Tag Archives: Linux

Building a Wifi Radio – Part 2, Choosing an Embedded Platform

This is the second part of an ongoing series about building a low cost, open source streaming internet radio.  if you haven’t already, check out part one for some background about the project.

Onward…

In part one, I discussed the merits of streaming internet radio and the motivations for my Wifi Radio project.  Now it’s time to start looking at what hardware can make this project a reality.  Before we get started, let’s review the requirements list from last time.

Requirements:

  • Wireless connectivity through existing Wifi network
  • Audio output (preferably 44kHz, 16 bit stereo)
  • An integrated amplifier and speaker(s)
  • Shoutcast/MP3 streaming audio decode
  • Several builtin station presets
  • A display to indicate the station and currently playing song
  • Simple user interface, using standard radio controls (volume, tune, etc)
  • 110VAC operation

There are two additional requirements that I implied in the first post but forgot to include explicitly:

  • Cheap, priced below a commercial streaming radio – target < $100.
  • Small size so it can be portable (no desktop PC’s allowed!)

Selecting the hardware:

How do these requirements translate into hardware?  Let’s take a stab at what features we’d like in an embedded platform.

  • A wireless interface
  • Audio output
  • Sufficient system resources (CPU, memory, etc.) to decode MP3s
  • Some extra IO for a control panel and display
  • Low cost
  • Small size
  • Ease of development

The size and cost aspects pushed me towards an embedded system instead of a small form factor PC like any of Shuttle’s XPC offerings or a nano-ITX board.  To me, “Ease of development” equals Linux, so I wanted something well supported by Linux and an active open source development community.

There are quite a few embedded Linux platforms out there, with a wide variety of prices and features.  I looked at a few of them, including:

  • The Tin Can Tools Hammer – very impressive ARM9-based board with USB, lots of RAM and flash, lots of IO, and best of all the footprint of a 40-pin DIP package (breadboard compatible!).  No wireless and relatively steep pricetag ($160).


  • TI‘s Beagle Board – Incredible featureset including DVI output and a 600MHz ARM Cortex core.  No wireless and price is stunning for what you get, but overkill for this project ($150).  (Must keep in mind for future projects!)


    ASUS WL-520gU Wireless Router

  • Consumer wireless routers like the Asus WL-500gP v2 and WL-520GU – builtin wireless (yay!), USB, 240MHz Broadcom 5354 core, decent RAM and flash, cheap. Newegg has the WL-520GU for an incredible $26 after rebate (normally $50). The higher end WL-500g has more memory and flash and an integrated USB 2.0 hub (2 external ports).  Newegg has the WL-500g Premium V2 for $50 after rebate (normally $80). Both versions are a steal for what you get.

Tiny, under $50 and with built-in wireless, the Asus WL-520GU is the clear winner for this project.  The downside?  Since this router was never intended to do anything other than, well, route, we’re going to have to crack it open, modify it, and void the warranty.  In addition, there is no tech support and we’re going to have to spend some extra time hacking around to get it to do what we want.

Here it is in all it’s glory:

Asus WL-520GU Wireless Router Asus WL-520GU Wireless Router

Here’s a sneak peak of the inside:

Asus WL-520GU Wireless RouterAsus WL-520GU Wireless Router

This router is supported by OpenWRT, an open source Linux distribution for small embedded devices.  Ignore the work-in-progress designation, it works, trust me!

Although the router lacks builtin audio, that is easily solved with an $8 SYBA SD-CM-UAUD USB Stereo Audio Adapter. There have been reports that the WL-520GU only supports USB 1.1 reliably, but USB audio doesn’t require USB 2.0 so it’s not an issue for us.  For full USB 2.0 support, look at the WL-500gP v2 instead.

So far we have $58 into the project ($38 if you are lucky enough to get the rebate) and we have an embedded Linux computer, a wireless interface, and an audio output.  Not bad!

That’s it for part two!  In part three I’ll install a serial port on the router and get ready to reflash the stock firmware with OpenWrt.  At that point we’ll be able to start listening to some tunes!

Update: I posted detailed specs for the WL-520GU and a couple more photos here.

Update 2: I posted some images of the $8 USB-Audio Adapter I am using as well.

Update 3: Part three is now available.

Update 4: There is a new Wifi Radio Discussion Forum, hop over there to ask questions about the project or see what other people are working on!  (4/12/09)

Building a Wifi Radio – Part 1, Introduction

This article is the first of a series that will document the development of a low cost, open source wireless streaming internet radio receiver.  All construction details, including schematics, source code, and even the design process itself will be documented on this blog.

Comments and (constructive) criticism are welcome. Click here to post a comment.

