A Logic Block Enabling Logic Configuration by Non-Experts in Sensor Networks Susan Cotterell and Frank Vahid * Department of Computer Science and Engineering University of California, Riverside {susanc, * Also with the Center for Embedded Computer Systems at UC Irvine This work is being supported by the National Science Foundation and a Department of Education GAANN Fellowship

2 of 15 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) Military Applications Medical Monitoring Environmental Monitoring Home Automation Structure/Building Monitoring

3 of 15  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 Introduction Photo: Jason Hill Flexible, hard to program Easy to use, inflexible

4 of 15 eBlocks Overview 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 Boolean Blocks Outputs yes/no/error Future implementations - Integer Users connect blocks to create working customized application CODES/ISSS’03, SECON’04, DATE’05, SPOTS’05, HCII’05 Light Sensor yes/no Magnetic Contact Switch yes/no Button yes/no Motion Sensor yes/no 2-Input Logic yes/no Tripper yes/no Toggle yes/no Electric Relay yes/no LED yes/no

5 of 15 2-Input Logic Configure Logic Block to turn led on when it’s night and when door is open A’B’ Need a function of light sensor output and contact switch output – use Logic Block 2-Input Logic Creating an application with eBlocks  Create an application to detect if the garage door is left open at night Light Sensor We want to detect night – use light sensor Light Sensor Magnetic Contact Switch We want to know if garage door open – use contact switch Magnetic Contact Switch 2-Input Logic A’B’ LED Need something to indicate garage open at night – use led LED Plug pieces together and the system is done!

6 of 15 Building eBlocks Systems  The same basic blocks can be used in a variety of applications 2-Input Logic A’B’ Light Sensor Magnetic Contact Switch LED Garage Door Open At Night Detector Motion on Property Detector Motion Sensor 2-Input Logic A+B Prolonger Beeper Sleepwalker at Night Alarm Tripper Motion Sensor 2-Input Logic A’B Light Sensor Button Beeper Animal Videoing System Motion Sensor 2-Input Logic A+B Prolonger eBlock to Camera Interface Light Sensor Many of these system utilize a logic block

7 of 15  Original logic block was simply a truth table Select desired output for each input condition, by moving a switch  Informal experiments to test general usability of eBlocks Users unable to configure the logic block successfully  Need for a better logic block interface Blocks must be self-explanatory Users prefer exploratory learning [Gammon, 1999][Sikorski, 1998] Motivation ABOutput noyesno yesnoyes noyes no yes Logic Block configurable DIP switch

8 of 15 Written Experiments – Truth Table  Written experiment given to students Typical majors include psychology, business, etc.  Randomly distributed 3 different versions of quiz Each contained same introduced and asked students to configure the logic block motion sensor light sensor Logic block B A yes = motion detected no = no motion detected yes = light detected no = no light detected

9 of 15 Low success rates -- was it the use of variable names? Used English instead of variables – slightly better, but results still poor. Also checked to see if writing out the equation helps -- still yielded poor results. Written Experiments – Truth Table QuestionTruth table with variables (11 students) Truth table with English (9 students) Boolean equations (9 students) Motion at night36%22%11% Motion0%56%0% Motion at night or no motion in day 0%22%0% Motion or night0%11%0% Detect motion at night? A A A’ B B’ B Detect motion at night? motion no motion light no light light no light What would be the corresponding equation needed to detect motion at night (i.e. F=ab+a’b)? F = Gave same truth table quiz (w/variables) to six students in digital design course 90%Motion or night 90%Motion at night or no motion in day 90%Motion 100%Motion at night Truth table with variables (6 students) Question

10 of 15 eBlock Simulator  Developed eBlock simulator to aid in testing Enables wider participation Allows students to test resulting behavior of configured system Self-contained instructions, to prevent variations due to administrator

11 of 15 Logic sentence outperforms table based blocks Color seems to help truth table based blocks Simulator Experiments  Defined new “improved” versions of the logic block  Simulator instantiated blocks, users simply needed to configure logic block  Students were non-engineering majors Comprised mostly of business, history, dance, etc.  Allotted 15 minutes for quiz QuestionPhrased truth table (33 students) Phrased truth table embedded in sentence (30 students) Colored truth table embedded in sentence (32 students) Logic sentence (32 students) Daytime Doorbell (AB) 15%20%22%38% Garage open at night (A’B’) 16%13%25%19% A B Combine A is yes, B is yes A is yes, B is no A is no, B is yes A is no, B is no The output shouldbe yes when: yes no: Phrased truth table yes no the output should be AB When the input is out Combine A is yes, B is yes A is yes, B is no A is no, B is yes A is no, B is no Phrased truth table embedded in sentence yes no The output should be When the input is out AB AB AB AB AB Combine Colored truth table embedded in sentence Combine AND OR yes no When A is yes no B is then the output is yes Logic Sentence

12 of 15  When consider close to correct responses (1 switch wrong), logic sentence shows better success rate  Logic sentence is slightly better  Motion on property, a more difficult problem, shows a better success rate Simulator Experiments yes no The output should be When the input is out AB AB AB AB AB Combine Colored truth table embedded in sentence Combine AND OR yes no When A is yes no B is then the output is yes Logic Sentence  Tested top two designs on students in an introduction to programming course  Simulator instantiated blocks, users simply needed to configure logic block  Allotted 15 minutes for quiz QuestionColored truth table embedded in a sentence (15 students) Logic Sentence (17 students) Daytime doorbell (AB) 47% (47%)47% (71%) Nighttime doorbell (AB’) 33% (52%)41% (76%) Motion on property (A+B) 33% (33%)65% (71%) 92% (100%)42% (67%)Daytime doorbell (AB) Logic Sentence (13 students) Colored truth table embedded in a sentence (12 students) Question  Had students in second course in programming try out the two blocks interfaces  Logic sentence success rate even more pronounced

13 of 15 Simulator Experiments 63% (63%)Motion on property (A+B) 50% (38%)Nighttime doorbell (AB’) 69% (77%)63% (69%)Daytime doorbell (AB) Intermediate Students (13 students) Non-expert students (16 students) Question Success rates for separate AND/OR/NOT blocks 65% (71%)Motion on property (A+B) 41% (76%)Nighttime doorbell (AB’) 92% (100%)47% (71%)Daytime doorbell (AB) Intermediate Students (13 students) Non-expert students (12 students) Question Success rates for logic sentence block  Also considered the use of separate AND/OR/NOT blocks versus a single logic block  Users had to instantiate these blocks within simulator  Comparable to best table based logic blocks  Logic sentence block preferable for physical implementation -- only 1 block needed Separate AND/OR/NOT blocks out A B AND out A B OR out A NOT Combine AND OR yes no When A is yes no B is then the output is yes Logic Sentence

14 of 15 Conclusions and Future Work  Presented a variety of logic block interfaces  Logic sentence best performing  Incorporating color in truth table improved table success rates; table has advantage of generality  Present/Future Work  Continue usability testing  Extend eBlocks to integer domain  Gain experience with use of eBlocks in real applications with variety of users  Pro-active healthcare (w/ Intel)  Agricultural monitoring (w/ Isca)  Environment monitoring (w/ UCR/UCLA)

15 of 15 Thank you for your attention.