Researchers at Disney Research and Carnegie Mellon University (CMU) have developed a system for finding computer bugs in small devices that scavenge their energy from their environment and are subject to intermittent power failures.
Whether these devices harvest energy from radio waves, solar energy, heat or even vibration, it's anticipated that they all will lose power from time to time and be forced to reboot. This unpredictable power cycling can result in code execution errors rarely if ever seen in continuously powered systems, which are difficult to diagnose with conventional debugging tools.
The Disney/CMU team built a hardware and software platform that can monitor and debug these intermittent systems without interfering with the device's energy state. They will present the Energy-interference-free Debugger (EDB) at the International Conference on Architectural Support for Programming Languages and Operating Systems, April 2-6 in Atlanta, Ga.
Common energy-harvesting devices range from the well-known solar-powered calculator to passive radio frequency identification (RFID) tags, which are energized when radio waves target the tags. Sensors for monitoring infrastructure or the environment increasingly scavenge energy from their environment because wired power or battery replacement isn't practical.
"The use of energy-harvesting devices will only proliferate as increasing numbers of sensor networks are deployed and other devices such as solar-powered microsatellites are invented," said Jessica Hodgins, vice president at Disney Research. "Creating reliable software for these devices is vital. To do that, we need tools to help us detect and correct bugs."
Unfortunately, most existing tools provide power to the device being monitored, making it impossible to search for errors associated with intermittent power, said Alanson P. Sample, research scientist at Disney Research and head of its wireless systems group. Mixed-signal oscilloscopes can passively monitor a device's energy level, but don't provide any information about the internal state of its software - and are expensive.
"Our hardware-software debugging tool is the first ever to bring essential, familiar application development support to these intermittent devices," said Brandon Lucia, assistant professor of electrical and computer engineering (ECE) at CMU. "The key to our approach is that we provide flexible debugging support without interfering with the target device's power system."
Two CMU ECE students and Disney lab associates - Alexei Colin, a Ph.D. student in ECE, and Graham Harvey, a senior in ECE - along with Lucia, worked with Sample to develop a debugging system that can be electrically isolated from the device that is being debugged.
The EDB system can passively monitor an energy-harvesting device for its energy level, input/output events, and program events. But it also has the capability to manipulate the amount of energy stored on the device, making it possible for an engineer to inject or remove power based on code execution, which makes it a powerful tool for finding intermittent bugs.
"We evaluated our prototype of EDB, including custom hardware, showing that it is energy-interference-free in both its passive and active tasks, and that it provides invaluable debugging information that is out of reach using existing tools and techniques," Colin said.
This work was supported by the National Science Foundation. For more information, visit the project web site at http://www.disneyresearch.com/publication/intermittent-energy-harvesting-systems/.
About Carnegie Mellon University
Carnegie Mellon is a private, internationally ranked research university with programs in areas ranging from science, technology and business, to public policy, the humanities and the arts. More than 13,000 students in the university's seven schools and colleges benefit from a small student-to-faculty ratio and an education characterized by its focus on creating and implementing solutions for real problems, interdisciplinary collaboration and innovation.
About Disney Research
Disney Research is a network of research laboratories supporting The Walt Disney Company. Its purpose is to pursue scientific and technological innovation to advance the company's broad media and entertainment efforts. Vice Presidents Jessica Hodgins and Markus Gross manage Disney Research facilities in Los Angeles, Pittsburgh and Zürich, and work closely with the Pixar and ILM research groups in the San Francisco Bay Area. Research topics include computer graphics, animation, video processing, computer vision, robotics, wireless & mobile computing, human-computer interaction, displays, behavioral economics, and machine learning.