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

authored by

Christoph Riggers, Jens Schleusner, Oliver Renke, Holger Blume

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 github.com/IMS-AS-LUH/t41-tri-sync-ptp.

Organisation(s)

Architectures and Systems Section

Type

Conference contribution

Pages

91-96

No. of pages

6

Publication date

2024

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Information Systems and Management, Hardware and Architecture, Computer Networks and Communications, Computer Science Applications

Electronic version(s)

https://doi.org/10.1109/rtcsa62462.2024.00022 (Access: Closed)