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Title: Environment Replay for Low-End Reactive Embedded Systems
Authors: Seetharam, Adarsh
Advisors: Dr. Eric Rotenberg, Committee Member
Dr. Frank Mueller, Committee Member
Dr. Alexander Dean, Committee Chair
Keywords: embedded benchmark
universal remote control
recording inputs
input virtualization
interrupt replay
Issue Date: 6-Jan-2005
Degree: MS
Discipline: Computer Networking
Abstract: Existing benchmark suites for embedded systems focus on batch processing applications to simplify portability. However, embedded systems are typically tightly coupled to the external environment through input/output (I/O) operations, resulting in reactive, real-time rather than batch behavior. Furthermore, often the environmental state is not dependent on program progress, so portions of the program may block until an environmental change occurs, limiting the impact of a faster processor or more efficient code. Existing benchmark suites ignore these important aspects, leading to one-dimensional characterizations of embedded systems. This work offers methods to record and play back environmental inputs within the limited resources available on common low-end microcontroller units (MCUs). We modify input operations in the source code at the C level, creating a record version and a replay version. For recording, input data is captured and stored as the program executes. This data is analyzed, compressed and converted off-line into a series of time-dependent events. During replay, the input operations read the compressed environmental input event data, rather than the environment. These changes allow virtualization of input operations, resulting in C code which can easily be ported to different processors for batch-mode performance evaluation, yet still react to the original event timeline. Our methods are demonstrated with a universal infrared remote control application. Environmental inputs are recorded on an 8-bit MCU, processed and replayed. We then evaluate the impact of a higher clock rate and also porting to a 16-bit MCU. We characterize memory requirements, response times and the implications of porting interrupts.
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