Mainstreaming Motes in Undergraduate Computer Engineering Curriculum

1. The Flock:Mainstreaming Motes into the Undergraduate Computer Engineering Curriculum Waylon Brunette Department of Computer Science & Engineering University of Washington (joint work with Bruce Hemingway, Tom Anderl, and Gaetano Borriello) IEEE Computer, August 2004 The Flock

2. Outline • A short personal history • A quick overview of UW curriculum and CSE466 • Sensor networks in an undergraduate curriculum • Conclusion The Flock

3. Undergraduate History • UW- BS in Computer Engineering (2002) • Plant Care - undergraduate research project • sensors monitor plant’s health, robot waters at the right time • A. LaMarca, W. Brunette, D. Koizumi, M. Lease, S. Sigurdsson, K. Sikorski, D. Fox, G. Borriello. Making Sensor Networks Practical with Robots. 1st International Conference on Pervasive Computing (Springer-Verlag Lecture Notes in Computer Science Vol. 2414), Zurich, Switzerland, pp. 152-166, August 2002. • A. LaMarca, W. Brunette, D. Koizumi, M. Lease, S. Sigurdsson, K. Sikorski, D. Fox, G. Borriello. PlantCare: An Investigation in Practical Ubiquitous Systems. 4th International Conference on Ubiquitous Computing (Springer-Verlag Lecture Notes in Computer Science Vol. 2498), Goteborg, Sweden, pp. 316-332, September 2002. • MULEs - senior capstone project • using mobility for connectivity in sparse sensor networks • R. C. Shah, S. Roy, S. Jain and W. Brunette, "Data MULEs: Modeling a three-tier architecture for sparse sensor networks", IEEE Sensor Network Protocols and Applications (SNPA), Anchorage, May 2003. • R. C. Shah, S. Roy, S. Jain and W. Brunette, "Data MULEs: Modeling and analysis of a three-tier architecture for sparse sensor networks", Elsevier Ad Hoc Networks Journal, vol. 1, issues 2-3, Sept. 2003, pp. 215-233. • S. Jain, R. C. Shah, W. Brunette, G. Borriello and S. Roy, "Exploiting mobility for energy-efficient data collection in sensor networks", IEEE WiOpt, 2004. The Flock

4. Computer Engineering Curriculum • In the dark ages • Computer architecture and CPU design • 1990s • Systems built around highly integrated microcontrollers or FPGAs • 2000s • Embedded software and operating systems • Application focused • Now, wireless communication opens up new vistas The Flock

5. UW – Computer Engineering • Shared core curriculum with CS program • Computer engineers specialization courses TechComm II TechCommI Engl. Comp. Adv Logic CapstoneDesign Digital Design Comp Org EmbeddedSoftware Languages Intro II Intro I CSE Elec Networking DiscreteMath CS Theory CSE Elec OS DataStructures Math 124/134 Math 125/135 Math 126/136 Math 308/318 Stat 390/391 Circuits Phys 121 Phys 122 Intro EE The Flock

6. CSE 466: Software for Embedded Systems • Course Goals • Basic microcontroller architecture • Motivation for their special features that distinguish them from microprocessors • Interfacing techniques • Connecting microcontrollers to sensors and actuators (both digital and analog) • Panorama of design considerations and constraints • Issues that must be addressed by software developers of embedded systems • Power management methods • Basic communication protocols • Both wired and wireless • Facility with a complete set of tools for embedded systems programming • Emphasis on debugging and testing • Implement at least two embedded systems • particular focus on interaction between multiple devices • communication between devices and general-purpose computers The Flock

7. CSE 466: Course Project • Complete a large project that embodies the major course topics • Project should be simple but expandable • The project should include: • Multiple device communication • Deal with constrained resources • Control hardware by directly manipulating the I/O • Introduce an embedded OS • Participate in a multi-agent project – team effort • Use current technology The Flock

8. The Flock Project • Used motes to teach the concepts of the class and at the same time exposed students to an emerging technology • Combine: • Sound Generation • Emergent Behavior • Ad hoc networks • Subjective Goal: • Generate behavior that mimics the effect of birds cooperating to sing the same song but vary the particular song over time – in our atrium • Meets Project Goals: • Requires use of timers, radio communication, and direct manipulation of hardware for sound generation The Flock

