Cross Controller Clock Synchronization for Distributed DAQ Systems
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Solution Overview
Problem
Current high-performance synchronization technologies are limited in their ability to synchronize multiple instrumentation devices across multiple systems, often requiring all devices to be connected to a single controller and struggling with combining triggers, especially when trigger conditions are temporary or based on digital patterns.
Innovation Solution
A system that generates local reference clock signals aligned via high-precision time protocols like IEEE-1588 or GPS, allowing each DAQ card to produce a local sample clock and trigger clock, which are synchronized across subsystems, enabling precise synchronization of triggers and data acquisition across multiple instrumentation devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all devices are connected to a single controller for synchronization, then synchronization performance is improved, but system complexity and scalability deteriorate
Solution Approach 1:
The system divides the synchronization architecture into multiple independent subsystems, each with its own controller. Each subsystem synchronizes devices locally with high precision, while subsystems themselves are synchronized through a higher-level protocol (IEEE-1588 or GPS). This segmentation allows the system to scale to many more devices without increasing the complexity of individual control paths.
Solution Approach 2:
The patent introduces an intermediary synchronization protocol (IEEE-1588 PTP or GPS) that mediates between multiple independent subsystems. This intermediary layer allows subsystems to maintain their own local synchronization while still achieving system-wide synchronization, avoiding the need for a single centralized controller.
2Reliability
If a single controller is used to synchronize triggers across multiple devices, then trigger synchronization is improved, but the ability to handle temporary or digital pattern-based trigger conditions deteriorates
Solution Approach 1:
Each subsystem controller independently evaluates its own trigger conditions (including temporary conditions and digital patterns) and generates local trigger events. This segmentation allows each controller to be highly adaptive to its specific trigger requirements while maintaining synchronized timing across the entire system through the hierarchical synchronization architecture.
Solution Approach 2:
Each subsystem is equipped with local intelligence to handle specific trigger conditions appropriate to its function. The local controller can recognize digital patterns, respond to temporary conditions, and generate triggers autonomously, while still maintaining system-wide synchronization through the hierarchical protocol.
3Productivity
If multiple subsystems operate independently with local clocks, then system scalability is improved, but synchronization precision between subsystems deteriorates
Solution Approach 1:
The system uses segmentation at two levels: local device-level segmentation where each device has its own precise clock, and subsystem-level segmentation where each controller manages multiple devices. The hierarchical synchronization protocol bridges these levels, allowing precise local operation with scalable system-wide coordination.
Solution Approach 2:
The IEEE-1588 PTP or GPS synchronization protocol provides continuous feedback between subsystems, allowing each subsystem to adjust its local clock based on timing information from other subsystems. This feedback mechanism maintains high synchronization precision across the entire distributed system.
Data Source
AI summary
A system may include a plurality of subsystems, e.g. instrumentation units housed in separate chassis, each chassis including multiple instrumentation devices, e.g. data acquisition cards. Each subsystem may generate a local reference clock, which may be phase aligned and locked with respect to one or more similar reference clocks of other subsystems, via a high-level precision time protocol (PTP). Each instrumentation device within a given subsystem may generate its own sample clock based on the local reference clock, and may generate its own trigger clock based on its own sample clock. All trigger clocks may be synchronized with respect to each other through a future time event issued using the PTP, and each instrumentation device may then use its trigger clock to synchronize any received trigger pulses, which may also be issued through future time events using the PTP. This results in synchronizing the received triggers across all participating instrumentation devices across all participating subsystems, ensuring that data acquisition is properly synchronized across the multiple subsystems.