Sensor Network Synchronization via Master-Slave Delay Compensation
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Solution Overview
Problem
Existing sensor networks with digital outputs face challenges in synchronizing measurements across multiple sensors, particularly time-of-flight sensors, which is crucial for accurately determining the instantaneous position of moving targets, as current connections do not allow all sensors to be driven simultaneously.
Innovation Solution
A synchronization method where one board acts as a master and others as slaves, using an I2C bus to calculate and apply delays to ensure all boards end their acquisitions at the same instant, with the formula Ri=(N−i)*C+CN−Ci determining the delay for each board, allowing simultaneous data acquisition across a network of sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a parallel link is used to connect multiple sensor boards to a single processor, then all sensors can be driven simultaneously, but the connection complexity and cost increase significantly
Solution Approach 1:
The patent introduces a master board as an intermediary between the processor and slave boards. The master board manages the I2C bus communications and coordinates acquisition commands, eliminating the need for complex parallel connections while maintaining synchronization. This mediator approach resolves the contradiction by providing centralized control through a simple serial bus instead of complex parallel wiring.
Solution Approach 2:
The system performs preliminary calibration by measuring acquisition durations for each slave board and calculating individual delay values before actual synchronized acquisition. This preliminary action allows the system to compensate for timing differences inherent in serial communication, enabling synchronized measurements despite the sequential nature of I2C bus access.
2Device complexity
If a serial bus (I2C) is used to connect sensor boards, then the connection simplicity and cost decrease, but the sensors cannot be driven simultaneously due to sequential access
Solution Approach 1:
The system performs preliminary measurement of acquisition durations for each slave board during a calibration phase. These measurements are used to calculate precise delay values that compensate for the sequential access nature of I2C communication. By applying these pre-calculated delays, the system achieves synchronized acquisition endpoints despite the inherent time offsets in serial communication.
Solution Approach 2:
The system dynamically adjusts the acquisition start time for each slave board based on its position in the I2C bus access sequence. The master board calculates and applies individual delays to each slave's acquisition start command, transforming the static sequential access limitation into a dynamic synchronized operation where all boards end their acquisitions simultaneously.
3Reliability
If individual delay calculations are applied to each slave board, then synchronized acquisition is achieved, but the processing complexity at the master board increases
Solution Approach 1:
The system performs all complex delay calculations during an initial calibration phase rather than during continuous operation. The master board measures acquisition durations for each slave board once, calculates the required delays using a simple formula based on board index and measured durations, and stores these delay values for reuse. This preliminary calculation approach eliminates ongoing processing complexity while maintaining synchronization accuracy.
Solution Approach 2:
The system transforms the synchronization problem from a complex real-time calculation task into a simple parameter lookup operation. By changing the acquisition duration parameter for each slave board based on its index position and pre-measured values, the system achieves synchronized operation through simple parameter adjustment rather than complex real-time processing.
Data Source
AI summary
The invention relates to a system comprising a plurality of boards, each of which comprises a sensor and a control processor. The boards are connected together by a serial bus. One of the boards acts as master and the others as slaves. The master board is suitable for accessing the measurements of the plurality of boards and for sending these measurements, via a UART connection, to a host processor. The acquisition of the measurements takes place according to a specific synchronization method.