually hunted out the necessary .CAB files (as spotted in the output pane of VS during deployment) onto the device, learning during the process that they must be installed to 'This Device' and none of the other options for .CAB installation.

These tricks eventually coaxed windows into running my program. Fortunately my luck changed at this point.

I discovered a very useful way of quickly starting the emulator without having to wait for the deployment of all the library files each time. Basically, once it has successfully deployed once, enter the settings>memory>running programs and then stop all processes. Save the state (File>Save State) and close the window. Next time you hit debug it will load much quicker.

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