Christmas Lights (redux)

Last year, if you'll remember, I did a half-assed job of putting together a musically coordinated christmas light rig, and promised to Do Better this year. Lucky for me I was vague because under-promising made over-delivering a lot easier. :)

What I did manage to do was tackle last years technical debut, and get the code cleaned up. I've named it Lumen and put it up on Github.

Lumen has two modes, record and playback. When launched in record mode, you use the a, s, d, f, j, k, l, and ; keys to "play" the 8 outputs to the music. You can think of it as a sort of reverse Guitar Hero. It's not as easy as it sounds (not for me anyway). It takes practice, at which point you're so sick of the song that if you never hear it again it'll be too soon.

Playback mode can be used to either drive the lights, or to run a simulation to check your work. Here is what it looks like in simulation:

And here is what it looks like For Real:

Christmas Lights

We put up lights each year for the holidays, and while I don't mind having the house decorated, I do not like having to put them up. Despite this, I feel mounting pressure each year to Do Better, which by default means more lights and decorations, which in turn mean even more work.

The year before last I had the idea that if I worked smarter I might avoid working harder, and that one of those musically synchronized setups would be pretty sweet. Problem is I came to this conclusion in October of 2008, and that didn't leave enough time to properly procrastinate before throwing something together at the last minute, so I was forced to postpone. This past year though I was able to spend a solid 11 months procrastinating, which still left a couple short weeks to hurriedly throw something together.

So long story short, I did it, I put together a controller that sets christmas lights to music. And, providing that you weren't privy to all of the nasty hacks and ugly short-cuts, it was actually kind of neat of to watch. Obviously though, I'm not entirely happy with the results, so I'm considering this year a practice run, and hope that with this as a basis to build upon, next year it will be pretty sweet. So treat the rest of this post as more of a rough brain-dump than a recipe or step-by-step, and hopefully it will prove interesting for comparison purposes next year.


Normally this is where I'd expound on some of my research, the options I investigated, costs, ease of use, etc. That's not going to happen because with all of the procrastination this project required, I simply didn't have the time. Instead I went straight for a pre-assembled parallel port relay board, and I took a page out of this guys book and mounted it in a plastic tool box.

I used some cheap extension cords, fixed to the ends of the toolbox with cable connectors, and wired it all together inside. The relay board needs a power supply, so there is an outlet inside for that.

A cord that exits the rear of the toolbox gets plugged into the mains to supply power to the whole thing, but since we're combining electricity and the great outdoors, a GFI is a must.

I scored this parallel cable in an old pile of hardware. It worked great once I got the zip drive that was attached to it off and in the trash.

Finally, I made use of an old PIII notebook.

Christmas light controll

I know, it's not much to look at. Sue me.


There are 8 pins on a parallel port that are (were) used to send character data to printers, and it's these 8 pins that are used for outputs. That means controlling the outputs is as simple as writing to that byte. The pyparallel library makes this even easier, so for example, I was able to use something like the following, ran from a cronjob to start and stop the lights each day.

python -c 'import parallel; parallel.Parallel().setData(0)'

I wired everything up to the normally closed contacts of the relay board so the lights would fail-safe. In other words, you have to turn the relay on, in order to turn the corresponding lights off. The setData(0) above switches on all of the lights by turning the relays off, killing the lights is as easy as changing that to setData(255).

Initially I had the idea that I'd whip up something to analyze an audio track; that the light show would essentially be a visualization of the waveform. That, as it turns out isn't the panacea that it would seem. Sure, the lights will flash in a way that seems vaguely in response to the music, but the results are just not as coordinated, or ordered, as the samples you see on the Internet.

So I then moved on to the idea of creating a time-series of output states that could be "played" along with the audio, but I was naive to believe that I could hand-craft this data file, so before all was said and done, I'd also written a PyGame application for keying in the outputs as the music played, and visualizing it during playback.

Finally, only after getting everything working I found out that the way "professionals" do this is actually pretty similar to what I came up with, only using MIDI, so I will definitely be looking into that before next year.

Lowest Common Denominator

From the git-svn manpage:

For the sake of simplicity and interoperating with a less-capable system (SVN), it is recommended that all git svn users clone, fetch and dcommit directly from the SVN server, and avoid all git clone/pull/merge/push operations between git repositories and branches. The recommended method of exchanging code between git branches and users is git format-patch and git am, or just 'dcommit’ing to the SVN repository.

Running git merge or git pull is NOT recommended on a branch you plan to dcommit from. Subversion does not represent merges in any reasonable or useful fashion; so users using Subversion cannot see any merges you’ve made. Furthermore, if you merge or pull from a git branch that is a mirror of an SVN branch, dcommit may commit to the wrong branch.

Or put another way. Because Subversion can't merge for shit, neither can Git if you expect to integrate the two.


NP: Blood Milk and Sky, White Zombie

Thrift Packaging

My latest project at work is Cassandra, a distributed, eventually consistent, column oriented data store. It's somewhere between Dynamo (Cassandra's original author worked on Dynamo), and Google's BigTable. It was developed as an internal application at Facebook, later open sourced, and is now an Apache incubator project.

The external interface to Cassandra is thrift-based. Thrift is a framework for creating network services, services that communicate using a compact binary data format. It's similar to Google's Protocol Buffers, but with more of a focus on RPC, and greater language coverage, (much greater actually). The bottom line, any application that uses Cassandra for structured data storage is going to need Thrift. So, I filed an ITP (Intent To Package) and have started work on packaging it for Debian.

Thrift is an interesting project to package as it has an architecture specific application (C++), 6 architecture specific and 5 architecture independent libraries, and covers 12 different languages. That's right, 12.

I'm still somewhat undecided on a game plan; the options I've considered so far are:

  1. Convince upstream to split their source tree and distribute all of these libraries separately, allowing them to be packaged by people with the skills and/or motivation for each.
  2. Split the source myself and package the bits that are most important to me.
  3. One source package based on the official upstream release, with binary packages for each of the components that I need/am comfortable maintaining. Folks interested in the parts not packaged could step up to the plate and contribute their time.
  4. Best-effort packaging of most/all of the libraries upstream ships with the proviso that for any I'm not comfortable seeing in a release, and for which no one has stepped forward for, they would be removed prior to Squeeze.

I've already taken a stab at #1 and it didn't seem promising. #2 is an option I still consider on the table but I'm a little concerned that it could lead to a mess. #3 and #4 really boil down to the same thing, collaborating with others to package as much as possible while maintaining the standards everyone expects from Debian. I guess I'm currently leaning toward some variation of #3 or #4, probably through the use of collab-maint or a dedicated Alioth project.

For the time being, my efforts can be tracked in Git here, so drop me a line if you're interested in joining the fun!

NP: Sand and Mercury, The Gathering