Archive for the ‘code’ Category

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How much did I spend on electricity to do that?

Friday, November 27th, 2009

Selecting a chunk of a graphTime for number 73 in my never-ending list of ever-so-slightly-different things to try with a graph of home energy usage data

🙂

This time… working out the electricity used (and the cost) of doing… well, something in particular.

We already have live graphs (Switch something on and watch the graph shoot up. Switch it off and watch the line drop.)

And we’ve already got graphs with hourly, daily, or monthly totals.

But if I boil a kettle, how do I know how much that cost?

The live graph shows you the shape of the usage curve for a particular appliance.

What I wanted was to be able to start the live graph running, switch something on, then after it’s finished, go back to the live graph, see the bump in the graph for when I did that, and measure the area under it – giving me my total energy usage for that time.

A quick bit of Python-tinkering later, and here we go…

Click-and-drag to highlight a span of the graph, and the Python script calculates the area (more-or-less) under that part of the curve, using this to calculate how much energy I used during this time.

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Posted in code | 2 Comments »

Augmented reality for Hursley

Friday, November 6th, 2009

screenshot : click for better resolution imageOne of the themes at openMIC this week was augmented reality, and a topic that came up a couple of times was Layar.

Layar is a mobile app for Android and iPhone that lets you display location-based information overlaid on a real-time camera view.

For example, the screen normally shows a viewfinder-like view from your mobile’s camera.

Search for “coffee” and a bunch of markers appear on the view, showing you where the nearest coffee shops are.

As you move the phone around, the markers follow the approximate location of the places they are showing you.

That’s assuming you want to search ‘Google Local’, but that’s not the only option. Location data is provided through “layars”, and there are layars available for location-tagged Wikipedia articles, Flickr photos, brightkite users, and more.

The interesting thing talked about at openMIC was the Layar API which lets anyone create a new Layar with their own information.

So I decided to spend a quiet Friday afternoon in the office creating a Layar for around Hursley. 🙂

This means a phone with the Layar browser installed can browse and search for points of interest around the site.

It was really very easy, so I’ll quickly outline the steps involved.

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Tracking my location on TV

Wednesday, October 21st, 2009

Location tracking on TV

This is what you see if you press the “Find Dale” button on my TV remote control.

(Well, actually the “Teletext” button… cos I wasn’t using it, and there isn’t another button that makes any more sense!)

The on-screen-display adds a message at the bottom of the screen for a few seconds, saying my last recorded location and when I was there.

People following me on twitter may have noticed me talking about setting up a new home media server: a small Linux server that has become our Freeview box, PVR, home photo album, and music server.

And now it’s set up, it is surprisingly easy to do amazingly useful, and not-at-all annoying things like this! 😉

In my defence, I stopped just short of making the script poll for my location and display an on-screen message whenever my location changes. Which would’ve been very cool, but probably drive my family nuts. So I compromised with a script that runs when you press a button on the remote.

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OAuth authentication from a mobile device

Monday, August 31st, 2009

I wrote a post a couple of weeks ago in which I whined about the difficulties in creating a good user experience for a mobile client that authenticates with an OAuth provider.

I was pleasantly surprised (and a little honoured!) to get a comment on the post from Chris Messina reminding me that the way to address the usability issue isn’t to revert back to using usernames and passwords, but for us to all work to improve the usability of OAuth.

Sufficiently inspired, I went back and had another go.

It’s still not quite there, but I think it’s better.

As Andy pointed out last time, not everyone has a Windows Mobile device to try my code on, so this time I tried recording a screen capture of it.

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(Another!) Mobile app to share where you are

Saturday, August 29th, 2009

Mobile location sharing is something that I keep coming back to: from finding where my phone is using GPS, Bluetooth, WiFi Access Points, GSM Cell Ids, using my own hand-rolled systems or newer services like Google Latitude, dopplr, OpenCellID and Brightkite.

There is something about the promise of location-based apps which I find very exciting.

This is my excuse, at any rate, for sharing my latest bit of tinkering. 🙂

The stuff that I’ve tried so far has been focused on long-term sharing – apps intended to run in the background on your phone all the time, sharing your location with a pre-arranged list of friends and family who have signed up to the same service.

I’m playing with an app which comes at this from the other angle: an app for specific occasions to share your location. Not something to run in the background all the time, but an app to use when you want to let someone know where you are – a specific person. This could be a friend or family member, or a colleague or client (perhaps someone who hasn’t signed up to any service that you have).

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Accessing authenticated Google App Engine services from a .NET CF client

Monday, August 24th, 2009

Google App Engine (GAE) gives you an easy way to build and host web applications for free.

For any address you specify in your GAE app, you can require users to be authenticated. For example, if you have this in your app.yaml:

- url: /authme
  script: myAuthenticatedService.py
  login: required

When a user goes to http://yourapp.appspot.com/authme in their browser, they get taken first to a google.com logon page and promtped for their google username and password.

Only if they authenticate correctly will Google pass them back to your page, and let them access your /authme page.

(This is kinda nice, because as a GAE app developer, you shouldn’t need to see the user’s password. Although, I guess most users won’t make a distinction between typing in their username and password into the google.com login page and into a login form on an appspot.com page.)

If you are writing browser-delivered apps, this is all fine and works as described. This is slightly trickier if you are writing a web service that you want to be accessed by a client app. I wanted to access a GAE web service from a mobile client – this is how I’m doing it.

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Stripping out MIME headers

Tuesday, August 18th, 2009

A couple of years ago, I wrote a small plugin for Outlook Mobile (the version of Outlook that you get on Windows Mobile phones) to help me triage my emails.

The idea was to make it quicker to process my email from my phone, by adding a couple of context menu items to emails that let you create a new To Do item in Outlook Tasks, or a new diary entry in Outlook Calendar.

So if someone sends you an email asking you to do something, with one tap you can create a new To Do list item, pre-filling it with information from the email.

And if someone sends you an email about an event or meeting you need to go to, with one tap you can create a new Calendar item, prefilling it with information from the email.

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Where did your electricity come from?

Monday, August 17th, 2009

Where did my electricity come from?It’s been a while since I posted about CurrentCost stuff, so time to share another little idea.

Last night I made a start on adding a new graph type to my CurrentCost application.

Instead of only displaying how much electricity you’ve used, the new graph displays the split of how that electricity was generated.

Realtime figures for the “energy mix” of ratios of different generation methods used in the UK National Grid are available in an XML feed that updates every five minutes.

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