Bluetooth 4.0 LE on Raspberry Pi with Bluez 5.x

By | Published: January 21, 2013

Over the holiday I had a little time to fiddle with the Raspberry Pi I got earlier in the summer and I started wondering how hard it would be to get a Bluetooth LE adapter working. It turned out not to be as hard to get working as I thought it might be thanks to recently added support in the Bluez 5.x Bluetooth stack. What follows is the information you need to get things going.

To start with I picked the IOGEAR Bluetooth 4.0 USB Micro Adapter (GBU521) that can be found on Amazon for just $13 since it looked like the chip it uses is decently supported with recent Linux kernels. The only issue I had is the size itself, if it didn't have a little nub on the end it would be too small to pull back out of the USB plug.

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Posted in hardware, linux, programming | Tagged , | 1 Comment

Direct Browser Uploading – Amazon S3, CORS, FileAPI, XHR2 and Signed PUTs

By | Published: September 2, 2012

I've been hacking around with FileAPI and XHR2 in HTML5 recently (more on why hopefully in another month or so). So when Amazon announced S3 CORS support I figured I should create a demo of directly uploading a file to S3 from a browser.

The first thing to understand is that while the upload happens directly to S3 there still needs to be some server side code that signs the URL used by the PUT call. That bit of code is really simple and I'm including an example at the end for both PHP and Ruby. If you want to skip to the fun part you can check out the PHP and Ruby example code on github (instructions there on deploying to Heroku as well).

Second there are a good number of technologies involved here so I've compiled a list of helpful links in case you aren't already familiar with them and/or want a reference:

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Posted in programming | 7 Comments

Embed Ruby in Your iOS Apps Using mruby

By | Published: May 8, 2012

I've been playing with mruby for the past week or so. If you haven't seen it yet it is an embeddable version of Ruby. The first thing I wonder about when I heard about mruby last year a RubyConf was embedding it in iOS apps. Now that the initial version has been released I figured I would give it a try.

There are a few things to take into account before diving into this. The first is that the mruby project is very new and there are a number of gaps in the language support right now but the goal is to support the ISO definition of Ruby at some point. The second thing to know is that I'm talking about embedding Ruby here and not writing iOS apps using Ruby. I'm more interested in the potential of Ruby as a scripting language for something like a game. If you want to look into writing iOS apps using Ruby check out RubyMotion or the MobiRuby project (MobiRuby is based on mruby).

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Segmenting WebM Video and the MediaSource API

By | Published: January 3, 2012

For a while now I've seen people ask when support for Apple's Pantos HTTP live streaming would make it past Safari and iOS. The answer seems to have been that it wasn't clear that Pantos streaming was the best option and something else would come about eventually that would be more flexible. There have been other options but they involve either Flash or Silverlight and most people want something that works with html5 video. After a long wait it seems like the time is getting close now with the MediaSource API.

The MediaSource API has experimental support in Chrome and can be enabled by using the chrome://flags option. To see it in action you can go to the MediaSource demo page. You can also read a litte more about it here although the spec linked to above is probably a better place to learn about it.

A while ago I created a tool for segmenting H264 video in a Pantos compliant way. When I saw the MediaSource API I wondered how the same type of tool might fit in. The first thing to note is that the Pantos draft describes a complete technique for video streaming while the MediaSource API gives you the tools to stream video and leaves the technique. What follows is a simple technique for segmenting a WebM video in a way that allows standard streaming with the MediaSource API in the same fasion as the Pantos draft technique. While this example will not support variable rate streams it could be expanded to do so and would be the next logical step.

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Posted in utilities | 4 Comments

Range Requests with Ajax

By | Published: November 22, 2011

I ran across something the other day that made wonder about doing range requests using ajax. For some reason it wasn't obvious at first if this would be easy but as it turns out it is.

If you aren't familiar with range requests head over to the HTTP RFC and check out the range header. Your web server needs to support range requests for this to be useful but most do so that shouldn't be a huge issue. As a bonus you will find that some CDNs support range request as well (Amazon S3 for example).

