TY - GEN

T1 - PTP-Synchronized Tri-Level Sync Generation for Networked Multi-Sensor Systems

AU - Riggers, Christoph

AU - Schleusner, Jens

AU - Renke, Oliver

AU - Blume, Holger

N1 - Publisher Copyright: © 2024 IEEE.

PY - 2024

Y1 - 2024

N2 - 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.

AB - 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.

KW - MCU

KW - PI-controller

KW - PTP

KW - Precision Time Protocol

KW - SMPTE

KW - Tri-Level Sync

KW - camera

KW - synchronization

UR - http://www.scopus.com/inward/record.url?scp=85207070117&partnerID=8YFLogxK

U2 - 10.1109/rtcsa62462.2024.00022

DO - 10.1109/rtcsa62462.2024.00022

M3 - Conference contribution

SN - 979-8-3503-8796-4

SP - 91

EP - 96

BT - 2024 IEEE 30th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA)

ER -