Table of Contents:

  1. Building a Wifi Radio – Part 1, Introduction (you are here)
  2. Building a Wifi Radio – Part 2, Choosing an Embedded Platform
  3. Building a Wifi Radio – Part 3, Hacking the Asus WL-520GU
  4. Building a Wifi Radio – Part 4, Installing OpenWrt
  5. Building a Wifi Radio – Part 5, Let’s Make Some Noise!
  6. Building a Wifi Radio – Part 6, A Conversation with Mpd
  7. Building a Wifi Radio – Part 7, Building an LCD Display
  8. Building a Wifi Radio – Part 8, Adding a Tuning Control
  9. Building a Wifi Radio – Part 9, A Few Odds and Ends
  10. Building a Wifi Radio – Part 10, Building the Box

Some background:

According to Wikipedia, in 1993 the first internet radio program began distribution.  At that time, radio programs were manually downloaded to be played later on the user’s home computer; the user experience was far from that of listening to a traditional broadcast radio receiver.  It was not until several years later that streaming radio became common, giving birth to internet radio stations that could be listened to much like traditional radio, but with several advantages.  Most notably, internet radio stations were (and still are for the most part) largely devoid of on-air advertising, and stations anywhere on the globe could be received by anyone with access to the internet.  Over time, improvements in audio compression (such as MP3) and larger end user bandwidth improved the fidelity and reliability of internet radio.  The birth of common standards like Shoutcast made it possible to listen to many stations with a single player program, like Winamp.

Today, most music playback software supports streaming radio in some way.  iTunes features thousands of streaming radio stations and even supports Shoutcast streams so that users can easily add additional stations of their own.

The beautiful thing about streaming radio is the huge diversity in programming that is available.  Many college radio stations have a streaming server, like KDVSDigitally Imported hosts many electronic and dance music streams that give the listener the choice to listen to specific genres like ambient or gabber hardcore (whoa).  Broadcast radio usually lumps all electronic dance music into one category, much to the dismay of their listeners (who probably tuned out during the commercial break, anyway).  Gems like Slay Radio specialize in music you would never hear on broadcast FM, like Commodore 64 remixes.

In the past couple years, products have started to appear that mimic the form and function of a traditional radio, but play internet radio instead.  Good examples of these are the Roku SoundbridgeRadio and the ASUS Internet Air.  Remote speaker devices, such as the Apple Airport Express, require a PC to receive and relay streaming radio but achieve a similar end result (but don’t really look much like a radio).

The Wifi Radio project:

I have been wanting to build a streaming radio for some time.  I frequently work in my garage, where I occasionally use my Macbook to play music through a small amplifier and bookshelf speakers.  The problem is that my laptop is not always set up in the garage, and greasy fingers are not a good thing to have around a white laptop, period.  I could simply buy an internet radio, but I couldn’t stomach the $150-$300 price tag on most players for such a luxury.

So I decided to build one instead.

I started the design process by drafting an outline of desired features, and then breaking them down into wants and needs, while trying to keep the project scope under control.

Requirements:

  • Wireless connectivity through existing Wifi network
  • Audio output (preferably 44kHz, 16 bit stereo)
  • An integrated amplifier and speaker(s)
  • Shoutcast/MP3 streaming audio decode
  • Several builtin station presets
  • A display to indicate the station and currently playing song
  • Simple user interface, using standard radio controls (volume, tune, etc)
  • 110VAC operation

Optional features:

  • Line output (to connect to a receiver/amplifier)
  • Web server for configuration/management
  • Ability to play files off a USB stick or iTunes server

Definitely won’t be a feature:

  • Any kind of over-the-air radio tuner
  • Commercials
  • Pledge season
  • Morning DJ’s
  • “Blah, blah, blah.”

Now that we’ve defined the project…  it’s time for a commercial break.  That’s it for part 1 of this series.  Stay tuned for part 2, where I’ll talk about choosing an embedded platform for the design and why Linux is so awesome!

Update: Part two is now available, click here to see it!

Update 2: There is a new Wifi Radio Discussion Forum, hop over there to ask questions about the project or see what other people are working on!  (4/12/09)

Update 3 (6/1/09): I finally added a table of contents to the top of this post to help everyone (including me) navigate the series!

Old Dell + Debian Etch = Instant Development Server

Earlier this year I replaced my desktop PC, a Dell Dimension 4700, with a Mac Mini as part of my effort go 100% Mac for my home computing.  OS X is a terrific platform for the desktop power user because it looks great, feels great, is well supported by open source projects.  It also runs on a variant of Unix giving you full shell access and lots of other great stuff.

Since then, the Dell has been sitting by my desk, waiting for a good use.  I already have a Linkstation Live that I use for a low power home server (print server, mt-daapd, subversion, samba, etc.) so I didn’t have an immediate need for another PC around the house.

Last week I started playing with OpenWRT as part of a neat new project that will be an upcoming feature on this blog.  I suddenly needed a Linux environment and some extra computing power to help build custom OpenWRT images.  Debian to the rescue!

Before anyone says anything, I don’t really have anything against the incredibly popular desktop Linux distro Ubuntu.  The real reason I choose Debian is that I know Debian, and Debian just works.  My new server runs headless and I use ssh to login and compile from my Mac, so the advanced graphical features of Ubuntu would be lost on me.

Installing Debian is a breeze.  Within 30 minutes of burning the Debian quick start CD, I was up and running.  After installing a few addon packages, I was compiling OpenWRT images.

Instant development server.  Awesome.