PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems

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Original languageEnglish
Title of host publication2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA)
Pages91-96
Number of pages6
ISBN (electronic)979-8-3503-8795-7
Publication statusPublished - 2024

Abstract

Synchronization of sensor devices is crucial for concurrent data acquisition. Numerous protocols have emerged for this task, and for some multi-sensor setups to operate synchronized, a conversion between deployed protocols is needed. This paper presents a bare-metal implementation of a Tri- Level Sync signal generator on a microcontroller unit (MCU) synchronized to a master clock via the IEEE 1588 Precision Time Protocol (PTP). Cameras can be synchronized by locking their frame generators to the Tri-Level Sync signal. As this synchronization depends on a stable analog signal, a careful design of the signal generation based on a PTP-managed clock is required. The limited tolerance of a camera to clock frequency adjustments for continuous operations imposes rate-limits on the PTP-controller. Simulations using a software model demonstrate the resulting controller instabilities from rate-limiting. This problem is addressed by introducing a linear prediction mode to the controller, which estimates the realizable offset change during rate-limited frequency alignment. By adjusting the frequency in a timely manner, a large overshoot of the controller can be avoided. Additionally, a cascading controller design that decouples the PTP from the clock update rate proved to be advantageous to increase the camera's tolerable frequency change. This paper demonstrates that a MCU is a viable platform to perform PTP-synchronized Tri-Level Sync generation. Our open source implementation is available for use by the research community at https://github.com/IMS-AS-LUH/t41-tri-sync-ptp.

Keywords

    MCU, PI-controller, PTP, Precision Time Protocol, SMPTE, Tri-Level Sync, camera, synchronization

ASJC Scopus subject areas

Cite this

PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems. / Riggers, Christoph; Schleusner, Jens; Renke, Oliver et al.
2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA). 2024. p. 91-96.

Research output: Chapter in book/report/conference proceedingConference contributionResearchpeer review

Riggers, C, Schleusner, J, Renke, O & Blume, H 2024, PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems. in 2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA). pp. 91-96. https://doi.org/10.1109/rtcsa62462.2024.00022
Riggers, C., Schleusner, J., Renke, O., & Blume, H. (2024). PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems. In 2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA) (pp. 91-96) https://doi.org/10.1109/rtcsa62462.2024.00022
Riggers C, Schleusner J, Renke O, Blume H. PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems. In 2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA). 2024. p. 91-96 doi: 10.1109/rtcsa62462.2024.00022
Riggers, Christoph ; Schleusner, Jens ; Renke, Oliver et al. / PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems. 2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA). 2024. pp. 91-96
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abstract = "Synchronization of sensor devices is crucial for concurrent data acquisition. Numerous protocols have emerged for this task, and for some multi-sensor setups to operate synchronized, a conversion between deployed protocols is needed. This paper presents a bare-metal implementation of a Tri- Level Sync signal generator on a microcontroller unit (MCU) synchronized to a master clock via the IEEE 1588 Precision Time Protocol (PTP). Cameras can be synchronized by locking their frame generators to the Tri-Level Sync signal. As this synchronization depends on a stable analog signal, a careful design of the signal generation based on a PTP-managed clock is required. The limited tolerance of a camera to clock frequency adjustments for continuous operations imposes rate-limits on the PTP-controller. Simulations using a software model demonstrate the resulting controller instabilities from rate-limiting. This problem is addressed by introducing a linear prediction mode to the controller, which estimates the realizable offset change during rate-limited frequency alignment. By adjusting the frequency in a timely manner, a large overshoot of the controller can be avoided. Additionally, a cascading controller design that decouples the PTP from the clock update rate proved to be advantageous to increase the camera's tolerable frequency change. This paper demonstrates that a MCU is a viable platform to perform PTP-synchronized Tri-Level Sync generation. Our open source implementation is available for use by the research community at https://github.com/IMS-AS-LUH/t41-tri-sync-ptp.",
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