CAN Bus Transceiver Circuit with Asynchronous Receive Mode Control
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Solution Overview
Problem
The CAN bus system is vulnerable to malfunctions, where a single faulty device can disrupt communication among all devices, particularly in critical automotive applications, and existing solutions fail to prevent a faulty control node from jamming the bus with excessive or incorrect data, even if syntactically correct.
Innovation Solution
A transceiver circuit with a control input port and filter circuitry that allows asynchronous switching to receive mode, preventing data transmission from a faulty node while still allowing data reception, using a control signal independent of network traffic, and a monitoring unit to verify data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single device is allowed to transmit data freely on the CAN bus, then communication functionality is maintained, but the device may jam the bus by sending excessive or incorrect data
Solution Approach 1:
A transceiver circuit is introduced as an intermediary component between the control node and the CAN bus. This transceiver includes a control input port that receives control signals to enable or disable data transmission, acting as a mediator that can block faulty data while allowing legitimate communication to proceed through the bus.
Solution Approach 2:
The system implements feedback mechanisms where control signals are sent back to the transceiver circuit based on the status of the control node. When a node is detected to be faulty or sending excessive traffic, feedback control signals are generated to prohibit transmission from that node, creating a closed-loop control system that maintains bus reliability.
2Measurement precision
If fault detection circuitry monitors message syntax to detect faults, then protocol violations can be detected, but syntactically correct malicious messages cannot be detected
Solution Approach 1:
The system performs preliminary actions by implementing control logic that prevents transmission before faulty data can jam the bus. The control input port receives control signals that enable or disable the transceiver in advance, stopping potential malicious transmissions before they reach the CAN bus, rather than reacting after detection.
Solution Approach 2:
The control node is segmented into separate functional components: a control input port for receiving control signals, a transceiver unit for actual data transmission, and monitoring logic. This segmentation allows independent control of the transmission function, enabling the system to block faulty data at the transceiver level while maintaining other functions.
3Reliability
If the transceiver is switched to receive mode asynchronously to prevent transmission, then faulty nodes are prohibited from transmitting, but coordination with network traffic is lost
Solution Approach 1:
The filter circuit implements periodic sampling and filtering of control signals to determine when to switch the transceiver to receive mode. By periodically evaluating control signals and filtering out spurious or premature switching requests, the system achieves reliable asynchronous switching that prevents bus jamming while maintaining proper operation.
Data Source
AI summary
A transceiver circuit for communicating data over a CAN bus having a first and second bus line the transceiver circuit comprising: a data input port, a data output port, a CAN-bus transceiver unit having a receive data output port for providing data received from the CAN-bus, and a transmit data input port for receiving data to be transmitted to the CAN-bus; a control input port for receiving a control signal indicative of whether transmission of data from this transceiver circuit to the CAN-bus is allowed or prohibited; a filtering circuit adapted for filtering the control signal received on the control input port and for providing a filtered control signal; a logic circuitry adapted for configuring the CAN-bus transceiver unit in receive mode based on the debounced control signal irrespective of ongoing communication on the CAN-bus.