Electronic Blocks The Wood and Nails of SensorBased Embedded Systems

1
Electronic Blocks -- The Wood and Nails of
Sensor-Based Embedded Systems
Frank Vahid Professor Dept. of Computer Science
Engineering, University of California,
Riverside (Also with the Center for Embedded
Computer Systems, UC Irvine) http//www.cs.ucr.edu
/vahid, http//www.cs.ucr.edu/eblocks
Graduate Students Susan Cotterell (Lysecky),
Ryan Mannion, David Sheldon, Kelly Stephenson
(graduated MS) This work is being supported by
the National Science Foundation (CCR-0311026)
2
Introduction

• 1998 Simple Problem
• Garage door open at night
• Simple system
• If garage open at night, blink LED in bedroom

3
Investigated Solutions -- None Easy

• Basic components
• Contact switch, light sensor, logic IC,
  microcontrollers, wireless tx/rx, LED
• Issues electronics, programming, development and
  test equipment
• Home-automation components (X10)
• Electric outlet oriented, home automation
  focused, non-intuitive
• Off-the-shelf solution
• Costly (75), hard to find, not customizable
  (two garage doors?)
• Gave up, but noticed missing technology
• Why cant I just connect a contact switch, light
  sensor, logic, transmitter, receiver and LED?

4
Noticed Similar Problems for a Few Years

• Applications
• Sleepwalker detector (from friend, then nursing
  home employee)
• Conference room occupied status system (company)
• Temperature logging system (department, proof of
  building AC problems)
• Endangered species video system (colleague in
  environmental science)
• Carpooler arrived notifier (friend)
• Second home water leak detector (insurace
  underwriter)
• Large domain, all buildable with right
  sensor-based blocks

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Revisited in 2001

• Electronic Building Blocks -- senior design
  project
• Two A students
• Did terrible
• Blocks not intuitive, not power efficient,
  limited applications
• Problem was harder than originally thought
• Previous research didnt help
• Educational blocks
• Logiblocs, MagicBlocks, Logidules
• Board based, non-intuitive, not low power
• Electronic Blocks (Legos)
• Simple toy for young kids
• Programming for novices
• Lego Mindstorm (MIT research), Phidgets, Robobrix
• Teaches programming using robot, several-day
  learning curve

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Observation and Solution

• Observation Microprocessors cheap/smaller
• Solution Put microprocessor in dumb components
  (sensors, buttons, LEDs) to enable easy
  connection
• eBlocks
• Easy-to-use matchbox-sized embedded system
  building Blocks -- just connect
• No voltage issues, programming, development
  tools. Garage-open-at-night buildable in minutes.
  Huge variety of applications.
• Lasts for years or more
• The wood and nails of embedded systems
• Enables novices to build useful systems
• Skilled users can do even more
• 2003 NSF project began

Courtesy of Joe Kahn
7
Research Issues

• Human-computer interfacing
• Block set for novices
• Design individual blocks
• Communication
• Need new digital abstraction
• Mass producible but tunable nodes
• CAD tools for novices

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1. HCI -- Block Set Definition

• Block set for novices
• Tradeoff
• Coarse-grain blocks simple library, intimidating
  block
• Fine-grain blocks simple blocks, intimidating
  library (and networks)
• Built 100 physical prototypes
• Observed dozens of people (college, high-school,
  senior citizens, kids)
• Built simulator -- more people
• http//www.cs.ucr.edu/eblocks

vs
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1. HCI Block Set Definition

• Yes/no blocks
• Block set
• Sensors (motion, light, button, ...)
• Output (LED, buzzer, electric relay, logger)
• Compute
• Combine, Invert, Yes Prolonger, Toggle, Once-yes
  Stays-yes, Pulse Generator
• Result of several iterations and refinements

Found yes/no better than 0/1, true/false, on/off
Found users need to see yes/no values
in
in
Was logic
out
out
out
prolong time
Was delay
Was tripper
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1. HCI -- Design of Individual Blocks (Logic)

