This document proposes pluggable real world interfaces that allow objects to have embedded software and sensors. It describes a two-step approach where real world interfaces with hardware are first deployed to objects, giving them awareness of their context, and then logic can be deployed through a network. This would allow objects like chairs to have code stored in them to recognize their state and interact in an office environment. The implementation uses small sensor nodes and a Java virtual machine to execute code on the objects. An evaluation shows the overhead is small and sensors can easily fit on low-cost memory. The conclusion is that context-awareness can be achieved by storing code in physical objects, and embedded systems can benefit from virtual machine abstraction.

1. Pluggable Real World Interfaces
Till Riedel*, Phillipp Scholl*, Christian Decker*, Martin Berchtold* and Michael Beigl**
(*TecO, University of Karlsruhe, **DUS, University of Braunschweig)

2. Smart Items

Interface the world (context awareness)

Push Logic to the Item (ad-hoc collaboration)

Example:
− Chairs
− Pen
− Sponge
− Doorplate
− White board
camera
AwareOffice
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3. Logic on the Item

should extensible and adaptable

should be sensor hardware independent

needs execution and communication platform
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4. Real World Interfaces

recognize static and dynamic context of object
− e.g. so. I am a chair and so. is sitting on me, ...

depends on sensor types
− Acceleration sensors, pressure sensor, ball switches

depends on sensor placement
− Direction, seat/arm rest

depends on mechanical model
− swivel chair, easy chair, stool
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5. Key Ideas

Execute instead of describing sensor semantics
− Unlike SensorML, IEEE 1451

Abstract Real World Interfaces
− As High-Level Interfaces
− accessible through Programming Language
− Use type hierarchies and reflection

Bundle Software and Hardware
− Enable production of Smart Objects
− Physically enabled code deployment
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6. 2-Step Approach

Deploy Real World Interfaces with Hardware
(Sensors+Interpretation)

Deploy Logic with Network
Architecture
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7. Implementation

Load code from object into (virtual) machine

Execute Static Initializers

Item becomes “aware”

Discover

Deploy Logic
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8. Platform

Particle Sensor Nodes
− PIC18F6720: 8bit, 5MHz
− TR1001 low power radio

21-Pin FCI Conan Connector

Various Sensors Boards
− SPI, I²C, PWM,
1Wire, Analog

Particle Java VM
− supports javac
− code compression
− class loading
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9. Evaluation

Execution overhead : 30x (from external flash)

Object overhead: 3 byte

Code size for Sensors
− ADXL210: 167 byte
− Ballswitch: 29 byte
− TC74: 120 byte
− Microphone: 49 byte
− TSL2550: 295 byte
− TSOP36236: 49 byte
Fits easily on cheap ROM/Flash
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10. Conclusion

software engineering needs to consider
“hardware context”

context-awareness can be just storing code in
the right place

embedded design can profit from
virtual machine abstraction
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11. Thank you!
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