eBlocks

1
eBlocks An Enabling Technology for Basic Sensor
Based Systems
Susan Cotterell, Ryan Mannion, Frank Vahid,
Harry Hsieh Department of Computer Science and
Engineering University of California,
Riverside susanc, rmannion, vahid,
harry_at_cs.ucr.edu http//www.cs.ucr.edu/eblocks
Also with the Center for Embedded Computer
Systems at UC Irvine This work is being
supported by the National Science Foundation
(CCR-0311026)
2
Introduction

• Sensor networks are emerging as an important
  general computing domain
• Small inexpensive battery-powered sense and
  compute nodes
• Tens to thousands of nodes
• Wired or wireless communication
• Stringent requirements (power, cost, size)

Environmental Monitoring http//www.greatduckislan
d.net/ http//today.cs.berkeley.edu/retreat-6-03/
Military Applications http//robotics.eecs.berkele
y.edu/pister/29Palms0103/
Home Automation http//www.smarthome.com
Structure/Building Monitoring http//www.mrr.dot.s
tate.mn.us/research/MnROAD_Project/MnROADProject.a
sp
Medical Monitoring http//www.eecs.harvard.edu/md
w/proj/codeblue/
3
Introduction

• Potential sensor network application developers
  may not be computer programmers
• Instead, engineers, scientists, office workers,
  homeowners, etc.
• Existing programmable nodes
• Flexible, but require programming
• Existing off-the-shelf end applications
• Specialized, so hard to customize
• Expensive due to small volumes
• Our solution eBlocks
• Enables non-programming users to create simple
  but useful customized sensor network applications

http//www.xbow.com/
Flexible, hard to program
Photo Jason Hill http//www.dustnetworks.com/
Easy to use, inflexible
http//www.smarthome.com
4
eBlocks Overview

• eBlocks (UC Riverside)
• Began as low-cost reusable basic building blocks
• Enables non-programmers to create basic but
  useful sensor-based applications
• Function of each block is pre-defined
• Block types
• Sensors motion, light, contact, etc.
• Output led, electric relay, beeper, etc.
• Compute logic, prolong, toggle, etc.
• Basic configuration required (dials, switches)
• Communicate wireless point-to-point link
• Users merely connect blocks to create working
  customized application
• Evolving into a spatial programming methodology
  for sensor networks with programmable nodes
• CODES/ISSS03, SECON04, CHI05, DATE05

5
Creating an application with eBlocks

• Create an application to detect if the garage
  door is left open at night
• Choose which blocks to use
• Plug blocks together using standard plugs
• Configure blocks if needed (e.g. logic block)

Need something to indicate garage open at night
use led
We want to detect night use light sensor
Need a function of light sensor output and
contact switch output use Logic Block
We want to know if garage door open use contact
switch
Configure Logic Block to turn led on when its
night and when door is open
Block Connectors
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Building eBlocks Systems

• The same basic blocks can be used in a variety of
  applications

7
Inside eBlocks Technology

• Tiny computer in every block
• Even the simplest button
• Enables low-power, and easy connection
• Block asleep gt99 of time
• But user doesnt notice
• Communicates tiny computer packets, lt 0.1 of
  time
• Connecting eBlocks actually creates a computer
  network
• Use PIC microprocessor costing lt1, consumes
  little power
• Same processor as in blinking tennis shoes
• Currently in the process of patenting eBlocks
• Method of adding computing intelligence to
  previously passive components, method of using
  such computers to reduce power.

8
Design Entry/Simulation

• User specifies and tests block design
• Java-based simulator
• Blocks added to workspace by dragging blocks from
  Available eBlocks tray
• Connections created by drawing lines between
  blocks
• User can create, experiment, test and configure
  design

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Synthesis -- Partitioning

• Mapping of pre-defined blocks to programmable
  blocks
• Problem map pre-defined blocks to minimum
  number of programmable blocks
• Intermediate blocks (non-sensor, non-output)
• We assume 2-input/2-output programmable block
  available
• Partitioning problem differs from existing
  problems
• Classic bin-packing or knapsack algorithms
• But we need to be conscious of two constraints
  number of inputs and number of outputs
• Two-dimensional bin-packing problem (cutting
  stock problem)
• But number of inputs and outputs of programmable
  block are mutually independent
• FPGA synthesis, namely DAG covering
• But we do not require all nodes to be covered
• Our goal is to minimize block count, many focus
  on minimum-delay solutions or approximations
• Many solutions permit replications contrary to
  our goal of minimizing block count

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Synthesis -- Partitioning Strategies

• Exhaustive
• Search every combination of n blocks into n
  programmable blocks
• Extremely long run times (hours)
• Aggregation
• Clusters nodes into subgraphs, continue adding
  blocks until unable to fit into programmable
  block
• Unable to take advantage of convergence thus
  yields non-optimal results

• Developed a new heuristic PareDown
• Based on a decomposition method
• Takes advantage of convergence
• Unconstrained by depth at which heuristic looks
  ahead
• Runtime complexity O(n2)

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Synthesis -- Code Generation

• For each partition a syntax tree is generated to
  represent equivalent functionality of the
  partition
• Able to generate C code for each partition to
  download unto a programmable block
• Simulators interpreter able to evaluate syntax
  tree and simulate corresponding behavior

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Experiments

• Conducted numerous experiments in 2003-2004
• Physical Prototypes
• Nobody reads/follows the instructions
• Re-designed blocks to be self-explanatory
• Added debugging lights to indicate block status
• Simulator
• Allows rapid iterations of eBlock design
• Eliminates hardware ambiguities (i.e. power
  switch, crossed connections)
• Enables a wider participations
• Enables us to save various user-defined systems
  for later analysis

13
Physical Prototype and Simulator Usage Summary

• Non-computing users - non-science,
  non-engineering users (psychology, business, etc.
  majors)
• Beginner users - Students in their first
  introductory to programming course (lt10 weeks)
• Intermediate users - Students with 2-3
  programming courses
• Advanced users - Students with both programming
  and electronics experience
• Miscellaneous - Middle school or high school
  kids, non-engineering adults

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Usability of eBlocks
Total number of students is higher than
previous table because individual students may
have participated in multiple tests

• Student participants of various expertise levels
• None of the students had previous experience with
  eBlocks
• More than half of the students were able to build
  the first three systems in less than 10 minutes
• Compared to the days to weeks required by
  advanced students to build similar systems
  without the benefit of eBlocks

15
Conclusions and Future Work

• Summary
• Presented physical prototypes and graphical tool
  that can be used by non-computing specialists to
  develop basic sensor/actuator applications
• Summarized usage in a large variety of user
  experiments
• Present/Future work includes
• Extend eBlocks to integers (presently Boolean)
• Deployment of real systems
• Proactive health care (Intel)
• Insect monitor and automated pesticide deployment
  (Isca Corporation)