CAN Bus ASC Protocol Switching for Overhead Reduction
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Solution Overview
Problem
The CAN bus communication system faces limitations in capacity utilization and transmission rate due to high protocol overhead and physical constraints, leading to inefficient data transmission and potential collisions, with existing technologies unable to effectively address these issues.
Innovation Solution
A communication system that switches between CAN and ASC data frames using different physical protocols, allowing for higher bus clock rates and reduced protocol overhead, with a third operating mode for device synchronization that prevents error counter increments during power-up, enabling efficient data transmission and error handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CAN data frames are used for data transmission, then reliable communication with error handling is achieved, but protocol overhead increases to approximately 55% and capacity utilization decreases to approximately 50%
Solution Approach 1:
The communication system segments the transmission medium into two distinct protocols: CAN data frames for reliable communication and ASC data frames for high-capacity transmission. This segmentation allows each protocol to optimize for its specific function, with CAN handling error-prone transmissions and ASC handling bulk data transfer, thereby resolving the contradiction between reliability and productivity
Solution Approach 2:
The communication system implements multi-functionality by enabling the same physical bus to operate with two different protocols (CAN and ASC). The system can dynamically switch between CAN mode for reliable communication and ASC mode for high-capacity transmission, allowing a single system to serve multiple communication needs and resolve the trade-off between reliability and productivity
2Speed
If transmission rate is increased beyond 1 Mbit/sec, then data transmission speed improves, but signal transit times exceed bit time causing arbitration problems and collisions
Solution Approach 1:
The system replaces the CAN arbitration mechanism with a time-division multiplexing approach using ASC protocol. Instead of relying on bit-level arbitration that fails at high speeds, the system uses time-sliced ASC frames with explicit addressing and acknowledgment mechanisms, allowing high-speed transmission while maintaining arbitration reliability through different technical means
3Speed
If transmission rate is increased to improve data speed, then transmission efficiency improves, but signal flanks become steeper resulting in higher radiant emittance and poorer EMC properties
Solution Approach 1:
The system uses periodic time-division multiplexing with ASC frames, transmitting data in structured time slots rather than continuous high-speed CAN traffic. This periodic structure allows for controlled signal transitions and reduces peak radiant emittance, improving EMC properties while maintaining high average transmission rates through efficient time utilization
4Adaptability or versatility
If device is powered up and switched to normal operating mode, then full functionality is available, but error counters may be incremented due to lack of synchronization causing premature error_passive or bus_off states
Solution Approach 1:
The system implements a preliminary synchronization phase during power-up where devices operate in a restricted mode before transitioning to full functionality. This preliminary action establishes time base synchronization and communication parameters before enabling full device capabilities, preventing error counter increments and ensuring reliable operation from startup
Data Source
AI summary
A communication system having one CAN bus and at least two devices interconnected by the CAN bus is described, at least one of the devices including: i) a CAN controller, which is suitable for transmitting CAN data frames over the CAN bus using a first physical protocol in a first operating mode; ii) an asynchronous serial communication interface unit, which is suitable for transmitting ASC data frames over the CAN bus using a second physical protocol in a second operating mode; iii) a first switching means, which is suitable for switching the first operating mode and the second operating mode depending on at least one agreement in effect between the device and at least one of the other devices; and iv) another switching means, which is suitable for switching the device to a third (restricted) operating mode, which differs from the first operating mode and the second operating mode, for powering up the device.