CAN Frame Bit Stuffing Limitation via Tuning Field
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Solution Overview
Problem
The existing CAN protocol experiences communication jitter and reduced error detection reliability due to uncontrolled bit stuffing, which affects synchronization and timing accuracy in distributed control systems.
Innovation Solution
A method is introduced to compose electronic signals with a data field and error control field, using tuning bits to prevent the generation of stuff bits in the error control field, ensuring deterministic transmission times and improved reliability by employing a coding technique like 8B9B to eliminate stuff bits from the data field and controlling them in the error control field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bit stuffing is performed to maintain synchronization in the receiver, then synchronization accuracy is improved, but communication jitter increases due to variable transmission time
Solution Approach 1:
The patent applies preliminary action by pre-calculating the number of stuff bits that will be inserted into the data field before the error control field is generated. This allows the transmission time to be determined in advance, eliminating communication jitter while maintaining synchronization accuracy through controlled bit stuffing.
2Ease of operation
If bit stuffing is performed automatically by the CAN controller, then ease of operation is improved, but reliability deteriorates due to adverse influence on error detection ability
Solution Approach 1:
The patent segments the communication frame into data field and error control field, and applies different processing rules to each. The data field undergoes controlled bit stuffing with pre-calculated stuff bit positions, while the error control field is generated separately based on the stuffed data field. This segmentation allows automatic operation while preserving error detection reliability because the error control field is calculated after stuffing is complete.
3Adaptability or versatility
If the number of stuff bits is variable depending on data content, then adaptability is improved, but manufacturing precision deteriorates due to variable frame duration
Solution Approach 1:
The patent applies preliminary action by pre-calculating the exact number and positions of stuff bits in the data field before generating the error control field. This pre-calculation enables the transmitter to determine the complete frame duration in advance, achieving deterministic timing while maintaining adaptability to different data contents through controlled stuff bit insertion.
Data Source
Figure 1
AI summary
A method for composing an electronic signal comprising a stream of bits arranged in a communication frame including a data field and an error control field, in which a sequence of consecutive bits of the same value equal in number to a predetermined stuff bit threshold limit causes at least one sequence break bit of the opposite value (stuff bit) to be inserted, and in which the error control field is calculated as a predetermined function at least of the current value of said data field, characterised in that the method comprises partitioning the data field in an effective data field, including a sequence of payload bits, and a tuning field, including a tuning bit string of a predetermined length, and selecting a tuning bit string from a predetermined set of tuning bit strings, in such a way that the concatenation of the selected tuning bit string and the error control field calculated as a function of at least said effective data field and of said selected tuning bit string does not include a series of consecutive bits of the same value in a number equal to the said predetermined stuff bit threshold limit.