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Issue #218 September 2008
Second Place WIZnet iEthernet Design Contest 2007
Content Collection and Display
Build an Internet-Connected News Ticker
by James Blackwell
James no longer has to turn on a TV or computer to get news updates. His innovative design retrieves news headlines from RSS feeds and constantly scrolls them across a dot-matrix LED display. The system checks for updates every 15 minutes.
Start | Some Challenges | The Hardware | WIZnet Makes It Easy | Main Board Firmware | News Update Task | DHCP | DNS | HTTP | Display Task | Slave Board Firmware | Have Fun | Sources & PDF
When I first heard about WIZnet’s iEthernet 2007 design contest, I was really excited about all of the possibilities an integrated Ethernet chip would open up to smaller microcontroller-based systems. I knew there were tons of networking applications that I could create (e.g., web servers, remote sensor networks, and home automation/control systems). But many of the designs that first came to mind had already been done to death, and when it came down to finding a new project, I struggled a bit. Having missed the last few Circuit Cellar contests, I knew I had to get an entry done for this one.
At the time, I was messing around with interfacing dot-matrix LED displays to microcontrollers. I showed a friend how to make customized messages scroll across a display by programming a computer a certain way. (He wasn’t exactly a Circuit Cellar reader.) He was really interested in the stock market, so he thought it would be nice to have a scrolling stock ticker similar to those shown on some financial television programs. I thought it was a really good idea, but rather than scrolling stock information, I decided to scroll up-to-date news headlines.
Luckily, there are many news organizations that provide free news updates via the Internet. Nearly all of the major ones provide really simple syndication (RSS) feeds for news headlines as well. RSS gives content providers a way to distribute periodically updated material. Conveniently, RSS uses XML, so the relevant data is well-structured for processing by clients.
To retrieve the news headlines, I wrote a cut-down HTTP client and XML parser. I wanted the device to operate without any action by the user, so I implemented a domain name service (DNS) and dynamic host configuration protocol (DHCP) client in order to use dynamic IP addressing. Every 15 min., the device renews its client IP, requests the IP of the BBC News RSS server, parses the XML for news headlines, and scrolls them across the display (see Photo 1).
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| Photo 1—Check out the LED news ticker in action. Actually, you can’t really see the full extent of the action. Still pictures don’t show scrolling very well. Use your imagination! |
The system features a Microchip Technology PIC18F2525, PIC18F2221, and a WIZnet WIZ810MJ Ethernet module. In this article, I’ll describe how I used these building blocks to design the news ticker.
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