Authors in this issue range from a columnist who reintroduces us to the advantages of switched-capacitor filters to a frequent contributor who discusses his first encounter—and project—with the credit card-sized Raspberry Pi computer.
Columnist Robert Lacoste recently rediscovered one of his 1981 magazines, 
which included an article on switched-capacitor filters. “Since mastering switched-capacitor filters is now mandatory for many mixed-signal designs, I thought: Why not refresh the topic for a Circuit Cellar Darker Side article?” Lacoste says. Beginning on page 56, Lacoste shows you how to modify a simple one-pole RC filter into a switched-capacitor filter.
Frequent contributor Brian Millier placed his name on a waiting list to purchase his first Raspberry Pi. He finally received it in late 2012 and started the project that would inspire his two-part series “Raspberry Pi I/O?Board” (p. 42). The series explores the strengths 
and weaknesses of the single-board computer (SBC)?and explains the versatile I/O board he developed for it. “In the time since I received my Raspberry Pi, one of the board’s developers has designed an I/O board called the Gertboard. I feel my board is quite distinct and has some advantages over the Gertboard,” Millier says.
Speaking of the Raspberry Pi’s developers, this issue includes an interview with “RPi hardware guy” Peter Lomas (p. 38). He looks at the growth in popularity of the Raspberry Pi since its initial launch and shares how the nonprofit Raspberry Pi Foundation plans to foster its mission of promoting the $35 SBC as a tool to teach children computer skills and encourage inventiveness.
This month’s issue offers many other interesting reads. For example, columnist Jeff Bachiochi continues his series on creating user-friendly graphic displays. Part 1 focused on the microcontroller used to create his serial display. Part 2 discusses implementing dynamic button commands (p. 70).
In Part 4 of his “Testing and Testability” series (p. 52), columnist George Novacek explains 
the importance of an electronic system’s internal diagnostics. In addition, columnist Bob Japenga wraps up his “Concurrency in Embedded Systems” series by focusing on file usage (p. 48). “Modern embedded systems are doing more than I ever imagined when I first started,” Japenga says. “Adding a file system to your design can provide significant advantages to improve your product.”
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This issue also presents two more final installments. One describes how to use a DSP-SQL interface to access large amounts of data (p. 20). The other outlines a DIY SBC project (p. 30).
Editor’s Note: The Client Profile focusing on Beta LAYOUT in Circuit Cellar’s June issue (p. 16) included incorrect information. Tony Shoot can be reached at tony@beta-layout.us. Visit circuitcellar.com/featured/client-profile-beta-layouts online to see the full profile.
Circuit Cellar's editorial team comprises professional engineers, technical editors, and digital media specialists. You can reach the Editorial Department at editorial@circuitcellar.com, @circuitcellar, and facebook.com/circuitcellar
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