1. June 2008 WEI Short Course 1 Wireless Embedded InterNet working Foundations of Ubiquitous Sensor Networks EPIC – Open Embedded Networking Platform David E. Culler University of California, Berkeley

2. June 2008WEI Short Course2 On-line reference http://www.eecs.berkeley.edu/~prabal/projects/epic/

3. June 2008WEI Short Course3 Epic Core

4. June 2008WEI Short Course4 Overview 2 binary Inputs 2 binary Outputs Convert switch to digital value external voltage sel. 4 analog Inputs signal conversion Epic core Trim Pot Power pins IO pins user buttonreset button Alkaline battery Li Ion battery USB Epic USB LEDs 5v TTL reg

5. June 2008WEI Short Course5 Turning a switch into a digital input Many sensor are switches Two “states” but not digital –Open => no current –Closed => no voltage drop Cap charges to Vacc when open Cap discharges to GND when closed V acc GND switch D VDVD V tL V tH

6. June 2008WEI Short Course6 Digital Inputs

7. June 2008WEI Short Course7 Digital Outputs Two screw terminals provide access to digital outputs Output voltage selected by jumper Feeding through pFET –Closed when gate is Low Gate controlled by MCU pin Port 5.0 => Dout0 Port 5.1 => Dout1

8. June 2008WEI Short Course8 Ratiometric sensor V a = V acc * R sens / (R comp + R sens ) use V ref = V acc D = M * R sens / (R comp + R sens ) V acc GND Resistive Sensor VAVA R comp R sensor

9. June 2008WEI Short Course9 Analog Inputs

10. June 2008WEI Short Course10 Analog Inputs (cont)