This detailed book chapter describes how to add a Linux-based, Bluetooth-connected control interface to a scrolling LED sign. The 35-page chapter is excerpted from Make Projects: Small Form Factor PCs, a 232-page O'Reilly book featuring nine interesting and instructive embedded projects, many based on Linux.

(Click for larger view of book cover)

The Make Projects book was written by Duane Wessels and Matthew Weaver. Weaver works on small-form-factor access points and solar-powered servers, for a wireless ISP in Colorado. Wessels previously authored O'Reilly books on HTTP caching and on Squid, the open-source caching HTTP proxy server he co-developed and maintains.

The bluetooth sign project

The Bluetooth sign project described in the sample chapter is based on a Bluetooth-enabled Gumstix SBC (single-board computer) along with a serial port add-on board, packaged in a “Waysmall” case.

Gumstix Waysmall connected to a laptop serial port
The Bluetooth sign project also makes use of a scrolling Pro-Lite LED sign with a serial control interface. The sign comprises a 7 x 80 LED matrix, and measures about four inches high and two feet long.

The Pro-Lite sign has a 7 x 80 LED grid
Typically, Pro-Lite signs are attached directly to PCs, and controlled using a serial API. In this project, the book authors have worked out how to attach the tiny Bluetooth-enabled Gumstix PC to the back of the sign. This allows messages to be posted to the sign from Bluetooth-enabled devices, using applications such as “BTControl,” as depicted at right.

Suggested applications include status boards for network operations centers, custom news and stock tickers, display of IM or IRC messages, artist and title display for digital music systems, public transit information systems, or just to allow people to have fun posting messages from their cell phones.

Click here to download the complete 35-page chapter:

Chapter 9: Building a Bluetooth LED sign

Other chapters in this Make Projects book include:

• Creating a digital audio jukebox with infrared remote control
• A digital video recorder (DVR) using MythTV
• A home network gateway using a Soekris net4501, OpenBSD, and packet filter
• A network monitor using a Soekris net4801, FreeBSD, arpwatch, nagios, snort, and RRDTool
• A WiFi extender using an Access Cube
• A portable, USB-powered bridging firewall using OpenBlockS and SSD Linux
• A WiFi SSH client based on first-generation Zipit chat toy

Availability

Make Projects: Small Form Factor PCs (ISBN: 0-596-52920-1), by Duane Wessels and Matthew Weaver, is available now, priced at $15.99, from booksellers or direct from O'Reilly's Maker Media division.

The downloadable chapter provided via the above link is copyright (c) 2006 O'Reilly Media. All rights reserved. Used with permission from the publisher.

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