The HAL Project
Ah, the joys of hacking Linux on inexpensive commodity hardware. We are the Montréal community wireless group Ile Sans Fil, which was covered in this magazine in October 2005. During the last three years, we have deployed embedded systems that run Linux in public spaces across our city in an effort to encourage local communities. Our all-volunteer group now has more than 100 hotspots located in cafés, libraries and parks around the city, and more than 26,000 users. To accomplish this, we used the Linksys WRT54G, a favorite of hackers, and developed the captive portal suite WifiDog.
Our latest project is HAL, the Local Artist Hub (the acronym works in French). HAL boxes are small NSLU network storage devices that we install locally at certain of our Wi-Fi hotspots and then remotely fill with music and movies by local creators. Because the box is directly on the local area network, the content can be streamed at HDTV resolution without stalls or buffering and without bandwidth charges. Plus, because we use Zeroconf, the user's media player discovers the content automatically. Besides promoting serendipitous discovery, the user gets to interact with the content using a familiar interface that is specifically designed for rich media. We hope to make HAL servers a cultural meeting spot—an easy way for passers-by to engage with works by artists from that community.
The technologies we have plugged together also can be used in many ways, either as single installations or deployed in networks across multiple sites. In this article, we describe our setup so that you can get started on your own projects.
HAL uses the NSLU2 network device from Linksys. It's a small board with a 266MHz XScale CPU (ARM architecture, by Intel), two USB 2.0 ports and one 10/100Mbps network interface. The NSLU2 is another favorite among hackers. There are two alternative firmwares available for it, Unslung and and OpenSlug, both of which are supported by an active community. We've chosen OpenSlug for this project.
As we cannot vouch for the electrical system at the venue, we physically wire the boards with an auto-on circuit. If you want instructions on how to do that, you should visit the Web site and read through the appropriate disclaimers about voiding your warranty and burning down your house.
Because the NSLU doesn't have any built-in storage, we connect a small Seagate 5GB hard drive. The hard drive we use has the form factor of a small hockey puck. Richard Lussier, our local hardware maven, was able to package both the hard drive and the NSLU board tightly in a new enclosure, while maintaining the access to the other unused port. We suggest you do the same, if you can find your own Richard.
HAL uses the open-source media distribution software Firefly Media Server (formerly known as mt-daapd), developed by Ron Pedde. Firefly servers stream media with Apple's daap protocol, making the HAL box accessible for anyone running iTunes or any other daap-enabled media player. And, Firefly does not have the five connections per day restriction of iTunes servers, which is a plus.
To install Firefly, you need to have Linux on the NSLU2. Because the NSLU2 is an ARM architecture, you need Linux binaries that have been cross-compiled for the NSLU2. If you want to try the system before flashing anything, you can install the x86 binary packages for Windows and Linux on your computer.
The OpenSlug distro contains most of the needed tools and libraries, already cross-compiled and ready to go. Whatever was missing we cross-compiled ourselves, and we put the resulting binaries on the Web for you to use. Near the end of the installation instructions below, you will launch a script that will download and install them.
To simplify the daap stream discovery process, we use multicast dns (m-dns) technology as defined by the IETF's Zeroconf Working Group. This is the same technology that printer manufacturers employ to make installation and configuration seamless for Mac users. We use the m-dns dæmon included in Firefly, which does not implement any of the extra functionality available in the protocol beside daap. This is okay; daap is all we need.
Finally, we push the content to the HAL boxes from a central server via rsync and a series of small bash scripts.