Serial Port Clock Synchronization for Precise Meter Timestamping
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Solution Overview
Problem
Existing industrial electricity meters face challenges in achieving precise time synchronization for event timestamping without incurring high costs or security vulnerabilities, as current methods like hardware signals and NTP servers are costly and easily hackable.
Innovation Solution
A method for synchronizing the internal clock of an electricity meter using a serial link with an external apparatus, such as a modem, allowing for secure and cost-effective time synchronization by receiving a reference time and generating interrupts to set the current time accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hardware signal (TOP SYNCHRO signal) is used for time synchronization, then time synchronization precision is improved, but device complexity and cost increase due to dedicated port requirement
Solution Approach 1:
The serial port is configured to perform multiple functions: normal serial communication and time synchronization. By reconfiguring the same physical port between communication mode and interrupt mode, the invention eliminates the need for a dedicated synchronization port, thereby reducing device complexity and cost while maintaining synchronization precision
Solution Approach 2:
The serial port dynamically switches between two operational states: communication mode for data transmission and interrupt mode for time synchronization. This dynamic reconfiguration allows a single static physical port to fulfill multiple functional roles, resolving the contradiction between precision and complexity
2Measurement precision
If NTP server via radio link or wired link is used for time synchronization, then time synchronization capability is improved, but security deteriorates because these solutions are easily hackable
Solution Approach 1:
The existing serial link infrastructure acts as an intermediary channel for time synchronization. By embedding synchronization commands within the existing secure communication protocol between the meter and the external device, the invention leverages the established security of the serial link rather than creating a new vulnerable synchronization channel
3Measurement precision
If dedicated port is added for hardware signal synchronization, then time synchronization precision is improved, but cost increases
Solution Approach 1:
The invention makes the existing serial port universal by enabling it to handle both communication tasks and time synchronization tasks. This eliminates the need to manufacture meters with additional dedicated synchronization ports, thereby reducing manufacturing cost while maintaining high synchronization precision through interrupt-based timing
Data Source
AI summary
A method for synchronising a clock of an electricity meter which includes a first processing unit including a first port arranged to be connected to an external apparatus, having the following steps: receiving, via the first port, a first frame containing a reference time; configuring the first port to operate in an interrupt-triggering mode; receiving, via the first port, a pulse that specifies a synchronisation time, and triggering an interrupt that leads to the reference time being recorded as a current time at the synchronisation time; reconfiguring the first port so as to communicate via the first port using the serial link.