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Testbeds for wireless IoT devices facilitate testing and validation of distributed target nodes. A testbed usually provides methods to control, observe, and log the execution of the software. However, most of the methods used for tracing the execution require code instrumentation and change essential properties of the observed system. Methods that are non-intrusive are typically not applicable in a distributed fashion due to a lack of time synchronization or necessary hardware/software support. In this article, we present a tracing system for validating time-critical software running on multiple distributed wireless devices that does not require code instrumentation, is non-intrusive and is designed to trace the distributed state of an entire network. For this purpose, we make use of the on-chip debug and trace hardware that is part of most modern microcontrollers. We introduce a testbed architecture as well as models and methods that accurately synchronize the timestamps of observations collected by distributed observers. In a case study, we demonstrate how the tracing system can be applied to observe the distributed state of a flooding-based low-power communication protocol for wireless sensor networks. The presented non-intrusive tracing system is implemented as a service of the publicly accessible open source FlockLab 2 testbed.

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Designing and testing low-power wireless communication protocols often requires experimental deployments on real hardware in realistic settings. Infrastructure testbeds have the advantage that they allow reproducible results using different network configurations. However, most testbeds are either in-or outdoor only and do not span long and short ranges at the same time. In this work, we present an extension to the popular FlockLab testbed on a campus-scale in order to better support testing of long-range communciation, for example using the LoRa modulation. Different to existing LoRa test networks where specific protocol layers are fixed, we support custom modification above the physical hardware (above PHY) which allows the development and testing of alternative full custom MAC layers that are not based on LoRaWAN. CCS CONCEPTS• Networks → Wide area networks; Sensor networks.