• Previous research -- Everyday people dont do
  logic, confuse AND/OR
• Young, D. and Shneiderman, B. A Graphical
  Filter/Flow Representation of Boolean Queries A
  Prototype Implementation and Evaluation. Journal
  of American Society for Information Science 44
  (1993).
• Pane, J. and Myers, B. Tabular and Textual
  Methods for Selecting Objects form a Group. Proc.
  Visual Languages (2000).
• We wanted a single block easier to change, fewer
  blocks in network
• Collaborated with Crista Lopez, HCI researcher
  (UC Irvine) studies ongoing

Original logic block -- Complete failure
Slightly better, still lt20 success
1
2
50-60 success (90 with some training), but not
general
Work ongoing for integer blocks
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2. Communication

• Continuous voltage between blocks -- too much
  power
• Need packets microprocessor can sleep between
• Need new digital abstraction mapping packets to
  Boolean signals
• Like mapping of voltage levels to Boolean signals
• Shannon, C. A Symbolic Analysis of Relay and
  Switching Circuits. Trans. AIEE, Vol. 57, 1938,
  pp. 713-723, Dissertation, Electrical Engineering
  Department, MIT, Cambridge, 69, 1940.

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2. Communication -- Digital Abstraction

• Mapping packets to a continuous model

desired signal
time
packets sent on signal changes only
f
t
f
Problem What if source fails or is disconnected
-- indistinguishable from continued false
Solution define maximum inter-packet time
constraint
lt
lt
maximum inter-packet time violation causes error
values in the received signal
error
error
lt
lt
f
t
f
f
sending packets on signal changes and within
maximum inter-packet time would result in the
desired signal being received
f
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2. Communication -- Digital Abstraction

• Problem sink node designer must know minimum
  packet separation, lest he/she overdesign
• Solution define minimum inter-packet time
• Creates tradeoffs for source node designers too

• Several similar issues (e.g., treatment of
  errors, startup conditions, block latency, etc.).
  
• Resulting constraints define a node technology
  library

Solid basis for node design, composition, and
operation -- work ongoing
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3. Mass Producable but Tunable Nodes

• Node performance (lifetime, reliability, ...)
  heavily impacted by parameters
• Packet constraints, baud rate, voltage levels,
  frequency, error checking bits, ...
• Observed by us and others
• Adlakha et al 2003 Yuan/Qu 2002 Tilak et al
  2002, Heinzelman et al 2000.
• Applications performance goals differ
• Lifetime, reliability, responsiveness, ...
• Solution
• Design highly-parameterized node
• Develop methodology for
• Node developer
• Application developer (node user)

Software Configurable Node Parameters
Voltage
0xFF
Clock Frequency
0xC3
Baud Rate
0x1A

Endangered Species Videoing System
1 2 3 4 5 6 7 8 9
AB
Sleepwalker at Night Alarm
0xFF
0xC
0x1
AB
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3.Mass Producable but Tunable Nodes --
Methodology
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3. Node Characterization
Determine parameters based on hardware options
(uC, sensors, etc) and software options
(protocols, application requirements, etc)

• Done by node developer
• Consists of 3 stages
• Computation and Communication Parameter
  Definition
• Design Metric Evaluation Equations
• Parameter Interdependence

Based on datasheets, determine interdependencies
between parameters
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3. Application Characterization

• Done by Application Developer
• 2 Types of objective functions
• Overall Objective Function
• Weighted sum
• Foverall (A Flifetime) (BFreliability)
  (C Flatency) (D Fresponsiveness)
• Designer specifies the relative weight
  (importance) of each metric
• Design Metric Objective Functions
• High-level metrics considered lifetime,
  latency, reliability, responsiveness
• Designer must specify what values are good and
  bad for each metric (1-good, 0-bad)

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3. Feedback to Application Developer

• Automated exploration
• Simulated annealing search
• Feedback to application developer
• Ultimately yields tuned parameter values
• Downloaded onto nodes

Config. A
voltage 5V frequency 32k Hz ecc hamming1
Config. B
voltage 4V frequency 300k Hz ecc crc
Prototype tool built, work submitted to upcoming
conference
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4. CAD Tools for Novices

