CAN Bus Receiver Synchronization Without Differential Lines
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Solution Overview
Problem
Existing downhole logging systems face challenges in synchronizing receiver units over a control area network (CAN) bus without separate differential lines, which are often not feasible due to tight input/output budgets and added complexity in tool assembly.
Innovation Solution
The system synchronizes receiver units using a control area network (CAN) bus by transmitting a ready for synchronization command and a start synchronization command, enabling a start synchronization interrupt to capture formation signals, and employing in-phase detection to reduce cross-talk disturbance, eliminating the need for additional differential lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate differential lines are used for synchronizing receiver units, then synchronization reliability is improved, but device complexity and I/O budget requirements worsen
Solution Approach 1:
The patent merges the synchronization function with the existing CAN bus communication infrastructure. Instead of using separate differential lines for synchronization, the system transmits synchronization commands (ready for synchronization command and start synchronization command) through the CAN bus, which is already established for data communication between the master control unit and receiver units. This eliminates the need for additional dedicated synchronization wiring while maintaining reliable synchronization across all receiver units.
2Measurement precision
If separate differential lines are used for synchronizing receiver units, then synchronization accuracy is improved, but I/O budget requirements worsen
Solution Approach 1:
The CAN bus is designed to perform multiple functions: it handles both regular data communication and synchronization commands. The same communication channel used for transmitting logging data and control signals is also used for transmitting ready for synchronization commands and start synchronization commands to all receiver units. This multi-functional approach eliminates the need for additional I/O resources dedicated solely to synchronization, optimizing the I/O budget while maintaining synchronization accuracy.
3Device complexity
If CAN bus is used for synchronizing receiver units, then device complexity is reduced, but synchronization deterministic behavior worsens
Solution Approach 1:
The system employs a two-stage synchronization protocol where the master control unit first transmits a ready for synchronization command to all receiver units, allowing them to prepare their interrupt handlers and ensure they are ready to receive the actual start synchronization command. This preliminary action ensures that when the start synchronization command is transmitted, all receiver units are in a known ready state, reducing uncertainty and improving deterministic behavior despite using the shared CAN bus.
Solution Approach 2:
The synchronization protocol incorporates feedback mechanisms where receiver units acknowledge receipt of synchronization commands through the CAN bus. The master control unit monitors these acknowledgments to ensure all receiver units have properly received and processed the ready for synchronization and start synchronization commands. This feedback loop ensures deterministic synchronization behavior by verifying that all units are synchronized before proceeding with signal capture.
Data Source
AI summary
In a logging system (100), multiple receiver units (106) are synchronized over a control area network (CAN) bus (110) without use of separate differential lines. A ready for synchronization command is received over the CAN bus (110). In response to receiving the ready for synchronization command, a start synchronization interrupt is enabled. A start synchronization command is then received over the CAN bus (110). In response to receiving the start synchronization command, the start synchronization interrupt is triggered for capturing formation signals which are produced responsive to excitation signals from a transmitter unit (104).