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Using WebP to Reduce Native iOS App Size

By | Published: June 29, 2011

Last year Google released WebM as an alternative to h264 encoded video. They followed that up with the release of WebP as an alternative to JPG. Ever since the release I've been thinking about giving it a try on iOS to see how well it might work to reduce application size. As a bonus to reduced size, WebP also supports an alpha channel that JPG doesn't (there is more information available on the original release blog post).

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Posted in programming | Tagged , | 9 Comments

Using the Google Closure Compiler in Java

By | Published: March 8, 2011

I recently had a chance to try out Google's closure compiler. The closure compiler is similar to the YUI compressor except that along with minimizing it may rewrite the JavaScript. If you want to understand more about what it does start at the overview documentation and then go from there.

What I needed was a way to use the closure compiler in an Ant task. The Ant task that comes with the library is good but there wasn't a way for me to integrate it into an existing system that wasn't going to change. After looking around for some example code and not finding any I went into the library's Ant task and figured out how to wire it all up myself.

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Google Analytics Dashboard WordPress Plugin Version 2.0 Released

By | Published: February 22, 2011

It has taken me a while but I've finally been able to release version 2 of the Google Analytics Dashboard WordPress Plugin. The primary enhancement of this version is that it no longer blocks the dashboard, posts or pages interfaces while loading. The next major change is an upgrade to using Google's OAuth login system (see my Google OAuth example using PHP for more information on how I did that if you are interested). The old login system is still available but the OAuth login is the one to use going forward and I may remove the old one at some point. The move to OAuth along with the refactoring I did to the code will allow support for other Google sites such as Feedburner. As a bonus I also moved the caching system to the newer WordPress transient storage interface. The use of the transient storage interface should fix one of the biggest issues people have seen in the past so no more worrying about finding a temp directory that is writable.

Here are a list of the major changes:

  • The dashboard panel now loads asynchronously so the entire dashboard doesn't block while it is loading
  • Made the analytics column in posts and pages load asynchronously so that it doesn't block the loading of the page
  • Added support for Google OAuth logins
  • Use transient API support with wordpress version 2.8+
  • Added ability to support multiple analytics sources

Some other minor changes:

  • Stop unlink warnings when caching won't work
  • Refactored code so that major parts are split into classes
  • Refactored code to better seperate UI code
  • Fixed mime type not being sent correctly for admin area javascript file
  • Fix bug in wordpress version checking
Posted in utilities | Tagged | 1 Comment

Google OAuth for Installed Apps PHP Example

By | Published: February 8, 2011

I have been working on a long needed update to the Google analytics dashboard plugin for WordPress and one of the items I had on my TODO list was using Google's OAuth login instead of the old ClientLogin. Setting OAuth up for a WordPress plugin is complicated because it isn't a hosted application and as such I can't register it to get OAuth keys. That is where a special way of doing OAuth comes in called OAuth for installed apps.

There seems to be a lot of general documentation on how to do OAuth but there wasn't much about using it for installed apps so what follows is an example using PHP that is basically what went into the plugin update.

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Java AirPlay Client

By | Published: January 25, 2011

Ever since getting one of the new AppleTV devices I have been wanting to fiddle with AirPlay. I finally got around to looking at a dump of the traffic between an iPad and the AppleTV over Christmas and was surprised at how simple it was. Soon after I noticed a blog post about AirFlick for the Mac. AirFlick was close to what I was wanting at the time but I really wanted something that would let me control AirPlay from Linux or Windows.

I decided to make something that could run anywhere so I created my own AirPlay client called AP4J. I used Java and a pure Java Bonjour implementation called JmDNS so AP4J can run anywhere Java runs.

The current version only has the ability to control an AirPlay device. That means you have to supply a location that has a compatible video (h264 encoded) but once playing you will have control over the video just as you would using the iPad or iPhone. The next step will be to add the ability to directly serve videos instead of only being able to control the playback of videos. My goal will be the ability to run AP4J on my Windows Home Media server where I can have it stream videos to my AppleTV.

I have tested AP4J on Linux, Windows and Mac but only extensively on Linux. I have also tested a number of sites that have compatible videos available, a few of those are listed here:

Now for a couple screen shots. This is what you see after starting the server and going to the web interface:

This is what it looks like when a video is playing:


Posted in utilities | Tagged , | 4 Comments