• Problem 1
• Application developer may not have full set of
  blocks
• Solution
• Allow computer-capture using full set, use
  technology mapping techniques
• Problem 2
• Application developer may create inefficient
  solution
• Solution
• Allow computer capture, optimize network
• Combine both techniques into CAD tool

Prototype tool built, work submitted to upcoming
conference
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5. New Research Direction -- Spatial Programming
of Basic Sensor Networks

• Sensor networks evolving
• Programming is hard e.g., Horton, SECON04
  keynote
• Sensor network programming languages are for
  expert programmers, e.g.
• SQTL - Shen, C., C. Srisathapornphat, C. Jaikaeo.
  Sensor Information Networking Architecture and
  Applications. IEEE Personal Communications,
  August 2001.
• Sensorware - Boulis, A., M. Srivastava. A
  Framework for Efficient and Programmable Sensor
  Networks. Open Architectues and Network
  Programming Proc., 2002.
• But many sensor network developers are not
  programmers
• Scientists, engineers, healthcare workers,
  homeowners, etc.
• Programming is difficult for ordinary people
• Pane, J. Myers, B. (1996), McIver, L.,
  Conway, D. (1996), Patil, B., Maetzel, K.,
  Neuhold, E. (2001), Soloway, E., Bonar, J.,
  Ehrlich, K. (1983).
• Fortunately, low-end sensor networks require only
  simple programming

High-end sensor networks Expert programmers
Low-end sensor networks Non-programming developers
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5. Spatial Programming using eBlocks

• Novices had great success build eBlock systems
  (physical and on computer) -- use as programming
  paradigm

Spatially-Oriented Paradigm
Temporally-Oriented Paradigm
eBlocks
C Code
bool inputA P01 bool inputB P02 bool
output P03 void main() if (inputA
YES inputB YES) output YES
else output NO
µC
LEGO Mindstorms
µC
Programmable eBlock
RCX Brick
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5. Spatial Programming using eBlocks

• Tested 20 recent high school graduates
• Asked them to build equivalent systems using
  temporal (LEGO Mindstorms) and spatial (eBlocks)
  programming paradigms
• 30 minutes to build 6 designs

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5. Spatial Programming -- Only Minutes to Program

• User captures design using eBlocks Simulator
• Synthesis tools partition design based on types
  and number of programmable blocks available
• Synthesis tools generates C code for each
  partition

include ltpic.hgtinclude sci.h include
io.h include constants.h Unsigned char
data_val ERROR ... main(void) unsigned I,
j TRISB 0 ...
main(void) ORTA 0xff CMCON 0x07
TRISA 0x00 TRISB 0x02 asm("CLRWDT")
...
R. Mannion, H. Hsieh, S. Cotterell, F.
Vahid System Synthesis for Networks of
Programmable Blocks. Design, Automation and Test
in Europe (DATE), March 2005.
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5. Spatial Programming -- Only Minutes to Program

• After synthesis, user can program a physical
  programmable eBlock via a PC cable

Synthesis
Program a Programmable eBlock
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5. Programming Directions

• Increasingly abstract behavior capture

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Future Work Extending eBlocks to Integers

• Extend to integer eBlocks
• Sensors
• Temperature, speed, distance, sound, etc.
• Display
• LCDs (of varying sizes), data logger, etc.
• Communication
• Integer Logic, wireless rx/tx, etc.
• Number of potential embedded systems we can
  design increases tremendously
• Configuration problem becomes harder
• More options than just yes/no
• Design space becomes larger

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Applications

• Tremendously diverse applications buildable with
  just a dozen blocks
• Present applications being considered
• At-home monitoring of aging parent to detect
  trends or daily situation
• with Intel
• Customizable victim notification system
• With ADV, proposal in final stages with DOJ
• Localized organic pesticide meterer based on
  insect counts
• With ISCA Corp.
• Endangered species videoing system
• With UCR environment science colleagues

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Conclusions

• Everyday people can use eBlocks to build basic
  but useful systems
• Required careful block set definition and block
  design
• Extensive ongoing and future research
• Integer blocks
• Digital abstraction
• Mass producable tunable nodes
• CAD for node users
• eBlocks as a spatial programming paradigm