9. Course Structure • 10 week course • Taught using bottom up approach • Incremental laboratory projects to familiarize students with tools and components The Flock

10. Motes and TinyOS • Motes • Worked well with existing curriculum • ATMega16 and avr-gcc were already used • Standard platform with built-in radio and other hardware • Existing TinyOS code base • Convenient form factor for adding sensors • TinyOS • Event-based style helped students understand: • Time constraints • Code structure (need to write short non-blocking routines) • Existing modular code base saved time • Made a more complex project possible • Provided a degree of abstraction The Flock

11. Amplitude Sustain level Attack Decay Sustain Release Sound Generation • Used PWM with low pass filter to generate sound • Taxes the systems memory and CPU • Wave and sequence tables used to generate the sound take up a large part of memory • Uses many processor cycles, requiring efficient coding • Many students used a 15.625kHz sampling rate on the mica2dots (4 MHz crystals) • Processing had to complete in 256 cycles • Timing errors are easily detectable (<10 ms) • Gives quick feedback on program accuracy • Code inaccuracies are generally audible The Flock

12. Student Input • Presented a simplified algorithm • Purposefully incomplete • Wanted student feedback • Experience the design process and how to deal with ambiguities • Initially presented the flock concept in the context of emergent behavior and cellar automata • Final algorithm incorporated many student suggestions • Increased student interest • Students became involved in making sure the project worked The Flock

13. Flock Basic Behavior • Sing the same song for a little while • Songs start, then spread, then die out • Over time, different songs emerge as dominant for some period The Flock

14. Flock Network Design • Uses received radio packets to generate behavior • Packet is sent when a song is completed • Radio packets collected over random amount of time (bounded by min/max) • Decisions depend on neighbor nodes • Nodes with closer proximity are more heavily weighted when choosing next song • Utilizes signal strength to give the closer mote more weight The Flock

15. Dynamic Flock • Designed for non-deterministic group behavior • Adjustable network parameters • Allows flock behavioral control • Allows change in avg sound density • Allowed evaluation of individual nodes • Inject commands via the radio • Start/Stop • Update global parameters • Max number of song repetitions • Listen times • Threshold • Probabilities • TxPower The Flock

16. The Concert • The final exam for the class was a concert • Each student had a mote to contribute (50 motes) • Same rules, different code in each mote • The mote had to “qualify” • Testing scripts were used to simulate the flock to eliminate nodes that would cause problems • Used for grading projects The Flock

17. Flock Expansion • Add light sensors to determine day or night • Change sounds • Day – Bird calls • Night – Crickets • Both – Babbling stream, or other sounds • Would require sensors to aggregate data • Sensors near lights that are on 24/7 would need the aggregated data to determine day or night • Add microphone to determine when its appropriate to make noise and what volume is appropriate • Further vary the songs based on network traffic The Flock

18. Mote integration in CSE466 • Fit in well with the rest of the course material • Successfully introduced students to an embedded OS • Reinforced layers of abstraction with modular design • Allowed a more complicated project to be completed • Event-based style reinforced non-blocking and short routines • Presented debugging challenges for students • Reinforced the earlier concepts of debugging • Fewer I/O options on motes than breadboard • Needed to debug hardware so they could hear the sound output and ensure their timing was correct (simulator doesn’t work well) The Flock

19. Course Challenges • Installation of tools on lab image machines • Conflicts between specialized and pre-installed versions • Specializing generic software can be a problem • Increased emphasis of testing tools • Must be easy to use – e.g., logic analyzer for sensor nets • Created broadcast test fixtures – simulation not enough • Institutionalize teaching materials • Generic sensor network kit • Do not require a local expert • TinyOS is a moving target The Flock

20. Sensor network education • Integration into undergraduate curriculum enables sensor network senior projects and participation in research projects • Exposes students to emerging technology • Allows application focused projects that energize students to complete more challenging assignments • Friends and family can understand the application • Feeds into more specialized/focused graduate courses that emphasize open research questions The Flock

21. Conclusion • Successful in integrating traditional course topics with sensor networks • Effective use of TinyOS to illustrate embedded software abstraction layers • Second iteration this year is developing a package of materials for distribution • Several students were already able to employ motes in their capstone projects (follow-on course) • Leads to increased undergraduate participation in research projects that use sensor networks • Working toward a permanent installation in CSE atrium The Flock