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Wireless Embedded InterNet working Foundations of Ubiquitous Sensor Networks EPIC – Open Embedded Networking Platform. David E. Culler University of California, Berkeley. On-line reference. http://www.eecs.berkeley.edu/~prabal/projects/epic/. Epic Core. Overview.
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Wireless Embedded InterNetworkingFoundations of Ubiquitous Sensor NetworksEPIC – Open Embedded Networking Platform David E. Culler University of California, Berkeley WEI Short Course
On-line reference • http://www.eecs.berkeley.edu/~prabal/projects/epic/ WEI Short Course
Epic Core WEI Short Course
Overview Convert switch to digital value reset button user button Trim Pot LEDs 2 binary Inputs 5v TTL reg 2 binary Outputs Li Ion battery external voltage sel. Epic USB Epic core USB 4 analog Inputs Alkaline battery IO pins signal conversion Power pins WEI Short Course
Vacc D switch GND 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 VtH VD VtL WEI Short Course
Digital Inputs WEI Short Course
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 WEI Short Course
Vacc Rcomp VA Resistive Sensor Rsensor GND Ratiometric sensor • Va = Vacc* Rsens / (Rcomp+ Rsens) • use Vref = Vacc • D = M * Rsens / (Rcomp+ Rsens) WEI Short Course
Analog Inputs WEI Short Course
Analog Inputs (cont) WEI Short Course