Distributed Measurement System for Performance Evaluation of Embedded Clock Synchronization Solutions

Distributed, real-time, safety-critical systems gain wide-scale acceptance in the automotive, aerospace, industrial, science, telecommunication, energy distribution, and audio-video distribution applications. In these systems, Time-Sensitive Networking (TSN) can provide the required real-time and reliable communication services. TSN requires precision, hardware-assisted time synchronization provided by the IEEE 802.1AS-Rev or its progenitor, IEEE 1588. IEEE 1588 has a long history in distributed measurement systems, such as vehicular test systems, energy distribution, astrophysics, communication systems such as 4G and 5G, etc. Most modern hardware supports the hardware requirements for IEEE 1588 or IEEE 802.1AS-Rev in some respect; however, software support is very limited on network embedded microcontrollers (MCU), i.e., most modern MCUs do not have open-source, free SW support for time synchronization. We have developed flexPTP (https://github.com/epagris/flexPTP), an open-source, open-licensed PTP implementation for MCUs based on FreeRTOS (embedded real-time OS for MCUs) and lwIP (a TCP/IP stack for MCUs). During the development of the project, we have also created a distributed measurement system for the performance evaluation of flexPTP, which is built into flexPTP. The system can be used during development, but it is also applicable for online monitoring. The data collection component of the distributed measurement system collects data from the MCUs running flexPTP in a lightweight, low resource utilization, platform-independent, MCU-conform way, and forwards the information to a central node, on which data storage, analyses, and presentation can be done. We have also developed a WEB application for online supervision of synchronization in a browser. The system also has a self-discovery feature, allowing developers to identify all nodes capable of running the data collection component of the measurement system. In the paper, we will also present the initial performance evaluation results collected from our implementation. The measurement system can be also adapted to other online and/or offline performance evaluation projects in distributed, embedded systems with some modifications.